Finished with my valve junior...for the moment

Discussion in 'Amps & Cabs' started by acdcrocker, Jul 11, 2006.

  1. acdcrocker

    acdcrocker Member

    Joined:
    Sep 24, 2005
    Messages:
    564
    Likes Received:
    0
    Location:
    USA
    Here are some more pics of the finish modded amp:

    [​IMG]

    [​IMG]


    Complete list of mods:

    -Replaced jack with an insulated one(Cliff 502)
    -Installed jumper on the back of the PCB board
    -Replaced C1 and C2(signal capacitors) with .022 SoZo mustard caps
    -Replaced C3 and C4 with 3.3uF caps
    -Replaced C5 with a 1000uF cap
    -Replaced R8 with 1.5K
    -Replaced R9 with 620 ohms for more crunchy tone
    -Cut traces and ran heater wires above the board  (with rectified tube heater voltage)
    -Referenced R10 and R11 to pins on EL84
    -Lowered B+ voltage with a 1K/5 watt resistor
    -Added 100uF/450V cap
    -Added wire running from volume pot wiper to pin 7 of the 12AX7
    -Replaced R1 with a 1 meg resistor
    -Replaced R2 with a 10K resistor
    -Added a standby switch
     
  2. Bonfire

    Bonfire Active Member

    Joined:
    Mar 12, 2006
    Messages:
    1,381
    Likes Received:
    0
    Location:
    Victoria, Australia
    technically (and therefore sonically), what does changing the values of caps 3, 4 and 5 do? same for R8 and R9...

    woo! sounds like you had fun doing that! (p.s. i just found the perfect tone like angus has on let there be rock live the movie in paris, using the MXR (still in bits) and crunching the valve junior! SWEET!) ;D
     
  3. acdcrocker

    acdcrocker Member

    Joined:
    Sep 24, 2005
    Messages:
    564
    Likes Received:
    0
    Location:
    USA
    [quote author=Bonfire link=topic=9380.msg124134#msg124134 date=1153721177]
    technically (and therefore sonically), what does changing the values of caps 3, 4 and 5 do? same for R8 and R9...[/quote]

    No problem.
    C3 and C4 are the cathode bypass caps for the first and second gain stages on the 12Ax7. Lowering the value of these  genarally get rid of the flabby bass that this amp has stock. (C3, and C4 are 22uF stock. I changed this to 3.3uF)

    C5 is the cathode bias cap for the El84. Sometimes in single ended amps, 22uF(stock C5 amount) for the cathode bias cap is a bit small and en-larging this value often smooths out the tone. (I used 1000uF)

    Now, R8 and R9 are the cathode resistors for the first and second gain stages of the 12Ax7. Larger values reduce gain, smaller values give more gain in cathode resistors. The stock cathode resistors(R8 and R9) are 2K. I reduced R8 to 1.5K for more crunch, and lowered R9 to 620 ohms for more crunch.

    Here is an intersting page that you might find usefull. http://www.diystompboxes.com/pedals/tubedummy.html

    yea I had lots of fun and I learned a TON! i might be ready to build my first 18watter!!  :) ;)

    congrads on your tone!! finding the right angus tone always puts a smile on my face! ;D
    you gotta get some pics man!!

    good luck

    scott
     
  4. Bonfire

    Bonfire Active Member

    Joined:
    Mar 12, 2006
    Messages:
    1,381
    Likes Received:
    0
    Location:
    Victoria, Australia
    thanks dude! that makes sense! great link! but now, why did you lower the B+ voltage? and was it on all tubes?

    [quote author=acdcrocker link=topic=9380.msg124140#msg124140 date=1153724576]
    yea I had lots of fun and I learned a TON! i might be ready to build my first 18watter!! :) ;)
    [/quote]

    sounds like an adventure! keep us updated if you do proceed! O0

    yeah i know, but the board from hasnt come from the US yet, so it still looks like a pile of junk...but when its done, you better hope you dont have a 56k modem! :lol:

    keep it real lads
     
  5. acdcrocker

    acdcrocker Member

    Joined:
    Sep 24, 2005
    Messages:
    564
    Likes Received:
    0
    Location:
    USA
    [quote author=Bonfire link=topic=9380.msg124155#msg124155 date=1153737898]
    thanks dude! that makes sense! great link! but now, why did you lower the B+ voltage? and was it on all tubes?[/quote]

    no problem man! Glad I can help!
    I lowered the B+ voltage on the El84 only. I did this because it was at a ridiculous 165 volts!! This means two things.

