Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: spunko on April 19, 2022, 12:11:14 pm
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Hello, basically what the tittle says.
Would it hurt to change the three original 22uf to 27uf/500 on a Hot Rod (or any similar amp)?
I have F&T kits for the amp, but a friend just arrived from USA and gave me a bunch of 500v nichicons (47uf and 27uf) he bought from mouser.
I'm just curious if this, or any amp will work well with those values?
Thank you very much.
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They'll work fine. In the grand scheme of things 22uF to 27uF isn't much of a difference.
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Wow, I just found out F&T was bought by Mersen in 2021. I have been buying F&Ts just fine until now. I find mostly F&T/Mersen caps on some web pages.
I suppose they are the same quality but with new name.
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...change the three original 22uf to 27uf/500 on a Hot Rod (or any similar amp)? ...
A couple of points:
1) the actual capacitance of electrolytic caps is variable between caps of the same uF rating and across frequencies. For filter caps, a 22uF rated cap might measure 20uF or 25uF for the corner frequency that we're concerned about shunting out of the PS rail.
2) 'R' and 'C' are variables in a frequency equation, and you need to change either variable quite a lot in order to make a substantial difference in an expected frequency roll-off point for the R/C filter.
e.g. for f = 1/[2Pi.C.R] where you have a 22uF cap following 4k7 power supply resistor (where 1uF = 1millionth of a Farad):
f = 1/[(44/7) x 0.0000022F x 4,700R] = 15.4Hz
But if you replace the cap with 27uF in the same filter:
f = 1/[(44/7) x 0.0000027F x 4,700R] = 12.5Hz
Either way you won't notice diddly squat in the LF roll-off point in your guitar amp (Bottom E on a Bass guitar in standard tuning is ~41Hz - guitar ~82Hz)
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You have good answers
Yes
You won't hear any sound difference.
I often do this.
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Thank you very much for taking the time to explain.
Thanks the answers, I learn a lot in this forum =)