just dumping some text files

Discussion in 'Tone Zone' started by ess, Jan 29, 2005.

  1. ess

    ess Guest

    SG SUPREME


    The new king of the "solid guitars", the SG Supreme is a direct descendant of Gibson's original solidbody guitar, the Les Paul. The Supreme features a AA figured maple top, on a mahogany back with superior
    Specifications:
    Top Species: AA flame maple
    Back Species: mahogany

    NECK
    Species: Mahogany
    Peghead Pitch: 17°
    Thickness at 1st fret: 0.800"
    Thickness at 12th fret: 0.895"
    Neck Joint Location: 22th fret
    Headstock Inlay: split diamond
    Headstock Binding: single-ply

    FINGERBOARD
    Species: Ebony
    Scale length: 243/4"
    Nut Width: 111/16"
    Width at 12th fret: 2.062"
    Frets: 24
    Inlays: split diamond
    Binding: single-ply

    HARDWARE
    Plating Finish: Gold on Emeraldburst and Lavaburst, Chrome on Midnightburst
    Bridge: Tune-o-matic
    Tailpiece: Stopbar
    Knobs: Black top hat with inserts
    Tuners: Grover Kidney

    ELECTRONICS
    Pickups: Two '57 Classic humbuckers
    Controls: Two volume and tone, three-way switch

    CASE
    Exterior: Black Reptile Pattern Hardshell
    Interior: Dark Grey Plush with Black Shroud
    Silkscreen: Silver 'Gibson USA' logo

    Available Colors: Fireburst , Midnight Burst , Emerald Burst
    Les Paul appointments including a bound ebony fingerboard, bound headstock, gold hardware, split diamond inlay, and now with humbuckers.



    ============================================================





    SG STANDARD


    Gibson's new solidbody guitar of the '60s, the SG, broke through traditional concepts of solidbody electrics and became an instant classic. The SG body style has remained in production since its first appearance in 1961
    Specifications:
    Body: Mahogany

    NECK
    Species: Mahogany
    Profile: Rounded
    Peghead Pitch: 14°
    Thickness at 1st fret: 0.818"
    Thickness at 12th fret: 0.963"
    Heel Length: 0.625"
    Neck Joint Location: 19th fret
    Headstock Inlay: Crest

    FINGERBOARD
    Species: Rosewood
    Scale length: 243/4"
    Total Length: 18.157"
    Nut Width: 111/16"
    Width at 12th fret: 2.062"
    Frets: 22
    Inlays: Pearloid Trapezoid
    Binding: single-ply

    HARDWARE
    Plating Finish: Chrome
    Bridge: Tune-o-matic
    Tailpiece: Stopbar
    Knobs: Black Top Hat with silver insert
    Tuners: Schaller Green Key ELECTRONICS
    Neck Pickup: 490R Alnico magnet humbucker
    Bridge Pickup: 498T Alnico magnet humbucker
    Controls: Two volume, two tone, three-way switch

    CASE
    Exterior: Black Reptile Pattern Hardshell
    Interior: Dark Grey Plush with Black Shroud
    Silkscreen: Silver 'Gibson USA' logo

    STRINGS
    Brite Wires .010-.046



    =============================================================



    SG SPECIAL FADED



    The new Worn Cherry and Worn Brown finishes give this classic model the look of well-worn, well-loved instrument.
    Available Colors: Worn Cherry , Worn Brown
    Specifications:
    BODY
    Species: Mahogany

    NECK
    Species: Mahogany
    Profile: Rounded

    FINGERBOARD
    Species: Ebony
    Scale length: 243/4"
    Nut Width: 111/16"
    Inlays: Pearloid Dot

    HARDWARE
    Plating Finish: Chrome
    Bridge: Tune-o-matic/Stopbar

    ELECTRONICS
    Neck Pickup: 490R Alnico magnet humbucker
    Bridge Pickup: 490T Alnico magnet humbucker
    Controls: Two volume, two tone, three-way switch

    Controls: Two volume, two tone, three-way switch

    CASE
    Exterior: Black Gigbag
    Interior: Black Padded
    Silkscreen: White 'Gibson USA' logo

    STRINGS
    Brite Wires .010-.046



    =============================================================




    SG SPECIAL


    Since the first version of the SG Special in 1961, the Special has represented the combination of looks, functionality and value that is the hallmark of the SG series. Available Colors: Blue Teal Flip Flop , Platinum , Ebony* , Wine Red*

    Two new colors enhance the Special's looks. Viewed from different angles, the Blue Teal Flip Flop finish changes color through the spectrum of blues and greens.

    The Platinum SG Special features a total monochrome look including Platinum headstock, brushed chrome hardware, silver (non-metallic) pickguard, and ebony fretboard minus the inlays.
    Specifications:
    SG Special
    Manufactured in: Nashville, TN

    BODY
    Species: Mahogany

    NECK
    Species: Mahogany
    Profile: Rounded
    Neck Joint Location: 19th fret

    FINGERBOARD
    Species: Rosewood, Ebony on Platinum
    Scale length: 243/4"
    Total Length: 18.062"
    Nut Width: 111/16"
    Frets: 22
    Inlays: Dot, None on Platinum

    HARDWARE
    Plating Finish: Chrome, Brushed Chrome on Platinum
    Bridge: Tune-o-matic
    Tailpiece: Stopbar
    Knobs: Black top hat with silver insert, Silver top hat on Platinum
    Tuners: Green Key, Kidney on Platinum

    ELECTRONICS
    Neck Pickup: 490R Alnico magnet humbucker
    Bridge Pickup: 490T Alnico magnet humbucker
    Controls: Two volume, two tone, three-way switch

    CASE
    Exterior: Black Gigbag
    Interior: Black Plush Padded
    Silkscreen: White 'Gibson USA' logo

    STRINGS
    Brite Wires .010-.046


    ============================================================


    Tony Iommi Signature SG



    The Tony Iommi Signature SG is a tribute to the distinct sound and legendary rock anthems from his over twenty-five years with Black Sabbath.

    Available Colors: Ebony
    This new SG features an ebony finish and dual Tony Iommi Signature pickups. The truss rod cover features a signature decal and the inlays are silver crosses
    Specifications:
    Manufactured in: Nashville, TN

    BODY
    Species: Mahogany

    NECK
    Species: Mahogany
    Peghead Pitch: 17°
    Thickness at 1st fret: 0.800"
    Thickness at 12th fret: 0.895"
    Neck Joint Location: 22th fret

    FINGERBOARD
    Species: Ebony
    Scale length: 243/4"
    Total Length: 18.831"
    Nut Width: 111/16"
    Width at 12th fret: 2.012"
    Frets: 24
    Inlays: Iommi Crosses

    HARDWARE
    Plating Finish: Chrome
    Bridge: ABR
    Tailpiece: Stopbar
    Knobs: Black top hat with insert
    Tuners: Grover Kidney

    ELECTRONICS
    Pickups: Tony Iommi Humbuckers
    Controls: Two volume, two tone, three-way switch

    CASE
    Exterior: Black Reptile Pattern Hardshell
    Interior: Dark Grey Plush with Black Signature Shroud
    Silkscreen: Silver 'Gibson USA' logo

    STRINGS
    Brite Wires .010-.046

    OTHER
    Tony Iommi signature on truss rod cover


    ============================================================


    ANGUS YOUNG SIG SG


    For over 25 years, the scorching riffs of Angus Young have driven the anthems of AC/DC up the charts and around the world.
    Available Colors: Aged Cherry
    Gibson's new Angus Young Signature SG is a faithful reproduction of the artist's trademark axe.

    Designed and manufactured to Angus' exacting specifications, this SG has exactly what it takes to rock 'all night long.'
    This new SG features an engraved lyre vibrola, an Angus Signature treble pickup along with a '57 Classic rhythm pickup, a 'Devil' peghead decal and comes with a special Angus Young Signature SG hardshell case
    Specifications:
    Manufactured in: Nashville, TN

    BODY
    Species: Mahogany

    NECK
    Species: Mahogany
    Peghead Pitch: 17°
    Thickness at 1st fret: 0.775"
    Thickness at 12th fret: 0.875"
    Neck Joint Location: 19th fret
    Headstock Inlay: 'Devil Signature' decal

    FINGERBOARD
    Species: Rosewood
    Scale length: 243/4"
    Total Length: 18.137"
    Nut Width: 1.625"
    Width at 12th fret: 2.032"
    Frets: 22
    Inlays: Pearloid trapezoid
    Binding: single-ply

    HARDWARE
    Plating Finish: Nickel
    Bridge: ABR
    Tailpiece: Engraved Lyre Vibrola
    Knobs: Black Witchhat with silver insert
    Tuners: Green Key
    ELECTRONICS
    Neck Pickup: '57 Classic Humbucker
    Bridge Pickup: Angus Signature Humbucker

    Controls: Two tone, two volume controls, 3-way selector switch

    CASE
    Exterior: Black Reptile Pattern Hardshell
    Interior: Dark Grey Plush with Black Signature Shroud
    Silkscreen: Silver 'Gibson USA' logo



    ============================================================






















    ==============================================================











    ==============================================================
    Tim Stanley's responses to pickup cavity shielding questions.
    Also see my grounding FAQ since shielding and grounding are related issues.
    ==============================================================

    IMHO, before you buy new pickups, do what the manufacturer failed to
    do properly - i.e., shield the cavity. That is the basis of many
    pickup problems - after that - decide if new pickups are in order.

    Vintage guitar collectors presumably prefer their vintage noise and
    should not follow the following advice as it will result in a quieter,
    but less valuable, vintage guitar.

    --------------------------------
    Material
    --------------------------------

    Stewart-MacDonalds (Athens, OH) sells mail order shielding paint.
    That is what I always use. One small can is enough for > 5 guitars at
    3 coats per guitar.

    Other people like to shield with foil/sheet metal. Seems hard to work
    with to me. But, no doubt it provides a lower resistance path to
    ground for that pesky noise. And it may be easier to attach the final
    ground wire to metal, than to the painted surface. Just make sure all
    of the pieces of tape/foil are electrically attached/soldered
    together, and then finally to the common ground point.

    Get a small (3/8" maybe) cheap tough paint brush from a hardware
    store. You will throw it away when you are done and you don't need
    a quality brush for this application.

    Get in a patient neat mood. This paint is a bit nasty (ventilation
    needed) and awkward to apply (light tar, well, it certainly ain't
    latex). If it gets on something it shouldn't be on - remove it right
    away. Really.

    --------------------------------
    Disassemble
    --------------------------------

    Unscrew all the pots and switches from the guitar and pickguard before
    you paint. Don't be lazy - completely disassemble everything so you
    do a complete job. Consider well that you are doing what the
    manufacturer was too cheap to do properly - this is no time to be
    lazy. Usually, the potentiometer case/switch case/jack case is metal,
    and screwing it down to your soon-to-be shielded pickguard or guitar
    will shield it as well. Very nice, indeed.

    --------------------------------
    Guitar
    --------------------------------

    Paint the interior of every cavity that you can reach. Paint the
    outside of the timber (under the pickguard) out and (*very*) slightly
    around the pickguard screwholes. Of course, take care that you don't
    go too far so that the shielding paint will remain under the pickguard
    and not ruin your axe's finish. At the same time, be sure to extend
    the lip out and around as many screwholes as possible. Then when you
    screw the soon-to-be shielded pickguard to the guitar, a connection is
    made between the shield on the pickguard and the cavity.

    --------------------------------
    Pickguard
    --------------------------------

    I paint the entire back of the pickguard, although it may not be
    really necessary on some guitars if the exposed (non-shielded) wires
    are only in the cavity. Do it anyway. Then, when the pickguard is
    screwed down to the guitar, it makes a connection with the shielded
    portion of the timber over the entire perimeter of the cavity. Now,
    the entire cavity interior is completely shielded.

    This is not a ground loop, rather, you have created a ground plane
    that surrounds all of your electronics. You do have only one
    connection, between the pickguard and the timber, it is just a large
    perimeter connection.

    --------------------------------
    3 coats
    --------------------------------

    Also, I use 3 coats for coverage and to reduce the sheet resistance of
    the paint shield. The paint is a bit thick - after it dries, you can
    visibly see the direction of your brush strokes. So, e.g., first coat
    is left to right; second coat is up and down, and third coat is
    diagonal. Thusly, at the end, everything is evenly covered despite
    your brush strokes.

    The paint seems impossible to remove from the brush, wet or dry. Wrap
    the brush in foil between coats and it will be just fine for a few days.

    --------------------------------
    Ground
    --------------------------------

    The paint shield has to be connected to the ground of the system. It
    is likely that the back of one potentiometer in the system has been
    used as a common ground point. As such, if the conductive
    potentiometer case is mechanically attached to the paint shield, then
    the paint shield is connected into the system.

    However, you might want to take a short pan head screw, and a bare
    wire, and mechanically attach the wire to the paint shield with the
    screw. Then, solder this wire to the back of the potentiometer with
    all of the other ground connections.

    In either case, use an ohm-meter to verify that the shield (whether it
    is paint, foil, tape) is well connected to the system ground.

    --------------------------------
    Ground loops
    --------------------------------

    One practical matter to remember, even for a college educated EE. All
    grounds are not alike. Be *very* careful not to create a ground loop.
    Follow these simple rules:

    + All grounds should come together at one and only one point
    (usually the back of a pot case).

    + Don't use the shield as ground, rather, use it to conduct
    noise to ground. The sheet resistance of the paint is at least
    a few ohms - not a good ground conductor, but low enough to
    conduct the noise to ground. Do you see the difference?

    + Thusly, there will *never* be two paths to ground.

    OK - all fine and well. After reassembly, you will see significant
    improvement. Works great for me. Fact is, single coils always pickup
    more noise than humbuckers.

