Manley STEREO VARIABLE MU LIMITER / COMPRESSOR - 1994 - 3/2004 - Manual (Page 11)

TECHNICAL NOTES
SWITCHING ON
The power switch is located on the right hand corner of the front panel. Flip the switch up to turn on the
Limiter Compressor and down to turn off .
TUBE LIFE
As with all tubes, their quality degrades with age. This is due to cathode emission, a natural process found in
all tubes. We recommend that you have your unit checked every 4-5 years, depending on usage, usually the
limiter will require re-tubing after this time has elapsed. Furthermore, any adjustments such as meter
calibration should be performed when the unit has sufficiently 'warmed up'.
NOTE
Almost all compressors have only two "gain" controls of a possible three: Input, Threshold and Output. With
all three theoretically one is redundant. Utilizing a Dual Input has confused some "engineers" when it was
needed for two different sounds. Simply find a good compromise position on the Dual Input and use the
Threshold and Output as usual. The Input control is very useful with stereo material - try it - but it is not
meant to be used for stereo "fades". Use it to set up a general level and final tweaking.
The principle of operation of this unit is based around a 5670 variable-mu (variable gain) double
triode operating in a fully balanced or symmetrical circuit.
Because of the need to preserve symmetry, a balance-adjustment pre-set potentiometer is placed
onthe vertical circuit board adjacent to the 5670 variable-mu double triode. This control is set so that the two
individual triodes amplify equally. (See Adjustments Section).
The benefits of utilizing a variable-mu vacuum tube as the 'heart' of the limiting (or compression)
function is that a widely varying range of input signals can be handled in a rapid-acting without introducing
harmonic distortion - unless the operator / engineer wishes to do so for creative reasons.
As with all compressor limiters there will be little change of gain reduction with various settings of
ATTACK and RELEASE controls using a sine wave source. With music there will be changes in the amount
of gain reduction with changes of these controls.
OPERATION
OPTIONS
EARLY VERSIONS
Originally we used 6386's as the variable MU tube. These are now too rare. They will not directly
replace the 5670 in your unit without component changes. The 7044 output tubes are an improvement on the
original 12BH7 - Higher output current and better consistancy being the prime reasons. We also improved the
transformers from the first units made.
Also available: MASTERING VERSION-- with 1/2dB THRESHOLD, and OUTPUT CONTROLS,
5 POSITION INPUT PRESET SWITCH, 12 POSITION ATTACK CONTROL. All built up on Grayhill sealed
gold contact switches for maximum sonic integrity, repeatability, and accuracy within immeasurable
tolerances. The panel has each step marked for precise recall. Retail price is $5,000 USD.
There is also an option to emulate the verticle/lateral switch found on Fairchild 670s. This provides for
some M/S coding/decoding. We provide both input and output switches.
Other possibilities include sidechain inserts, remote metering, etc. Avoid ordering all possible options -
there is only so much we can fit.
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