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Old 12th December 2015
Lives for gear
jjblair's Avatar
Originally Posted by Jamie Mac View Post
to my knowledge:

B and C both have a K49 capsule, AC701k tube (the switch to ac701k was made before the B suffix though) and a higher output transformer.

The C introduced a PCB in the microphone in stead of point to point wiring and self biasing with lower noise.
Jamie, I'm not sure that the early transformer has lower output, but the frequency response is certainly different. Could be wrong about the output, though.

And just to put a finer point on it, some M49b mics came with M7 capsules, but no M49c mics did. And yes, the b has a forced bias cathode, and the c, like all Neumann mics labeled "c", has the self biasing cathode.

Also, it is not uncommon to find pre "c" versions switched to the "c" circuit, with the self biasing cathode.