    G'luck,

    T
    ---------------------------------------------------------------------------
    Related questions and comments
    ---------------------------------------------------------------------------

    --------------------------------
    It doesn't matter
    --------------------------------

    | Also, it seems that shielding the pickup cavity may have pretty irrelevant
    | results because the pickups sit so far out of the guitar (at least
    | according to Foley's book) -- any opinions on this?

    I disagree. I have Foley's book. Foley is correct that the part of
    the pickup sticking out of the guitar is not shielded and will not be
    helped. But part of it is below you pickguard - the back of which
    will be shielded - and will be helped. Also E and B fields might get
    sufficiently weakened by the shielded *plane* of the pickguard in
    which the pickup sits. (and I can't recall my physics well enough to
    give details - heck, I can't remember what to do with my thumbs when I
    am playing guitar, nevermind describing the direction of E/M
    fields...). There is no question that the pickup's orientation with
    respect to the electric and magnetic fields affects the amount of
    noise picked up. I think Foley's point, of course, is that the pickup
    has an *enormous* amount of wire in it, and any non-shielded part may
    come to dominate overall shielding impact.

    BUT - IMHExperience - especially with single coil Strats - shielding
    makes a real difference. Audible. This is not a "silver wire" sort
    of improvement, if you have been reading that thread. This is not an
    alder vs. ash Strat sort of thing. It is positively real and I bet it
    could be quantified with normal lab-bench instruments by first year
    electrical engineering students.

    In fact, FYI - Gibson (at least used to) shield their cavities with a
    thin brass plate. On an old SG I own, with two humbuckers connected
    with manufacture-supplied very high quality shielded cable, the brass
    plate serves only to shield the cavity wiring. Therefore, ergo etc.,
    it must be of some value, else they would have saved their pennies and
    left it out.

    I have paint shielded two Strats and one Gibson SG. I have paint
    shielded two additional loaded pickguards that I swap back and forth
    on one Strat. All with one can of paint and there is more left. 3
    liberal coats each. It matters.

    --------------------------------
    Shielded cable
    --------------------------------

    | is it the wiring, which has been redone several times with new shielded
    | wires and new solder. Amp, cable, etc. have been the same.

    OK - just be *sure* that the shielding in the shielded wire is not
    causing a ground loop somewhere. In nearly all instances, the shield
    of the cable should be connected at *one*and*only*one* end. Otherwise
    it is a ground loop. It may or may not matter. Since that sort of
    answer sucks, my philosophy is to never have one.

    I use shielded cable from the input jack to the first connection in
    the cavity. I hook up the hot and the shield on both ends. This wire
    carries hot and ground from the cable into the guitar. Ground is
    hooked up at both ends.

    The wires to many pickups is made of shielded cable, e.g., the PAFs on
    my old Gibson SG - always hook the shield to the system ground point.

    I do not use shielded wire on point to point internal connections for
    several reasons:

    1) I find its size awkward to work with in tight cavities and on
    complex wirings.
    2) I find the extra ground connections for each shield to make
    for very sloppy wiring jobs prone to human errors. I am human.
    Intermittent wiring errors cause me to lose my temper and that
    takes all the fun out of playing guitar.
    3) I shield the cavity of my guitar with shielding paint, and as such,
    do not require additional shielding on each and every wire.

    That's it. The rest of my internal wiring is done with regular,
    appropriate small gauge wire. I have done the Dan Armstrong scheme
    twice and that is the most intricate and complex (and most cool)
    wire-intensive wiring design I know. In both instances, I also added
    push-pull phase switches, too. I depend on shielding paint to shield
    the wires inside of the cavity from external noise. I have had no
    problems with this approach. I avoid shielded cable except where I
    can not shield cavities. It is too hard to use in small spaces and
    short lengths.

    --------------------------------
    Pickup Covers
    --------------------------------

    Some netters have gone to the trouble of shielding the inside of
    pickup covers and feel that it helps alot. A reasonable thing to do,
    after all, consider the metal cover on the Gibson PAF humbuckers. I
    use a (really) old (really) noisy Dimarzio Super Distortion Single
    coil in the bridge position of a strat. The plastic pickup cover
    slides on and off very simply. I painted the inside of the cover, and
    made sure that this cover shield got connected to the rest of the
    cavity shield. I found no audible difference with this improvement
    and A/B tests were pretty easy to conduct. So, my experience
    shielding covers, with *this* pickup on *this* guitar differs from
    other netters. Consider that I had already fully shielded the cavity
    when I did this test. Perhaps I already removed *most* of the noise,
    and the incremental improvement was too small to audibly discern.
    Perhaps others shielded the pickup covers prior to shielding the
    cavity, and so achieved large improvements since there was so much
    room for improvement (this is what I suspect leads to the difference
    in perception). Perhaps my environment is too quiet to really stress
    the extra cover shielding. Perhaps my cover shield connection to the
    cavity shield is inadequate. Yet again, YMMV.

    Finally, some netters feel that a using a shielded pickup cover vs.
    unshielded pickup cover makes the pickup sound different. Probably
    does. Again, we can get in E and B field issues and I currently lack
    the inclination to get out my physics books to refresh my
    understanding. I personally can not tell a difference with my limited
    experience. But let's face it, some people remove those metal PAF
    covers so I assume they have an _actual_ reason. I mean a reason
    besides "Joe Smoke of my fave band Thunderous Lightning removed his
    PAF covers just before he was electrocuted due to a faulty string
    ground caused by a roadie who got bad shielding information from some
    pinhead on the Internet and this is my tribute to him", or "a Guitar
    Player article told me to and I do everything they say".

    --------------------------------
    Aluminum Foil
    --------------------------------

    | to have to do it myself. What I want to know is, could I do it with
    | the aluminium foil kicking about the kitchen, plus some glue? I intend
    | to do the pickup cavs, the trem cav, and the control cav over again,
    | plus the insides of the pickup surrounds for that wee bit extra!
    | What do you think??

    I have attempted this before. In principle, you can, in practice, you may
    have troubles because:

    1) the foil is too flimsy, it rips and tears too easy, even doubled up,
    2) it is hard to reliably attach it to the guitar (I tried thumbtacks),
    3) you certainly can not solder to it.
    4) I could not to a neat job. And messy jobs end up with shorts and other
    problems that must be avoided.

    But, your milage may vary.

    --------------------------------
    Misc
    --------------------------------

    | From what I understand, I just stick in the tape and solder it all
    | together? Seems like the solder connections could be iffy. After that I
    | would then solder a wire from one of the tape segments to ground? I have

    Yup - to one and only one point. A common ground lug - much like the
    ones on the back of the one of the pots in most implementations. In
    fact, simply connecting the shield to that point will do the trick.

    | While paint is more expensive, if it makes life simpler I may go with the
    | copper shielding paint. Any opinions on that?

    It is nickel actually, methinks. Hard to say. Probably not copper
    though. I have no complaints with the paint, I have never used
    tape/foil. People who have claim it is no problem.

    G'luck,


    =============================================================

    Digest of pickup cavity shielding articles

    Newsgroups: rec.music.makers.guitar
    From: joebac@cup.hp.com (Joe Bac)
    Subject: Shielded Strat = less humm
    Date: Mon, 28 Nov 1994 19:41:10 GMT
    Organization: Hewlett-Packard

    Hey folks - over the thanksgiving holiday I decided to take the time to shield
    my main gigging strat. For the most part, I can deal with the humm/buzz when
    I'm not in any high gain mode, but there's those times when the next tune in
    a set requires a high gain right from the start. And there's that annoying
    buzz that drives everyone nuts before you get the tune counted off. Well
    doing lots of shielding helps tremondously. Here's what I did...

    First I painted all the pickup and electronics cavities with shielding paint.
    I put two thick coats on. Then I got some rolls of that copper shielding
    tape. For each pickup - I first wrapped black electrical tape around the
    bobbin. Then a strip of copper tape over it. Make sure it does not touch
    the hot lead wire from the pickup. Then take a loose leaf paper hole puncher
    to a strip of copper tape that is traced to the top of a pickup. Then punch
    out holes for the magnets. Place it over the top of the pickup and make
    contact with the copper tape that surrounds the sides. Also place a strip of
    copper tape on the back side of the pickup (no holes needed on the back side).
    Then make small solder connections among the three pieces of tape. You can
    connect to the black wire terminal of the back side of the pickup for
    grounding. Repeat this for the other two pickups. Now if the back side of the
    pickguard is not covered with shielding foil, then take strips of the copper
    tape, in rows, to the back of the pickguard. You should, but don't have to,
    connect each strip with a little dab of solder. Reinstall all your electronics
    to the pickguard. If you did everything right, there should be a common
    ground to the whole pickguard assembly.

    Now, if there is no ground lug in the guitars cavity (which is now painted),
    pick a spot and make one. A ground wire should run from the whammy bar
    spring retainer to this ground lug. The guitar jack ground wire goes to
    the lug. Of course this lug is screwed in the painted cavity area. Then
    a ground wire runs from the lug to your favorite ground spot on the pickguard
    assembly (this is usually the casing of the neck pickup's tone control.

    For extra effort - you can replace the hot wires of the pickups with shielded
    wires. Also do this with the hot wire from the jack to the volume pot.

    If all goes well, there will be far less buzz when the strat is being used
    in a high gain situation.

    One final note - TAKE YOUR TIME, BE PATIENT. AND MAKE SURE NO SHIELDING
    MATERIALS TOUCH THE HOT SIDE OF ANY OF THE PICKUPS. Test this with an ohm
    meter before you plug in.

    It works - good luck!

    --
    Joseph G. Bac Phone: 415 691-5417 Fax: 415 691-5030
    Hewlett-Packard Co. ARPA: joebac@cup.HP.COM
    100 Mayfield Ave. MS 36LF UUCP: hplabs!hpiatmh!joebac
    Mountain View, CA 94043
    ---------------------------------------------------------------------------
    Date: Tue, 29 Nov 1994 13:49:48 GMT
    To: tjs@eecs.umich.edu
    Subject: Re: screening. latest..
    From: Chris Herron <ncah@dcs.ed.ac.uk>

    I spoke to Kent Armstrong today, he designs pickups here in Britain,
    plus is the distributor for WD. products + parts. He supplies
    self-adhesive copper foil in sheets of 8ins by 12ins. (by the way, he
    also does aluminium solder - he suggested I use it with Alu. foil and
    a pritt stick, but recommended the copper stuff). I think you might be
    able to get copper foil from WD in the states, and it could be quicker
    than painting on conductive paint, plus it solders ok.
    ---------------------------------------------------------------------------
    Newsgroups: rec.music.makers.guitar
    From: joebac@cup.hp.com (Joe Bac)
    Subject: Re: Shielded Strat = less humm
    Date: Fri, 2 Dec 1994 19:23:01 GMT

    Hey folks - After reading some of the follow-up posts about overkill etc.,
    in how I described the shielding - let me explain why I did what I did.
    I've gotten sick and tired of the noise problem on stage. So I asked the
    guitar tech who I go to about what to do. The guy I go to was/is the
    tech for the Doobie Bros and was on the road with them during all those
    glory days. Now I was only thinking of painting the cavities - when I
    mentioned this to Mark, he got this crazed look in his eyes and said, "Joe,
    you what to shield the **** out of it". Then he proceded to pull out the
    materials and told me what to do - so that's what I did and it works. Some
    people believe that shielding the pickups will effect the tone. As far as
    I can tell, my tone is the same. So I guess what I'm saying is I'm glad
    to have a guy like Mark around and I'm glad I took his advice.

    --
    Joseph G. Bac Phone: 415 691-5417 Fax: 415 691-5030
    Hewlett-Packard Co. ARPA: joebac@cup.HP.COM
    100 Mayfield Ave. MS 36LF UUCP: hplabs!hpiatmh!joebac
    Mountain View, CA 94043
    ---------------------------------------------------------------------------
    From: nyeda@cnsvax.uwec.edu
    Newsgroups: rec.music.makers.guitar
    Subject: Re: Damn Traffic Light!
    Date: 17 Jan 95 22:30:44 -0600
    Organization: University of Wisconsin Eau Claire

    joebac@cup.hp.com (Joe Bac) writes:
    >My rig has to get placed right in a window. So now it dawns on me to
    >look where the traffic signal box is located and the sucker is right
    >outside where my amp sits [...] I'm thinking of making some sort of
    >shield that I can place behind my amp in the window.

    A big piece of window screen or hardware cloth should work. It will
    work best grounded to something like a pipe with a length of wire but
    this may not be necessary.

    David A. Nye MD (nyeda@uwec.edu) * Midelfort Clinic, Eau Claire, WI
    For all but the elite, work holds less promise, less purpose, less
    security and less dignity than a generation ago -- Peter T. Kilborn

    From: bj059@freenet.carleton.ca (David O'Heare)
    Newsgroups: rec.music.makers.builders
    Subject: Re: Shielding Strat - Suggestions?
    Date: Fri, 10 Mar 1995 11:20:15 -0500

    A while ago, mitchell@panix.com (Paul Mitchell) wrote:

    > I have a '57 reissue Strat which is a fine instrument, except for the
    > inevitable hum. Stew-Mac has a kit, and also sells rolls of copper tape.
    > Sounds like the copper tape would do me; I'm good at soldering.

    Paul:

    I've shielded a bunch of instruments. It isn't tough. It can be
    time-consuming, and finicky, but it isn't hard.

    I've used 4" wide adhesive-backed copper tape (available at stained-glass
    supply stores) and 8" wide light copper foil (bought at a Tandy Leather
    store, intended for embossing). Both work fine. Line the appropriate
    cavities with the stuff, and leave 1/2" or so lip on the top of the
    guitar. In profile (bad ASCII art):

    _ _
    | |
    |____|


    Solder any edge joints together. Sand or steel-wool the areas where you're
    going to solder; the surface has to be really clean to get a joint to work
    at all. You will need a pretty hefty soldering iron to join pieces, too;
    the stuff works real good as a heatsink. This explains why electronics
    people use 15 watt irons, and stained glass people use 100 watt irons. Be
    careful to not damage the finish, at least in visible places.

