Film capacitors for decoupling

[rotation]

Hi!

On schematic for preamp (EF83-ECC88) i'm making at the moment are two pairs of 10u and 0.1u (both film, non-polar) decoupling caps, connected from B+ (310V) to the ground.


I'm wondering if i can parallel 10u cap with 250V versions which are easy to get.
I know i could use lytic instead, but i want this preamp to be exactly like original so i will use film caps for decoupling.

Can anyone explain me why are film caps better for this application?

[kmtang]

Try it out and judge by yourself.

Johnny

[SY]

A 250V cap across a 310V rail is NOT a good idea! Use a 400V or higher rating.

The advantage of film caps for decoupling is their superior high frequency performance. The frequency at which they start to look inductive is orders of magnitude higher than an electrolytic.

[Eli Duttman]

SY is correct. If sourcing a film part of suitable value is difficult, use a 'lytic, and bypass it with a film part, whose value is 10% of the 'lytic. Bypassing 'lytics with film parts significantly reduces ESR and ESL.

[rotation]

Originally posted by kmtang
Try it out and judge by yourself.

Johnny

Originally posted by SY

I wil try film vs lytic and SS vs tube regulated PSU.


A 250V cap across a 310V rail is NOT a good idea! Use a 400V or higher rating.

The advantage of film caps for decoupling is their superior high frequency performance. The frequency at which they start to look inductive is orders of magnitude higher than an electrolytic.

Ok, so i really can't cut corners here..

Thanks!