    1) A single ended amp with a EL84's sweet spot (on the B+) is about 300 volts, and if its anything above 312 volts the tone gets farty at high volumes.

    2) If an EL84's plate(B+) voltage is that high(365volts) it can shorten the life of the tubes.

    will do, will do!

    ;D ;D cant wait! its a PCB right?

    if you have any more questions I'd be glad to answer them. :)

    take care
     
  6. the bacon

    the bacon Member

    Joined:
    Jul 8, 2006
    Messages:
    712
    Likes Received:
    0
    Location:
    Indiana
    WOW! :o :Droolin:

    i may have to get the valve junior
     
  7. In The Light

    In The Light Member

    Joined:
    Jun 3, 2006
    Messages:
    171
    Likes Received:
    0
    Location:
    Norwich, Connecticut
    [quote author=the bacon link=topic=9380.msg124211#msg124211 date=1153770618]
    WOW! :o :Droolin:

    i may have to get the valve junior
    [/quote]

    but to do what he did, you have to have some understanding of how an amp works...what makes the sound, and some elctrical know-how...
    i could build an 18 watt mashall clone if i had directions, but i would always have someone there knowing what he is doing (my stepdad is my electrical go to guy, hes a big electronics engineer for submarines and stuff..he built me a little comp pedal once (it has since died from constant gigging))...and you really should know certain electrical things, such as how resistors, transformers (thinks of that awesome cartoon), caps, tubes, and rectifiers work,what they do, and how they will affect the sound...

    also check this out
    [quote author=GearPig link=topic=9380.msg121586#msg121586 date=1152691082]
    Glad you're ok. For those who don't realize, not only can an amp sohck you, it can kill you - even a little amp, and even anunplugged amp. Yep, that's right. An unplugged amp can still be storing active electrical current that can wax you, so if you don't know your business stay the hell away from amp inards.


    [/quote]

    and i am not saying you do not know these things, or you cannot learn these things, i am saying there is a fair amount of knowlegde to know before you jump in to a project...there is some trial and error kinda testing, but you atleast have to know somethings..and if you know these things, or have someone to teach you and show you along the way thats great, but dont be little bacon who decides to take his amp apart and fix it, only to die in the process...
     
  8. Spunky

    Spunky Active Member

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

    You are not done yet.......it is time to replace the puny OT with the Hammond 125ESE......
    The stock is 7.6k, the Heyboer from Doberman but it is 2.5k, 4k or 6k. The optimal is 5k for the EL84 which is on the Hammond OTs.
    The stock and the Heyboer OT's are more better matched for a 6V6/6L6, not the EL84.

    Is the OT the same in the VJ head and in the combo? I think the PT in the head was a lot bigger than the Rev 1 combo. With the Rev. changes in both the head and combo, are they the same now?

    Hopefilly, I will have my 125ESE today and I'll install it.
     
  9. the bacon

    the bacon Member

    Joined:
    Jul 8, 2006
    Messages:
    712
    Likes Received:
    0
    Location:
    Indiana
    [quote author=In The Light link=topic=9380.msg124223#msg124223 date=1153773781]
    [quote author=the bacon link=topic=9380.msg124211#msg124211 date=1153770618]
    WOW! :o :Droolin:

    i may have to get the valve junior
    [/quote]

    but to do what he did, you have to have some understanding of how an amp works...what makes the sound, and some elctrical know-how...
    i could build an 18 watt mashall clone if i had directions, but i would always have someone there knowing what he is doing (my stepdad is my electrical go to guy, hes a big electronics engineer for submarines and stuff..he built me a little comp pedal once (it has since died from constant gigging))...and you really should know certain electrical things, such as how resistors, transformers (thinks of that awesome cartoon), caps, tubes, and rectifiers work,what they do, and how they will affect the sound...

    also check this out
    [quote author=GearPig link=topic=9380.msg121586#msg121586 date=1152691082]
    Glad you're ok. For those who don't realize, not only can an amp sohck you, it can kill you - even a little amp, and even anunplugged amp. Yep, that's right. An unplugged amp can still be storing active electrical current that can wax you, so if you don't know your business stay the hell away from amp inards.


