API Audio The Channel Strip - Manual (Page 13)

4.0 Dynamic Processing: 527 Compressor
4.1 527 Compressor Overview and Features
The API 527
Compressor takes it's
place alongside the
family of API VCA based
compressors, the 225L
and the 2500 Stereo
Bus Compressor.
Anyone familiar with
those units will
immediately be at home
with the 527.
Features common to the line like "feed forward" (NEW) and "feed back" (OLD) gain reduction methods
selectable on the front panel, provide a choice of "that old way", or "the new way" of compression, for
the highest level of flexibility in signal gain control. The "old way" or Feed-Back method is what most of
the classic compressors used for the gain control circuit. The "new way" gain reduction is more typical of
the newer VCA type compressors that rely on RMS detectors for the gain control voltage.
There is a "SOFT"/"HARD" KNEE switch for an "over-easy" type compression resulting in a very natural,
uncompressed sound or a typical sharp knee type that lends itself to a much more severe limiting effect.
The patented THRUST® function can be switched in and out via the front panel as well, applying a high
pass filter before the RMS detector circuit that preserves that punchy bottom end.
A SIDE CHAIN input is provided for keying and external detector path processing.
The 527 Compressor sections of two or more Channel Strips can be linked together via a DC link
allowing multiple units to be combined for stereo and multichannel applications.
The output level remains fairly constant regardless of the threshold or ratio control, much like the
"more/less" Ceiling control on the API 525 Compressor. This allows for live adjustments without any
noticeable gain changes in the program level.
The 527 Compressor makes use of the 2510 and 2520 discrete op-amps and exhibits the reliability, long
life, and signature sound which are characteristic of API products.
Features
• Feed-forward or feed-back compression
• Hard or soft knee compression
• Patented THRUST® switch for frequency dependent side chain control
• Continuously variable detented THRESHOLD control
• Continuously variable detented ATTACK and RELEASE controls
• Continuously variable detented RATIO control
• 10 segment gain reduction (GR) meter
• Side chain input
• LINK switch for multiple unit interdependent compression linking (stereo compression)
• COMP BYPASS switch with hard relay bypass when in the "Out" position
• Can be moved to POST EQ
• Audio circuit uses the 2510 and 2520 discrete op-amps
12