The Neumann CMV-563 microphone body can be used with different capsules including the famous M7 (cardioid) and M8 (figure eight). This unit was getting noisy and swapping the tube did not entirely solve the problem. The two critical capacitors are a polystyrene cap which couples the capsule to the tube, and a film cap connecting the tube to the output transformer. We decided to replace the third cap as well, although it was not original (green chicklet cap in the Before photos). The polystyrene cap requires extra care. A heat sink during soldering prevents damage to the component, then everything in this high impedance area must be carefully cleaned. Any flux or oils from fingers can cause noise. The other two caps were replaced with Wima film caps, increasing the size of the output cap to 1mfd. This was a really tight fit, but worth it. In the end, with a fresh NOS tube (not shown) the mic sounds great and the noise floor is much lower.
Before – cheap replacement cap
Original polystyrene cap
Heatsink on the new polystyrene capacitor
Original output coupling capacitor
Wima 1.0uf output coupling capacitor
