OPTIMOD SURROUND PROCESSOR OPERATION
3-31
threshold. At LESS-MORE = 10, the processor’s gain below threshold has increased to
9 dB.
Instead of adjusting L
ESS-MORE, you can adjust the FINAL LIMIT DRIVE control (which
what L
ESS-MORE actually does). Do not set the FINAL LIMIT DRIVE control below “0”
with this preset; doing so will compromise system headroom.
Adjusting the LESS-MORE or FINAL LIMIT DRIVE controls is equivalent to si-
multaneously decreasing the threshold and increasing the make-up gain
in a protection limiter having threshold and output make-up gain con-
trols.
PASS-THROUGH: This is the only factory preset that invokes the Pass-Through struc-
ture (see Pass-Through on page 3-22). It usually edited to set the desired pass-
through gain and the result is then saved as a User Preset.
PROTECT:
This is a two-band preset designed to produce no gain reduction unless it
encounters unusually high input levels caused by operator error. It uses the 2B com-
pressor to control excessive levels, so it is more forgiving than the L
OOK-AHEAD and
P
ASS-THROUGH presets, which offer only peak limiting.
SOFT KNEE 5B; SOFT KNEE 2B: These presets are “zeroed-out” starting points for
mastering applications, particularly where soft knee compression is desired. These
presets need to be manually tweaked to complement the program material being
processed. See Using the 8685 for Production and Mastering starting on page 3-73.
These
presets are phase-linear. They set all equalization flat and turn off the AGC.
The multiband compressor (two-band or 5-band) is set to supply a very soft-knee
compression characteristic with approximately 5-10 dB of gain reduction. The ratio
for a given compressor starts out at 1:1 and ends up at
∞:1 when the input level is 20
dB above threshold.
Mastering engineers will certainly want to adjust the compression thresholds and
band coupling to complement the program material. The ratio and knee controls
are adjustable separately for each band’s compressor. For example, one might want
to use a low ratio and soft knee in bands 1-4 while using a higher ratio and/or
harder knee in band 5 (for de-essing).
The 8685’s powerful equalization section is, of course, also available. Additionally,
these presets set the look-ahead limiter drive control conservatively, which ensures
highest quality. However, the 8685’s look-ahead limiter can be driven quite hard
Preset Names Normal Less-More
AGC+FLAT LIMITER 5.0
LOOK-AHEAD LIMITER 1.0
PASS-THROUGH 5.0
PROTECT 1.0
SOFT KNEE 2B 5.0
Table 3-2: Pass-Through, Protection and AGC Presets
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