1965 - The CMT 30 F / CMMT 30 F / CMMT 30 AF for the French market

In France in those days, use of the Sogie connector R7EMM was widespread. So SCHOEPS created special versions of the CMT series with this Sogie connector. Since the French broadcast organization insisted on being able to use the capsules of their older M 221 microphones, the CMT 30 F got the same capsule adaption (with a polarization voltage of 120V instead the 60V of the standard CMT series). These CMT 30 F corresponded to the CMT 3p models, i.e. with reverse polarity of the phantom power (12V with the plus pole grounded). This led to a situation in which, after some number of years, most of these microphones had to be converted to the current 12-Volt standard (negative pole grounded). To distinguish these ugraded models from the standard CMT 30 F, they were engraved CMT 30 FN (for negative pole grounded). If the Sogie connector was replaced by a modern XLR connector the CMT 30 FN became a CMT 30 FNU.

The next step was very revolutionary and led some years later to the Colette series. In order to minimize the visible size of the microphone, a patented construction allowed the user to separate the capsule part from the amplifier part by means of a special cable. The capsule was screwed onto a preamp head which could be screwed onto the amplifier or a cable in between.
The CMMT 30 F-311F series was born, consisting of:

- CMMT 30 F-M311F pre amplifier head with a FET impedance converter
- CMMT 30 F-K311F cable extension (4 leads plus shield)
- CMMT 30 F-V311F microphone amplifier starting with a bipolar transistor

These two parts could be separated by a cable extension (4 leads plus shield).

The next step of evolution reduced the required leads in the cable and offered DC coupling between capsule head and amplifier. The CMMT 30 AF series only needed a two-wire-plus-shield cable. The CMMT 30 AF series consisted of the following components:

- CMMT 30 AF-M pre amplifier head with a FET impedance converter (see picture)
- CMMT 30 AF-K cable extension (2 leads plus shield)
- CMMT 30 AF-V microphone amplifier starting with a bipolar transistor, DC coupled to the FET of the capsule head.

The picture shows the contacts of the CMMT 30 AF series. The contact principle was continued by other manufacturers some years later.

Picture above: Good design is sometimes copied. Here you see a French replica of the CMT 30 F amplifier


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