02-14-2018, 12:11 PM
Thanks for all the input, it has been educational. I did some searching on ESL and ESR (equivalent series inductance and resistance) for the various types of capacitor, and they are different and must be accounted for in design. As Morzh said, when in doubt, pull up the spec sheet.
But fortunately these parasitics become issues mostly at higher frequencies. My take-away is that for the audio coupling (not DC filtering, not RF) , the parasitic effects are negligible, and thus there is not much impact on the specific choice of cap. For the RF and IF sections, however, one is clearly getting into the regimes where the parasitics become non-negligible, and cap choice is more critical. Clearly the designers back in the 30's understood this well and hence chose mica caps for the small values.
But fortunately these parasitics become issues mostly at higher frequencies. My take-away is that for the audio coupling (not DC filtering, not RF) , the parasitic effects are negligible, and thus there is not much impact on the specific choice of cap. For the RF and IF sections, however, one is clearly getting into the regimes where the parasitics become non-negligible, and cap choice is more critical. Clearly the designers back in the 30's understood this well and hence chose mica caps for the small values.
