master volume control for AA764 champ

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phsyconoodler
Junior tube assistant
Posts: 1
(2/20/04 5:28 pm)
  master volume control for AA764 champ
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 is there anyone that can tell me how to put a master volume control on my aa764 champ chassis? I am a newbie and need to be walked through it.this is my first real amp project and i need some expert help.by the way, the amp sounds awesome and has no problems. thanks
phsycnoodler
 
phsyconoodler
Junior tube assistant
Posts: 2
(2/26/04 12:12 am)
  champ AA764
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 hi there,
no one amswered my post,so i found out how by myself; a master volume does not work on an amp with only two gain stages. I found another way to get the distortion i needed.
 
eddiejg
Senior tube assistant
Posts: 236
(2/26/04 9:47 am)
  champ AA764 Master Volume
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 Hi-
Glad you figured out how to get what you wanted.
However, there is 1 way to add a master volume to a single-ended amp with only 1 preamp tube.
Replace the 220K grid load resistor for the power tube with a 250K audio pot.
You can wire up the pot as a variable resistor going to ground.
Or wire it as a pot with the wiper going to the grid of the power tube.
I've also used a 500K pot for more overdrive, but I usually make other mods to keep it from getting too farty.
-Ed
 
phsyconoodler
Junior tube assistant
Posts: 7
(3/7/04 9:55 pm)
  Re: champ AA764 Master Volume
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 I tried the master volume mod and it totally did not work.I changed everthing back to the original and use a boss ds-1 for my distortion. I like the champ without the tone circuit for distortion,but the clean tone is really muddy.I put a switch in to take the tone circuit in and out.
Thanks anyway
 
phsyconoodler
Junior tube assistant
Posts: 31
(4/14/04 11:10 pm)
  Re: champ AA764 Master Volume
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 Hi There,
Why didn't the master volume pot work? If you described it right,it should work.I must have done somethig wrong wiring it in,because I just ended up with two volume controls that competed with each other like a 5e3's do.What did I do wrong/
Any thoughts?
Thanks, phsyco

 
zachsdad
Posts: 11
(4/15/04 5:45 am)
  Master Volume
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 Just replace the grid load resistor on the output tube with a 250KA pot. The wiper goes to one wing and they go to ground. The other wing goes to the grid of the 6V6. Works well if done correctly. Remember, don't be afraid to experiment, thats where the fun is.

Leslie
 
phsyconoodler
Junior tube assistant
Posts: 32
(4/17/04 5:40 pm)
  master volume aa764
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 Zachsdad
If I read you right,wire one wing to the wiper,and then both to ground,and the other to the tube grid.Will this work well on a champ with only one preamp tube?
I will try it. Someone else mentioned a 500k pot with some mods.Any idea what mods?
Thanks for the tips!
Phsyco
 
zachsdad
Posts: 13
(4/17/04 6:47 pm)
  master volume aa764
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 Correct. Will work fine. Dont know about the 500K. Probably give some different tones. Experiment. It may be something you like.
 
phsyconoodler
Junior tube assistant
Posts: 34
(4/17/04 10:35 pm)
  Re: master volume aa764
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 zachsdad,
Thanks for the tip! I am in your debt.
Phsyco
 
delux1959
Junior tube assistant
Posts: 91
(4/18/04 9:41 am)
  master volume
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Ken Fisher describes how to do that in Gerald Webbers book, "Tube Amp Talk for the guitarist".

 
 
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