F765 500 Series Compressor/Limiter
Operation Procedure: Quick Start
This is the ADR recommended set-up procedure to get the audio levels set up properly.
a). Set the COMPRESSOR 'RATIO' switch to 1:1 (non-operative) and the PEAK LIMIT switch
to ‘ON’ (or 'PRE.EMPH' if your application will require de-essing) and the channel OUTPUT
control turned down.
b). With the SYSTEM bypass switch to ‘OUT’ (i.e. by-passing the F765 vari-loss amp section)
the audio levels to/from the F765 should be established in the usual way as though the F765
were not in the signal path. The audio level feeding the F765 should be peaking to at least
-10dBm, but preferably to 0dBm in order to obtain maximum compression possibilities.
c). Having established the normal level, switch the F765 SYSTEM bypass to ‘IN’ and adjust
the channel INPUT control until the overall amount of gain reduction likely to be required is
indicating on the meter (example: 8dB). At this stage the Peak Limit section is working and
red indicator will be flashing.
d). Turn up the channel OUTPUT attenuator and adjust so that the level is peaking to the
same level as the direct (dry) signal. This is best done under dynamic signal conditions rather
than with a tone if monitoring with VU meters. A relevant direct comparison is now available
between direct and compressed signal at the flick of the SYSTEM ‘IN' / 'OUT’ switch at closely
approximating peak levels.
e). With the COMPRESSOR 'RATIO' control select the ratio required (e.g. 2:1) and adjust the
COMPRESSOR 'THRESHOLD' control until the red LIMIT LED only indicates on peaks above
the amount of compression required (move the threshold down from ‘0’ towards the -20 point
until the red LIMIT LED goes out, then come back one position. The PEAK LIMIT section will
then operate on any further unexpected increase in level. The amount of compression may be
changed by increasing/decreasing the channel INPUT control and adjusting the compressor
threshold to adjust the relationship between compression and peak limiting. Once set-up it will
not be necessary to alter the channel OUTPUT level (as per step ‘d’). It is important to note
that the THRESHOLD control is based off of the
output
of the Vari-Loss Amp (preamp), not
the input level as in modern VCA type compressors.
f). The 'RELEASE' time in the compressor section will be adjusted for effect as well as the
'ATTACK' time.
g). In adjusting the compressor section always reference it to the PEAK LIMIT even if the
PEAK LIMIT is then switched out during operation. This maintains the optimum signal-to-
