satisfied with the gain, push the rotary control again and the cursor will move back to the gain field
and can be moved down to select different items. This procedure applies to all parameter
adjustments
Compression AC Threshold:
The compression AC threshold determines at which level the compressor activates. Please note it is
displayed in dBu not in the standard U.S. studio level of +4 dBu. This allows to easier match the
maximum input of A/D converters almost always specified in dBu.
Compression Ratio:
This parameter determines the “strength” of the compression, higher numbers indicate more
compression. It is the relationship between output level and input level if the output level is above
the AC threshold.
Ti
m
e Constant:
The F660 employs the same 6 different time constants as the original Fairchild 660/670. Number
one is the fastest and shortest and number 6 is the slowest and longest. Number 3 is always a good
starting point.
Fast Attack:
The attack time can be changed in all 6 time constants by selecting faster attack times. Since the
Fairchild time constants are more than simple integrating filters, it is impossible to set a value for
this parameters. The actual attack is a combination of the selected time constant and the selected
fast attack mode.
DC Threshold:
The Fairchild 660/670 has a fixed DC threshold of 2 volts. The F660 allows the user to select
between 0.5 and 5 volts. Lower values result in stronger compression. The 2 volt setting is the
default and used to reference the AC threshold.
Bypass:
If bypass is turned on, the main input and outputs are connected and the F660 is taken out of the
signal pass. This is very useful for comparisons of the direct and compressed sounds.
Side Chain:
If Side Chain is set to ON, the side chain input is activated and the side chain is disconnected from
the output. Inserting a high-pass filter between the side chain output and input can be used to avoid
compression in unwanted frequency ranges. An example is using a high pass filter to form an de-
esser.
Fredenstein F660A Manual Release 1.0 Oct 17, 2014 Page 4