    Screw a small eyebolt into the cavity, right through the shielding
    material, someplace where it won't interfere with the controls and
    switches and stuff. Solder it to the shielding stuff. This will be your
    central grounding point.

    Strats *used* to have a light metal plate under the pickguard; I don't
    know if the reissues do or not. If not, construct a sort of suitable plate
    (that light sheet copper works well, light aluminum should be okay) that
    surrounds the pickups and makes contact with the lip on the top of the
    guitar. Be *real* careful if you must solder; you should probably not
    solder the edges while in contact with the pickguard. To be safe, solder a
    wire to the pickguard shield and run it to the eyebolt. Don't solder that
    yet.

    Get some braided shield from your favorite electronic store and cover the
    pickup wires; you'll have to unsolder them from the pots/switch to do
    that. Leave a tail off the end of the shield, and run it to the eyebolt.

    Solder a wire to the back of the pots, and run it to the eyebolt. Cover
    the wires to the output jack with more braided shield. Solder the shield
    to the sleeve contact of the jack, and run a tail from the shield to the
    eyebolt.

    Solder the whole works at the eyebolt together.

    Find the ground wire that runs from the bridge to the control cavity, and
    disconnect it at the control cavity end. Unsolder it, don't cut it, and
    insulate the cut end.

    Put the whole works back together, and try it. If you still have hum, then
    you'll need to reconnect the ground wire from the bridge. If so, use a
    resistor and capacitor in parallel (I don't have the values at hand) from
    the end of the ground wire to the eyebolt.

    Share and enjoy.

    > If you've been through the process, please let me know what would be
    > effective, if anything.
    > --
    > Paul Evans Mitchell <mitchell@panix.com>
    > 212-858-1676 Follow your bliss.
    --
    David O'Heare +1 613 765 3478 (W) +1 613 729 4830 (H)
    bj059@freenet.carleton.ca
    (Don't reply to the address in the header; I won't get the message)
    I speak for nobody but me.

    Newsgroups: rec.music.makers.builders
    From: mwseniff@rs6000.cmp.ilstu.edu (Matt Seniff)
    Subject: Re: Shielding Strat - Suggestions?
    Date: Fri, 10 Mar 1995 17:03:50 GMT
    Organization: Illinois State University

    Paul Mitchell (mitchell@panix.com) wrote:
    : I have a '57 reissue Strat which is a fine instrument, except for the
    : inevitable hum. Stew-Mac has a kit, and also sells rolls of copper tape.
    : Sounds like the copper tape would do me; I'm good at soldering.

    : If you've been through the process, please let me know what would be
    : effective, if anything.
    : --
    I've done it to my guitars and have the following comments:
    #1 the edges of the tape can be very sharp and will slice your fingers up so
    use some sort of tool to press it in place with I used a small screwdriver
    handle and then a wood dowell rod for this.
    #2 Overlap all the joints and then solder them ( the adhesive on the Stew-Mac
    stuff works great so no worries there) also bring the tape up out of the
    control cavity and on to the top surface under the pickguard preferably over
    the screw holes in the body surface that mount the pickguard so that when you
    reinstall the pickguard you have multiple connections making a good low
    impedance connection with the cavity shielding. Becareful when soldering on
    the pickguard as it is easy to distort it with heat. Solder all joints (You
    could tack it at several points on the pickguard to minimize overheating the
    plastic) down their whole length in the control cavity. Make a good central
    ground point and tie all grounds to this point (i.e. string grounds etc.).
    Finally I treated the copper foil around where the pickguard screws go with
    Caig Cramolin R-5 and P-5. Finally check from one end of the foil to the ohm
    meter your reading should be close to those of shorting the leads together way
    less than 1 ohm with most meters. Good luck! matt



    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~




    ---------------------------------------------------------------------------------------------


    Covers and capacitance




    Guitar pickup covers are an example of a small aspect that can make an appreciable difference. The metal covers on Gibson, Fender, DeArmond, Gretsch and other pickups have more than a visual effect. Metal covers, including Telecaster bridge covers, are used as shielding against RF (radio frequency) interference, making the guitar quieter. A byproduct of having grounded conductive metal or shielding paint near a pickup’s coil is a high-end attenuation (cut) caused by a capacitance effect. This is the same effect that will make your guitar set-up sound warmer—or duller, depending on your perception—when you use a longer cable between the guitar and the amp. A five-foot cable will give a slightly brighter sound than a twenty footer.

    Pickup covers are typically made from nonferrous (iron-free) metals such as brass or nickel-silver, and are usually plated with nickel, chrome, gold, or black chrome finish. If a cover were to contain iron, it would alter the pickup’s magnetic field, thus changing the pickup’s tone and response significantly. A prime example is the copper-plated steel plate used under original ’50s Tele bridge pickups to focus the magnetic field up toward the strings. This helped give those old pickups their bite and presence.

    Just for fun, take a piece of steel, about 1/2" x 2-1/2" x .060", and put it underneath your favorite single-coil pickup, as shown in the photo at left. The magnets will hold it in place. The pickup will have a new sizzle that may give you the “edge” you’re looking for. This can also be useful for getting more of a Tele sound from a Strat bridge pickup. If you like it, you'll have to glue the steel in place with silicone or a glue that will isolate vibration. If you don’t, she’ll squeal like a pig!


    Humbuckers without covers may look cool to some players, but they're defenseless against aggressive picks and playing styles that can penetrate the protective tape around the coils. A coil can be broken, leading to some serious repair work. The cover also warms the tone of the humbucker, which may or may not be to your liking. Much of the ’60s and ’70s craze to remove humbucker covers can be traced back to Jeff Beck, who was trying to get a slightly brighter tone from his Les Paul.

    The moral of the story? Guitars are machines in which every component has a role in the overall tone and response. The right combination of stuff will sing! Remember too, that the amplifier is just as important. Use equipment that's suitable for the sound you want. Use the set-ups of your favorite players as guidelines for your own sonic impact. And don’t forget about the little stuff, because even a simple pickup cover can affect your tone.




    -------------------------------------------------------------------------------------------------------------





    Potting




    Potting a pickup is a technique used to help eliminate unwanted microphonics. Some pickups are not potted from the factory. While it’s not necessary, potting is generally a good idea. Here are the common pickup potting materials.

    Wax
    Pros: Works for most pickups, it’s non-toxic, easy to deal with, cheap, and you can undo it if something goes wrong. Wax has a traditional appearance, and it works great for humbuckers with metal covers.

    Cons: If the wax is too hot you can warp or melt plastic bobbins. If the wax is way too hot you have a potential fire on your hands! Make sure that the wax never smokes—that’s an indicator that it’s getting too hot. Never try heating your wax on the kitchen stove or in a microwave oven because hot paraffin, and especially paraffin vapors, can ignite. It’s best to wax pot outdoors until you have your methods refined and have eliminated any fire hazards.

    Application: After a pickup has been wound, and the output wires are attached and assembled, suspend the pickup in canning paraffin mixed with 20% beeswax, heated to 145-150° Fahrenheit. After ten or fifteen minutes all of the bubbles should have risen out of the pickup, and all of the voids within the pickup should be filled with a coating of wax.

    Pull the pickup out of the wax and suspend it over the wax pot letting the excess wax drip back into the pot. Then lay the pickup on a paper towel and allow it to cool to touch. Carefully remove any excess with a paper towel before the pickup completely cools to room temperature.

    Stewart-MacDonald’s Hot Glue Pot (#0668) has a thermostat designed to heat hide glue to about 145°. Keep the pot at least 2/3 or 3/4 full. It can operate with less liquid, but the wax may get too hot.





    --------------------------------------------------------------------------------------------------------------





    capacitance





    Well most likley what you want is a .015 or a .022 cap The .015 will cut off less treble.

    Basically what you want to see in the number is that the higher the number, the lower the cutoff frquency is. See, a cap (in a guitar circuit) will take off the higher frequencies starting at a certain point. The tone control adjusts the volume of that range





    "However, there is a much simpler reason that there is such a wide variety in the tonal response of guitars of similar construction -- different capacitance values in the tone controls. Consider, at twenty percent tolerance, one guitar may have a tone capacitor of .024uf while another has a capacitor of .016uf (using ".02uf" capacitors). That's a total variation of 40% and makes a significant difference in the tone."







    A "cap" short for "capacitor", is what separates a volume control pot from a tone control pot. A capacitor bleeds out a certain amount treble to the ground, based on the capacitor's vaule. The higher the vaule, the more treble the cap bleeds out to the ground, resulting in a bassier tone. A capacitor doesn't add bass, it just simply removes a portion of the treble based on the capacitor's vaule. By picking a certain capacitor vaule we can passively increase/decrease the amount of bass/treble our tone pot is able to dial into.


    We measure capacitors in microfards, (mF), (mfd) or (µF), any abbreviation is acceptable.Most manufactors will sell capacitors under the (µF) abbreviation. (0.050mF) - (0.001mF) caps are used mostly on electric guitars tone pots. (0.100mF) - (0.050mF) caps are mostly used on electric basses. The larger the vaule (0.100mF) the more bass your tone pot will be able to dial into. The smaller the vaule (0.001mF) the more treble you will be able to dial into. If you are looking for the brightest possible tone, then you can remove your capacitor all together. It would render the tone pot useless though. Without a capacitor in the way, you would get the "true" tone of the pickups.

    =============================================================












    SG Series




    In 1961, these instruments were originally intended to bring a new style to the Les Paul line, but without Les Paul's
    approval they were renamed the SG, in 1963. The first two years of instruments in this series have Les Paul logos on
    their pegheads or the area below the fingerboard.


    SG STANDARD - double sharp cutaway mahogany body, layered black pickguard, one piece mahogany neck, 22 fret
    bound rosewood fingerboard with pearl trapezoid inlay, tune-o-matic bridge/side-pull vibrato,blackface peghead with
    pearl logo inlay, 3 per side tuners, nickel hardware, 2 covered humbucker pickups, 2 volume/2 tone controls, 3 position
    switch. Available in Cherry finish. Mfd. 1963 to 1971.

    SG Deluxe - double cutaway mahogany body, raised layered black pickguard, mahogany neck, 22 fret bound rosewood fingerboard with pearl block inlay, tune-o-matic bridge/Bigsby-style vibrato tailpiece, blackface

    peghead with pearl crown/logo inlay, 3 per side tuners, chrome hardware, 2 covered humbucker pickups, 2 volume/2 tone controls
    mounted on layered black plate, 3 position switch. Available in Cherry, Natural and Walnut finishes. Mfd. 1971 to
    1974.

    SG STANDARD REISSUE I - similar to SG Standard, except has pearl block fingerboard inlay, stop tailpiece, pearl crown peghead inlay, chrome hardware. Available in Cherry finish. Mfd. 1972 to 1981.

    SG Standard Reissue II - same as SG Standard Reissue I. Available in Cherry and Sunburst finishes. Mfd. 1983 to
    1987.

    SG Standard Reissue III - similar to SG Standard Reissue I, except has trapezoid fingerboard inlay. Available in
    Ebony and Wine Red finishes. Mfd. 1989 to 1990.

    SG STANDARD (SGS-) - double cutaway mahogany body, mahogany neck, 22 fret bound rosewood fingerboard with pearl trapezoid inlay, tune-o-matic bridge/stop tailpiece, blackface peghead with pearl crown/logo inlay, 3 per side
    tuners with plastic buttons, chrome hardware, layered black pickguard, 2 covered humbucker pickups, 2 volume/2 tone
    controls, 3 position switch. Available in Candy Apple Blue (disc. 1994), Candy Apple Red (disc. 1994), Ebony (EB),
    Heritage Cherry (HC), Natural Burst (new 1999, limited edition), and TV Yellow (disc. 1994)finishes. Current mfr.

    SG Standard With Maestro (SGS-) - similar to SG Standard, except features a Maestro vibrato tailpiece. Available Ebony (EB) finish. Mfr. 1996 to date.

    '61 SG REISSUE (SG61) - double cutaway mahogany body, mahogany neck, 22 fret bound rosewood fingerboard with pearl trapezoid inlay, tune-o-matic bridge/stop tailpiece, blackface peghead with pearl plant/logo inlay, 3 per side
    tuner with pearl buttons, nickel hardware, layered black pickguard, 2 covered humbucker pickups, 2 volume/2 tone
    controls, 3 position switch. Available in Heritage Cherry (HC) finish. Mfd. 1986 to date.

    THE SG (STANDARD) - double cutaway walnut body, walnut neck, 22 fret ebony fingerboard with pearl dot inlay,tune-o-matic bridge/stop tailpiece, blackface peghead with pearl crown/logo inlay, 3 per side tuners, chrome hardware,ഊlayered black pickguard, 2 covered humbucker pickups, 2 volume/2 tone controls,
    3 position switch. Available in Natural satin nitrocellulose finish. Mfd. 1979 to 1981.

    The SG (Deluxe) - similar to The SG (Standard), except has mahogany body/neck. Available in Antique Mahogany,Ebony, Natural and Wine Red finishes. Mfd. 1979 to 1985.

    SG Exclusive - similar to the the SG (Standard), except has mahogany body, black finish, cream binding on neck,cream pickguard, cream pickup covers, gold knobs, quail tap switch, TP-6 stop tailpiece, and truss rod cover that reads
    Exclusive. Mfd. 1979 only.

    SG CLASSIC - double sharp cutaway mahogany body, patterned after the late 1960s SG Special, 2 P-90 pickups, 22 fret bound rosewood fingerboard with pearloid dot inlays, tune-o-matic bridge with ABR tailpiece, available in Ebony
    Stain or Heritage Cherry finish. New 1999.

