Capacitors voltage rating

krm76

Member
2012-12-10 5:00 pm
Hi,

I'd like to change some of the capacitors from my chinese valve phono stage and althought I have found most of them, there some that do not match the voltage rating.

My question is if the capacitors need to work close to their voltage rating level in order to be efficient.

Thank you
 

31697B

Disabled Account
2012-05-19 12:53 am
If they are not electrolytics, then the answere is No.
But for long life use a film capacitor that is rated as high voltage or higher than the power supply (B+).

If they are electrolytics then the answere is sometimes you get a little better performance running them closer to caps max Dc rating.

Thx-RNMarsh
 

jcx

Member
2003-02-17 7:38 pm
..
but for safety, long life caps should be derated - operated with actual in circuit V at some fraction of their rated V

used to be that for Al electrolytics recommended factor was ~ 80%

actual circuit conditions also need allowance for AC line variations, transformer regulation - easily another 20-30%

depending on topology, a coupling cap could see full supply V if a heater dies, and amp load goes to zero too - so would have to apply all factors together
 

31697B

Disabled Account
2012-05-19 12:53 am
When Nelson mentioned the elna silk caps i tested several -- for coupling where you have to use an electrolytic the higher voltage caps had lower THD


This has been generally true of all make and brands of electrolytics and was discussed a few decades ago.

Another maybe forgotten parameter which indirectly affects the performance is the higher temp rated electrolytics (105C) are better still over same value/voltage.

Good to keep putting this info out every so aften. Or it gets lost and has to get rediscovered/invented.

Thx-RNmarsh
 
The DC voltage PLUS the transient spikes will sometimes exceed the Voltage rating of the capacitor.
It is these excursions that exceed rating that use up the life of the capacitor.

If the cap can never have a transient spike applied to it then it can be run at 100% of voltage rating.

If a cap is regularly exposed to transient spikes then expect it to have a shorter life no matter what DC voltage is applied during normal running.

My opinion based on what I read.