Waves Abbey Road EMI TG12345 User Manual - page 5
Waves / Abbey Road TG12345
User Guide
5
The TG12345 has a unique spread control, which is an MS matrix-type process. This control can
decrease and increase the level of the sides without touching the level of the mid.
Waves has also added several features not in the original console: (1) a high-pass filter on the
sidechain that helps preserve low frequencies during compression, (2) a mix control that gives you
control over the balance of the compressed and non-compressed signals, just as in parallel
compression, (3) drive, (4) noise.
1.4 Concepts and Terminology
VCA
A VCA, or voltage-controlled amplifier, is an amplifier that varies its gain depending on a control
voltage, such that the input voltage determines the output voltage. The TG12345 includes a VCA-
based compressor. However, whereas most VCA-based compressors only attenuate the signal
(voltage in > voltage out), the TG12345’s compressor also amplifies it (upwards compression) at
very low levels (below 1.5 V).
In the graph above, the Y axis represents the amount of amplification or attenuation in dB, while the
X axis represents the input to the VCA in volts (0 dBfs = 13.875 V). As the graph shows, signals
below 1.5 V are boosted while signals above 1.5 V are attenuated. The VCA input is triggered by
the feedback signal through the sidechain.