| CMS
Module 1047 is a functional circuit package designed for use
in Euro-Rack electronic music synthesizers. In honor of the
late inventor, Dennis Colin, we have recently renamed it "The
Colin Multimode Filter".
The CMS Module 1047 is a functional
circuit package designed for use in Euro-Rack electronic music
synthesizers. This unique and complex circuit utilizes 3 discrete
ARP / Wilson current mirror VCAs to produce it's distinctive
and highly resonant sound. The new improved front panel is
now made of a special material that has the image impregnated
into the aluminum surface. It will not fade over time or wear
off from finger action.
The unit consists of a highly
resonant filter with voltage controlled frequency and resonance,
and provides high pass, band pass, low-pass, and notch outputs.
The filter is capable of providing a wide variety of formant
shaping and tonal modulation. The band pass response is that
of a natural acoustic resonator, and is most useful in synthesizing
instrumental timbres. In addition, the high degree of stable
resonance and frequency tracking accuracy attainable enables
the filter to perform precise, narrowband spectrum analysis
of audio signals.
The center frequency of the
band pass output is the cutoff frequency of the high pass
and low pass outputs, and is referred to as "Fc".
Fc may be set by the frequency knob over the range of 16 Hz
to 16 KHz. Control signals applied to any Fc input will change
the center frequency from the knob setting by 1 octave per
volt when the knob above the control input is at maximum.
Control signals from the individual inputs are summed with
the Fc knob controls, and may be positive, negative, or audio.
With the RESONANCE (Q) knob
at minimum:
The band-pass output has a
gain of 0.5 at Fc and attenuates 6 db per octave above and
below Fc.
The high pass output has unity
gain from Fc to 20 KHz and attenuates 12 db per octave below
Fc.
The low pass output has unity
gain from DC to Fc and attenuates 12 db per octave above Fc.
The notch output has flat response
everywhere except for a deep (40 db) notch at a frequency
determined by the NOTCH FREQ knob. With this knob set to 12
O'clock, the notch occurs at Fc. NOTE: The notch output is
effective only at low Q.
As the RESONANCE (Q) knob is
turned up, a resonant peak occurs at Fc in all four outputs,
except in the notch output when the notch frequency is at
Fc. The gain at this peak is numerically equal to the "Q",
and the 3 db bandwidth of this peak is equal to Fc/Q. Thus,
as Q is varied from 0 to 10, the bandwidth varies from 2 Fc
(2 octaves) to Fc/512 (1/32 of a semitone).
Operational tip: When using
high resonance, the audio input control may have to be turned
down to prevent overload. Try backing off on the input signal
when using resonance. The unit has a good signal to noise
ratio, so you don't have to run the input on "10"
all the time, except when there is no resonance. The more
you add resonance, the more you should back off the input
signal. You will get a better sounding resonance also.
The Q may be controlled by external
signals. The Q control characteristic is exponential; that
is, each volt applied to a "Q" input doubles the
Q when the input knob is at maximum.
The dedicated v/oct input is
calibrated to a 1V per octave scale.
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