DigiTech VCS1 Owner's Manual page 14

Creative effects are possible with sidechain gating as well. Sustained sounds from a synthesizer can
be layered onto real drums without MIDI using the technique described in the preceding paragraph.
Run a synth tone such as noise, or a pure sine wave into the line input of the VCS-1 and out to a
mixer channel. Into the sidechain return, run a signal from a snare or bass drum track. This "trigger"
track must be well isolated to work properly so use the other channel of the VCS-1 to gate any
unwanted sounds.
"Ducking" or "keyed attenuation" are useful combination effects of a compressor and sidechain.
This is used often in hotels where the level of background music is reduced when an announcer
speaks into a microphone. It is also used in the studio to reduce the level of sustained effects such as
reverb or echo when the instrument is played and raise the effect level when the instrument stops
sounding. This serves to accentuate the effect but not wash out the instrument. The audio signal you
want to duck (such as the background music or reverb) is connected to the VCS-1 Line input and the
audio signal you want to override the input signal is connected to the Sidechain Return. The amount
of attenuation is controlled by the Ratio and Threshold controls, but varying the amount of level
received from the Sidechain Return works also.
Understanding VU Meter and Clip LED Readings
The functions of the VU Meter and Clip LED combine to give an excellent indication of average
and peak levels. The ballistics of the VU Meter are optimized to show the subjective loudness of the
audio material. Quick peaks have little effect on meter movement because to our ears, constant mod-
erate levels will appear subjectively louder than lower levels with higher transient peaks.
Because the VCS-1 is unity gain device, the VU meter is mostly used in gain reduction mode to
show the amount of compression rather than input or output levels. If you plan to use the VU meter
to monitor input or output levels, it must be understood that actual levels generally exceed what is
shown on the meter. This is especially true with transient-rich percussive tracks. The meter level
may show -20 VU but the actual level may be +10 dBu or higher.
Should you need to add gain to a weak input signal or increase level lost to compression, you may
need to use the VU meters to ensure you are not adding too much. You can increase the Tube Gain
or Output level controls to increase meter movement until the Clip LED lights. The Clip LED lights
at +18 dBu, 3 dB before the VCS-1 circuitry clips. While this is generally the amount of headroom
professional gear has, it may be excessive for semi-pro or amateur gear. In this case, you should
check that the input level meter in the next device in the chain is not reporting a clip.
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