Restored Telefunken Ela MZ 028/1 (Neumann CMV3A) Bottle Microphone Circa 1935

I am very pleased to offer the first of six 1930's Neumann CMV3 / CMV3A microphones that are being restored by Leo Schaal of Schaal Audio.  This is the Telefunken export version of the CMV3A, and is the same model.  The bayonet top cap is engraved on one side "Georg Neumann & Co. Berlin SO16", and on the other side, "Ela MZ 028/1".

The mic is in superb condition, and has been brought to perfect working order by Leo Schaal.  Electrolytics have been replaced, and the mic's operating voltage has been modified from 90 volts to 180 volts, bringing the mic's frequency range and transient response up to the performance of an M49 or U47.  

I asked Leo to outline the voltage modification, and he explained the following:

The operation voltages has been changed from 90V to 180V, and the anode resistor from 10kOhm to 46kOhm. The tube's anode voltage remains 65V but the load on the tube is now lower, and it can put its output power into the transformer instead of the anode resistor. As such, we benefit from the color of the transformer, and a higher sound level from the tube.  As well, the character of the sound is lighter.
This resistor value has risen over the years in Neumann tube microphones, up to 150kOhm in the U67. However, as the RE084 tube takes a 2,5mA current, the anode resistor value of 46kOhm is the optimal value for this tube and circuit.  The mic sounds older with the 10k resistor, but the original 1930's sound would be too "vintage" for most engineers in terms of modern functionality - the original circuit has a narrower frequency range, and lacklustre SNR.
There is a voltage divider in the mic that produces a 45V polarization voltage from the 90V operation voltage. These resistors have been adapted to the new operation voltage with an additional increase to the polarization voltage providing 78V.  A higher voltage here means more output from the capsule which results in a higher SNR. Typical values for an M7 are 63V (U47) up to 80V (in the CMV563).
The mic sounds fantastic, with great depth and character, and a resilient ability to capture intense source volume and transient attacks musically.

The mic comes with a newly machined connector (I am having a quantity of these machined, please stay tuned), and a Leo Schaal power supply.  It has its original RE084 tube, which tests very well, and is performing perfectly.

Please have a listen to the film below to hear this mic.  It is presently being offered with a prewar Telefunken Ela MZ032/2 capsule (cardioid M7), which is what you hear in the sample.  The capsule sounds great, and has its original membrane.