Cathode Bypass Cap Question

[gregsk777]

Hi,

I was wonder if a 25uf/25v cathode bypass cap can be replaced with a 22uf/450v cap? Does the 450v make a difference? Is it a bad idea?

I'm asking because I may have to replace some other electrolytic caps and many caps are rated for 450v, 500v and 600v.

Thanks, Greg

[Bruce / Mission Amps]

Hi,

I was wonder if a 25uf/25v cathode bypass cap can be replaced with a 22uf/450v cap? Does the 450v make a difference? Is it a bad idea?

I'm asking because I may have to replace some other electrolytic caps and many caps are rated for 450v, 500v and 600v.

Thanks, Greg

Just do it... there will be some who'll say a high voltage cap run at low voltages will be bad for the cap but the truth is that the cap will be run at such a low voltage that it won't probably make any more difference then if it is connected to nothing sitting on your shelf at zero volts....or in the amp

[gregsk777]

Hi Bruce thanks for the info. I will give it a try.

I was also actually thinking about experimenting a bit and trying a 10uf or 16uf cap because my Dual Showman sounds real boomy at higher volumes. The only 10uf or 16uf caps I can find are rated at 100v or way above.

Thanks, Greg

[defaced]

Have fun, 25v caps till your heart's content:
Aluminum Electrolytic Capacitors - Leaded

and if you don't mind radial caps,
Aluminum Electrolytic Capacitors - Leaded

[Wilder Amplification]

Just do it... there will be some who'll say a high voltage cap run at low voltages will be bad for the cap but the truth is that the cap will be run at such a low voltage that it won't probably make any more difference then if it is connected to nothing sitting on your shelf at zero volts....or in the amp

But...but..but...if you run a high voltage cap, you won't be able to push it into cap distortion and it won't sound good. jk

[Hardtailed]

High-voltage parts are bigger and costlier. They work, but the added bulkiness is completely unnecessary.

[Hardtailed]

Hi Bruce thanks for the info. I will give it a try.

I was also actually thinking about experimenting a bit and trying a 10uf or 16uf cap because my Dual Showman sounds real boomy at higher volumes. The only 10uf or 16uf caps I can find are rated at 100v or way above.

Thanks, Greg

From a 25uF to a 16uF is not much difference. It still gives you full gain way down under a guitar's range.
You may want to try something as low as 1-2uF (depending the resistor's value).

Also, you'll get a bigger effect by making the coupling cap after the first stage smaller. The AC30 Top Boost channel uses a tiny 500p there! Marshalls are usually 0.022uF while some Fender are as big as 0.1uF.

Going to something like 0.01uF or even 0.0047uF work wonders for some people (that's still way bigger than the Top Boost's 0.0005uF!)

[Ronsonic]

It'll work, but why waste a $5 part where a $0.25 part will do fine. Oh, and will fit better.

As was mentioned you have to go well down in value to make a difference.

[mooreamps]

Hi,

I was wonder if a 25uf/25v cathode bypass cap can be replaced with a 22uf/450v cap? Does the 450v make a difference? Is it a bad idea?

I'm asking because I may have to replace some other electrolytic caps and many caps are rated for 450v, 500v and 600v.

Thanks, Greg

The forward voltage drop across the cathode resistor is about 1 1/2 volts. I would never do it because I would never use a 450 V cap in that location ; not that I use any cap in that location.


Secondly ; WITF is "you won't be able to push it into cap distortion and it won't sound good". Don't you people have any clue how this stuff works?


-g

[Wilder Amplification]

Secondly ; WITF is "you won't be able to push it into cap distortion and it won't sound good".

It's a new thing called a "joke"...hence the grinning smiley and the "jk" abbreviation after the fact.

Don't you people have any clue how this stuff works?

-g

This coming from someone who couldn't figure out how a stacked BR power supply worked via looking at the schematic.

[Hardtailed]

Secondly ; WITF is "you won't be able to push it into cap distortion and it won't sound good". Don't you people have any clue how this stuff works?

He did say j/k (just kidding)

I believe he is making fun of all the myths surrounding "mojo" in tube amplifiers.
Underspec'ed caps don't distort, they blow

[jrfrond]

Besides the added cost, you'd be hard-pressed to find any sonic difference between a 22, 25 or 10uF cap. The corner frequencies for all three of these values is down in the "mud zone" anyway. So if you have something even close in value, it will work perfectly.