M 221

Common name: Schoeps M 221

Production Status: Discontinued / Vintage

The M 221 is a small diaphragm vacuum tube microphone amplifier based around a Telefunken AC701 vacuum tube with interchangeable capsule produced between 1953 and 1985 in several variants: M 221, M 221 A M 221 B , M 221 H, CMMT 30, plus Telefunken, Siemens and EAG versions. The AC701 uses a feedback circuit to stabilise the non-linear distortion factors of the amplifier circuit. The 1956 M 221 B version has a different thread for capsule mounting, similar to later Schoeps microphones but current capsules are not compatible because of different polarisation voltages. The threads of the M 221 are different from those of the M 221 A, Telefunken ELA M 155 and French Broadcasting (RTF), CMMT 30 and from those of the M 221 B and the corresponding capsules require 120 V polarisation. Capsules with 120 V polarisation included the M 934 a switchable between omnidirectional and cardioid, M 939a omnidirectional for diffuse-field pickup, the M 939b omnidirectional for near-field pickup and the front ringed M 934 cardioid. M 221 B capsules with newer thread and requiring 60 V polarisation included the 934b switchable between cardioid and omnidirectional, MK 22 and MK 23 omnidirectional, MK 24 cardioid and MK 241 hyper-cardioid, MK 28 figure of eight and the side-address multi-pattern (omnidirectional, cardioid, figure of eight) MK 26. The standard version has a 200 Ohm output impedance. A 50 Ohm version with 6 dB less output and indicated by a red dot is available on request. Also available is an M 221 H version with high immunity to radio frequency interference. The M 221 was badged and sold by Telefunken as the ELA M155/1 omnidirectional, ELA M 155/2 omnidirectional and ELA M155/3 cardioid. It was also badged and sold by EAG.

Electrical Characteristics

Frequency Response
Hz - kHz
Output Sensitivity
mV/Pa
Max SPL
Max SPL, THD:
Self Noise (CCIR)
dB
Self Noise (DIN/IEC)
dB-A
Output Impedance
200Ω
Recommended Load
Powering
Supply Current
mA
Alternative Powering

Switchable Options

Pad
Filter/EQ

Physical Characteristics

Connector
Tuchel 3470 (7-pin)
Connector notes
Tuchel T 3470 on M221 BH
Available Colours
Nickel. Black.
Weight
83 g
Length
140 mm
Min diameter width
Max diameter
20 mm
Depth

Accessories

Included
N20B Power supply. Microphone case.
Optional