TL Audio A3 - Manual (Page 15)

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extent as the Soft knee is more gradual around the Threshold point.
Unlike some compressors, the Threshold control on TLA units including the
Ebony A3 starts at a ‘zero point’ value in the counter-clockwise position, and
decreases to a ‘minus’ value as you rotate the control clockwise. The reason for this is
as you turn the Threshold control on the Ebony A3 clockwise (i.e. towards the
negative region) then the degree of compression will increase. We think this is logical,
whereas the common method of turning the control ‘down’ to achieve more
compression is not - but beware, some other compressors may work in the opposite
direction!
Ratio .
Once the input signal has crossed the threshold, the degree of gain reduction is
determined by the Ratio control. The Ratio control is calibrated in decibels and is
simply the change in output level that results from a given change in input level. An
uncompressed signal will have a 1:1 compression ratio - every 1dB change in input
level results in the same 1dB change in output level. A compression ratio of 1:3, for
instance, means that a 3dB change in input level will only give a 1dB change in output
level. For more severe compression, simply turn up the Ratio control.
The Ebony A3 offers a wide range of ratios from 1:1.5 (gentle compression) through
to 1:30 (limiting). Limiting effectively clamps the input signal at the threshold level no
matter how much the signal is increased: this can be useful when trying to ensure that
the signal doesn’t exceed a certain level - for instance to prevent a digital recorder
distorting through overload.
Attack and Release.
The Attack time sets how quickly the compression is applied once the threshold has
been exceeded, and the Release time sets how quickly the compression is released
(and the signal returns to normal) once the signal drops back below the threshold. The
Ebony A3 Attack and Release controls each allow a choice of 2 switched positions
either ‘Slow’ or ‘Fast’.
The speed of the Attack and Release should in general be able to work with the tempo
of the signal. For example if the signal is a snare drum, by monitoring the gain
reduction it is possible to set the Release to allow the compression to fully recover (i.e.
the gain reduction needle will settle back to 0dB) before the next snare beat. This
prevents the second snare beat being reduced in level in comparison to the first. One
side-effect of having an incorrect release setting is distortion on low frequency signals,
which can particularly occur when using a fast release setting on bass heavy signals -
the compressor is forced in and out of compression during one cycle of the waveform,
and distortion results. The Ebony A3 has a built-in “Hold” facility which delays the
onset of release for approximately 10mS after the input signal falls below the
threshold. A slow release time should be used if distortion is still experienced.