API Audio 527 Compressor/Limiter

Discrete Compressor, Re-Issue. Originally released in the 70's, the API 525 is a "feedback" type compressor, such as the 1176 and 660, etc. An input (threshold) control and output (make-up gain) control are provided. An additional "Ceiling" fine tune function modifies threshold and make-up gain for precise changes in compression without changes in output.

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/p-pop reduction. The 525 is an identical re-issue of one of the most popular API products ever.

The API 525 is perhaps the most successful solid state feedback compressor in history. It delivers dynamics control behavior unlike VCA "feed forward" compressors so common today. A remarkable multi-function "ceiling" control 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. This re-issue design has been taken from the original blue prints and spec control drawings from the API archives.

        FEATURES

• Audio circuit uses the 2510 and 2520 Discrete Op Amps with transformer output
• Continuously variable detented Threshold control
• Continuously variable detented Attack and Release controls
• Continuously variable detented Ratio control
• Output Fader level control
• 10 segment VU/Gain Reduction meter with selector switch
• Overload LED
• "Link" switch for multiple unit interdependent compression linking
• "New"/"Old" switch for feed-forward or feed-back compression
• "Hard"/"Soft" compression curve knee switch
• Patented "Thrust" switch for frequency dependent side chain control
• "IN" switch with hard relay bypass when in the "Out" position