101 uses for the MOTM-700 (comparator, noise gate)
1999-05-19 by Dave Bradley
That dang 700 is turning out to get used for all kinds of stuff in my setup,
just as the web site marketing blurb promised. Let's share patches for the
different uses we come up with for this module. In addition to switching 2
signals, here's a couple more to get started:
1. Noise Gate - I'm using the ring modulators as extra VCAs until my system
expands. While they work great for VC of control voltages, they have a
little bleed through that is audible when you use them for audio VCAs. So
patch the 700 as a noise gate. RM out to 700 B IO, nothing to A IO. X IO is
the final audio output. Patch the EG controlling the RM also to CV in.
Adjust the Switch knob to set the threshold that the signal gets gated off.
Variation 1 - use the Out- of the EG, plug RM out into 700 A IO instead.
Variation 2 - to noise gate an audio signal, split the signal and plug into
both CV and B IO, or generate the CV signal from an envelope follower.
2. Comparator - an incredibly useful device. In case you're unfamiliar with
what a comparator does, it compares an input signal voltage to a threshold
voltage you set with a knob, and turns on a gate signal at its output
whenever the input voltage exceeds the threshold. Here's the patch:
You want the output to switch between +5V (or some positive voltage, call it
V+) and 0V. At some point I will bring +5V out onto a jack somewhere in my
system, but for now I can get V+ from the output of an 800, with nothing
plugged into Gate, and sustain voltage turned up.
Plug your input signal to be compared into CV. Your comparator gate signal
will be X IO (substitute C,D,Y for the second router if you use it instead).
If you want a positive logic output gate signal (output at V+ when input
exceeds threshold), plug V+ into B IO. For a negative logic output gate
(output at V+ when input is LESS than threshold), plug V+ into A IO. Leave
the other IO unplugged, since it is normalled to ground.
A couple of comparator uses:
1. Plug Random signal in, get random gate signals out, control the density
with the Switch knob.
2. SYNC LFO START TO NOTE START. Several people have been talking about this
already. Send the gate signal from your MIDI/CV not only to the EG, but to
the 700 CV input. Plug the comparator output into a MOTM-300 sync jack (set
to hard), and tune it very low as an LFO. Plug the output of this LFO into
another MOTM-300s FM input to hear the results. Since the sync input wants
to see a negative edge to trigger, patch the comparator for a negative logic
output gate as I detailed above. Actually in this case, since the gate
signal is already essentially digital (on or off only), we are using the 700
technically as an expensive digital inverter instead of a comparator.
3. Sawtooth (or other waveform) to pulse wave converter. Why do this when
it's already built into the VCO, you ask? I dunno - maybe you want to
generate two pulse waves of different widths from the same VCO.
This comparator would be a lot more powerful if the threshold could be
voltage controlled. Maybe Paul will consider a dedicated Voltage Controlled
Comparator module<g>. This module could also be patched as a front end for
the 700, to give voltage controlled switching threshold capability to the
700.
Enjoy.
Dave Bradley
Principal Software Engineer
Engineering Animation, Inc.
daveb@...
just as the web site marketing blurb promised. Let's share patches for the
different uses we come up with for this module. In addition to switching 2
signals, here's a couple more to get started:
1. Noise Gate - I'm using the ring modulators as extra VCAs until my system
expands. While they work great for VC of control voltages, they have a
little bleed through that is audible when you use them for audio VCAs. So
patch the 700 as a noise gate. RM out to 700 B IO, nothing to A IO. X IO is
the final audio output. Patch the EG controlling the RM also to CV in.
Adjust the Switch knob to set the threshold that the signal gets gated off.
Variation 1 - use the Out- of the EG, plug RM out into 700 A IO instead.
Variation 2 - to noise gate an audio signal, split the signal and plug into
both CV and B IO, or generate the CV signal from an envelope follower.
2. Comparator - an incredibly useful device. In case you're unfamiliar with
what a comparator does, it compares an input signal voltage to a threshold
voltage you set with a knob, and turns on a gate signal at its output
whenever the input voltage exceeds the threshold. Here's the patch:
You want the output to switch between +5V (or some positive voltage, call it
V+) and 0V. At some point I will bring +5V out onto a jack somewhere in my
system, but for now I can get V+ from the output of an 800, with nothing
plugged into Gate, and sustain voltage turned up.
Plug your input signal to be compared into CV. Your comparator gate signal
will be X IO (substitute C,D,Y for the second router if you use it instead).
If you want a positive logic output gate signal (output at V+ when input
exceeds threshold), plug V+ into B IO. For a negative logic output gate
(output at V+ when input is LESS than threshold), plug V+ into A IO. Leave
the other IO unplugged, since it is normalled to ground.
A couple of comparator uses:
1. Plug Random signal in, get random gate signals out, control the density
with the Switch knob.
2. SYNC LFO START TO NOTE START. Several people have been talking about this
already. Send the gate signal from your MIDI/CV not only to the EG, but to
the 700 CV input. Plug the comparator output into a MOTM-300 sync jack (set
to hard), and tune it very low as an LFO. Plug the output of this LFO into
another MOTM-300s FM input to hear the results. Since the sync input wants
to see a negative edge to trigger, patch the comparator for a negative logic
output gate as I detailed above. Actually in this case, since the gate
signal is already essentially digital (on or off only), we are using the 700
technically as an expensive digital inverter instead of a comparator.
3. Sawtooth (or other waveform) to pulse wave converter. Why do this when
it's already built into the VCO, you ask? I dunno - maybe you want to
generate two pulse waves of different widths from the same VCO.
This comparator would be a lot more powerful if the threshold could be
voltage controlled. Maybe Paul will consider a dedicated Voltage Controlled
Comparator module<g>. This module could also be patched as a front end for
the 700, to give voltage controlled switching threshold capability to the
700.
Enjoy.
Dave Bradley
Principal Software Engineer
Engineering Animation, Inc.
daveb@...