ampage Tube Amps / Music Electronics	For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

Coupling and bypass cap tweaks

:

11/30/2005 9:51 AM

Coupling and bypass cap tweaks

I know this ground has been covered many times before, but I never paid too much attention. Sorry.

Anyhow, I'm in the process of a 5E3 build right now. I'm thinking of using a 10uF bypass cap on V1, a 5uF bypass cap on V2a, and .047uf coupling caps to the volume controls and from the phase inverter. Will these changes result in a massive decrease in low end or will they just tame the "flub"? I know I can always swap parts in and out, but I really don't like to do that in a tweed chassis.

I'm also thinking of running 6L6's in this amp from time to time, if that makes a difference.

Thanks all.

Bob Arbogast

11/30/2005 9:21 AM
M. Ron	I've been a fan of your webiste and amp builds over the last couple years. I have not yet experimented with bypass cap values, so will leave that to the other folks. I have replaced all the 0.1 caps with 0.047 caps and it does reduce the low end mud by quite a bit, which makes the amp sound more clear and defined overall.

11/30/2005 9:36 AM

I didn't know, so I decided to experiment.
to 'try to put Vague notions aside.
Still pretty vague...
I started with one first side [that'd be influencing chII Vol I think] at 1/2 of 2k7 [two 2k7's paralleled with a 2u2 bypass cap] and 1k5/2u2 [or was it 4u7?] on the other side, going through and mounted at one side of a switch that 're'couples the two cathodes.
Hitting the switch makes a 'difference' [standard 'small size diff'] and It takes just a bit of bass off.
Overall I'd guesstimate [since I didn't have instant A/B comparisons from stock to mod] there is less bass with the switch in either position compared to stock.
I clipped one of the 2k7's from it's paralleling the other one.

11/30/2005 1:25 PM
Bob Arbogast	Also: 1st filter for 6L6's? Would a 22uF filter be adequate when running 6L6's in a 5E3, or would a 30uF be a better option? Thanks. Bob

11/30/2005 2:25 PM
Todd	What is the maximum capacitance that can be put after a 5Y3 tube rectifier? I do not recall off the top of my head but I thought the RCA manual listed the maximum capacitance for the 5Y3-GT as 20 mfd. While I have never heard of problems with the standard 22 mfd after a 5Y3 tube, I am not sure if 30 mfd would cause problems.

11/30/2005 2:59 PM
thorny	Re: Coupling and bypass cap tweaks Try the coupling caps first in my opinion. Then listen. Then try the other changes - one by one - and listen. This way you will know the effect of each individual change. I like the sound with .047s and some folks like the .022s too. I also like the tone stack mod with it. Thorny

12/1/2005 12:51 PM
s2	What I would do here is similar to what Thorny recommends. I change all the .1uF to .022uF (if the player is primarily into buckers) or .047uF (if he is into singles). I leave the bypass caps alone in this particular amp. Another thing I do pretty often is use .047uF on the dark channel and .022uF on the bright channel.

Page 1 of 2