Cathode Bypass capacitor voltage rating

[rafafredd]

I am building a tube amp that has only a few volts bias (like 1.5v DC or so) on the cathodes, bypassed with a big lytic cap.

Can I use a capacitor with very low voltage rating (like 4v or 6.3v) for bypass, or should I consider also the AC voltage across it?

I ask because I see all the time people using 25v and 35v for cathode Bypass, but I though that going lower wouldn't really be a Problem. Is it right?

On the other hand, on the output Stage, if the cathode cap wasn't there, it would develope up to 10-15v AC Peak to Peak on the cathodes before clipping. So, should this AC voltage be considered for the voltage rating when the cathode cap is in place?

I though I could just ignore it, as the voltage isn't really there (or is it???) when the cathode is bypassed, and consider only the very low bias voltage, and then using 6.3v Bypass capacitor, that are smaller and cheaper than 25v or 35v in the same capacitance value.

Any thoughts???

 

[rafafredd]

Sorry... Double posted it in the Drawing Board.

Tried to remove it, though, and can't do it. The software won't let me, for some reason.

I am not sure anyway if it's a DrawingBoard or a Lab question.

So, please, moderador, remove one of the threads according to your judgement.

Thanks!