cap sub

[ineedahobby]

what is a suitable audio grade sub for a mica cap? the circuit is a low level amp in a pre amp. polypropylene? polystyrene? teflon?

[nightanole]

What does it do, what size, and what voltage? A mica cap might just be filtering out rf noise and not worth replacing with something better. Or it might not be in the audio path to begin with.

[ineedahobby]

they are in a phono pre amp board in a dynaco pat 5 bifet preamp i am thinking of rebuilding. 2700pf 500v 2% i want to replace them because they are 30 yrs old and from what i've read there are better caps for audio out there these days.

[firechief]

27000 pf is .027 ufd and is probally a frequency setting part as opposed to a bypass cap.
Is this a phono pre amp? If so the value is quite important. Silver mica caps are real good quality parts. I would be tempted to use the same kind. Really we need more information, like schematic, or at pictures of the inside. Please provide the brand and model.

[ineedahobby]

they are in a phono pre amp board in a dynaco pat 5 bifet preamp i am thinking of rebuilding. 2700pf 500v 2% i want to replace them because they are 30 yrs old and from what i've read there are better caps for audio out there these days.

[Conrad Hoffman]

Silver-micas are generally excellent audio caps and lose nothing with age. They're also usually close tolerance. I'd stick with it. If I just couldn't help myself I'd only replace it with polystyrene, polypropylene or Teflon, in that order. I don't have the blind respect for Teflon that some do ;-)

In more detail, silver-mica caps have somewhat more dielectric absorption than you'd expect, given their very low dissipation factor, but it doesn't translate into any specific audio complaint.