    SG CUSTOM - double sharp cutaway mahogany body, mahogany neck, 22 fret bound ebony fingerboard with pearl block inlay, tune-o-matic bridge/side-pull vibrato, multi-bound peghead with pearl split diamond inlay, 3 per side
    tuners, gold hardware, white layered pickguard, 3 covered humbucker pickups, 2 volume/2 tone controls, 3 position switch. Available in Black, Cherry, Tobacco Sunburst, Walnut, White and Wine Red finishes. Mfd. 1963 to 1980.

    SG DELUXE (SGD+) - double cutaway mahogany body, slim tapered mahogany neck, 22 fret rosewood fingerboard with pearl dot inlay, tune-o-matic bridge/Bigsby-style Maestro tremolo, blackface peghead with pearl logo inlay, 3 per
    side tuners, chrome hardware, pearloid pickguard, 3 chrome-covered mini-humbucker pickups, volume/tone controls, 6
    way rotary "chickenhead" switch. Available in Blue Ice (BI), Ebony (new 1999), and Hellfire Red (HR) finishes. Mfr.
    1998 to date.

    SG/LES PAUL W/DELUXE MAESTRO (SG61) - features traditional SG style with Maestro deluxe vibrola, two '57
    Classic humbucker pickups, black pickguard, Hertiage Cherry finish. New 1999.

    SG JR. - double cutaway mahogany body, mahogany neck, 22 fret rosewood fingerboard with pearl dot inlay, tune-o-matic bridge/stop tailpiece, 3 per side tuners with plastic buttons, nickel hardware, black pickguard, single coil pickup,
    volume/tone control. Available in Cherry finish. Mfd. 1963 to 1971.

    SG Jr. (Current Mfg.)(SGJ-) - double cutaway mahogany body, current production model with choice of Ebony or
    Wine Red finish. New 1999.

    SG SPECIAL - double cutaway mahogany body, mahogany neck, 22 fret rosewood fingerboard with pearl dot inlay,stop tailpiece, blackface peghead with pearl logo inlay, 3 per side tuners with plastic buttons, nickel hardware, layered
    black pickguard, 2 single coil pickups, 2 volume/2 tone control, 3 position switch. Available in Cherry and Whitefinishes. Mfd. 1963 to 1971.

    SG Special 3/4- similar to SG Special, except has 3/4 size body, 19 fret fingerboard. Available in Cherry Red finish.
    Mfd. 1959 to 1961.

    SG Professional - similar to SG Special, except has a pearl logo, 2 black soap bar P-90 pickups.
    Available in Cherry,Natural and Walnut finishes. Mfd. 1971 to 1974.

    SG Studio - similar to SG Special, except has no pickguard, 2 humbucker pickups, 2 volume/1 tone controls. Availablein Natural finish. Mfd. 1978 only.

    SG SPECIAL (SGSP) - double sharp cutaway mahogany body, maple neck, 22 fret rosewood
    fingerboard with pearldot inlay, tune-o-matic bridge/stop tailpiece, blackface peghead with silkscreened logo inlay, 3 per side tuners, chromehardware, black pickguard, 2 humbucker pickups, volume/tone controls, 3 position switch. Available in Alpine White
    (disc. 1998), Ebony (EB), Ferrari Red (FR), Ebony Stain (new 1999, limited edition), Plum (new 1999, limited edition), Creme (new 1999, limited edition), and TV Yellow (disc. 1994) finishes. Current mfr.

    SG SUPREME (SGSU) - double sharp cutaway mahogany body with AA flame maple top, mahogany
    slim tapered(1959 style) neck with ebony fingerboard featuring split diamond inlays, bound neck and headstock, 2 P-90A black
    pickups, tune-o-matic bridge and stop tailpiece, gold hardware, Fireburst finish. New 1999.

    SG TV - double rounded cutaway mahogany body, mahogany neck, 22 fret rosewood fingerboard with
    pearl dot inlay,tune-o-matic bridge/stop tailpiece, 3 per side tuners with plastic buttons, nickel hardware, black pickguard, single coil pickup, volume/tone control. Available in Limed Mahogany and White finishes. Mfd. 1959 to 1968.

    SG-X LIMITED EDITION (SGX-) - double cutaway mahogany body, mahogany neck, 24 3/4" scale, 24 fret rosewood fingerboard with pearl dot inlay, tune-o-matic bridge/stop tailpiece, blackface peghead with logo, 3 per side
    tuners, chrome hardware, white pickguard, 500T exposed polepiece humbucker pickups, volume/tone
    controls, coil-tap mini-switch. Available in Carribean Blue (SB), Corona Yellow (SY), and Coral (SC) finishes. Mfr. 1998 only.

    SG-X (SGX-) - similar to the SG-X. Available in Ebony (EB) and Dark Wineburst (DW) finishes. Mfr. 1998 to date.

    SG-Z (SGZ-) - double cutaway mahogany body, slim tapered mahogany neck, 24 fret bound rosewood fingerboard with pearl split diamond inlay, tune-o-matic bridge/Z-shaped stop tailpiece with strings through-body, blackface
    peghead with pearl Z/Gibson logo inlay, 3 per side tuners, black chrome hardware, pearloid
    pickguard, 500T singlecoil/490R humbucker exposed polepiece pickups, volume/tone controls, 3 way selector toggle. Available in Platinum
    (PL) and Verdigris (VG) finishes. Limited Mfg. 1998 only.

    SG '90 SINGLE - double sharp cutaway mahogany body, pearloid pickguard, maple neck, 24 fret
    bound ebony fingerboard with pearl split diamond inlay, strings through anchoring, blackface peghead with pearl crown/logo inlay, 3
    per side tuners, black chrome hardware, humbucker pickups, volume/tone control, 3 position switch. Available in
    Alpine White, Heritage Cherry and Metallic Turquoise finishes. Mfd. 1989 to 1990.
    SG '90 Double - similar to SG '90 Single, except has single coil/humbucker pickups. Mfd. 1989 to
    1992.

    SG-100 - double cutaway mahogany body, black pickguard, mahogany neck, 22 fret rosewood fingerboard with dot inlay, tunable stop tailpiece, 3 per side tuners, nickel hardware, single coil pickup, volume/tone control. Available in Cherry and Walnut finishes. Mfd. 1971 to 1972.

    SG-200 - similar to SG-100, except has 2 single coil pickups, slide switch.

    SG-250 - similar to SG-100, except has 2 single coil pickups, 2 slide switches. Available in Cherry Sunburst finish.

    SG I - double cutaway mahogany body, black pickguard, mahogany neck, 22 fret rosewood fingerboard with dot inlay,tunable stop tailpiece, 3 per side tuners, nickel hardware, single coil pickup, volume/tone control.
    Available in Cherry and Walnut finishes. Mfd. 1972 to 1979.

    SG II - similar to SG I, except has 2 single coil pickups, slide switch.

    SG III - similar to SG I, except has 2 single coil pickups, 2 slide switches. Available in Cherry Sunburst finish.




    Gibson Tuners

    The configuration of the Kluson tuners used on Gibson instruments can be used to date an instrument.
    Before 1959, all
    Kluson tuners with plastic buttons had a single ring around the stem end of the button. In 1960, this was changed to a double ring configuration.


    Gibson Peghead Volute

    Another dating feature of Gibsons is the use of a peghead volute found on instruments between 1970 and 1973. Also, in 1965 Gibson switched from 17 degrees to 14 degrees on the tilt of the peghead. Before 1950, peghead thickness varied,
    getting narrower towards the top of the peghead. After 1950, pegheads all became one uniform thickness, from bottom to top.


    In 1970, Gibson replaced the black tinted piece of wood that had been used on the peghead face with a black fiber that
    the logo and other peghead inlay were placed into. With the change in peghead facing came a slightly smaller logo lettering. In 1972, the i dot reappeared on the peghead logo. In 1981, the n is connected at the top of the o. There are a
    few models through the years that do not follow this timeline, ie: reissues and limited editions, but most of the production instruments can be found with the above feature changes.




    =-============================================================




    truss rod adjustment



    The purpose of the truss rod is to counter the pull of the strings and to maintain relief in the neck. Relief is the slight forward bow that allows notes to be played without buzzing. Truss rod adjustment is not hard to do, but must be done carefully. The results of a mistake can be disastrous - broken neck, broken fingerboard, broken truss rod, etc.

    The first thing to do is to make sure that you have the right tool. Most acoustic guitars are adjusted with an allen wrench. Make sure you have one that exactly fits. (They often come with the guitar) The nuts on electric guitars can be much more varied. If this is an adjustment that you will be doing on different guitars.

    The next thing to do is to determine if it needs be tightened or loosened. If you are unsure, see the page on setup. (There is a description there on how to check the neck relief.) A quarter turn is often all that is needed. If you need to tighten the truss rod, loosen the strings first. This will help prevent damage to the threads and allow the adjustment to set into the neck. After tightening it a quarter turn, tune back to pitch and check the relief again. If the nut will not tighten, try loosening it first. If it loosens, but will not tighten beyond where it was originally, it may be at the end of the threads. If this is the case, then the truss rod will need to be repaired or the neck heat-straightened. Never force a nut to tighten. If you hear any cracking or popping sounds, stop! Take your instrument to an experienced repair person and bring your checkbook. If the nut was snug to begin with, you shouldn't have to tighten it over 3/4 turn.

    If the truss rod needs to be loosened, the strings can remain at full tension. This will help the adjustment to set into the neck. Try a quarter turn and then check the relief. Sometimes it helps to gently lift the head of the neck while holding it down in the middle. This should only be done with a few pounds of pressure, too much could damage your guitar. This should bring results quickly. If there is no change, then try another quarter turn. If this does not bring a change, the neck may need to be heat-straightened.

    If a truss rod adjustment does not change the relief in the neck, heat straightening can usually fix it. This involves clamping the neck to a special tool that heats the neck. Besides actually bending the wood, the procedure also allows the glue under the fingerboard to soften and shift slightly. The neck is then allowed to cool while still clamped to the tool. This will cause it to set into a new shape with either more or less relief depending on how the tool was setup. This can cause the truss rod to be more responsive.

    ==============================================================







    Truss Rod Adjustment
    and

    Neck Relief



    Most modern steel string acoustics use an adjustable truss rod to set the neck relief but this is not always the way it was. Gibson developed the adjustable truss rod that became a standard production feature for all their instruments after 1922. Martin first used a non-adjustable steel T-bar for neck reinforcement in 1934. In 1967 they started using a square tube. And in 1985 Martin finally started installing an adjustable truss rod.

    Gauging The Relief

    Checking and adjusting the truss rod for correct neck relief is the next step in a set-up. Neck relief is the amount of bow or bend in the neck that matches the arc of the vibrating strings and allows the strings to vibrate freely without buzzing on the frets. The correct amount of relief depends on how hard your attack is on the strings. To check the relief, first sight the neck by holding the guitar out in front of you (the end of the body should be on the floor or table and the headstock should be pointed at you) supporting the underside of the head stock, and at arm's length, sight the length of the neck. Take note of any condition that may be present in the neck; bow-in, bow-out, straight, high frets, twist or humps. This will tell you a lot about the general health of a guitar as well. Further check the relief by using a capo to hold down the strings at the first fret and then fret each string at the fourteenth fret, and take note of the amount of gap under each string at the seventh fret. This gap is usually between about .010" to .025" if the relief is adjusted correctly.
    The first three conditions; bow-in, bow-out, and straightness may be adjusted by means of the truss rod. Twist to the neck is a non-adjustable characteristic of some guitars, and if it is not severe, will not significantly affect the playability of the guitar. High frets can be reseated.


    You can gain access to the truss rod adjustment either at the headstock under the plastic cover plate, or through the sound hole at the butt end of the neck. The adjustment end of the rod in most modern import guitars is usually a 5mm hex socket head, so you need a 5mm Allen hex wrench to make the adjustment. But beware, not all makers use this size or type. If you do not have the right tool for the job, get the right tool before you begin.

    The initial adjustment can be made with the strings off. This will give you a feel for the truss when the 175 pounds of string tension isn't pulling back at it. The type of wood used in the neck will also have an effect on the way the truss works. For instance if the neck is made from mahogany the initial adjustment, with the strings off, may be to have more of a negative relief (bow out/back bow). If the neck is made from maple the initial adjustment with the strings off may be to have a zero relief (flat or straight).

    After making the initial relief adjustment, string up the instrument with the type and gauge of string you are going to use. Bring the strings up to pitch. Let the instrument sit for an hour or so to let the strings stretch a little and then retune and check the relief. The neck should now have pulled up a little from your initial adjustment. Again, hold down each string at the first fret and the fourteenth fret, and then take note of the amount of gap under each string at the seventh fret. Is the gap between about .010" to .025"? If not, the next adjustment will be at this point.

    If the neck pulled up more than anticipated, the gap is too great, and you will have to tighten the truss a little more. This second adjustment is made with the strings on but with the tension backed off. Depending on how much of a gap is still present will determine how much more adjustment is necessary. Perhaps a 1/8th turn or 1/16th turn is all that is needed.

    If the neck relief remained negative or pulled up to a straight condition, you will have to loosen the truss a little. Again, with the strings on, but tension backed off, loosen the truss 1/16th turn at a time and recheck the relief. After the seco
     
  2. ess

    ess Guest

    Guitar Setup




    A setup should include setting the action, checking the intonation (in electric guitars), and checking anything else that may affect the playability of the instrument. Make sure that the tuners are working and not coming lose. Look for anything that might need tightening - strap buttons, knobs, pots, jacks, etc. It only takes a minute to do this, and during a setup, you have the chance to really look closely at these things. Before any adjustments are made to the action, remove the strings, clean the fingerboard, check the tuners, (no better time to do this) and put on a set of new strings. While you can make the adjustments with old strings, the measurements may change when the strings are replaced, so start with new strings that are of the brand, type, and gauge that the player likes.

