Specifications

33
Microphone Amplifier
has input transformers. The filter in the standard version
of the CMC 6 has a corner frequency of 20 Hz and a
slope of 12 dB/octave, while in the standard version of
the CMC 5 this filter has a corner frequency of 30 Hz
and a slope of 6 dB/octave (but please see the follow-
ing section on variant versions).
Variant Amplifier Versions
Special versions of the CMC 5 and / or CMC 6 are
available with different gain (amplification factor) or
extended frequency range. Either type of amplifier can
be specially ordered, or retrofitted at the factory, to
have a different (e.g. lower) low-frequency limit from
the standard version (see, for example, the ”linear”
version listed below).
Please note:
The two amplifiers in a stereo pair of microphones
should be of the same type.
On request, we can select ”matched pairs” of cap-
sules with equal sensitivity and frequency response for
critical applications, at slight additional cost.
CMC ”linear”
CMC microphone amplifiers normally have a gradual
rolloff in response below 30 Hz (20 Hz in the CMC 6)
to guard against infrasonic disturbances from various
sources such as air movement and vibration. However,
when using pressure (omnidirectional) trans ducers,
particularly with digital recording, it can be desirable to
pick up frequencies below 20 Hz without attenuation.
The special technology of the CMC microphone ampli-
fiers makes this possible; on request we can deliver
microphone amplifiers with response that is flat to as
low as 3 Hz.
Caution must be advised with respect to infrasonics,
however. Since pressure transducers can pick up very
low frequencies, ventilation systems in large spaces
(churches, concert halls) or traffic rumble can create a
problem. With pressure gradient transducers the risk is
even greater. They are far less sensitive to very low fre-
quency sound, but respond much more strongly to
low-frequency mechanical stimuli such as air currents
and solid-borne noise. Such signals may be below the
audible range of frequencies, but they can overload
electronic circuitry and produce severe distortion, par-
ticularly in transformer-coupled circuitry.
CMC 6 Uxt – the 40 kHz Version
This version is indicated by the letters ”xt” engraved
on the microphone's output socket as shown at right.
It extends the frequency response of the axially
addressed Colette capsules beyond 40 kHz.
The frequency response curves on these pages were
obtained with standard CMC amplifiers such as the
CMC 6. Curves obtained with the CMC 6xt (special
Frequency response curve MK 4 + CMC 6 xt
50 100 200 500 1k 2k 5k
20k 50kHz
10k
+10
0dB
-10
-20
COLETTE
modular