Thanks everyone for your suggestions. Something came to mind tonight. I think that the AKG capsules polarize at 62V, but I believe that the KM84 circuit is 48V.Will the AKG capsules work with the Neumann voltages, and if so, will this affect the sound? Perhaps the pcb for this project would have to have a voltage converter for the proper AKG polarization voltage.
You might look at using 0.1uf C0G capacitors in parallel. Mouser carries both 50V and 100V parts in the 1206 form factor. If you're willing to do a little SMD, you should have no trouble fitting 10 in parallel on the back of the PCB.IIRC, they're around a buck each, so at $10 for a 1.0uf cap you're still well in under the price of most fancy foil caps.
Look for Evox Rifa MMK, believe me you want it.so it don't have to be 1uF. Look from 470nF-1uF range.
Maybe sounds a little crazy, but they're guaranteed to fit and should be the best dialectric that will fit, about as good as polyprop or polystyrene and much better than polyester, at least quantitatively (see the CB articles).Then again, I haven't compared polyester and polypropylene head-to-head in mic coupling applications. Interested to know what you heard with polypropylene that made you dislike it. (My fav DIY mic has a tantalum coupling cap... so lower distortion, lower dissipation factor, etc, is obviously not always better, though in a semi-scienctific blind test I did once--preamp output coupling cap--I found a polyester box cap to be subjectively musically inferior to polypropylene).
Ok thanks, if I use a metallized cap here, then the MMK seems to be the way to go.Would a great foil cap be massive overkill? I actually think that a 100V RelCap TFT could fit inside with a small cutout in the pcb.I'm not an EE, and I was wondering how that cap value affects the frequency response. It's not wired up as a filter, is it?