M 221 Overview - M 221 A - M 221 B - M 221 BH - M 221 F - M 221 Telefunken - The Capsules of the M 221

The SCHOEPS Condenser Microphone M 221 / M 221 A

The M 221 was introduced in 1955. Taking advantage of the TELEFUNKEN AC701k valve, the M 221 was the very first tube microphone on the market with a diameter of only 20 mm. The M 221 A was manufactured in limited quantities for just a few months. Following improvements to the design the M 221 B was introduced. The most obvious difference between the A and B versions was the way the capsule was mechanically adapted to the amplifier body. The M 221 A type has female threads and the B model male threads (the same as the current generation SCHOEPS Colette Series amplifiers but with a different contact plate). As the electrical circuitry is very similar in all types, you may use the new power supply NTM 221 with the included K5 TU cable for all versions.


The SCHOEPS Condenser Microphone M 221 B

Condenser microphones of the M 221 B series are proven small microphones for studios. Their good electroacoustic properties (for these times) ensure that they are capable of a wide range of applications in sound recording for radio, television and music recording. The special characteristic of this model series is the use of a uniform microphone preamplifier the M 221 B, with a wide range of microphone capsules each designed to respond to specific requirements of different types of professional sound recording.

The M 221 microphones are very constant and uniform in their technical
values.The microphone amplifier contains all amplifier elements. An AC701 (AEG-Telefunken) tube is used.

The microphone output impedance is 200 Ohms. On delivery the M 221's output could be soldered to an output impedance of 50 ohms, the output level then being 6 dB lower. The 200 ohm model is characterized by a blue mark at the lower end (plug side) of the casing, the 50 ohm model is characterized by a red point. The microphone amplifier is provided with a 6-pole plug connection (T 3402, Tuchel). The microphones are insensitive to low frequency magnetic fields and to interfering influences of external high frequency fields because of the twin leg output transformer design.

As mentioned above the M 221 B worked with a polarization voltage of 120V but in 1970 the German Siemens company ordered an OEM version with 60V only (the reason is not handed down).
The very last twenty pieces M 221 B were manufactured in 1985.

The RF-proof Design M 221 BH

In very strong RF fields, such as those that occur in the immediate vicinity
of very large transmitting or radar plants, it is recommended that a microphone amplifier M 221 BH be used. As with the standard M 221 B, the optional use of the same microphone capsules is possible. The technical details of both amplifiers are likewise the same however, the RF-proof model is provided with another plug (T 3470, Tuchel) of larger diameter.

The SCHOEPS Condenser Microphone M 221 F

From 1962 on both the M 221 and later the M 221 B have been manufactured as 'F' version, too. The only difference is the Sogie plug of the M 221 F which often causes malfunctions as it tends to go loose during recordings. If possible we recommend to change this plug to the small Tuchel T3402 for which cables are still available. The M 221 F can utilize the new power supply NTM 221 but requires an adapter cable.

The M 221 Made For Telefunken

With identical dimensions and specifications the M 221 was also fabricated for the German manufacturer Telefunken as M155/1 (omni), M155/2 (omni) and M155/3 (cardioid). For decades SCHOEPS and Telefunken associated successfully. SCHOEPS produced a number of microphones for Telefunken and was in no small part the reason why Telefunken microphones are so highly regarded today.


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