I have two very clean API 525 compressors. this Auction is for one of them.  Here is one of two Vintage API 525 compressors for sale. These units were Recently re-capped with Panasonic FC 105 degree celsius capacitors. This Auction is for one API 525 Compressor Specs from API: Features 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  Originally released in the 70's, the API 525 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.