    After the strings are replaced, the check the action. The height of the strings above the frets is what we are talking about here. There are three points of concern in setting the action. The height of the strings at the nut, the relief in the fingerboard, and the height of the strings at the bridge. If one of these is off, it is impossible to set the action with just the other two. Frequently, I find guitars that have what looks like the correct string height in the middle of the fingerboard, but because the nut is too high or the relief is too flat, the instrument buzzes severely. I have found that the order of adjustments makes a difference in the ease and accuracy of the end result.

    The first step is to check the neck relief. This is the slight forward bow in the neck that allows the notes to ring clear in the lower frets. This is done by holding the 6th string down at the first fret and at the fret where the neck joins the body. Look at the height of the string above the 7th fret. There should be a gap of approximately 1/64”. If the gap is larger than this, then you will need to tighten the truss rod. If the gap is too small or non-existent, the truss rod will have to be loosened. One sign of too little relief is buzzing across first seven frets. You should also check the relief on the first string. It should be the same as on the 6th. If there is a significant difference, the neck could be twisted. If this is the case, then take it to someone experienced in this type of repair (Severe cases may require a new neck).

    After the relief is set, then check the height of the strings at the nut. This is done by measuring the height of the 6th string above the first fret. There should also be about 1/64” gap. If you press the string down at the first fret and look at the height at the second fret, that should be about the gap at the first fret with the string open. If it is less than that, the string will buzz. Use nut files (available from Stewart MacDonald’s and others) to cut the slots to the correct height. If you cut too deeply, do not despair. Fill the slot with a small drop of superglue and sprinkle a small bit of baking soda on the glue. Do not breathe the fumes that will come off of this. This will instantly set hard and then can be re-cut. Repeat this process for all of the strings.

    When the nut height is good then set the height of the strings at the bridge. This adjustment will vary for each individual player. If the saddle pieces have individual height adjustments, make sure that the radius of the saddle matches the radius of the fingerboard. Then take measurements at the 5th fret and at the 12th fret. On electric’s I adjust the height of the 6th string to 3/64ths” at the 5th fret and 4/64ths” at the 12th fret. The first string is set 1/64th” lower at both positions. For acoustic guitars, I set the height slightly higher (up to 1/64th”) on both strings (see the page on carving saddles coming soon). At this height you should be able to play without any buzz. Some players prefer a slightly lower action and will accept some buzzing. Other players play very hard or use a slide and prefer a slightly higher action.

    After the action is set, check the rest of the guitar for playability. If you have a guitar with adjustable saddles, check the intonation. Use a good tuner for this. Tune the instrument to pitch. The note at the 12th fret of each string should be exactly one octave higher that the string open If the note at the 12th fret is sharp, then move the saddle away from the neck. If the note at the 12th fret is flat, move the saddle closer.

    One last thing to do is to check for loose strap buttons. These only take a minute to fix and can prevent disaster. If the screw won’t tighten, remove it , insert a tooth pick in the hole and replace the screw.


    --------------------------------------------------------------------------------------------------------------




    Lead Capacitance





    Years ago when I started to take an interest in playing guitar I noticed that my guitar sounded different with certain leads, some were brighter and clearer than others. Even though the same guitar and amp are used at the same settings some leads just gave a better sound.

    One of the main reasons for this is the capacitance of the leads. Without going into great technical details, capacitance is the reaction between the inner (signal carrying,) and the outer (shield,) parts of the cable. If a lead has a high capacitance, signals are able to leak from the inner to the outer parts of the cable and are lost. This particularly affects high frequency signals or high notes and harmonics.

    It is the harmonics that give an instrument its distinctive tone, loose these and your instrument will sound flat and dull.

    The longer the lead the higher the capacitance. Also, a poor quality or poorly connected plug can impair the signal at either end of the lead. This is also true of audio hi-fi cables and interconnects.

    Your guitar pick ups are actually small electric generators, as you pluck a string this vibration sets up a tiny voltage in the pickup which is passed through the volume and tone controls down through your lead and into the amplifier. This voltage really is tiny and believe me when I say that it doesn't take much to loose part of it.

    If you want to get the best sound out of your instrument the lead must be made from cable which exhibits as low capacitance as possible and is correctly terminated.

    Each lead I make is individually constructed using high quality low capacitance cable and quality plugs. Once constructed, additional insulating sleeving is applied to the central signal carrying wire and the plugs are permanently sealed, heat shrinkable cable is then applied to the plug and the lead for a permanent bond.

    All cables come with a lifetime gurantee and certificate giving the measured capacitance of that particular lead. I do not expect any of my leads to fail which is why I am confident enough to give a lifetime guarantee with each purchase.

    When ordering please specify whether you want straight or right angled jack plugs or one of each.

    --------------------------------------------------------------------------------------------------------------




    Rewiring a Humbucker for coil tapping and phase reversal.





    See the Les Paul Humbucker page for photographs of an actual modification.

    The following considers modifying the bridge pickup only; it is possible to apply the same mod to the neck as well, which will increase your options tremendously. However, working inside a Les Paul cavity is not the easiest of options and undertaking both pickups is quite a job. The following will give very pleasing results. A word of caution before you start this job - make sure you can finish it. Modifying pickups is really fiddly and requires top quality soldering, a small slip with cutters or soldering iron can render a lovely very expensive instrument tatty looking. Remember also that the next people who will judge your modifications will be the audience and a guitar, which crackles or suddenly goes silent does leave a lasting impression with people. So, if you are still keen and confident read on.

    You will need two tone pots, which incorporate a switch; the pull types with a double pole changeover switch are ideal because these can directly replace your existing tone pots. Do not be tempted into drilling an expensive guitar, an extra hole can knock your value down by 25%. Before you start or unsolder anything make sure that the guitar cavity is deep enough to take these pots.

    Firstly strip down the bridge pick up and disconnect the coil connection from the pickup chassis, also find the point at which the two coils are joined and solder a fresh lead to it – this is the centre tap. You should now have three connections all going to the coils, one to each end and one to the centre tap. All three connections should be connected via shielded cable and the three outer shields (braiding,) should be soldered directly to the pickup chassis and the cables carefully threaded through the pickup outlet hole. At this point you should have a total of six electrical connections; three wires to the coil connections and three shields all going to the pickup chassis, you are only going to connect the other end of one these shields so insulate the other two. You now have four connections, three to the coils and one to the pickup chassis. This is the pickup modified and the cover may now be replaced and resoldered if necessary. As a precaution you may measure the resistance of the coils with an ohmmeter. The measurement from the centre tap to either of the other connections should be about 3000ohms, the measurement between the two outer coil ends should be about 6000ohms and there should be no measurement between any of the coil connections and the pickup chassis. The values of 3000 & 6000 ohms are approximate and will vary with each pickup but the centre tap should always be half of the total.

    Next step; replace one of the tone controls with a pot, which includes a pull switch. Wire the outer two connections through the switch so that when the switch is pulled it reverses the coil connections. This means that alternatively one is `hot` and the other `ground` - this is now the phase reversal switch.

    Next. Replace the other tone control with a pull switch type control and wire it so that when the switch is pulled up the centre tap of the coils in connected directly to ground. This effectively turns the bridge pickup into a single coil pickup.

    All three connections to the pickup coil will have screened braiding and they all should be soldered to the pickup chassis. However, only one of the braids should be connected to the guitar ground (earth). Connecting all three may cause an effect known as an "Earth loop" so remember to insulate the two that you don't connect. It is usual to use the pot covers as earthing points so remember to solder the earthing connection which was on the old tone control covers to your new ones.

    Apart from the tone control connections the centre tap control should now have two connections to the switch, one to the centre coil tap and one to earth (ground.) Whilst the phase reversal switch should have all six connections used up to fully reverse the coil.

    Now what we have is a bridge pickup, which may be switched in and out of phase with the neck one and may also be converted into a single pickup. When the pickup selector is in centre position (both pickups on) a breathtaking new range of sounds are available by placing them out of phase with the bridge acting as either a Humbucker or single coil. As the two vol. controls are adjusted the amount of phase cancellation can be varied. The`acoustic` sound I refer to is the Humbucker out of phase, which also sounds great through a chorus.

    Gibson vol. pots are more expensive that other makes but they are very well made and stay in the position you turn them to. This is why I use the tone pots as the replacements as these are not critical. Try to get 500k pots as these give better treble response. Vol. pots should be `audio taper` (logarithmic) and tone pots should be `linear`, if you are unable to get linear pots for the tone you can get way with logarithmic but you will not get away with replacing vol. pots with linear ones. Almost all pots with switches are supplied as logarithmic.

    A word of caution, this is a long job there is no way of rushing it (takes me a full day's work,) and you need to make sure your soldering is tiptop. If soldering or engineering is new to you it is wise to spend some time practising on things that don't matter - that doesn't include a Gibson! If you fancy making the modification but don't fancy dismembering your pickup I undertake pickup modification by post for you to refit into your instrument.


    --------------------------------------------------------------------------------------------------------------




    ABOUT GUITARS AND PICKUPS



    The electric guitar is still an acoustic instrument. Four equal componants make up the tone of the instrument, the pickups, the wood, the amp and speakers and the guage and height of the strings. The wood of a guitar can absorb some frequencies and resonate at others. The pickups can only pick up what the string is doing so if you have a guitar that absorbs frequencies between 150 and 450hz, you will have thin sounding treble strings. If your guitar resonates well between those frequencies you will have more solid treble strings. Guitars that are more resonant allow you to use a lower output, brighter pickup and still get the same volume from the instrument. Lower output pickups also give more of that twang on the wound strings. For this reason we sell more stock pickups than over wound models. We also caution our customers not to ask for more power than they actually need - - for every 5% more turns on any pickup, you will get 5% more mid-range but 5% less high-end.




    HOW A PICKUP WORKS



    A magnetic pickup is a coil of wire around a magnet(s). A steel string vibrating close to the magnet pushes and pulls the magnetic field through a stationary coil. This "induces" a signal which will be amplified. What type of magnet structure and coil determines the tonal characteristics. Our pickups are offered in a variety of outputs in as little as 2.5% increments to fit the needs of any guitarist’s taste. More turns on any pickup will give a stronger, thicker but darker sound. Stronger pickups sound better for single string playing (plain strings). Lower output pickups sound better in chords (wound strings). All of our pickups are potted in wax for reduced micro-phonics and better durability.

    On most guitars, we recommend the bridge pickup to be 10-15% stronger than the neck pickup. Our Replacement Strat Style and Replacement Tele Style sets reflect this. In P-90's or Humbuckers, we let the customer suggest ballpark ohm readings. (i.e. Humbucker set 8K neck - 9K Bridge).



    "FINE TUNING"
    There are many ways to tweak a guitar’s tone:



    Lowering pickups into the body may sound better, but will produce less output. Experiment with pickup heights until you find your own "sweet spot." ALNICO rod pickups that are too close to the strings can "pull" the string out of tune, especially on the bass side of neck pickups. Bigger frets, heavier bodies and maple face plates can add to the highs and thin out the midrange, as do heavier nuts (brass) and bridges (locking tremelos). Shielding, on the other hand, reduces highs by raising the capacitance of the circuit. Shielding the coil has more of this effect than shielding the body cavity because it places the shielding closer to the coil itself. Therefore, we do not recommend shielding the coils or the inside of plastic covers because of potential damage and shorting out of the pickup. Volume pots put a small short across the pickup dampening highs so a larger value pot will make a guitar a little brighter and a smaller value pot will make it darker. A resistor can be added across the pickup (hot to ground) to achieve resistances between standard pot values. ( a 330k resistor added to a 250k pot gives a 145k short across the pickup).



    =============================================================




    standby switches



    From postmaster@triodeel.com Sat Oct 2 13:55:38 CDT 1999
    Article: 205949 of alt.guitar.amps
    Path: geraldo.cc.utexas.edu!cs.utexas.edu!arclight.uoregon.edu!logbridge.uoregon.edu!sunqbc.risq.qc.ca!novia!sequencer.newscene.com!not-for-mail
    From: Ned Carlson <postmaster@triodeel.com>
    Newsgroups: alt.guitar.amps
    Subject: Re: Stand-By Switches and Tubes Theory
    Date: 2 Oct 1999 01:08:06 -0500
    Organization: Triode Electronics
    Lines: 75
    Message-ID: <37F5A1AE.AF055396@triodeel.com>
    References: <19991001142854.21067.00000604@ng-co1.aol.com>
    Reply-To: postmaster@triodeel.com
    X-Mailer: Mozilla 4.61 [en] (X11; I; Linux 2.2.10 i586)
    X-Accept-Language: en
    MIME-Version: 1.0
    Content-Type: text/plain; charset=us-ascii
    Content-Transfer-Encoding: 7bit
    Xref: geraldo.cc.utexas.edu alt.guitar.amps:205949

    Kent Pearson wrote:
    >
    > I've heard that it's best for the amp and/or the tubes to allow the tubes to
    > warm up for a minute or two on stand-by before switching to play mode.

    This isn't a bad idea...since you've got a standby switch, why not use it.
    But lots of tube amps were made that had no standby at all. AAMOF, I've got
    a couple Bogen MO-100 tube PA amps here, diodes and no standby.
    Since Bogens were typically used in places like hospitals and
    schools, one can figure they were either run 24/7 or
    got hit with a turnon surge every morning.

    Directly heated rectifiers like 5U4 and 5Y3 are not a slow
    warmup device, despite rumors to the contrary.
    A simple voltmeter check will verify this.

    Fortunately for most tube amp owners, nearly all
    tube amps used in audio frequency service (which includes
    guitar amps), either apply a negative voltage to the grid
    of the output tubes at the time the power is applied,
    or have a cathode resistor to limit current.


