The Neumann UM 57
Multi-Pattern Tube Condenser Microphone

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The Neumann/Gefell UM 57 is a large-diaphragm tube condenser microphone manufactured by the Neumann company of Gefell, Germany, currently known as Microtech-Gefell.

The mic used the Gefell company’s famous M7 capsule. This was a dual-diaphragm, center-terminated capsule with a PVC (plastic) diaphragm. It supported three polar patterns via a switch on the power supply: Cardioid, Omni, Figure of 8.

Neumann/Gefell UM57 Schematic: The amplifier circuit is nearly identical to the Neumann/Gefell CMV 563, another tube mic manufactured at the Gefell factory. Both used the EC92 triode.

The UM57’s legacy was celebrated during Microtech Gefell’s 75th anniversary in 2003, with the introduction of the limited-edition UM 75, which was presented as a recreation of the UM57. However, numerous differences existed between these two microphones:

• The UM 75 used an EF86 pentode.
• The EM 75 used an updated circuit, similar to the UM 92.1 S (itself a modern reinterpretation of the UM 57).
• The UM 75 used a transformer from AMI/Tab-Funkenwerk.
• The UM57’s transformer was made by Gefell; the model number is T551.

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Download the specifications for this mic, in German.

English translation of the PDF as best we could:

The UM 57 microphone is a high-quality, universally usable condenser microphone with switchable direc­tional characteristics. Omnidirectional, cardioid and figure-8 polar patterns can be switched on by remote control. Switching is done using a rotary knob on the associated power supply unit. The change in the direc­tional characteristic enables the most favorable adapta­tion to the acoustic recording conditions that are present in each case.

The microphone capsule is a pressure gradient receiver with two gold-plated plastic membranes. The capsule and the microphone amplifier form a unit and guarantee a high degree of operational reliability thanks to the stable mechanical structure. The microphone is con­nected using the microphone connection cable C 57. The length of the cable between the microphone and the power supply unit can be up to 100 m. The power supply unit UN 61 is provided for the power supply. If the microphone is connected to a power amplifier with a 100 mV input, the UN 61 V power supply unit with a built-in transistor amplifier must be used.

Either a tripod in conjunction with the MH 43 micro­phone holder or the TS 58 table stand can be used to attach the microphone.

The mains connection unit UN 61 is used to power the NEUMANN condenser microphone UM 57 from the 220 V AC mains. It is equipped with a rotary switch, with which you can switch between the desired recording choral effects. The operating voltage required for the microphone is stabilized against mains voltage fluctua­tions by a stabilizer tube. The heating voltage is set to the target value of 5.8 V using a rotary control. In the case of cable lengths of more than 100 m between the mains connection unit and the microphone, the rotary control mentioned above must also be adjusted in order to compensate for the voltage drop in the line.

All of the fittings are recessed into the front walls and are therefore protected against damage. On the front there is a mains switch, fine-wire fuse 0.1 A, control lamp and type plate. The Kobelon connections for the mains connection with earthing contact and the two NEUMANN connection sockets are on the back.

Before the microphone is put into operation, it is con­nected to the mains adapter with the microphone connection cable C 57. The C 55 connecting cable is provided for the audio frequency output. Silk junction boxes are identified by information signs.

If the Gerot is connected to the neutral conductor of the AC network using the Schuko plug, a double earthing occurs if the following amplifier is already connected to the neutral conductor. In order to avoid any mains hum coupled into the system, the negative line can be discon­nected from the housing on the mains connection unit by screwing the socket head screw over the earth socket out of the upper threaded hole and screwing it into the lower one. Our transistor amplifier type TV 61 can also be installed in the mains connection device.

Testing and Maintenance

NEUMANN microphones are manufactured with great care and precision. Careful handling guarantees that the devices will continue to function properly. We recom­mend that repairs to NEUMANN microphones be carried out in our workshop, otherwise the guarantee will not be maintained.

The following information is provided on the express con­dition that all work carried out on NEUMANN mi­crophones is carried out at your own risk.

1. All repair work on the microphones should be carried out with great care and cleanliness by competent technicians.

2. It is recommended to obtain replacement tubes EC 92 from us! Commercially available tubes are not always suitable because they have not been tested for low noise and low ringing.

3. It is a good idea to periodically check the power adap­ter for the correct voltages with the mic connected.

4. Capsules can only be properly repaired in our repair department. Any outside intervention is inexpedient.