Upgrading a VOX AD50VT Valvetronix

Discussion in 'Amps & Cabs' started by Dorian, May 8, 2005.

  1. Spunky

    Spunky Active Member

    Joined:
    Dec 12, 2004
    Messages:
    4,109
    Likes Received:
    1
    Location:
    Redondo Beach, California
    Ess was right!

    There is like 1/16" top and bottom around the 10" speaker in the VOX.
    No way a 12" will fit in!
     
  2. Spunky

    Spunky Active Member

    Joined:
    Dec 12, 2004
    Messages:
    4,109
    Likes Received:
    1
    Location:
    Redondo Beach, California
    Thank you Paradox,

    I just pulled the trigger on one. I looked around and this was the best price out there....
    There are other brands but everything is double the price or more. I just need a full range speaker to replace the cheapie that came in the AD30VT. The bass response of the stock speaker is terrible (like none or stutter). I have to crank the bass tone control to max and the mid to 3/4 to even get close to a G12M. I sure hope this is the ticket. The advertisement says it has a touch of the British sound so it will be a good match for a VOX.
    What sold me was that they sell a 32 ohm version specifically to replace the CTS speakers in the old SVT cabinets. I had a 1972 SVT 8X10 cab and they are awesome. I figured if the speaker was appropriate for bass, it would have nice bottom and as it is a colorless guitar speaker, it would stay clean and have full range at the 50 watt rating for a modeling amp. Once installed and tested, I'll make my report. I'll make test .mp3's of before and after the speaker replacement.
    Other than bolting on a rotary baffel for a leslie effect, I can't think of another mod I can make to the amp.
    NOS RCA 12AX7 tube, external cabinet jack with automatic internal speaker shut off, upgraded speaker....what's next?


     
  3. RightTurn

    RightTurn Member

    Joined:
    Jul 5, 2005
    Messages:
    52
    Likes Received:
    0
    Location:
    New York City
    cool thread.  i was thinking about upgrading my AD50VT which is a good amp but it's hard to leave well enough alone. maybe put this cloth on as finishing touch to replace metal diamond plate.
    [​IMG]

    p.s - i spilled coffe down the top vents and it still works, guess that means it's a good amp- sounds a little warmer though :)
     
  4. skidshark

    skidshark Active Member

    Joined:
    Dec 12, 2004
    Messages:
    8,439
    Likes Received:
    6
    Location:
    tenn-O-see
    those vents seem to be located on the top of the valvetronix for a reason......i find that vodka really brings those marshall emulations alive!! :lol: :uglystupid2: :whip2:
     
  5. Six String

    Six String Moderator Staff Member

    Joined:
    Dec 11, 2004
    Messages:
    13,566
    Likes Received:
    1,130
    Location:
    Warsaw, In
    .......... new theory Skids............ differant brews for differant sounds. Cool! 8)
     
  6. vic108

    vic108 Well-Known Member

    Joined:
    Dec 12, 2004
    Messages:
    6,843
    Likes Received:
    81
    Location:
    Mudwogweap, VA
    So...boys & girls. The big hairy amp guys made big changes to the Vox amp
    that the pinheads at the factory would have a heart attack over...

    Now that time has elasped, what do the rough and tumble amp guys think
    of their handiwork? Are they happy? Has the house burned down? Are they
    hitting on more chicks? Did they ever get that nasty stain out of their underwear?

    I jammed a half dozen times with this amp, 4 times at home with just another guitarist
    and twice in a real barroom...once jamming to Blues CD's and once jamming with another
    guitarist AND a bass player.

    One thing I noticed is that the amp sounds GREAT with the changes - not only do I think so,
    but the guys I played with did too (which is a good sign). Since I didn't play out with this amp
    before I made the changes, so I can't say how it was before but a FEW of the clean settings
    had to be cranked up to MAX just to hear them over the other amps whereas the more dirty
    settings were PLENTY loud (and then some) with the other amps and the room.

    All and all, I'm happy with the results!
     
  7. Voxman

    Voxman Moderator Staff Member

    Joined:
    Dec 11, 2004
    Messages:
    14,189
    Likes Received:
    528
    Location:
    LINY and Satillite Beach
  8. ess

    ess Guest

    [move]i just nicked that amp fire gif[/move]
     
  9. RightTurn

    RightTurn Member

    Joined:
    Jul 5, 2005
    Messages:
    52
    Likes Received:
    0
    Location:
    New York City
    [quote author=Voxman link=topic=2535.msg47501#msg47501 date=1122512713]
    [​IMG] [​IMG] VOX
    [/quote]

    i dont know looks like a fender burning therr, love the little punk dude gettin down jammin'.
     