    Also,
    > I've heard that it's best to put the amp on standby for a minute or two before
    > powering down. My understanding is that this practice will help to get the
    > most life out of your tubes. Can someone elaborate on that a bit? Why is
    > that? To Stand-by, or not to Stand-by . . what goes on? That is the
    > question!

    I would do exactly the opposite, turn off the power then LATER turn off
    the standby, so as to drain off the charge in the power supply
    capacitors.

    I've recieved some lengthy missives from certain folks regarding
    cathode stripping and possible damage from too fast warmup in tube amps.

    >From these I have determined the following:
    1.If you've got a tube regulated radar power supply on your B52-B bomber,
    you'd better use a tube rectifier, as using diode replacements that
    slap B+ voltage on cold 6336B tubes can destroy them.
    List price on 6336B is $141.00, which ain't chopped liver, especially
    if you have to replace them on taxpayer's money. So if you are
    a 3rd world dictator with some used B52-B's that need retubing,
    call us and get some 5R4-WGB tube rectifiers before you send your
    bomber fleet to carpet bomb suspected terrorist sites.
    2.if you've got an Wurlitzer bubble-tube jukebox, it uses
    a fast warmup circuit that jacks the filament voltage to
    over 9 volts when someone hits the selection button.
    So figure replacing 6L6's a bit more often than usual in these
    units...of course, if you've got $10,000 to blow on a jukebox,
    a few bucks replacing 6L6's probably won't bother you much.
    3.Tungsten and thoriated tungsten filaments (not ones you'll
    find in guitar amp) apparently aren't bothered by this at all,
    at least one BE has confessed to slapping thousands of volts
    of B+ on a cold 4CX20,000. This is a tube that lists for
    over $4500. Yep, a single tube that lists for $4500.
    Presumably if he'd screwed up and blown a $4500 tube, he might
    not have a job, but major market FM stations don't think much
    about blowing a million bucks for an AM drivetime DJ.

    Heck, I think a major market outlet could drum up some major
    drive-time cume numbers by hosting a political debate
    between me & Lord Valve. I can see it in the Pioneer Press,
    "Who the hell is Lord Valve?".


    --
    Ned Carlson Triode Electronics "where da tubes are!"
    2225 W Roscoe Chicago, IL, 60618 USA
    ph 773-871-7459 fax 773-871-7938
    12:30 to 8 PM CT, (1830-0200 UTC) 12:30-5 Sat, Closed Wed & Sun
    Magnequest Transformers stocked for Dynaco & Sunn!
    Order online at:
    http://www.triodeel.com/cgi-bin/miva?Merchant/merchant.mv+




    ============================================================


    Alesis.com


    Intro To Compression



    Version 1.00, August, 1996

    Signal Processing

    Introduction

    This tech note offers a basic explanation of compression for beginners. If you've just purchased a compressor and aren't sure how to use it, or are considering the purchase of a compressor, this note will help you understand what compressors are used for.





    What a compressor does


    Most types of signal processors, such as reverbs, equalizers, and delays, are designed to make an obvious change in the sound. But a compressor's action is much more subtle; when used properly, most listeners won't be aware that signal processing is being used. Only if you hear the original dynamic range of a signal and compare it to the compressed version will the effect be noticable. Yet, compressors are essential in modern audio work. Almost every lead vocal on a pop record is compressed during tracking or mixdown. Often the entire stereo mix may be compressed or limited during the mastering process. Finally, when you hear the song on your favorite radio station, it passes through yet another compressor before it's transmitted.


    A compressor/limiter, like the Alesis 3630 or NanoCompressor, is essentially an automatic volume control. Imagine an engineer with his hand on a fader and his eyes on an input level meter. As long as the meter stays below a certain point (the threshold), he leaves the fader all the way up and the gain is unchanged. But the instant the sound gets louder, the engineer pulls down the fader by a certain amount. After the sound gets soft again, the engineer will push the fader back up. That's what the compressor is doing, except much faster and more accurately than humanly possible.


    Paradoxically, by cutting the peak levels, a compressor allows you to raise the average level of a sound using the Output control and make it sound louder. By using the threshold and ratio controls, you can set a stable sound that will hold its position in the mix whether the singer is whispering or screaming.






    What the controls do


    Let's go back to the "engineer with his hand on a fader and eyes on the meter" analogy. The front panel controls simply tell the "engineer" what rules he should follow. [THRESHOLD] tells him how high the input meter can rise before he has to start pulling down the fader: if it's turned full clockwise, he won't pull down his fader until the red +6 LED comes on; if it's turned counter-clockwise, he'll have his hand on the fader even before the lowest green -30 LED lights. [RATIO] tells him how far he should "pull the fader down" when the signal is above the threshold level: should he pull it down just a little bit (compression) or pull the fader as far down as necessary to make sure the output level is never higher than the threshold (limiting)? The [HARD/SOFT] switch affects how he reacts as signal approaches the threshold: does he reduce it exactly by the ratio only after it crosses the threshold, or does he gradually ease into the full ratio as it gets close? The red LEDs of the reduction meter tell you how much the "engineer" is pulling down the "fader" at any time. If these LEDs aren't on, his hands are in his pockets.


    The [ATTACK] and [RELEASE] controls involve the speed of the engineer's response, as does the [PEAK/RMS] switch. Short attack times order the engineer to get his hands on the fader 1/10,000th of a second after he sees a too-loud signal; long attack times tell him to let transients less than 1/5th of a second pass. [RELEASE] tells the engineer how quickly he should push the fader back up again after a loud signal has stopped; when it's turned counter-clockwise, he pushes the fader back up instantly, and when it's full clockwise, he'll take three seconds to push his fader back up to unity gain. If the compressor is in PEAK mode, the engineer responds to the highest voltage peaks, and in RMS mode the engineer responds to the longer-term average signal level (and the [ATTACK] and [RELEASE] controls have no effect). It's as if the engineer is looking at a fast-acting LED meter in peak mode, and a slow old-style mechanical VU meter in RMS mode.


    The [OUTPUT] control is simply a gain control located after our "automatic engineer in the box". The [INPUT/OUTPUT] switch allows you to see the levels before the engineer does his job, or after.


    The most important controls are the [THRESHOLD] and [RATIO] knobs. They both interact to get the effect you want, and that requires some experimenting. For example, if your average input signal is 0 dB, a ratio of 2:1 with a threshold of -12 dB will give you 6 dB of gain reduction, as will a ratio of infinity with a threshold of -6 dB. But the latter setting will sound more "squeezed" than the former.


    Avoid common compressor mistakes

    Extreme settings will lead to extreme results. If you set an infinite ratio and turn the threshold down to -40 dB, the compressor will do what it's being told to do: turn the level way down. If you then try to compensate by cranking the [OUTPUT] control to its maximum, you'll amplify the noise of your mixer, EQ, mic preamp, and the compressor itself. The noise will fade itself in whenever the input signal stops, resulting in the classic "pumping" and "breathing" problems. Noise is present in every system, and improper use of any compressor will amplify it to an obnoxious level.


    If the ratio is set to 1:1, it doesn't matter where the [THRESHOLD] control is: the NanoCompressor is being told not to change the gain at all, even if it's above the threshold level. None of the REDUCTION LEDs will light, and you may as well have the NanoCompressor in BYPASS mode. Similarly, if the ratio is infinite and the threshold is high, or the input trim of the mixer or microphone preamp is too low, you will get no compression (and, if you raise the [OUTPUT] level control, you'll be amplifying the noise floor). For low noise operation, make sure your mixer, compressor, and amplifier settings are set properly. As a general rule, you want as much gain as possible in the front of the system (at the microphone preamp), so that a good line-level signal is travelling through the whole signal path. If you have a weak signal to start with, and then amplify it at the end of the signal path (by turning the main outputs of the mixer all the way up, for example) it will be excessively noisy.


    When using a compressor on a live P.A. system, improper settings can cause feedback. Make sure that a channel is well below the feedback point when there is no gain reduction active. If you hear feedback every time the music stops, you must lower the overall level of the system.


    About stereo compression

    The Alesis Nanocompressor is, in fact, two separate compressor channels joined by one set of controls. The detectors of the two channels are linked. This means that if the left channel's signal rises above the threshold, the right channel's gain will be reduced by the same amount as the left channel, and vice versa. This keeps the stereo image from wandering from left to right when compressing a stereo mix.


    The Alesis 3630 compressor allows you to to decouple the left and right channels into two mono compressors so you can plug one instrument into the left, and another into the right without them interacting.


    ==============================================================




    Caring For An Ebony Fingerboard




    Ebony is often the fingerboard material preferred on better quality instruments. An ebony fingerboard has several advantages over other materials: It is often chosen for its resistance to wear; it presents inlays well; and the hardness of the wood contributes to the tone produced by the instrument.
    Ebony also has several disadvantages when compared to a more resilient material like rosewood. Not only is ebony more brittle, but it is also less stable and therefore it tends to both shrink and crack more than other fingerboard materials. This shrinking is the cause of protruding fret ends and, as is often the case, dislodged frets or cracks.
    Coupled with the proper humidification of your instrument in the cold, dry months, routine care of an ebony fingerboard is your best guard against these problems. Our procedure for fingerboard care also serves to clean the fret board and frets.
    After removing the strings, wipe a liberal amount of lemon oil on the fingerboard and let it sit for a couple of minutes. The lemon oil will loosen any dirt or grime on the fret board. Next take a 3" X 4" piece of 3M gray scratchy pad and fold it in half. The green pads are too coarse and the white pads are a bit fine for this job. Vigorously rub the fingerboard and frets perpendicular to the length of the fret board (parallel to the frets).
    We now apply a moderate amount of Gibson fret board conditioner to the fingerboard. Most light machine oils will work well for this purpose too. Reapply a second coat of oil if it soaks into the ebony immediately. If there is still a bit on the surface after a minute or so, we are ready to finish up. With a rag folded into a ball, vigorously rub parallel to the length of the fret board in order to remove the excess oil and polish the ebony to a luster.
    If your fingerboard always seems to be dry, you may want to apply a bit of conditioner once a month or so, even if you decide to skip the cleaning portion of the process.





    ==============================================================




    What is impedance? And why does it do those terrible things?




    Beginners with electronics get down Ohm's law pretty quickly. The concept that Voltage, Current, and Resistance to electrical flow are related by the simple expression V=IR seems to set pretty easily. They usually learn about capacitors and inductors as "something else", not like resistors at all, but as perhaps a way to store energy or filter some frequencies from others. But sooner or later, they run up against the need to understand the effect of source impedance and/or load impedance, and things get un-simple quickly. Impedance seems to become a vague concept of something like electrical strength or drive capability, not simple at all, especially if the impedance in question involves capacitors or inductors, or (ugh!) both.

    It's not that complicated.

    Impedance is the generalization of the concept of resistance from DC to AC. That is, it's a way to represent how much current will flow with a specified (AC) voltage across the impedance. That is, if you have one volt AC across an impedance that lets one ampere of AC current flow, the impedance is defined by the AC version of Ohm's law and is one ohm.

    Since AC has not only amplitude, like DC, but also frequency and phase, this introduces the possibility that an impedance will not only allow a current to flow, but will change the phase of the signal, and respond with different amplitudes and phases as frequency changes. You can have a resistor, a capacitor, and an inductor that each have an impedance of one ohm (or a Kohm or a Mohm) at any given frequency.

    The resistor (ignoring the "imperfections" of parasitic capacitance, lead inductance, etc., which is usually valid at audio frequencies) will have the same impedance at every frequency. The capacitor will have an impedance that goes down with frequency (making the same assumptions as with the resistor, ignoring parasitics) and the inductor will have an impedance that goes up with frequency (ditto).

    We can calculate the impedance of any of these, given a frequency to work with.

    The cap is Xc = 1/(2*pi*F*C) and the inductor is Xl= 2*pi*F*L, so they vary linearly with frequency. As to phase, the inductor's voltage is always 90 degrees ahead of its current (the current takes some time to change); the capacitor's current leads the voltage across the cap, as the capacitance slows down voltage changes. If you can remember "E" for voltage, I for current, you can keep this straight by the phrase "ELI the ICEman", which is a nonsense way to remember "E leads I in inductors (L's)" and "I leads E in Capacitors (C's).

    In AC power line circuitry, where the "signal" on the line is always a fixed frequency, fixed amplitude sine wave, inductors and capacitors make perfectly good current limiters, better than a resistor would be because they cause no heat to be dissipated as a result of their current limiting. In fact, the impedance of inductors and capacitors is so different from a resistance that it's given a special name - "reactance". In engineering schools, impedance is expressed as a "complex" number represented by "Z". This Z is the sum of a resistance and some reactance, Z = R+jX. You won't need to know this, but I thought I'd mention it in case you had run across it and wondered.

    Ok, so how do we do some quick calculations of impedance?

    There are ways to do it that are analytically correct, but very confusing. There are more intuitive ways to find some approximations; we can ignore some things and simplify. I'm going to skip the correct-but-tedious stuff entirely.

    Any series element that has a very small impedance compared to the other things in series with it can be replaced with a wire for the purposes of calculations. Any parallel impedance that is very large can be replaced by an open circuit; these simplifications produce only tiny errors. When we come to things with similar (less than 10:1 differences) values in series we add them, and in parallel, we compute the parallel values.

    Using these approximations, we can usually get a pretty good idea of the source impedance (how much impedance is inherent inside a signal source) and the input or loading impedance (how much current it takes to drive a signal into it)

    Example: The input to an NPN transistor amplifier, with a pull down resistor of 1M to ground at the input, a capacitor of 0.1uF in series to the base, which also has a resistor of 220K to the positive supply and a resistor of 22K to ground, and a 1K emitter resistor from the transistor emitter to ground.

