[size=18]My clone has no headroom. If I run the volume past 1, all I get is drive. The tone is wonderful, but the flexibility is not. I think what I'm missing is the ability to clean up the distortion from the guitar volume control. If I set the amp volume control for the "lead" level with the guitar all the way up, I have to turn the guitar volume control almost off before it starts to clean up. Is there a way to adjust the gain structure of the amp so that I can get more control from the guitar? Thanks for your suggestions in advance.[/size]
D
Headroom-or lack thereof..........
Moderators: pompeiisneaks, Colossal
Re: Headroom-or lack thereof..........
The first question is what circuit did you decide to build?
A bit of a description of the amp's circuit would be helpful. I have found that the amp that I built did run out of "clean" when turning it above the 9 o'clock position on the volume control.
If this is a problem, the try replacing the 100K plate resistor on the tone control recovery stage with a 100K pot (be very careful now!)
Have one side of the pot go to the B+, the other side going to the plate of the valve. The wiper goes to the 0.0022uF coupling cap. I would recommend wrapping the pot with (a lot of) insulation tape so you can safely handle the pot.
The pot will act as a volume control. What you will be doing is adjusting the actually volume control of the amp to maximum, and using the pot to dial in the maximum amount of distortion/gain that you think you are likely to need.
This idea is a variation of Ken Fischer's circuit in the Komet amp. The pot has one advantage over K.F. idea, that being you can set it up the way you want it.
You can remove the pot and replace it with a voltage divider (two resistors) based on readings from the pot.
A varation that I heard was from Brent Williamson, where he use to swear by replacing the 100K plate resistor in the third stage and replace it with two 56K resistors and have the coupling cap (which goes to the P.I. stage) attached to the centre of the two 56K resistors. this would in principle do the same thing as the above mentioned circuit.
Try both and see how you go?
Hope this helps.
A bit of a description of the amp's circuit would be helpful. I have found that the amp that I built did run out of "clean" when turning it above the 9 o'clock position on the volume control.
If this is a problem, the try replacing the 100K plate resistor on the tone control recovery stage with a 100K pot (be very careful now!)
Have one side of the pot go to the B+, the other side going to the plate of the valve. The wiper goes to the 0.0022uF coupling cap. I would recommend wrapping the pot with (a lot of) insulation tape so you can safely handle the pot.
The pot will act as a volume control. What you will be doing is adjusting the actually volume control of the amp to maximum, and using the pot to dial in the maximum amount of distortion/gain that you think you are likely to need.
This idea is a variation of Ken Fischer's circuit in the Komet amp. The pot has one advantage over K.F. idea, that being you can set it up the way you want it.
You can remove the pot and replace it with a voltage divider (two resistors) based on readings from the pot.
A varation that I heard was from Brent Williamson, where he use to swear by replacing the 100K plate resistor in the third stage and replace it with two 56K resistors and have the coupling cap (which goes to the P.I. stage) attached to the centre of the two 56K resistors. this would in principle do the same thing as the above mentioned circuit.
Try both and see how you go?
Hope this helps.
Yours Sincerely
Mark Abbott
Mark Abbott
Re: Headroom-or lack thereof..........
The circuit I built is 95% like John Kelly Brown's drawing. I like your idea of the variable split load on the stage 3 plate. I've heard that it doesn't affect the tone, just the gain structure. I may try a 5 postition switch there and then I can leave it there if I like it.
Thanks for the suggestions.
D
Thanks for the suggestions.
D
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tubedogsmith
- Posts: 597
- Joined: Mon Jan 17, 2005 11:52 pm
Re: Headroom-or lack thereof..........
What are you using for a volume pot?
Re: Headroom-or lack thereof..........
Whoops! In my previous post I ment 2nd stage instead of 3rd stage.
I'm using a 1meg audio taper pot, (Alpha or Mouser?)
I'm using a 1meg audio taper pot, (Alpha or Mouser?)