uk flagEnglish

NL vlagDutch


RFT MV 691 / M 70



Thirty years ago the Berlin Wall was opened and the Iron Curtain crumbled. These days small segments of the Wall can be found not only in Germany, but around the globe.
Microphone-wise there is also a heritage from the People's Democratic Republic, spread among professional recording studio's of the world.

The most wide spread of these DDR siblings is the studio microphone system SMS 70: a fet pre-amplifier to be used in combination with a number of different screw-on capsules: the M 70 & M 94 cardioids, the M 93 omni, the M 73 shotgun, the UM 71 large diaphragm and the covetted UM 70 multi pattern large diaphragm capsule (the legendary M 7, as in the Neumann U 47).

Between 1960 and 1980, three pre-amplifiers were made: the MV 690/ 691 & 692. The MV 691 remains as most popular; the 690 is scarce, and for the 692 , with low cut and - 10 dB switches, sometimes less reliable components were used.

The system was powered by an external power supply, which could feed two pre amps. Today many of these MV 691s are converted to standard phantom power and can be directly fed from most modern mixing desks.

The microphones were labeled RFT (Radio und Fernmeld Technik) but were produced by the East German branch of the famous Neumann company and sound wise they are compared to their Western brethern, KM 84 (cardioid) and KM 83 (omni).

The DDR version is larger and somewhat noisier than the KM 84 but they cost a lot less on the second hand market and there are some modifications to make them as quiet as their nephews, that have a legendary sound. The MV 691 with M 70 or M 94 work wonderful on acoustic instruments.

Predecessors from West (KM 54) and East (M 582/ M62) were small tube models, made in a time when there was still some communication between the factories. The later transistor models were further developed from these.

The complete history of (East) Neumann Gefell, now Microtech Gefell, can be found here: Microtech Gefell history since 1928. The MV series were continued after 1989 and are still serviced on request.

In 1988 Neumann (West) decided to launch their own modular series: The KM 100 pre-amp, with KM 40, KM 50 directional and KM 30 omni capsules.

These and many more types feature in my book Witnesses of Words.. More information about that can be found at

wow cover

RFT MV 691/M70
Merkel with RFT mic

Top: RFT MV 691 with M 70 on marble RFT stand & M 73 shotgun capsule

Middle: DDR politician Lothar de Maziere & young Angela Merkel

Below: 1975 description of the SMS 70 system and frequency plots of Microtech Gefell MV 962 versions with M70 & M 94


RFT M 73 capsule
M 70 frequencies
M 94 frequencies