    Unstated but assumed is that the supply voltage is that, a pure voltage source with an impedance that is vanishingly small. We approximate that with a battery, which may have an internal resistance of only a few ohms. Since this is by far the smallest impedance here, we replace it with a short, our first approximation. So now we have the 220K and the 22K in parallel to ground from the base.

    Let's see about that input cap. The impedance can be as high as 1/2*pi*82Hz*1E-7 = 19.4K at the low end of the guitar range, and as low as 79.5 ohms at 20KHz. The 1M is much higher than the cap at all frequencies of interest, so we replace it with an open circuit and ignore it.

    So now we have a series cap going to the parallel combination of a 220K, a 22K, and a transistor base. Ack!! How do we compute that?

    It turns out that it's not that hard. If the transistor has a modest gain, say 100, the impedance seen at its base is the series combination of the current gain times any emitter resistance *including the internal base-emitter resistance*. Since we know (here's about seven pages of stuff I won't type) that the internal base emitter resistance is usually low, we'll assume it's zero and just use the 1K; that gives us an impedance as seen at the transistor base of 100*1K, or 100K, effectively in parallel with the 220K and the 22K. The actual value is somewhat higher, but is dominated by the emitter resistor. (Note - the transistor's internal base-emitter resistance can be computed simply, too - it's Rbe=25mv/Ie).

    So we do the calculation for parallel resistors, and get an equivalent resistance of close to 16.7K. That's NOT negligible compared to the capacitor, so we have to figure out what happens with frequency. However, now we have a simple way to calculate the impedance variation with frequency - the impedance will always be the sum of the capacitor's impedance and the equivalent resistance.

    We know that at high frequencies, the capacitor will eventually be much less than the 16.7K, so we'll be able to ignore the cap there. We know at lower frequencies the cap will dominate as its impedance gets much higher. We need to calculate the "turnover point" where the cap and the resistor have equal impedances; this will be where the input impedance stops looking like a capacitor and starts looking more like a resistor. That frequency is the one where the cap's impedance is 16.7K, or Xc=16.7K=1/(2*pi*F*C), or F = 1/(2*pi*R*C) = 95Hz.

    So while we can calculate the sum of the R and the Xc, we know that above 95 Hz, the input looks more and more like a 16.7K resistor as the capacitor Xc decreases.

    We made a lot of assumptions getting there, and we know that the numbers are not exactly correct, but they are very close, probably closer than our ability to get a transistor with Hfe=100. With a 16K +/- a few K load at the input to this amplifier, we know it's gonna suck treble out of guitar pickups because of the loading.

    The quick and dirty way of measuring input impedance with a variable resistor to halve the input voltage works, and gives a correct number at every frequency, but it gives you no insight into what is happening with frequency until you do enough points to find the turnover frequency.

    Output impedance can be calculated the same way, except that there is nearly always an active source like a transistor emitter or collector, a transformer secondary, etc. that has R's, C's and L's in series/parallel with it. In that case you figure the source impedance of the device that provides the energy, and then do the approximations and calculations toward the output node.

    This is only a very brief intro. In most cases, the real trick is to make the input and output impedances not matter: that is, you make input impedances large compared to the output impedances of whatever the signal source is, and make output impedances tiny compared to the load it's driving. A guitar pickup may have an impedance between 8K and 100K; in general, we want an input impedance of 1M or more to keep from loading a guitar down. An amplifer is loaded by 16, 8, 4 or 2 ohms; we want the amplifer to be much less than the load, maybe under 0.2 or less ohms.

    This is usually not possible with power outputs on tube amplifiers, but the calculation of the proper impedances and matching in vacuum tube amplifier power stages is a subject that deserves its own explanation.




    =============================================================





    Electricity



    Electricity is formed from the motions of electrons. These are the tiny (even by atomic standards!) carriers of electric charge. Because protons, the carrier of the positive electrical charge, are thousands of times more massive and bound in the nucleus of atoms, only electrons carry electrical charge in the more normal sorts of electricity we all encounter. The charge on one electron is incredibly tiny, so it takes enormous numbers of electrons moving to have electrical effects that we see in our everyday lives. An ampere of current is the movement of about 6.25x1018 electrons per second. A milliamp, which is a more normal size quantity for guitar effects, is one thousandth of that, or 6.25 x 1015 electrons per second. This is important to us because if we get down to few numbers of electrons, things get "grainy" as the effect of the random distribution of a few electrons may not have a smooth variation. Some vacuum tube circuits have this problem, a form of quantization noise.

    In the illustration at right, we see an illustration of the various kinds of atoms. At the left, the outer electrons are tightly bound to the atom. This is a characteristic of an insulator. On the right hand side, there are lots of free electrons that can move around within and among the atoms. This is a characteristic of a conductor. Usually the element displaying this are metals, and all the best conductors are metals. In the middle are materials which have some free electrons. These have various degrees of resistance to electrical flow.

    We have special devices to make electrons flow. The most common is a battery. A battery is two metallic plates (conductors for good transfer of electrons) separated by some chemical gook. If we assume that the shaded areas marked with "+"'s and "-"'s are the metallic terminals of the battery, the atoms inside the battery between the two plates undergo a chemical reaction that forces electrons to one terminal of the battery and removes them from the other side.

    We can think of a battery as an electron pump. The terminal with the excess of electrons is the (-) terminal and the one with a deficiency of electrons is the (+) terminal. Different mixes of chemicals have different amounts of "electron pressure" that they can exert. We call the "electron pressure" voltage. It's a measure of how hard electrons are being pushed to be somewhere else. Lead/lead sulfate and sulfuric acid batteries exert 2.2 Volts of force. Carbon/zinc/zinc chloride batteries exert 1.5V of force, as do alkaline cells. If we want more voltage/pressure, we stack a batch of cells up in series. A 9V battery is six carbon/zinc or alkaline unit cells in series in side one outer case.

    Notice that the drawing is marked "Battery/Fuel Cell". A fuel cell is just a battery that you can feed more chemicals into continuously and so instead of the chemicals all getting used up and the battery drained, we can just pump in more chemicals and the thing will keep putting out electrons until the fuel supplies run out.

    How many electrons can flow out of a battery or fuel cell at the same time depends on how big the surface area of the two plates is. In general, the more plate area, the more electrons can be pumped out at the same time. Remember, we call the number of electrons per second "current", so the bigger the battery, the more current it can supply. Because the chemicals inside the battery will have some resistance, there is a maximum current it can supply even if its (+) and (-) terminals are directly connected. The limit may be high, but it's there. More about this when we talk about resistors.

    Some special batteries can be recharged by forcing electrons back in the (-) side and pulling them out of the (+) side. This state of affairs requires that the chemical reactions be completely reversible inside the battery. Nickel-cadmium batteries (1.2V/Cell) and lead-acid (2.2V/Cell) batteries do this well. Ni-Cads are the common hand held chargeable batteries, and lead-acid is the basis of car batteries. Some other types of batteries can not be recharged because the chemical reaction inside the battery is not reversible. Carbon-zinc batteries are like this, as are all types of fuel cells.

    We can store electrons in a capacitor temporarily. A capacitor is kind of like a battery in that there are two metal plates separated by some insulator. There can be no electron flow between the plates in the sense of electrons actually moving across the insulator barrier. But if we put the plates very, very close together and pile up electrons on the (-) side and remove them from the (+) side by pumping them with a battery, the electrons piled up on the (-) side pull on the atoms with fewer electrons on the (+) side, setting up an electric field.

    If we then disconnect the battery, the piled-up electrons have nowhere to go. They just sit there because they're insulated on all sides and can't flow. The voltage remains on the capacitor because the electrons have been pulled away from the atoms on the (+) side, and so this electron pressure exists. If we connect a conductive wire from the (+) side to the (-) side, the electrons now have a path, and they run around to the (+) side and neutralize things out; the capacitor discharges just like the battery did, but since it was just pressure piled up across the insulator, it runs out of electrons faster than a battery of similar plate area does. The battery has all these electrons stored in the chemicals, the capacitor has them stored by separation.

    If you think about it, the energy is actually stored in the electric field, the pull the electrons have for the atoms in the opposite plate that have had electrons stripped off - kind of like stretching a spring.

    Another interesting aspect of electricity you may have noticed. Electrons can be "caged up" by insulators. There needs to be a way for electrons to flow in a complete circle (hey! circuits!) for the common forms of electricity to work. A battery needs to be able to pump electrons from its negative to its positive terminal through wires, resistors, etc. If there is no conductive path around the battery, no electrons flow, at least not for long. Remember that we hooked a battery to a capacitor? Current flowed until there were enough electrons on the negative plate of the capacitor and enough electrons missing from the positive plate so that the voltage of the electrons there/missing equaled the battery's pumping voltage, then the flow quit. What happens if we then quickly reverse the battery that charged the capacitor? All of a sudden, the positive (electron hungry!) terminal of the battery is connected to a rich source of electrons and the negative (electron full) side is connected to the electron hungry plate of the capacitor. Bango! The battery sucks in electrons from the negative capacitor plate, pumps electrons into the positive plate, then further pumps the capacitor with electrons in the reverse direction to what it used to be.

    If we keep reversing the battery quickly, we can make current flow rapidly back and forth. Instead of direct current (DC) we have alternating current (AC). So capacitors can conduct AC but not DC (at least not DC for very long).

    But first - we gotta talk about resistors. A resistor is a material that is neither a good conductor nor an insulator for electron flow. What happens in a resistor is that there are some free electrons so they can still flow through, but the atoms and electrons are arranged in a way that electrons flowing through literally bump into the atoms already there. They may bounce off, or get captured permanently, or may stay a while and then move on to hit another atom. Each time an electron hits an atom, it imparts some energy to the atom, and the atom vibrates a little harder. We call electron vibration in solids heat - the electrons are actually making the material hotter by whacking into the atoms as they go through. As a result, we have to pump the electrons to force them through, and the pumping energy gets eaten up by the collisions and make the material hotter.

    This is very important. For all common resistive materials, the pumping energy (voltage) is proportional to how many electrons go through (the current) in a linear way. We call the proportional constant the resistance, and this is measured in units of Ohms, after the fellow who discovered this.

    An ohm is one volt of pressure per ampere of current flow. A thousand ohms (or K ohm) is one volt per milliampere.

    Ohm's Law is one of the most fundamental things in electronics. It is entirely possible to have a career in electrical engineering with no other skills than an adroit application of Ohm's law. I've seen it done. So - MEMORIZE THIS!!! IN ALL THE POSSIBLE PERMUTATIONS!!!!

    Resistance = Voltage divided by Current => R = V/I

    Voltage = Resistance times Current => V = I*R

    Current = Voltage divided by Resistance => I = V/R

    It happens that we can express the energy that current flow leaves behind in any conductor of any kind, resistive or not, by multiplying the voltage across some bit of a circuit times the current flowing through it, or power in watts P = V * I

    Using Ohm's law, we come up with some other very useful relations;

    P = I2*R (by replacing V with I*R);

    P=V2/R (by replacing I with V/R)

    Just as you might think, the dimensions of the chunk of resistive material have something to do with the resistance. A short, wide block of resistive material has a lower resistance than the same amount of material squeezed into a long, skinny shape. Each material has a resistivity, or how much resistance it has per unit chunk of stuff; an actual resistor has length, width, and depth. The resistance is linearly dependent on the resistivity (given the symbol rho) and inversely dependent on the area of the material, so resistance R = (rho)*l / (area). "Rho" is the way you pronounce the Greek letter that sounds like "R", so it's a fancy say of saying "R for Resistivity" and leaving us the English "R" for the actual resistance.

    Magnetic fields have this odd relationship with electrical charges. It happens that there can be no electrical current without causing a magnetic field, although there can be a magnetic field without current. We've already seen that electrons cause electrical fields when positive and negative charges are separated. Opposite electrical charges attract; like electrical charges repel, so electrons like to stay as spread out as possible.

    Magnetic fields neither attract nor repel electons - they make them move sideways! And the electron has to be moving for this to happen. Imagine that the diagonal arrows in the illustration at the right are a portion of a magnetic field. If we shoot a single electron into this field, the electron is deflected sideways across the magnetic field. If the field is strong enough, the electron can actually be curled into a spiral or circle.

    This has some very odd consequences that you almost certainly have heard of.

    For instance - what happens if we have a portion of a magnetic field and a wire through it that carried a current? The electrons are moving through the magnetic field, and they experience the same force that they would if they were in free space.

    What happens is that they are forced to one side of the wire. In the illustration, imagine that the blue lines are a part of a magnetic field and that the electrons are flowing into the page. The edge of the wire is an insulating no-electron zone, so they're trapped in the wire. As you might expect, they start pulling the wire with them. The wire experiences a mechanical force that pushes it in the direction the electrons want to go. This is a real, measurable effect, and in fact is a classical experiment in freshman physics. It's also the basis of all electrical motors and relays.

    There's another consequence of this effect. Remember when we talked about resistors, how the total resistance was R =(Rho)*l/Area? If a magnetic field is forcing all the electrons to one side of a wire, doesn't that mean that the area of the wire that is effective in conducting electrons has gone down, and therefore the effective resistance has gone up?

    It absolutely does. This is kind of a "garden hose effect", where the resistance of a wire is increased by its being in a magnetic field. The amount of the effect is important in some transformer design; however, in some resistive materials, we can measure the voltage across the width of a strip of conducting material and actually measure the amount of electrons bunched up there as a result of a magnetic field. This is called the Hall Effect, and is the basis of a number of magnetic field detectors.

    Remember I said that current and magnetic fields are intimately related. Any time an electron moves, it causes a magnetic field to happen. The only way that this field could not make the electron curl up in little spirals is if the field is wrapped around the electron - and that's exactly what happens. Imagine that the red arrow in the illustration is a current flow, electrons moving through the wire. The resulting magnetic field will be wrapped around the wire in closed loops, as shown in blue. Magnetic field lines have the property that they are always a completely closed loop and are additive. It's possible to cancel out a magnetic field with an equal and opposite direction field.

