Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Willabe on September 15, 2016, 09:55:09 pm
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I saw this years ago in Vacuum Tube Valley, issue 16, P's 4 - 9.
It's to eliminate the back to back electrolytic current return flow from the B+ supply node for the power tube and the power tubes K bypass cap.
I'm going to set it up on my bread board with the Champ I still have on it.
Do you think it can also be done with a triode preamp gain stage too?
Has anyone tried this before?
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Why would you even want to do that? The voltage rating on the bypass cap will have to be the same as the voltage rating on the B+ filter caps. Sounds like a waste to me.
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Why would you even want to do that?
For the sound difference. They explain their reasoning in the VTV article.
The voltage rating on the bypass cap will have to be the same as the voltage rating on the B+ filter caps.
Radial e-caps that voltage/uF value are under $2.00.
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This implies that the signal source is or can-be also B+ referenced.
If the previous stage is transformer coupled, this may be trivial.
If the previous stage is resistance coupled, this is real-real awkward.
I think you will get a lot more buzz.
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If you give it a try, I would like to know what you discover
Ciao
Franco
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Well I tried it on my bread board today with a Champ set up on it.
I used a new 47uF @450v Panasonic E-cap. (The article said 10uF to 100uF, I might try it again with a 100uF just to make sure.)
Meh, it was actually a little dirtier/muddier not cleaner at all. It was easy to hear the difference, I had it wired up on 1P2T Carling switch. (Standard Fender ground switch.)
It was worth a try. :dontknow:
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I saw this years ago in Vacuum Tube Valley, issue 16, P's 4 - 9.
It's to eliminate the back to back electrolytic current return flow from the B+ supply node for the power tube and the power tubes K bypass cap. ...
A couple of points have been overlooked:
- Originally proposed for Single-Ended Triode output stage amplifier.
- For Hi-Fi.
- Proposed by folks who feels electrolytic caps degrade amplifier performance, so two 'lytics in series is "doubly-bad".
- "Ultrapath" cap was proposed to be an oil-filled cap ($$$).
The relatively high plate resistance of the pentode may have changed your observed results, as does using an e'lytic where the authors were trying to eliminate e'lytic caps. Of course, perfect reproduction of the preamp signal may not be desirable in a guitar amp (we can talk examples from tweed Fenders where "technically inferior" results in better performance for electric guitar sounds).