Neumann M49b Large Diaphragm Tube Microphone serial # 2721. Includes original wooden box and original power supply The M 49 was a multipattern large-diaphragm tube microphone with an important new innovation: the mic’s pickup pattern could be adjusted remotely, by a dial on the power supply.
Another new innovation was that the mic maintained nearly equal sensitivity and output level across patterns — unlike the U-47, for example, which was 5dB hotter in Cardioid than Omni.
Maintaining output level required a change in the polarization voltage circuitry. Whereas the U-47’s circuit would disconnect the capsule’s rear diaphragm in Cardioid mode, in the M 49 both diaphragms were always polarized — the front at a constant 60Vdc, and the rear from 0Vdc to 120Vdc. When set to Cardioid, the rear diaphragm polarization voltage was 0Vdc.
Like its omnidirectional sibling, the M 50, the M 49 was initially released with a Hiller MSC2 tube, soon replaced by the Telefunken AC701 subminiature triode.
The two mics are nearly identical in appearance; the primary distinguishing cosmetic feature is the color of the “jewel” above the Neumann badge. On the M 49, the jewel is red.
Output impedance was wired at 200 Ohms from the factory. The product manual advised that “by changing two links on the output transformer, the amplifiers can be easily changed to 50 Ohms whereby the output voltage falls by 6dB.”
Neumann M49 and M50 capsules. The capsule in the original version of the M 49 was Neumann’s PVC-diaphragm M7. This was subsequently replaced (as in the U47) with the Mylar-diaphragmmed K49. (The K49 was K47 capsule, identical in every respect but the name.)
Tech Notes: AC701 s/n 6204703 all original components on microphone except for capsule. wired for 200ohm EX Lansdowne studios. PSU recapped and overhauled.