    [/quote]

    and i am not saying you do not know these things, or you cannot learn these things, i am saying there is a fair amount of knowlegde to know before you jump in to a project...there is some trial and error kinda testing, but you atleast have to know somethings..and if you know these things, or have someone to teach you and show you along the way thats great, but dont be little bacon who decides to take his amp apart and fix it, only to die in the process...
    [/quote]

    in 5th grade i built a big lab of eletronics out of a cardboard box.
     
  10. In The Light

    In The Light Member

    Joined:
    Jun 3, 2006
    Messages:
    171
    Likes Received:
    0
    Location:
    Norwich, Connecticut
    okay, then go at it, but be carefull, bacon is good crispy, not burned... :lol:
     
  11. the bacon

    the bacon Member

    Joined:
    Jul 8, 2006
    Messages:
    712
    Likes Received:
    0
    Location:
    Indiana
    [quote author=In The Light link=topic=9380.msg124277#msg124277 date=1153786819]
    okay, then go at it, but be carefull, bacon is good crispy, not burned... :lol:
    [/quote]

    lol
     
  12. acdcrocker

    acdcrocker Member

    Joined:
    Sep 24, 2005
    Messages:
    564
    Likes Received:
    0
    Location:
    USA
    [quote author=Spunky link=topic=9380.msg124226#msg124226 date=1153774648]
    acdcrocker,

    You are not done yet.......it is time to replace the puny OT with the Hammond 125ESE......
    The stock is 7.6k, the Heyboer from Doberman but it is 2.5k, 4k or 6k. The optimal is 5k for the EL84 which is on the Hammond OTs.
    The stock and the Heyboer OT's are more better matched for a 6V6/6L6, not the EL84.

    Is the OT the same in the VJ head and in the combo? I think the PT in the head was a lot bigger than the Rev 1 combo. With the Rev. changes in both the head and combo, are they the same now?

    Hopefilly, I will have my 125ESE today and I'll install it.

    [/quote]

    Yea, I heard 5K is a very good match for single ended EL84 amp. I dont want to dish out all the cash though. Im going broke. BUT, I will probally end up getting it lol So I think I'll go for the DSE because its rated for 10 watts not 15 watts like the ESE. ANd its cheaper ;)

    Hmm. I think the OT is the same in the head and the combo.

    Cool. Tell how the OT swap goes!
     
  13. Bonfire

    Bonfire Active Member

    Joined:
    Mar 12, 2006
    Messages:
    1,381
    Likes Received:
    0
    Location:
    Victoria, Australia
    [quote author=acdcrocker link=topic=9380.msg124201#msg124201 date=1153767071]
    I lowered the B+ voltage on the El84 only. I did this because it was at a ridiculous 165 volts!! This means two things.

    1) A single ended amp with a EL84's sweet spot (on the B+) is about 300 volts, and if its anything above 312 volts the tone gets farty at high volumes.

    2) If an EL84's plate(B+) voltage is that high(365volts) it can shorten the life of the tubes.
    [/quote]

    I think you meant 365 volts in the first sentence lol

    ahh ok, that makes sense.... so i should probly measure the B+ voltage then... is there a way to calculate what resistance is needed (yeh...lemme guess....ohm's law??)?

    [quote author=acdcrocker link=topic=9380.msg124201#msg124201 date=1153767071]
    ;D ;D cant wait! its a PCB right?
    [/quote]

    yep! still waiting!

    thanks again!
     