  10. skidshark

    skidshark Active Member

    Joined:
    Dec 12, 2004
    Messages:
    8,439
    Likes Received:
    6
    Location:
    tenn-O-see
    hmmmm....looks just like my P.A. speaker!! :o
     
  11. Dorian

    Dorian Active Member

    Joined:
    May 8, 2005
    Messages:
    650
    Likes Received:
    188
    Location:
    LA area
    Timely questions, vic108. Let me first comment on questions one and two, mostly concerning the new loudspeaker. I really like my new Eminence Tonker. Its articulation is what I like most, even though this way it more prominently announces all mistakes in my technique.

    Take a look at a side view of the two speakers, the original VOX/Celestion (bottom) and new Eminence Tonker (top).
    [​IMG]

    The new red Eminence Tonker speaker is just about twice the weight of the original VOX/Celestion, and you can almost see this in the photo. It has a bigger voice coil and a far bigger magnet structure.

    What puzzles me is why the Tonker speaker has such better bass. If you look at the response curves that CharlieB showed on the first page of this thread, I would expect the Tonker to be a bit better in the bass, but not so much as it really is.  One possibility is that the VOX/Celestion is not quite a Celestion V12-60 (but then I would have to argue with CharlieB about this  ;D ). Another possibility might come about because the AD50VT has a sealed back. The air trapped in a "small" box acts as a spring that raises the speaker resonance frequency and suppresses the bass response. The importance of this effect varies from speaker to speaker, depending on cone mass and the stiffness of its suspension. I think that the Tonker has a stiffer suspension and a heavier cone, so it is less affected by the air backpressure in the box. The Celestion V12-60 might lose more of its bass response in a sealed box.

    A real complication is that the box of the AD50VT is not fully sealed. There are air ducts above the heat sinks of the output transistors, making a total opening of about 15 square inches. Maybe this speaker box was designed as a "ducted port enclosure"? For such speaker enclosures the sizes of the ducts are optimized for the lowest bass frequency, although ducted port enclosures typically have a rapid drop in output at yet lower frequencies.  Could the vent holes actually have been sized by VOX to optimize the bass specifically for the VOX/Celestion speaker? This would be most clever. Unfortunately, I have given away the original speaker, so I had to do the following test with the Eminence Tonker.

    The test is obvious -- cover tightly the vent holes, listen to the bass response, remove the cover, listen to the bass response, repeat. I used a board of soft pine to make the seal, weighted down with a couple of bricks. I was surprised by the result. The open low E string on my SG guitar was indeed perceptibly louder with the ducts open. The effect for the A string was little less, the D not at all. The D string on my EB3 bass was louder too with the ports open.  I think the AD50VT enclosure works effectively as a ducted port enclosure for the Tonker loudspeaker! The effect is small, maybe less than 2 dB, but it is real.  It seems just lucky for the characteristics of the Eminence Tonker. 

    Maybe someone with a AD50VT could please try the same easy test and let us know if you hear any difference? What you have to do is cover the vent slots with a rigid object such as a wood block, and make a reasonable seal. A good sustain with open strings will let you to use both hands to seal and unseal the vent holes. Can you hear a difference in the bass (it should lose bass response with the vents covered)?  I may be overestimating the cleverness of VOX engineeering, but it is possible that the vent slots actually were optimized for the bass response of the VOX/Celestion speaker.

    This ducted port behavior is probably not the main reason why my Eminence Tonker has better bass, but it is an effect that I think is cool.  The big issue is that the Tonker has a heavier and more stiffly-held cone than the Vox/Celestion. The Tonker cares less about being mounted in a relatively small sealed box. It also has a bit better characteristic bass response as shown in the first page of this thread too.

    vic108, my answers to your last three questions are No, No, No. :oops: But these questions are the important questions of life.  Amp modifications cannot rise to this level, can they?
     
  12. skidshark

    skidshark Active Member

    Joined:
    Dec 12, 2004
    Messages:
    8,439
    Likes Received:
    6
    Location:
    tenn-O-see
    perhaps the amp was designed to have a quality speaker....then the bean-counters changed it for their profit margins...

    i would imagine that some of the hairy amp engineers at the factory would feel good to know that some of us have found, noted, and cataloged the difference!!
     
  13. Voxman

    Voxman Moderator Staff Member

    Joined:
    Dec 11, 2004
    Messages:
    14,189
    Likes Received:
    528
    Location:
    LINY and Satillite Beach
    Without a doubt Skids....... Very nice read Dorian, thanks much.......
     
