• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Asc Oil Capacitors

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MlinarS

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Joined 2005
Hello,
As stated on the ASC site polypropylene in oil capacitors model X386S-20-10-440 and X386S-50-10-440 are rated 440 VAC. My question is, can they be safely used in PSU at 550 VDC. Does any of you have experiance with this capacitors in this situation? TIA for the input.
 
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Sherman

Member
Joined 2004
MlinarS said:
... polypropylene in oil capacitors model X386S-20-10-440 and X386S-50-10-440 are rated 440 VAC..., can they be safely used in PSU at 550 VDC....
Click to expand...


Hi,
I just built a PS with a B+ of 425VDC using ASC caps rated at 370VAC. Peak voltage before everything stabilizes hits about 510VDC. I'm using valve rectification and voltage goes slowly from 0 to 510-520VDC then drops pretty quickly back to 425.

The supplier I purchased the caps from indicated an ASC cap rated at 370VAC could be used in DC circuits up to about 600VDC. I don't think that 550VDC would stress a 440VAC cap.
 
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Sherman

Member
Joined 2004
MlinarS said:
...I read somwhere that VDC=VAC x 1.41, but I wasn't realy sure.
Some people say that this capacitors don't sound so good at first but they improve over time...
Click to expand...

Since rectifying AC (using SS rectifiers) generally results in DC voltage of about 1.41 x the AC voltage that is probably a good rule of thumb for using with the caps.

Maybe I wasn't listening closely enough at the beginning but I thought the amps sounded just fine with them from the start. I only have about 70 or 80 hours on them now so they are still pretty new. I would think that with new tubes, new trafos etc. it might be hard to pick out the effects of the caps.
 
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