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API 525 500 Series Discrete Compressor

Q&A SKU #L83785000000000
1295.0 $1,295.00
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Exact reissue of API's original 525 from the early 70's.

Originally released in the '70s, the API 525 500 Series Discrete Compressor is a "feedback" type compressor. An input (threshold) control and output (make-up gain) control are provided, along with an additional "Ceiling" fine-tune function which can increase gain reduction (lower threshold) while simultaneously raising output level to match, so the user can alter dynamics "on the fly" without level changes. A compression/limit switch sets ratio at either 2:1 or 20:1. Attack time is as fast as 15u/s. Four auto release modes are offered via two switches, 0.1s, 0.5s, 1.5s and 2.0s. A De-Ess function inserts an inverse vocal energy curve filter in the detector for effective sibilance/pop reduction. The 525 design has been taken from the original blue prints and spec control drawings from the API archives.

Release times vary with frequency, with high-frequency/full-bandwidth content released faster than lower frequencies for natural envelope tracking. Attack time is fixed, chosen to catch the fastest peaks, without "pumping". Equally useful as a tracking, mixdown or program compressor/limiter, the 525 utilizes "vintage" dynamics control and an easy-to-use multi-function control set. The 525 has a hardwire bypass switch, balanced input and a pinout that is the same as all the other 500 series modules. Two or more 525s can be linked for multi-channel compression.

The API 525 Compressor makes use of the 2510 and 2520 op-amps and exhibits the reliability, long life, and uniformity which are characteristic of all API products.


  • Exact reissue of API's original 525 from the early '70s
  • Peak detecting "feedback" compressor/limiter
  • Variable Threshold and Output levels
  • Unique "Ceiling" control combines key functions
  • Analog VU meter for monitoring gain reduction
  • 4 Switchable release modes
  • De-Ess function
  • Traditional API fully discrete circuit design
  • Active Balanced Input/Output
  • Hardwire bypass

For more features and more range. Order today.


525 500 Series Discrete Compressor Specifications:

  • Connector: API 500 Edge Connector - VPR Alliance Compliant
  • Input Impedance: 60K Ohms, Balanced
  • Output Impedance: 75 Ohms, Transformer coupled, Balanced
  • Maximum Input Level: +27 dBu
  • Maximum Output Level: +28 dBu
  • Attack Time: 15 micro seconds
  • Release Time: 0.1, 0.5, 2.0, 2.5 seconds
  • Slopes: Compression 2:1, Limit 20:1
  • Maximum Gain Reduction: 25 dB
  • Metering: Illuminated Analog Gain Reduction dB meter
  • Frequency Response: ±0.5 dB, 20 Hz to 40 kHz
  • Signal to Noise Ratio: 112 dB
  • Power Consumption: 3 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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