Orban OPTIMOD-FM 8500S Operating Manual page 166

3-2
OPERATION
•
Input meters show the peak input level applied to the 8500S's analog or digital
inputs with reference to 0 = digital full-scale. If the input meter's red segment
lights up, you are overdriving the 8500S's analog to digital converter, which is a
very common cause of audible distortion.
•
Gate LED indicates gate activity, lighting when the input audio falls below the
threshold set by the AGC gate threshold control (via the Full Modify screen's
control). When this happens, the AGC's recovery time is slowed to
AGC G
ATE
prevent noise rush-up during low-level passages.
There is also an independent gate for the multiband compressor (3-band
and 5-band). You can only see its action from the Optimod PC Remote
software.
•
Gain Reduction meters normally show the gain reduction in the multi-band
compressor. Full-scale is 25 dB gain reduction.
When the Five-Band structure is operating, all the meters indicate gain reduc-
tion.
When the Two-Band structure is operating, the Band 1 and 2 meters indicate
gain reduction in the Master and Bass bands, the Band 3 meter indicates the lar-
ger of the actions of the left and right HF enhancers, and the Band 4 and 5 me-
ters indicate left and right HF Limiter gain reductions.
•
Composite meter shows the output level of the stereo encoder before
the composite output attenuators. The meter's reading is calibrated in
percent modulation.
•
Multiplex Power Gain Reduction meter indicates the action of the ITU412
Multiplex Power controller. It shows how much the MPX Power Controller has
reduced the clipper drive, thereby reducing the average power in the processed
audio. It will show no gain reduction unless the MPX Power Controller is turned
on.
•
Multiplex Power Level meter indicates multiplex power according to the ITU-R
BS.412 standard. Its calibration will be correct if the Optimod's output level con-
trol was adjusted using the tone method (see step 11.D) and subsequent steps
starting on page 2-19) and the transmission path following the Optimod has no
overshoot. See ITU-R Multiplex Power Controller starting on page 3-72 for a full
discussion of the Multiplex Power Gain Reduction and Level meters.
•
Gate LED indicates gate activity, lighting when the input audio falls below the
threshold set by the multiband gate threshold control (with the Full Modify
screen's 2B G control). When this happens, the multiband compressor's recov-
ATE
ery time slows drastically to prevent noise rush-up during low-level passages.
•
AGC meter shows the gain reduction of the slow two-band AGC processing that
precedes the multi-band compressor. Full-scale is 25 dB gain reduction. You can
ORBAN MODEL 8500S