BSS Audio DPR-504 Owner's Manual - Manual (Page 16)

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7.3 Threshold
As previously mentioned in 'getting started', the threshold control is one of the
most important functions on any gate, and is used to set the level at which the
gate open sequence will commence, in relation to the input program signal
level.
With the control fully clockwise, at 'out', the gate will be held closed at all
times, and as the control is rotated counter-clockwise, the threshold point is
progressively reduced until at the -50dBv scale setting, the gate would be
virtually open at all times.
In application the control should be set to give the required degree of low
level signal block. The key level meter is used in conjunction with this
control as it gives precise information relating to this setting.
7.4 Key level meter
The total key side-chain signal level, after any external processing, is
displayed on this meter in two modes: as a bar indicating the average signal
level, and as a single segment indicating the instantaneous peak level. The
peak level always exceeds the average level and is displayed as a moving
dot above the average column, in a simultaneous manner. The dynamics of
this display are optimised for user visibility and accuracy, with the peak dot
exhibiting a damped decay response like a PPM meter.
The meter scale is centred around a 0dB calibration point which corresponds
to the level that initiates the 'gate open' sequence. Rotation of the threshold
control moves the key side-chain signal into this meter 'window', and gives
the operator a real-time picture of the relative position of the signal in relation
to the point at which the gate will trigger.
It is important to remember that this meter is showing the side chain signal,
and not the actual opening and closing of the gate. This is indicated by the
triangular gate open marker LED underneath. The meter scale is designed to
allow sufficient usable range both below and above the gate open point.
In application when the program signal is present, the meter will show below
full scale but above the threshold gate opening point. When the program
signal is not present, the meter will show spurious background noise at a level
which is below the 0dB scale point, and therefore not opening the gate. For
Operating Instructions