CMT 20 (1964) - The World's First Phantom-Powered Microphone
CMT 200 (1964)
CMT 100 (1965)


The CMT 20, launched in 1964, was a milestone for the company: the first
transistorized phantom-powered condenser microphone in the world. It was
powered by 8.5 Volts with the plus pole grounded. Low-noise FETs are used
today as impedance converters in the input stages of nearly every condenser
microphone on the market, but such components were not available at that time.
The only way to keep the noise low was to use a radio-frequency circuit in
which the capsule modulated an RF carrier.

The CMT 20 had a transformerless, balanced output stage which used coupling
condensers. Later the same year an improved version, the CMT 200, was
released; it was also phantom-powered (this time at 9-12 Volts, in view of its
becoming a studio standard) and its output was also transformerless, but this
time direct-coupled. A similar output circuit topology is still found in
Schoeps microphones to this day.

In 1965 the CMT 200 series was modified slightly to become the CMT 100 series,
which used 12-Volt parallel ("T") rather than phantom powering.

The CMT 20 / CMT 200 / CMT 100 was delivered as omni (CMT 22 / CMT 222 / CMT 122 and CMT 23), universal cardioid (CMT 24 / CMT 224 / CMT 124), close speech cardioid (CMT 240 / CMT 2240), switchable omni/cardioid (CMT 25 / CMT 225 / CMT 125) and switchable omni/cardioid/figure-eight (CMT 26 / CMT 226 / CMT 126) with single diaphragm design. The capsules' specifications were close to the data of the current capsules MK 2S, MK3, MK 4, MK 40, MK 5, MK 6 (see: www.schoeps.de)

They normally used a Tuchel T3262 plug but you could also order a RF-proof plug or an XLR plug.

The EST 20 mounting accessory allowed the user to combine two CMT microphones in a coincident stereo arrangement.

The CMT 20 / CMT 200 / CMT 100 microphone is not serviced by SCHOEPS any more.

RF technology of 1964: the internal design of the CMT 20


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