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OPERATION ORBAN Model 8400
background sounds and cause the AGC or multiband compressor to gate, effectively
freezing gain to prevent noise breathing.
There are two independent gating circuits in the 8400. The first affects the AGC and the
second affects the multiband compressor. Each has its own threshold control.
The multiband compressor gate causes the gain reduction in bands 2 and 3 of the multi-
band compressor to move quickly to the average gain reduction occurring in those bands
when the gate first turns on. This prevents obvious midrange coloration under gated con-
ditions, because bands 2 and 3 have the same gain.
The gate also independently freezes the gain of the two highest frequency bands (forcing
the gain of the highest frequency band to be identical to its lower neighbor), and inde-
pendently sets the gain of the lowest frequency band according to the setting of the
DJ
Bass
boost control (in the Equalization screen). Thus, without introducing obvious col-
oration, the gating smoothly preserves the average overall frequency response “tilt” of the
multiband compressor, broadly maintaining the “automatic equalization” curve it gener-
ates for a given piece of program material.
Note: If the Multiband Gate Thresh (Gate Threshold) control is turned Off,
the
DJ Bass control (in the Equalization screen) is disabled.
AGC Bass Coupling control sets the balance provided in the AGC between bass and the
rest of the frequency spectrum.
The AGC processes audio in a master band for all audio above approximately 200 Hz,
and a bass band for audio below approximately 200 Hz. The
AGC Bass Coupling control
determines how closely the on-air balance of material below 200 Hz matches that of the
program material above 200 Hz.
Settings toward 100% (wideband) make the output sound most like the input. Because
setting the
AGC Bass Coupling control at 100% will sometimes cause bass loss, the most
accurate frequency balance will often be obtained with this control between 70% and
90%. The optimal setting depends on the amount of gain reduction applied and on the
AGC release time. Usually, you will adjust the
AGC Bass Coupling control until the Mas-
ter AGC and Bass AGC Gain Reduction meters track as closely as possible unless you
want the AGC to provide some gentle automatic re-equalization of the input material.
With the
Master AGC Release control set to 2 dB/second, setting the AGC Bass Cou-
pling
control toward 0% (independent) will produce a sound that is very open, natural,
and non-fatiguing, even with large amounts of gain reduction. Such settings will provide
a bass boost on some program material that lacks bass.
With fast release times, settings of the
AGC Bass Coupling toward 100% (wideband) do
not sound good. Instead, set the
AGC Bass Coupling control toward 0% (independent).
This combination of fast release and independent operation of the bands provides the
maximum loudness and density on small radios achievable by the Five-Band structure.
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