The Microtech Gefell UM 57 is a vintage studio tube microphone produced as an original reissue of the historic Gefell UM 57. It is built around the original M7 capsule, featuring in house manufactured, gold plated PVC diaphragms. This capsule design is closely linked to early studio recording practices and continues to be used in professional environments that require consistent microphone performance.
The microphone employs a tube based preamplifier using the EF 86 pentode, operated in triode mode. Each tube is carefully selected for low noise and stable operation. This circuit supports a wide transmission range from 20 Hz to 20,000 Hz, making the UM 57 suitable for a broad variety of studio recording tasks. Sensitivity is rated at 17 mV/Pa at 1 kHz, with a nominal impedance of 200 ohms.
The UM 57 operates in conjunction with the UN 57 external power supply. This unit delivers the required operating voltages and allows remote switching between omnidirectional, cardioid, and figure eight polar patterns. The power supply supports mains voltages of 115 V or 230 V at both 50 Hz and 60 Hz. It is equipped with a power switch, a polar pattern selector, a 7 pin connector for the microphone, and a 3 pin XLR connector for the output signal.
Noise performance is specified at 16 dB(A) according to DIN EN 60268-4 and 24 dB according to CCIR 468-4. The signal to noise ratio is rated at 78 dB A weighted and 70 dB CCIR rated, referenced to 1 Pa at 1 kHz. The maximum sound pressure level is 120 dB at 0.5 percent total harmonic distortion, resulting in a dynamic range of 104 dB.
In terms of electrical operation, the microphone runs at an operating voltage of 120 V, with an anode current of 1 mA. The heater voltage is 5.8 V with a heater current of 200 mA. The EF 86 tube used in the circuit is selected for low noise and low susceptibility to ringing. Connection between the microphone and power supply is made via a 7 pin cable, while the audio output is provided on a standard XLR connector.
The UM 57 microphone and UN 57 power supply are supplied in a dedicated case with a fine hammered finish. The package also includes the C tube connecting cable and the EA 92 elastic microphone suspension. The microphone itself weighs 430 g and measures 197 mm in length with a diameter of 42 mm.