API Audio 527a

SKU: 527a

Discrete Compressor


About this item



API Audio 527a Features

  • Feed-forward or feed-back compression
  • Hard or soft knee compression
  • Patented THRUST® switch for frequency-dependent sidechain control
  • Continuously variable, 31 positions detented THRESHOLD control
  • Continuously variable, 31 positions detented RATIO control
  • Continuously variable, 31 positions detented ATTACK and RELEASE controls
  • Continuously variable, 31 position detented OUT (output) level control
  • 10-segment gain reduction/VU meter (GR/Output)
  • Overload LED
  • IN switch with soft and hard relay bypass
  • The audio circuit uses the 2510 and 2520 discrete op-amps

The API 527A Compressor/Limiter takes its place alongside the family of API VCA-based compressors, including the 225L compressor and 529, 2500, and 2500+ stereo bus compressors. Anyone familiar with these units will immediately be at home with the 527A.

Features common to the line include “feed-forward” (NEW) and “feed-back” (OLD) gain reduction methods selectable on the front panel, providing 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 feedback 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 filter before the RMS detector circuit that preserves that punchy bottom end.

Two or more 527A Compressor/Limiters 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 at the program level.

The 527A Compressor/Limiter 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.


Connector:API 500 Edge Connector – VPR Alliance Compliant
Input Impedance:120 K Ohms, Balanced
Output Impedance:75 Ohms, Transformer coupled, Balanced
Maximum Input Level:+26 dBu
Maximum Output Level:+ 30dBu
Output Fader Control Gain:-Infinity to +10 dB
Attack Times:1 millisecond to 25 milliseconds
Release Times:0.3 seconds to 3 seconds
Compression Ratios:1:1 to 1:Infinity
Threshold Control Range:+10 dBu to -20 dBu
Metering:10 Segment LED Meter showing either Gain Reduction (-1 to -24 dB)
or Output Level (14 to +14 dBu). Overload LED: +21 dBu
Frequency Response:+/- 0.5 dB 20 Hz to 40 kHz
Signal to Noise:110 dB
Power Requirements:3.5 Watts – VPR Alliance Compliant
Unit Size:1.5″ x 5.25″ x 7″
Shipping Size:4.5″ X 6.5″ X 10″
Unit Weight:1.8 lbs.
Shipping Weight:2.2 lbs.

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