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

OPERATION NOTES
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 than 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 to 4 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.
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