Polystyrene Caps vs Silver Mica?

[ajeffcote]

Hi, can anyone give me a little input on these? I've read that the PS caps sound smoother than the SM's, but still let the "shimmer" ring through. Any thoughts are most appreciated.

[Jazz P Bass]

Now it really does depend on the circuit/ application does it not.
Both capacitors have plusses & minuses.
Again, it depends on the application.
PS: Is "shimmer" an engineering term?

[Tom Phillips]

I have used polystyrene capacitors in circuits where I needed their negative temperature co-efficient to compensate for the positive temperature co-efficient of other parts in the same circuit. I have not used them in guitar amps and have never heard of the better sound claims you mentioned. Sounds like more snake oil to me. Who is making that claim?

[tedmich]

I like PS caps for small value films in spite of their often anemic leads and the danger of melting if I solder drunk, mica's are fine tech but more expensive and can have some of the same issues as ceramic, ie microphonics in high gain circuits. I just use N0G ceramics where mica's are indicated, like in Op amp decoupling.

[ajeffcote]

JP, the amp is an Allen Accomplice. I have very limited experience in electronics, built the Allen kit and re-built a Deluxe Reverb. No formal electrical education. My interpretation of the SM cap's sound would include something like "clear shimmering highs that can get ice-picky".
So, no, I guess "shimmer" is not an engineering term, unless one is a "shimmer" engineer.
Tom, the idea was planted at the Watt's Tube Audio site, and I read the same on TubeDepot's site. Does sound like snake oil. But people say the same about CC resistors, which I like and can hear a difference when compared to metal film and to a lesser extent carbon film types.
Anyway, I am re-building my Accomplice. I have had a low volume distortion/ghost note/? problem almost since I finished it. Had Sprague Atom caps that I think may have been the cause. So while it's apart I decided to re-build it using an assortment of F&T E-Caps, CC, CF and MF resistors, PS series OD, the yellow Jupiter and Cornell Dubilier film and foil caps, a different ground scheme(from a star ground) and whatever else comes to mind. The polystyrene caps also. Of course, with all the other changes final perceptions of the PS caps will be somewhat cluttered. But if they accomplish what I hope for I will post the results.
And I'm sure I will be asking for help from you guys.

[ajeffcote]

I like PS caps for small value films in spite of their often anemic leads and the danger of melting if I solder drunk, mica's are fine tech but more expensive and can have some of the same issues as ceramic, ie microphonics in high gain circuits. I just use N0G ceramics where mica's are indicated, like in Op amp decoupling.

The leads are quite flimsy. I can see how malted beverages could play a part in their early demise.
Have you noticed any sonic differences?

[tedmich]

I just use PP or mPP film and PS for lower values and have not noticed any obvious sonic differences; they are both low distortion, stable caps. I think some of the love of mica's is the SILVER mica part (oh! Bling!) but I do not have golden ears

there is a lot of voodoo down the "special cap road" which I try to avoid as I am po' and CHEAP

[ajeffcote]

I think you are right about the love of silver micas. I guess my tastes have evolved and I now need those gold foil-in-olive oil caps that are as we speak secretly being cryo treated.

[Gtr_tech]

I like the polystyrenes for bypass use on guitar vol pots. They work well in amps too in non-coupling applications (bypass, high freq bleed to gnd, etc.).

[Gtr_tech]

I think you are right about the love of silver micas. I guess my tastes have evolved and I now need those gold foil-in-olive oil caps that are as we speak secretly being cryo treated.

Heh...for that Italian tone eh? I wouldn't go the cryo route. I'd bake them for 40 mins at 375....

[ajeffcote]

Oh man, I forgot about this thread. But I just fired up my Allen Accomplice after the tinkering I have been doing. I put a PS in the tone stack and one for the second stage coupler. Also on the reverb tone pot. I do hear a little difference, but I think I prefer the Mica caps. I'll give it a couple of days before I open it up again. More tweaking. The Micas are going back in. Gonna try different output tube couplers also. The amo is still a little too boomy. I have an idea of how I want it to sound. Now I just have to get it to that place.
One plus for the polystyrene caps is their size. They will fit in tight spots.

[deci belle]

I like what Gtr-tech said about polystyrene on vol pot bypasses. I heard they are supposed to be audiophile-ish, but when I compared them to SMs when using them across PI plate resistors, the SMs were preferable to my ears (very subtly quieter+smoother sounding).