There are two simple ways to implement gates in the
studio. The easiest is simply buying a Noise Gate from the store. These can be
found in a stand-alone unit, or they can be part of a more complex unit, like a compressor
with noise gate. It's also possible (and probably more flexible) to create gates
with an analog synth (most monosynths or modulars will work).
To build your own noise gate, you need at least a fast VCA
and something to create modulation. Adding more modules will make things easier to
customize. The most simple implementation of a noise gate is silencing the output
when the input level is below a certain threshold. This can be achieved with in
several ways:
Input signal feeds:
VCA Audio in
Envelope Follower In
Envelope Follower Out feeds VCA CV In |
As the input signal gets
louder, the output gets louder as well. Setting the VCAs CV level will allow for
different "threshold" settings. In this case, the VCA gets louder and
softer depending on input level. This will be a very smooth acting gate... it will
always gracefully transition between open and closed, but will not produce a very
pronounced "gating" effect. |
Input signal feeds:
VCA Audio in
Envelope Follower In
Envelope Follower CV Out feeds Comparator Input
Comparator Output feeds Portamento / Glide Input
Portamento/Glide Output feeds VCA CV Input |
This is a more complex
setup. The use of a comparator gives a solid on/off level for the threshold.
Anything below the threshold, and the VCA will be fully closed. A signal above the
threshold will force the VCA open fully. The portamento or glide circuit is used to
smooth the abrupt open to closed transition of the VCA to avoid thumps and other
artifacts, as well as allowing you to preserve some of the natural decay of the input
sound. This is very similar to the design of a traditional "Noise Gate"
that you'd buy at the store. If your portamento has independent "Attack"
and "Decay" settings it performs the best. If you have a "Gate
Output" on your envelope generator, you can omit the Comparator. Feed the Gate
Out directly to the Portamento input. |
Input signal feeds:
VCA Audio in
Envelope Follower In
Envelope Follower Gate Out feeds ADSR Gate In
ADSR Output feeds VCA CV Input |
Here's a fun one to
implement. If you have a Gate Output on your envelope follower, try it. This
allows you to further shape the VCA envelope with an ADSR. If you don't have a gate
output on your envelope follower, the comparator module could be used as shown
in the previous example. |
In all of the above examples, I showed the input signal
creating the envelope for the VCA. It's really fun to use a different signal
instead. Try gating a hi-hat rhythm with your kick or snare feeding the envelope
follower. Or, you can simply use a gate signal from ANY source to control the ADSR
in the third example... the source could be an analog sequencer, a MIDI to CV converter,
an LFO, etc.
