©2015 - Compiled by Robert Anselmi
for full manual
Make Noise Optomix & modDemix
Low Pass Gate & VCA Mixer Modules
The
Optomix
is a two channel Low Pass Gate, providing simultaneous voltage control over amplitude and frequency content of a signal. It is in essence, a
Voltage Controlled Filter Amplifier (VCFA) that has an extremely organic response to control signals. Additionally, the Optomix offers a summing stage complete
with an auxiliary input, allowing for the chaining of multiple units to create larger mixes (this also works well in combination with the modDemix. The
modDemix
features 2 identical direct-coupled balanced modulator circuits that may be used together or independently for Ring Modulation, VCA, Mixer, Signal Multiplica
-
tion, Voltage Controlled Polarization, Attenuation and more.
CHANNEL 1 SIGNAL IN:
DC signal input, capable of ac
-
cepting audio or CV. Range: Up
to 18Vpp.
CHANNEL 1 SIGNAL IN:
DC signal input, capable of accepting audio or CV.
CARRIER CV IN:
Deter
-
mines amplitude & phase of
Channel 1 Signal In.
STRENGTH ATTENUA-
TOR:
Unipolar attenuator
for Carrier CV In: Normalized
to +5V so that with nothing
patched to the Carrier CV
In, the attenuator acts as a
manual Carrier attenuator.
Range: 0V-5V.
DAMP CV IN:
DC CV input for the cor
-
responding channel’s damping param-
eter. Normalized to +8V. Range: 0V-8V.
CONTROL CV IN:
DC, highly sensitive CV
input for the corresponding channel’s vactrol
gate. Normalized to +8V. Range: 0V-8V.
DAMP ATTENUATOR:
Uni
-
polar attenuator for the Damp
CV Input. With nothing patched
to the Damp CV In, the attenu
-
ator acts as a manual damping
attenuator.
CONTROL ATTENUATOR:
Unipolar
attenuator for the Control Input. With nothing
patched to the Control CV In, the attenuator
acts as a manual control attenuator.
CHANNEL 1 SIGNAL OUT:
DC output of the signal applied to the input,
as pro-cessed by the LPG. Range: 10Vpp (depending on settings and source
material).
Channel 1 vs Chan-
nel 2:
both channels are
identical, except as noted
here. If you don’t see a
description of the Chan-
nel 2 parameter, refer to
the Channel 1 descrip-
tions for information.
Channel 1 vs Channel 2:
Similar to the Optomix, both
modDemix channels are identical,
except as noted here. If you don’t
see a description of the Channel 2
parameter, refer to the Channel 1
descriptions for information.
STRIKE INPUT:
Gate input for striking or plucking the vactrol. Expects 8V
Gate. It acts as a fast attack envelope with slow amplitude response affecting
the LPG. Combined with the Damp parameter, Strike allows for the program
-
ming of percussive sounds (sharp Attack w/ CV Decay), without the need for a
separate envelope generator.
Further Information
Optomix:
As a VCA, Optomix has a moderate attack response and slow decay response, meaning that it turns on quickly, but takes a while to shut off,
yielding a smooth natural sounding decay to almost any sound processed dynamically. The sound is often described as “ringing,” and while the circuit is
not technically ringing, that does describe many of the sounds possible when using the Optomix to process complex signals generated through FM or Ring
Modulation. As a VCF it is a mild, nonresonant Low Pass circuit acting to gently reveal (or hide) the sharper edges of a sound. This characteristic also adds
to the “ringing” effect. As the amplitude of the sound decays, there is a simultaneous loss in high frequency content that is similar to the natural loss of en
-
ergy in idio and membranophonic instruments. The Optomix, being a vactrol-based circuit, will never have the speed or tight tolerances found in many other
VCA and VCF circuits. If you seek to program extremely short sounds, clicks, pops and ticks, then the Optomix is not the best choice. What the Optomix
does offer is extremely low noise and low distortion and a smooth, natural sounding circuit.
modDemix:
The modDemix consist of 2 identical direct coupled circuits that may be used together or independently to process audio or control signals
by means of amplitude modulation and the many derivatives of AM such as double/ single-sideband, voltage controlled amplification/ attenuation, voltage
controlled polarization or multiplication and of course, ring modulation. The modDemix is a specialized amplitude modulation circuit that could be thought of
as a “Thru-Zero VCA,” meaning that in addition to the AM, when the Carrier signal (called Carrier CV) changes phase, the resulting signal’s phase will flip as
well. What makes the modDemix unique when compared to other balanced modulators, is that because it is Direct Coupled, it will perform wonderfully both
as anaudio rate modulator to implement Ring-Modulation, and as a control rate modulator to implement multiplication of CV. Also, the circuit used will, with
ease, turn off around 0V at the Carrier CV In; a characteristic that makes the circuit behave very well as a VCA. Both circuits feed a “Sum” stage, allowing
the module to be used as a voltage controlled mixer. The Strength attenuators are “combo knobs,” acting as unipolar panel controls. In practice, this means
the summing stage can also be a mixer with amplitudes set by the 2 Strength controls. An Aux In allows for chaining multiple modDemix (or Optomix) units
to create larger mixes. The attenuator allows for setting the Strength or Level of the incoming signal. When performing ring modulation, adjusting Strength
will alter the integrity of the resulting modulated and/or demodulated signal, thus affecting the timbre as well as the amplitude. In most other uses, Strength is
directly related to the amplitude of the resultant signal.
AUXILIARY IN:
DC signal
input to the Sum circuit, to al
-
low for the chaining of multiple
Optomix and modDemix units to
create larger mixes. Capable of
accepting audio or CV signals.
Range: up to 10Vpp (depending
on settings and source material).
AUXILIARY IN:
DC signal
input to the Sum circuit, to al
-
low for the chaining of multiple
modDemix and Optomix
units to create larger mixes.
Capable of accepting audio
or CV signals. Range: up to
10Vpp (depending on settings
and source material).
CHANNEL 2 SIGNAL IN:
DC signal input, capable of ac
-
cepting audio or CV. Normalized
to Channel 1 Signal Out, for
series processing. Range: up to
10Vpp (depending on settings
and source material).
CHANNEL 2 SIGNAL IN:
DC signal input, capable of accepting audio or CV.
Normalized to Channel 1 Signal Out, for series processing.
CHANNEL 1 LEDs:
LED indication of signal activity in four quadrants. Verti
-
cal position represents amplitude and phase of input signal; horizontal position
represents amplitude and phase of Carrier CV In signal.
CHANNEL 1 SIGNAL OUT:
Output of the processed signal from Channel 1.
SUM OUT:
The sum or mix
of all signals processed by the
Optomix (Channel 1 & 2 In, and
Aux In) is sent out here. Range:
10Vpp (depending on settings
and source material).
SUM OUT:
The sum or mix of all signals processed by the modDemix (Channel
1 & 2 In, and Aux In) is sent out here.
