API 525 Compressor Limiter

Originally released in the 70’s, the API 525 Compressor Limiter 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, & 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 hard-wire bypass switch, a 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.

Features:

• Exact reissue of API’s original 525 from the early 70’s
• 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

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• Input Impedance: > 30 K Ohms, Balanced
  
• Output Impedance: 100 Ohms, Transformer coupled, Balanced
  
• Operating Levels: -15 dBu to +20 dBu
  
• Maximum Gain Reduction: 25 dB
  
• Noise: 98 dB below +10 dBu output, at 10 dB of Compression
  
• Harmonic Distortion: 0.5% Max, 30 to 20 kHz
  
• Attack Time: 15 micro seconds
  
• Release Times: .1, .5, 2.0, 2.5 seconds
  
• De-essing: Inversion of the Voice Energy Curve
  
• Slopes: Compression, 2:1, Limit, 20:1
  
• Metering: Compression or Limiting-Illuminated Analog dB meter, Shows Gain Reduction
  
• Frequency Response: ±.5 dB, 30 to 20 kHz
  
• Power Requirements: ±12/18 Volts/DC, @80 ma.
  
• Size: 1.5" X 5.25" X 7.5" Deep
  
• Size (Boxed for Shipping): 4.5" X 6.5" X 10"
  
• Actual Weight: 1.77 lbs.
  
• Shipping Weight: 2.17 lbs.