  14. SG dan

    SG dan Active Member

    Joined:
    Dec 13, 2005
    Messages:
    1,698
    Likes Received:
    0
    Location:
    toronto
    [quote author=In The Light link=topic=9380.msg124277#msg124277 date=1153786819]
    okay, then go at it, but be carefull, bacon is good crispy, not burned... :lol:
    [/quote]
    burned bacon makes me sad :cry:
     
  15. Spunky

    Spunky Active Member

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

    You also want to swap the diodes for the FREDs. It made a noticable difference in the tone of my amp in a very positive way.

    I finished the OT swap and all I can say is OMG...........
    Get the 125ESE...it is some serious iron and I cannot believe the difference it made in the tone and the crunch and overtones, not to mention the overdrive.......
    Besides swapping the tubes for decent ones, the OT is the second biggest difference.
    All the cap and resister mods help with fine tuning the tone but the OT is the heart and soul of the amp.
    I have $165.00 invested and it is a serious contender for a Marshall Plexi...Next are some Sozo caps.........

    [​IMG]
    [​IMG]
    [​IMG]
     
  16. Spunky

    Spunky Active Member

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

    The primary tabs on the motherboard were cold soldered. when I press the new ones on, they came loose.........
    This was the source of a background noise issue I had.....cold soldered because of the size of the tab pins......
    whisper quiet now and KILLS........ ;D
     
  17. acdcrocker

    acdcrocker Member

    Joined:
    Sep 24, 2005
    Messages:
    564
    Likes Received:
    0
    Location:
    USA
    Bonfire,
    I heard the 2nd generation Valve Jr. combo already has the lower B+ voltage. And if it is high, then yes, Ohms law  ;)

    Spunky,
    I already swapped the diodes for FREDS. To me, it really didnt make that much of a difference.

    Congrads on the new OT!!! How does it compare to stock? (Is it more bassy? Does it have more headroom?) And where did you purchase it from? Also, did you drill 2 new holes or just one paired with the stock hole?

    One more question lol...What is that 2nd pot for on the chassis?
     
  18. Spunky

    Spunky Active Member

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

    I found the FREDs smoothed out the sound a bit and added a musical tonality...just a tiny bit and barely noticeable but added a nice sound.

    The new OT is not more bassy...it is the same bass but tighter....makes the speakers stand up and work like erect nipplers...lol.
    Mid-range is better too...just less flubby and a lot more focused overall. The top end is the same.
    There is actually less headroom with the new OT which I am happy about....There seems to be less headroom with the 5K taps than the stock OT at 7.5k. PERFECT for me! ;)

    I bought the OT from stf-electronics.com and Pat is a great guy to work with and emails you right back immediately if you have a question or a problem.

    I used the origional hole closest to the edge of the chassis and drilled a new hole for the new and MUCH LARGER OT.

    The extra POT is the master volume. I am using a Weber MASS right now but it works very well as a stand alone head MA.

    I think the 5K taps on the OT give the amp the distortion it needs. I was able to be the feedback at lower volumes that I was looking for. If you want clean, the 125DSE and 125ESE both have the 10K taps that will give you more headroom. I think the stock OT with 7.5k tap is cool as a middle ground......I want a screaming banshee, not a jazz amp.... :lol:
    The 5K tap really lets the EL84 do it's Marshall brown sound thing..... ;)

    What difference did the Sozo caps make?
     
  19. acdcrocker

    acdcrocker Member

    Joined:
    Sep 24, 2005
    Messages:
    564
    Likes Received:
    0
    Location:
    USA
    Mmmm that OT sounds tasty!!! ;D I was hoping you said it had LESS headroom and you did! And thanks for answering all my questions. Your really convincing me to buy the ESE!! Its $43 with s/h on the link you provided. I'm most likely going to get it.

    Did you think it was less farty at high volumes with the new OT compared to stock?

    BTW, the SoZo's actually made a noticeable difference! I found using them made it a little darker sounding and more clear(sort of an oxymoron) if that helps. I think they made more of a difference than the FREDS made.
     
  20. Spunky

    Spunky Active Member

    Joined:
    Dec 12, 2004
    Messages:
    4,109
    Likes Received:
    1
    Location:
    Redondo Beach, California
    I have a couple of .022 Sozo's laying around.....May as well put them in..

    C1 and C2 eh?
     

Share This Page