UAD Powered Plug-Ins Manual
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Chapter 12: Fairchild 670
Time Constant
This 6-position switch provides fixed and variable time constants (attack and
release times) to accommodate various types of program material. Positions
1-4 provide successively slower behavior, and 5 and 6 provide program de-
pendent response. The values published by Fairchild for each position are in
below. The actual measured times are a bit different, but the overall
trend is the same.
Sidechain Link
When this control is set to Link, it causes the two channels of the compressor
to compress equal amounts. This does not mean that the compressor will be
equally sensitive to either channel however; that depends on the settings of
the other controls. It simply means that the instantaneous amount of compres-
sion for the two channels will always be the same.
Balance
Balance controls the bias current balance, and always goes with one channel
of the compressor, regardless of what the nearby ‘metering’ switch is set to.
The point of perfectly calibrated bias currents is achieved when the “dot” in
the screw slot is at 12 o’clock. At this setting, the amount of additive signal de-
flection (“thud”) which happens due to an attack is minimized. Setting this
control counter-clockwise from this position results in a thud of one polarity on
transients, and going clockwise produces a thud of opposite sign.
Table 12. Fairchild Time Constants
Time Constant
Attack Time
Release Time
Position 1
200 microseconds
300 milliseconds
Position 2
200 microseconds
800 milliseconds
Position 3
400 microseconds
2 seconds
Position 4
800 microseconds
5 seconds
Position 5
200 microseconds
Program dependent:
2 seconds for transients
10 seconds for multiple peaks
Position 6
400 microseconds
Program dependent:
300 milliseconds for transients
10 seconds for multiple peaks
25 seconds for consistently high program level
