hi there! i just got given a Neumann M7 capsule (the one that plugs into the top of a mic such as the blue bottle). On the box it states that the capsule is for the CM7151 microphone - I was wondering if anyone has any suggestions for a more up-to date circuit I could use that uses tubes/transformers that are still easily obtainable? Any help wld be most gratefully recieved! Cheers!