Short Description:

Single space compressor for the 500 series rack units. In Used, Mint condition

What We Think:

The API 525 is a re-creation of one of the earliest and most iconic solid-state feedback compressors in audio history. First designed in the early 1970s, this 500 Series module delivers the signature punch, character, and forward midrange saturation that put API on the map. Utilizing a feedback gain-reduction design—much like an 1176 or vintage Fairchild—the 525 reacts dynamically to the input signal, offering a warm, cohesive style of dynamic control that instantly glues audio to the front of a mix.

Despite its deceptively simple control layout, the 525 offers deep versatile control over transients and tone. Its release times are governed by a combination of release switches and a multi-function ceiling control, which simultaneously adjusts input gain and threshold while keeping the output level constant. Featuring discrete 2520 op-amps and custom transformers, it adds undeniable weight, speed, and vintage analog vibe to drum shells, electric guitars, and aggressive lead vocals.

Manufacturer Description:

525

Discrete Compressor, Re-Issue

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

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.

Specifications:

Specifications

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.