Manley STEREO VARIABLE MU LIMITER / COMPRESSOR - 1994 - 3/2004 - Manual (Page 10)

OPERATION NOTES
10
The "MANLEY STEREO VARIABLE MU LIMITER - COMPRESSOR" is designed for multiple purposes. The unit
can be used stereo or as 2 individual channels of limiting or compression. It can be used as a balanced line amp
capable of 24 db! of gain and as a pre-amp for low level signals. . With higher input gain settings the unit can be
used to create gentle tube distortion if desired. Modest settings will often enhance the signal in ways difficult to
describe however the range includes "tube warmth", richness and enhanced clarity and magic. We know several
famous producers and engineers that record every possible track, and the mix and then master through these
LIMITER-COMPRESSORS.
The attack and recovery controls are important to understand. The response to transients and percussive sounds
are affected by the attack control. Recovery is the time it takes for the gain to return to normal or zero reduction.
This is called "RELEASE" on some limiters.
We can use a typical mix with dynamic vocals, drums and bass for an example. With this example a fast attack
setting will react to the drums and reduce the overall gain. If the recovery is very fast then the gain will return to
normal quickly. This will have an audible effect of reducing some of the level and attack of the drums in the mix.
As the recovery is set slower the gain changes that the drums cause might be heard as "pumping". Now these gain
changes caused by the drums are pulling down vocals, some bass and causing volume changes. Slower recovery
settings will usually keep the gain changes more inaudible but will also lower the perceived volume. A slow
attack setting will tend to ignore drums and other fast signals but will react to the vocals and bass in our example.
A slow attack might also let a hard kick drum transient distort the next piece of equipment in the chain. We have
set up the unit so that medium settings of both controls provide good gain control and little change in mix values.
LIMITING OR COMPRESSION
Two basic rules of thumb with any compressor or limiter should be reminded.
Typical amounts of gain reduction shown by GR meter should be 2 to 6 dB. The more that the needle
swings the more likely the gain changes will be audible. Listen for objectionable "pumping" with fast settings.
Use your ears to determine optimum settings more than the meters. Some limiters add unpleasant
artifacts with any reasonable looking setting. This limiter may give some magic at unexpected settings. It may help
to use the bypass switch to compare the original input with the processed output to verify that an improvement
is real. Then, because the peaks are reduced, the final output can be adjusted a little louder that the input.
It should be borne in mind that the intended usage, and function therefore, is very different between limiting and
compression. In limiting mode we are seeking to control PEAK overshoots or the 'ceiling' level as inaudibly as
possible, normally in the 2 to4 dB area. By using compression we seek to "fold in" a ratio of, say, 20 or more into
10 dB. Both limiting and compression can produce the effect of increasing the average levels and background
noise - depending on the degree or amount of limiting / compression used. Because dynamic range and peaks
can be reduced, often overall loudness can be increased at the output. This is called GAIN MAKE-UP on some
compressors and is simply the OUTPUT ATTENUATOR with this unit. Limiters often are designed for very fast
attack times only. This assumes that the unit will almost always be used to prevent electronic clipping or overload.
Typically the release with these is slow to prevent audible damage to the mix. With this unit you can adjust the
attack, release and even the overload point in musical ways. Distortion can be creatively used by turning up the
INPUT and turning down the OUTPUTs while using very little or no COMPRESSION. The cleanest settings are
easiest to set up and most recommended for mixes. Set the THRESHOLD near "MIN", set the ATTACK near
"FAST" and adjust the INPUT for 2 to 4 dB of LIMITING, then adjust the OUTPUTS to reach the levels you want
or by comparing with BYPASS. You can fine tune the ATTACK, RECOVERY and THRESHOLD to taste from this.
Compression with this unit begins at the same threshold so to achieve similar amounts of gain reduction you may
have to turn up the INPUT or turn the THRESHOLD to "MIN". We also suggest while in "LINK" that both channels
are set up the same or similar. LINKing with one channel in LIMIT and the other in COMPRESS will not work.
The gain control chain is technically called a feedback circuit. Most modern compressors use a feedfoward circuit
which sounds unmusical to us but for features sake usually offers a Ratio control. Some engineers get great results
from blending the output of the limiter with the "straight" signal. This trick obviously is easier to do on individual
tracks and sounds like a very gentle compressor that lifts quiet sections.