565E
6
Setting the Threshold Control
The T
HRESHOLD
control sets the audio signal level where the compressor/expander/limiter begins
working. In the case of the compressor or limiter, the processor begins working once the signal has
exceeded the threshold level. For the expander, it begins working once the signal has fallen below
the threshold level.
For any of the three processors, the T
HRESHOLD
control setting also determines the degree or
amount of gain reduction. Thus, for the compressor, rotating the control counter-clockwise
(towards -40) results in increasing amounts of compression. For the expander, counter-clockwise
rotation raises the level that the signal must exceed to pass through the expander untouched. This
has the effect of shutting off the signal once you reach and then pass the threshold level.
For most compressor applications, moderate amounts of gain reduction are all that is required, 3-9
dB at the most. If you are using the compressor to minimize level changes of a wide range of
program material (automatic level control), then higher amounts of gain reduction are needed. In
typical compressor applications, program material with a very wide dynamic range calls for higher
amounts of gain reduction than program material with less dynamic range.
Note
With higher amounts of gain reduction, slower release times are recommended.
Interpreting the Displays
The 565E has one display per processing section. The three displays associated with the expander,
compressor and limiter indicate a parameter called gain reduction. Simply stated, the gain reduction
indication shows how far the gain or amplification was reduced from unity. Another way of looking
at this is: if the gain reduction display says 10 dB of gain reduction, switching the unit to bypass
will result in a 10 dB increase in the output level.
The output display indicates output level in dBu. For most applications, just make certain that you
never see the CLIP LED illuminate.
Using the Sidechain
The sidechain is a patch point in the control circuit of a dynamic range processor. It provides
access to the part of the circuitry that tells the VCA (voltage controlled amplifier) what to do. The
565Es sidechain is routed through a TRS jack labeled KEY INPUT. This jack is located on the
rear panel, and it provides both a send and return via the same jack. The sidechain connection
affects all three processors in the 565E.
The 565Es sidechain connections are derived from the balanced input stage, and they allow
access to the control circuits input signal. The control signal is derived from, but kept totally
separate from, the audio signal path. This means that the control signal can be processed outside
the 565E without actually processing the signal thats going through the VCA (the audio signal
itself). This presents some very interesting possibilities for changing or improving the operation of
the dynamic range processor.
The most common use of the sidechain is to make the action of the 565Es compressor/limiter/
expander frequency dependent, that is, to make it respond more (or less) to certain frequencies, by
inserting an equalizer in the sidechain path. Because the audio signal and the control signal remain
completely separate (even while the control circuit tells the VCA whether to turn the gain up or
down), you can equalize just the sidechain without changing the EQ in the main audio path.
This allows you to emphasize a frequency portion of the audio program so that this portion
dictates the behavior of the processing (for example, you can boost the appropriate high frequen-
cies to make the compressor behave like a de-esser), or to de-emphasize a frequency portion that is
controlling the audio more than you would wish (for example, with beat-heavy dance music, cutting
the low end can prevent the compressor from pumping and breathing with every kick drum beat).
