SCHOEPS
CMC MICROPHONE AMPLIFIER

• balanced, low-impedance output
• for use also with long cables (several hundred meters)
• can be used with active accessories (for miniaturization and special applications)

The CMC microphone amplifiers are not amplifiers in the classical sense. Their chief task is to convert the extremely high-impedance signal from the capsule to a very low-impedance one suitable for transmission through a microphone cable. The versions differ in their powering, connectors, output levels and surface finishes, but they all feature a Class-A output stage which has neither coupling condensers nor an output transformer. This leads to low source impedance (insensitivity to electrical interference), low distortion, and light weight.

CMC +5 dB (Formerly marked with a blue dot)
The sensitivity of a microphone using this type of microphone amplifier is 5 dB higher. This has little effect on its signal-to-noise ratio, but the maximum sound pressure level the microphone can then accept is reduced by 5 dB. The risk of overloading the input of the following device when high sound pressure levels are encountered is also increased.

CMC Linear (Formerly marked with a long dash)
In order to guard against infrasonic disturbances coming from various sources, such as air movement and vibration, the CMC microphone amplifiers have a gradual roll-off below 30 Hz with the exception of the CMC 6 (20 Hz). However, the use of pressure (omnidirectional and hemispherical boundary-layer) transducers, especially in conjunction with digital recording, allows frequencies as low as 16 Hz to be recorded. The special technology of the CMC microphone amplifier makes this possible. Upon request we can deliver microphone amplifiers having a flat response to as low as 3 Hz.

Here, caution must be advised with respect to sensitivity to infrasonics. Since pressure transducers can pick up very low frequencies, ventilation systems in large rooms such as churches and concert halls can create a problem. Pressure-gradient transducers, on the other hand, have much less acoustic sensitivity to these very low frequencies, but are much more sensitive to vibration and to air currents. These can produce very high infrasonic signal levels, especially outdoors in wind.

Although such signals are below the audible range, they can overload electronic circuitry and produce severe distortion.

© 1997-2012 Posthorn Recordings