4ms Shaped Dual EnvVCA, Руководство пользователя

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This means that if the Follow jack suddenly jumps up (for example, when a gate is applied), the
envelope will try to follow that jump by rising, but it can only rise as fast as the controls allow it. The rate
of change, or slew, is limited, thus we call the Follow circuit a “slew limiter”.
Note that the term “envelope voltage” in Rule 1 refers to the internal envelope voltage, which is the
signal on the Lin 5V jack. The is the envelope before the Shape controls, Level and Offset knobs, and
ENV jack output driver. This envelope has a maximum of 5V and minimum of 0V, which is why the
Follow jack only responds to voltages from 0V to 5V. The ENV jack’s output driver doubles the internal
voltage, so a 5V internal envelope corresponds to approximately 10V envelope on the ENV output jack
when Level is set to maximum and Offset is centered.
Armed with these two basic rules, we can now showcase some advanced uses for the Follow jack in
the following sections.
Audio Filter
The Follow jack can be used as an exotic audio low-pass filter by taking advantage of its slew-limiting
properties. First, the audio signal must be shifted up such that it’s within the range of 0V to 5V. Typically
a level shifter can be used to add the required DC offset. You may also need to attenuate the audio so
that it’s no more than 5V. Any signal outside this range will be clipped, resulting in harsh distortion.
Patch this adjusted audio into the Follow jack. Patch the ENV output jack to your mixer/amp. Turn
Level all the way up and turn Offset to center. To start, set the Rise / Fall sliders and switches to the
fastest positions. Send a steady positive voltage into the Time CV jack and turn the Rise/Fall CV knobs
all the way down.
At this point you should be hearing an audio signal that is similar to the original signal.
Now make the rise and fall times slower by adjusting the Rise/Fall CV knobs and sliders, or by
adjusting the CV patched into the Time CV jack. As you do this, you should hear the audio get more
muffled, as the slew becomes limited and higher frequencies can no longer pass.
To make more exotic sounds, try only adjusting the rise or the fall time. This will let the rising portions
and falling portions of higher frequencies pass differently, creating some unique harmonics.
Waveshaper
By limiting the slew, wave shapes with sharper transitions can be altered to have smoother transitions.
For instance, feeding a square wave into the Follow jack will produce a trapezoidal or triangular wave
on the ENV output jack. Adjust the Rise/Fall sliders and switches to get a maximum amplitude output
waveform while still performing the desired amount of waveshaping. These controls will need to be re-
adjusted if the frequency of the waveform changes. You may be able to use the Time CV jack and
Rise/Fall CV knobs to track the frequency and create a somewhat consistent variable-frequency wave
shaper. You can also change the curve of a wave using the Shape slider.
Portamento/Glide
The output of a CV/Gate keyboard or a sequencer is often a step-wave, meaning that the voltage jumps
(or “steps”) from one voltage to the next as the notes are played. When this is patched into a VCO, the
result is a sequence of notes that jump from one pitch to the next. Adding in some slew causes the
notes to “glide” from one pitch to the next. This effect is known as portamento or glissando. The
Shaped Dual EnvVCA can perform this effect by patching the step-wave into the Follow jack and
taking the output from the ENV output jack. The amount of glide effect is controlled by the rise and fall
times. If you’re patched into the pitch input of a VCO, you can adjust the tuning with the Level and
Offset knobs. Keep in mind that the Shaped Dual EnvVCA is not designed to be a precision
portamento effect, so tuning will not be accurate over a wide range.
Sidechaining (Envelope Following)
The Follow jack can be used to create an envelope that follows an audio signal’s envelope. This
envelope can be inverted and used to control a VCA, creating a “ducking” effect on another sound. This
technique is called sidechaining.
A common application is to use a kick drum to duck another sound source, for example, a background
drone. Patch an audio source that’s making a kick drum sound into the Follow jack of Channel B. Make
sure Cycle is off. Start with the switches at Med , the Rise slider all the way down, and the Fall slider in
the center. If you turn Level up, the ENV B jack will be outputting an envelope that roughly follows the
kick drum’s envelope. Adjusting Rise and Fall will control the attack and release of the envelope, that
is, how quickly the envelope responds to the attack and release of the kick drum.
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