Help choosing coupling caps

Atmasphere,

Thanks for the write up. Just for the record the Mundorfs are not paper in oil unless I read their homepage incorrectly.

I stand corrected! I have to assume that the paper and oil parts that I saw in their catalog a while back are no longer made.

I assumed from the size of the parts (they are used in the crossover of my speakers) that paper and oil was the technology.

So there would be no electrical leakage issue with the polypropylene parts.

Construction of SIO is somewhat ambiguous, as Mundorf mentions both polyprop and metalized paper construction:

"Our state-of-the-art metallised Polypropylen foils make it possible to maintain extremely exacting production tolerances that cannot be achieved with traditional oil/paper capacitor designs. This is also the first time that the benefits of oil-impregnated capacitor design have been successfully combined with the well-known long-term stability of metallised paper and internal series wiring for induction-free performance."

I believe the Silver/Gold version is dry, which may account for its temp rating to 85C, as compared to 65C for the oil versions. 65C could be problematic in a hot chassis.

After a bit of humming and hawing i'm going to try out the k40 PIO replacing the coupling caps in my tube amps.
These have great potential.... we shall soon find out

Thanks to everyone that posted ..your input is very much appreciated

Quick update
I used the mundorfs in my cdp and I really like the sound now hoping to get a similar performance with the Russian Caps in my Amps
IMO Russian caps in combination with Teflons is a very good mix