• 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.

Overdriven Capacitor?

dsavitsk said:
I dropped some Russian PIO caps into a working linestage as parafeed caps, and I seem to be overdriving them. Everything else I have tried in the circuit is fine, but these sound like the bass is clipping. I have used them elsewhere without noticing anything out of the ordinary -- can this actually happen?

I guess anything is possible,-- Have you checked these caps for any leakage or other faults that may be upsetting bias etc...?

Another thought, Are they actually the capacity they say they are-Within tolerance...?

If you can have a check with a 'Scope and sig-gen, maybe you can see whats happening

Personally I am not a fan of 'PIO' caps no matter what make....

Weird, You shouldnt have any issues-thats why I'm thinking there may be something wrong with them-, Although I'm not a fan of these type caps, I have used them and not noticed any weirdness....;)
What's the difference, exactly?

To me, overdriven suggests the circuit was run to beyond its maximum design ratings. A voice coil on a woofer may bottom out when overdriven. An amplifier may clip when overdriven. I'm not sure how the concept applies to a capacitor.

If you over-volt an electrolytic capacitor, an arc will occur between the plates (foils). This usually results in fire, explosion, and capacitor guts spewing out all over the place.

In this case, we might be arguing over semantics.
Gary P said:
The first thing I would check the capacitors for is leakage. If a parafeed cap has any DC leakage it could cause the transformer to saturate on bass passages.

I'll check that as it seems like the most logical posibility. The odd part is that the circuit is similar to Dave Davenport's differential parafeed, so the actual DC on the cap is minimal.