  14. RightTurn

    RightTurn Member

    Joined:
    Jul 5, 2005
    Messages:
    52
    Likes Received:
    0
    Location:
    New York City
    [​IMG]

    Heres my attempt at adding a little fire.  The new G12 has more bass and midrange, it isnt broken in but it's just starting to growl.  Those ARE coffee stains...the rest of the mess is old crap.  The G12 is also physically larger overall- Well thats the best GC had.

    Right no I am leaving back off and cracking the bass a little more than i could with it on.  I am thinking maybe a  cutting to a 1\4 back with black painted interior.
     
  15. skidshark

    skidshark Active Member

    Joined:
    Dec 12, 2004
    Messages:
    8,439
    Likes Received:
    6
    Location:
    tenn-O-see
    velllllly intellestinck!!!!
     
  16. Voxman

    Voxman Moderator Staff Member

    Joined:
    Dec 11, 2004
    Messages:
    14,189
    Likes Received:
    528
    Location:
    LINY and Satillite Beach
    [​IMG]  I wonder if we could install a baffle or port in the back panel to improve the sound? [​IMG]
     
  17. vic108

    vic108 Well-Known Member

    Joined:
    Dec 12, 2004
    Messages:
    6,843
    Likes Received:
    81
    Location:
    Mudwogweap, VA
    I guess the changes seen here will effect any stock amp...
    Stuff comes the factory with parts chosen by bean counters
    and not the tech guys. Sound and quality are pointless to them.

    What other amp mods have folks done around here?
    I mean ANY amp, no matter what brand, etc.....

    I think Spunky has changed his tubes out in his Mesa Boogie.....

    Maybe name a new section: MODS, MUCK, AND MAYHEM?
     
  18. Spunky

    Spunky Active Member

    Joined:
    Dec 12, 2004
    Messages:
    4,109
    Likes Received:
    1
    Location:
    Redondo Beach, California
    Vic,

    Spunky modifies everything he gets his hands on........

    Mesa Boogie, re-tubed for optimal sound (My opinion only) :)

    Champ, NOS tubes, single ground point and 10" Vox speaker O0

    Vox AD30VT, Jensen MOD speaker, external speaker jack with internal cut off, NOS RCA tube :crazy2:

    Fender 1963 Reverb, NOS tubes, modded to original specs :-*

    R7, Crossroads pups, RS vintage kit :roughup:

    SG Std, 57' Classic pups, RS vintage kit
    :dance:
    V, re-fretted with tallest/widest, bone nut, RS kit :funny:

    Std Strat, re-fret with jumbo frets and Tex-Mex pups, callaham bridge, sperzel locking tuners, bone nut, 3 ply p-guard, RS kit :notworthy:

    Std Tele, Texas Special pups, MOP pickguard, RS kit :whip2:

    Squire mini-strat, swap to lefty, Std pup set w/ RS kit :director:

    Peavey Foundation, custom paint, refret to jumbo, EMG pups, custom pickup ring/pickguard :uglystupid2:
     
  19. Voxman

    Voxman Moderator Staff Member

    Joined:
    Dec 11, 2004
    Messages:
    14,189
    Likes Received:
    528
    Location:
    LINY and Satillite Beach
    **** Vic speaking of beans I better go count mine![​IMG]
     
  20. Dorian

    Dorian Active Member

    Joined:
    May 8, 2005
    Messages:
    650
    Likes Received:
    188
    Location:
    LA area
    RightTurn - The Celestion Vintage 30 might be a really good replacement speaker for the AD50VT. It is certainly interesting -- please keep us posted about how you like it. The Vintage 30 was one of the three I considered seriously for my own upgrade, but it was a bit more expensive than the Eminence models. Also, I thought it would give more of a classic lead sound for all the amp models, but then, this might be a good thing. In the end, I went with the Tonker because I thought it would be a bit more neutral. (I didn't want to depart too far from the stock VOX/Celestion so I could understand the different amp models on their own.)

    When I was swapping tubes in and out, I ran the amp with the back off. It sounded pretty good this way, but I didn't make careful sound tests with and without the back. I do have one comment that may be of use. If you go for the partial back, I expect that the bass response will be about the same as with the open back you show in the photo. A partial back is quite open, so it shouldn't have much effect on the air backpressure against the speaker cone that raises the speaker resonance. The dispersion of the sound will be different with the partial back, however, but this also depends on amp placement, walls, etc.

    Incidentally, one other change I did after my speaker replacement was to tweak the heights of the pickups in my SG. I lowered them a bit for a sweeter sound. For me this makes a more pleasant combination with the new speaker. This is a really subjective thing, of course, and your taste may vary.
     

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