    If we have two wires side by side, with the same current flowing through each one, the two magnetic fields are equal but opposite in the area between the two wires. However, on the outside of the two wires, they are equal, but add in strength, so the effect is of having one field of twice the strength circulating outside both wires.



    Inductors

    Resistors in series

    Resistors in parallel

    Voltage dividers

    Thevenin and Norton

    Voltage and Current Sources

    Impedance - capacitive reactance and inductive reactance

    Resonance and damping

    Transistors




    Imagine that we set up an NPN transistor, a current meter and a battery as shown in the illustration. We hook this up so we can measure the battery current, connect the battery, and then look at the current meter. If the transistor is good, the current meter will read zero. This is because transistors are made to completely block current flow unless there is some current flow into the base terminal of the transistor. We've shown this with the little arrow indicating that Ib=0.

    If we set up a second battery to supply some base current, and put in a resistor to set a fixed limit on that base current, we can measure the amount of current that flows per unit base current. Let's say that we use resistor Rb to allow 1 micro-amp (1uA) of base current to flow through the base-emitter of the transistor. We read the Ic current meter and find that we have 500uA of collector current flowing. The transistor is providing us with a gain of 500. This current gain is often referred to as Hfe.

    For more fun, let's put a switch in series with Rb. If we click the switch back and forth, the transistor turns on and off. We can show this diagrammatically like this:



    Notice that when the switch is on, the current is limited to the amount of current into the base times the current gain of the transistor, Hfe. Since we now know Ohm's Law, we can calculate the currents. With the switch closed, the voltage across the resistor Rb is the difference between the Vb battery and the voltage at the base. With the emitter grounded, we can call the base voltage Vbe for "voltage from base to emitter". So the actual voltage if we connected a voltmeter just across Rb is Vb-Vbe. The current that flows into the base MUST be (Vb-Vbe)/Rb. So by changing Rb we can set the value of the base current, and therefore set the collector current, because the collector current is just Hfe times the base current, or

    Ic = Hfe* (Vb-Vbe)/Rb



    So let's change Ib. It is a quirk of bipolar transistors that Vbe is almost constant. So if we double Rb, the base current Ib is about half of what it used to be - Ib = (Vb-Vbe)/2*Rb. The illustration shows that the resulting collector current is also halved.



    Instead of throwing a switch, let's add an alternating current (that is, swings positive and negative, also called "AC") signal to the base by hooking in an AC signal source, shown by the circle with the squiggle in it. We'll convert this voltage source to a current by running it through its own separate resistor, Rs. What we find is that the steady current from Vb and 2*Rb sets a bias point with the collector current set at some intermediate value. The current from Vs adds to the steady Ib on the positive half of the AC signal, and subtracts from Ib on the negative half, so the collector current shows the same wiggles as the Vs voltage, with different unit, as it is a *changing current*, not a *changing voltage*.



    We also know from Ohm's Law that a resistor makes a fine current meter - the voltage across it is just the resistor value times the current. so let's put in a resistor instead of that current meter. If we were to measure the voltage just across the collector resistor Rc, we would find that the voltage exactly mimics what we saw from the current meter. But almost all electronics is done with only one reference point, called a ground point, so it would be more convenient to measure the voltage from the same point we have referenced the Vb and Vbe to. If we do that and measure the voltage from the collector to the emitter (Vce) we find that the collector current through the collector resistor eats up some of the voltage from Vbat, and we are left with Vbat-Ic*Rc across the transistor. This gives us the result that the voltage signal at the transistor collector is inverted compared to Vs. So transistor operation in this hookup gives an inverted voltage signal compared to the input signal. Notice that the emitter is common to both the input and the output circuit. Not much imagination is needed to name this a "Common Emitter" transistor circuit - and that's what it's called.

    I've added one more wrinkle. Remember that changing Rb lets us change the collector bias point? Let's make Rb a variable and see what happens.

    When we lower Rb, allowing a lot more current into the base, the no-signal collector current goes up. This makes the voltage drop across Rc larger, and leaves less of the Vbat voltage left for Vce. So the Vce bias point moves down towards 0Volt (because this circuit inverts the voltage) and the Vs signal just rides along. What happens when there is so much current going into the base with the sum of the static Ib current and the signal current from Vs that Ic*Rc is equal to Vbat? There is no more battery voltage left for the current in Rc to increase, so Vce hits 0 voltage and flattens out- there isn't any more voltage left for it go negative. The negative-going output signal is "clipped off" on the bottom.

    Likewise, if we increase Rb so the Vce bias point moves up (lower current in Rc, so the collector is closer to Vbat), the signal current can at some point try to pull current backwards out of the base. It's a quirk of transistor construction that we'll see later that this can not happen, so the base current goes to zero. That forces the collector current to go to zero, and there is then zero voltage drop across the Rc resistor. The transistor is temporarily turned off, so the Vce is just equal to the battery voltage, and the signal is again clipped off, this time on the positive going output.

    The clipping at the lowest Vce is called saturation because the transistor is already pulling all the current the rest of the circuit will let it have. The clipping at the highest Vce is called cutoff because the transistor current is cut all the way to zero. In between is the active or linear region.

    It's a pain to always have to use two batteries to run a transistor, so clever engineers have come up with several ways of doing this with only one battery. If we split Rb into two pieces, Rb1 and Rb2, and string them between Vbat and ground, it makes a voltage divider. The voltage at the center of the voltage divider is Vbat * Rb2/(Rb1+Rb2). Clearly, there is some resistance in series with the base from Vbat. If you do the math, the base "sees" a voltage that looks like a battery with a voltage of Vbat * Rb2/(Rb1+Rb2) through a resistance that is the parallel combination of Rb1 and Rb2. So by using one additional resistor and rearranging things a bit, we have the very useful result that we only need one battery.



    There are actually several ways to bias transistors, different arrangements of resistors that will leave the transistor conducting some current, and not at its cutoff or saturation points.







    ==============================================================




    sg special info



    I just found some info from the Blue Book on the Gibson website about peghead angles: From 1965 to 1972 Gibson used a 14 deg. angle. In 1973 they switched back to the earlier 17 degree angle.
    The volutes were used 1970 to 1973. Still can't find anything about the neck angle to the body.



    just found a '71 SG Special with dot markers and a bound fretboard; so, 1971/72 appears to be the cutoff point for the Specials.


    The period from 71-74 is quite confusing.
    A lot af changes mere made.
    In 71 the Standard was renamed to SG Deluxe , and the Speciel was named SG Profesionel. The Costum stayed Costum.
    Also the SG100 , SG200, SG250 and SG1 , SG2 and
    SG3 was introdused.
    The body was without the beveling and the "90 degree neck-pitch" started.
    The volute and the " made in usa" started here as well.
    In late 72 early73 The names were changed back again ,and so was the neck-pitch.
    In 75 everything was back to " normal" and the started to use 8 digits for the serial number.


    a production list that showed about 3300 Specials built in 1973, and about the same number of Standards. This is as close as I can remember to the actual figures.
    As for the neck pitch I suspect that 9 degrees was meant? The pitch on mine is pretty shallow, not like some new ones I've seen lately (which I believe are mimicking some other model years).

    I think the 9 degrees refers to the neck angle to the body? (that is very steep; mine's more like 4). The headstock is supposedly 17 degrees starting some time in the late sixties, perhaps in 67.


    Hey again. Most of my information is from : Gibson history vol2 by John Bu
     
  3. ess

    ess Guest

    might as well add this last bit... :lol: :lol: :lol:




    Covers and capacitance

    Guitar pickup covers are an example of a small aspect that can make an appreciable difference. The metal covers on Gibson, Fender, DeArmond, Gretsch and other pickups have more than a visual effect. Metal covers, including Telecaster bridge covers, are used as shielding against RF (radio frequency) interference, making the guitar quieter. A byproduct of having grounded conductive metal or shielding paint near a pickup’s coil is a high-end attenuation (cut) caused by a capacitance effect. This is the same effect that will make your guitar set-up sound warmer—or duller, depending on your perception—when you use a longer cable between the guitar and the amp. A five-foot cable will give a slightly brighter sound than a twenty footer.

    Pickup covers are typically made from nonferrous (iron-free) metals such as brass or nickel-silver, and are usually plated with nickel, chrome, gold, or black chrome finish. If a cover were to contain iron, it would alter the pickup’s magnetic field, thus changing the pickup’s tone and response significantly. A prime example is the copper-plated steel plate used under original ’50s Tele bridge pickups to focus the magnetic field up toward the strings. This helped give those old pickups their bite and presence.

    Just for fun, take a piece of steel, about 1/2" x 2-1/2" x .060", and put it underneath your favorite single-coil pickup, as shown in the photo at left. The magnets will hold it in place. The pickup will have a new sizzle that may give you the “edge” you’re looking for. This can also be useful for getting more of a Tele sound from a Strat bridge pickup. If you like it, you'll have to glue the steel in place with silicone or a glue that will isolate vibration. If you don’t, she’ll squeal like a pig!


    Humbuckers without covers may look cool to some players, but they're defenseless against aggressive picks and playing styles that can penetrate the protective tape around the coils. A coil can be broken, leading to some serious repair work. The cover also warms the tone of the humbucker, which may or may not be to your liking. Much of the ’60s and ’70s craze to remove humbucker covers can be traced back to Jeff Beck, who was trying to get a slightly brighter tone from his Les Paul.

    The moral of the story? Guitars are machines in which every component has a role in the overall tone and response. The right combination of stuff will sing! Remember too, that the amplifier is just as important. Use equipment that's suitable for the sound you want. Use the set-ups of your favorite players as guidelines for your own sonic impact. And don’t forget about the little stuff, because even a simple pickup cover can affect your tone.









    ==============================================================




    Bolt-On Necks


    Installation Instructions

    Here are some notes and helpful tips on installing and setting up a bolt-on neck. Most necks will require minor truss rod adjustment after installation. Please read the entire document prior to installing the neck.

    Attaching the neck
    Place the neck into the neck-pocket and check its fit. Ideally it should drop in, or be a little snug—you shouldn't have to force the neck into the pocket. If the body is unfinished and you are pre-assembling the instrument (highly recommended!), remember that the finish will make the neck pocket smaller—it will build up on the edge of the rout. Be sure to compensate for the finish buildup or the neck will be too tight after finishing.

    Next, locate and center the neck in the neck pocket/body. (Use a small clamp with thin wooden shims on the clamping surfaces to hold the neck in place during this process.) To double-check if the neck is centered on the body, take a long straightedge and place it along the edge of the neck. Be sure that a portion of the straightedge is over the body at the bridge's location. Compare the two sides of the neck, and where the straightedge hangs over the bridge (i.e. the straightedge may be even with the outside of the E-string saddles, the outer saddle height screws, the outer edges of the bridge plate, etc.).

    Drilling the neck bolt holes is one of the most critical operations in the construction of a bolt-on neck guitar. The holes must be properly sized and located so that the neck is secure in the pocket, insuring that the vibrations and resonance of the instrument are not compromised.

    Please note
    The two or three holes in the heel of our pre-finished necks are for manufacturing as well as holding the neck during the finishing process. They will not interfere with mounting holes or neck screws.

    If the body already has the neck holes, place the neck into the pocket (properly located and aligned with the bridge), and center punch or mark the locations to be drilled onto the neck. Insert the four neck bolts into their holes, and tap them with a hammer to mark their locations on the neck.

    If the body doesn't have the neck bolt holes drilled, use the neck plate to help locate them. The simplest way is to place the neck plate into the pocket and properly position it in the rout (refer to the drawing for the proper location). The measurement "A" is 5/8" for guitar, 1-5/16" for bass.

    After locating the plate, centerpunch your marks and drill the holes. Most body/neck mounting holes are 3/16" diameter, and they are slightly counter sunk on the backside of the body. We recommend using a drill press to maintain squareness and proper alignment.


    Next, you must drill the holes into the neck. After center punching the neck bolt locations, determine the proper size drill bit (most neck bolts use a 1/8" diameter bit) and chuck it into your drill. Place a neck bolt through the neck plate and body. Measure the amount of the neck bolt that extends up into the neck pocket, and mark your drill bit (a piece of masking tape around the bit works great) so that it will drill into the neck to that depth.

    Carefully drill the holes in the neck. Pull the bit out a few times while drilling each hole to clear the shavings packed onto the bit—when drilling maple or other dense hardwoods, drill the hole in gradual steps so the bit won't get too hot or clogged.

    Finishing
    Our 22-fret guitar necks and the bass necks are all finished in nitrocellulose lacquer, with satin lacquer on everything but the face of the headstock, which is high gloss. You can apply any finish you like to the unfinished bass guitar and baritone scale necks, but we usually recommend nitrocellulose since it is traditional and easy to use. You can stain the necks prior to finishing using Color-Tone concentrated liquid stains, if you want a more “vintage” look, for example.


    ==============================================================



    Okay folks, I did a little research. According to posters at the Gibson forum, including the Gibson tech, the current line of Gibsons use 300K linear volume pots and 500K audio tone pots. By current, they mean "post-Norlin" which would be 1986. Norlin took over in 1970 and were in power up until '86. During that time, Les Pauls used 300K volume pots and 100K tone pots (Lil' John says "Whooowhaaattt!!!)
    Upon discovering this, I took out the multimeter and sure is ****, my 78 SG has 100K tone pots in it. So I have 500K Linears (after market) for volume and 100K audios for tone. I just disconnected the tone pot to see what it would sound like. It was nice clean but a little too "Tele-ish" with distortion. I may actually wire my tone pots to the mini-switches left over from my humbucker days, so I can "true-bypass" the tone pots for clean work. As for volume, I would replace the 300's with 500's. I find it gives more range to the volume knob. But get audio taper, not linear taper like me, because I was a dumb-ass.
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice