Manual-5
adx
NOISE REDUCTION
The
adx
circuit is an automatic downward expander,
acting like a compressor running in reverse, making the quiet
parts quieter. This is valuable in reducing system background
noise. The MC 22 has an automatic expander set at a Ratio of
2:1 that is only active when the input level drops below -55
dBu. The
adx
LED illuminates when the downward expander
is active. See Figure 3 to the right.
LINKING IN STEREO
When using the MC 22 as a true stereo processor, with left
signal in Channel 1 and right signal in Channel 2, it is
recommended to turn the LINK switch ON to prevent large
balance and image shifts. While LINKed, both channels
attenuate by exactly the same amount when either Compres-
sor works, maintaining correct stereo imaging. For both
Channel detectors to contribute, set the controls to similar
positions in both Channels when LINKed. The
adx
circuits
are not linked.
Figure 3.
adx preset to 2:1 Ratio, Threshold at -55 dBu.
Vertical axis = output level, horizontal axis = input level.
MC 22 APPLICATIONS
TWO CHANNEL COMPRESSOR/LIMITER
In this case, the audio path on channel 1 is completely
separate from channel 2, allowing you to use it as a stereo
unit
or
for doing two completely different processes to two
completely different signals. For stereo use, the front panel
LINK switch allows you to link Channels. When either
Channel’s Threshold is reached, both channels compress
equally, preserving the stereo image. The higher of the two
Ratio settings will affect both Channels when the first
Threshold is reached, and the lesser Ratio setting affects both
Channels when the second Threshold is reached.
GUITAR & BASS
Where does the unit go in the signal chain? Well, that
depends on how you want it to function. If it’s a comp/limiter
for the input signal, it would go after the guitar (if the guitar
has a line-level output) and before the preamp. If it’s to
function as a limiter to protect the speakers in the rig, it would
go after the preamp and before the power amp. Another
method is to insert the unit in the effect loop of the preamp.
This allows the bass signal to be affected by the pre-amp first,
then the comp/limiter, and then sent to the power amp. This
can be desirable with tube pre-amps.
RECORDING
Use it on bass guitar, piano, drums, or vocals—as an
effect or to tailor dynamic range for a particular recording
medium. Patch it between line-level devices or in your mixer
inserts or “loops”. The MC 22 gives you more control and a
less tortured sound, and keeps instruments sounding “up-
front.” In digital recording, compress an extremely wide
dynamic range into a signal that won’t go into digital over-
load, i.e. severe clipping. This is really valuable during a live
digital recording when you just don’t know how loud it may
get, and digital distortion can ruin an otherwise good take. Set
both the THRESHOLD and RATIO relatively high, just
enough to limit the peaks.
Of special interest are instruments which have large level
differences in their tonal ranges. String pops on a bass are one
example, shrill peaks on a flute are yet another. The higher
tones require more breath and can seem much louder than
lower pitches. Another good application would be a drum mix
or vocal submix.
LONG DISTANCE LINE DRIVER
The MC 22 is excellent as a line level amp for driving
long lines (from the mixer to the stage for instance). With the
COMPRESSOR switch in the BYPASS position, the INPUT
LEVEL control and the output amplifiers remain in the
circuit. This provides a very low distortion, low noise line
driver. Balanced XLR connections are recommended for the
long run from the MC 22's outputs. A balanced piece of
equipment (equalizer or amplifier) must be used at the
receiving end of this long line.
For unbalanced systems, use the ¼" inputs on the MC 22
and use the balanced XLR outputs to run the long distance.
See the SOUND SYSTEM INTERCONNECTION section for
proper cable wiring.