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CP5176 FET Compressor



The CP5176 is a FET compressor based on the design that was originally used in the 1176 compressor, which has been adapted to the '500' format of API*.

This compressor became extremely popular because of some specific characteristics such as its ultra-fast attack time, as well as its unique sound, due to the FET transistor, the class A and the transformers.

It is typically used for compressing snare, vocals, guitars or drum bus in stereo.

The CP5176 adds a few features to the original 1176 such as a new ratio of 2, a high-pass filter in the side chain and a variation in the FET gain reduction circuit that produces more distortion.

Just install it in your API* compatible LunchboxTM rack and start working.



  • Original Cinemag (Reichenbach) transformers on input and output,
  • 5 ratios + SLAM mode (all buttons mode),
  • All discrete class A audio path,
  • DOA based, API* 2520 compatible, output stage (discrete Op-Amp),
  • High pass filter in the sidechain,
  • Distortion mode adds 3% of second harmonic, close to Rev A,
  • High resolution gain reduction meter,
  • Available assembled or as a full kit (everything included



1 Input Potentiometer that sets the signal level before compression. It defines the compression threshold.

2 Out Potentiometer that set the signal level after compression (make up gain).

3 Ratio Rotary switch that sets the compression ratio from 2 to 20. Ratio 2, allowing more subtle compressions, has been added to the original circuit. The SLAM mode is the "all buttons pressed" on the 1176.

4 Attck Potentiometer that sets the attack time: The delay before the compressor starts reducing gain.

5 Rel Potentiometer that sets the release time: Time that the compressor takes before returning to the "no gain reduction" state.

6 Gr High resolution gain reduction display: 16 LED's from -1dB to -22dB.

7 HPF Inserts a 80 Hz high-pass filter in the sidechain. Produces a Fat sound and eliminates bass driven pumping.

8 Dist Modifies the signal balance on the FET, adding second harmonic distortion. Close to the Rev A version of 1176.

9 Link Connects two compressors in stereo mode.

10 LED that shows the bypass status.

11 Off Compressor bypass button (hardware by relay).




1 Original Cinemag input transformer.

2 All discrete audio path with high grade components.

3 Discrete Op-Amp output circuit, pin compatible with API* 2520.

4 Original Cinemag output transformer.

5 Easy setup of 3 trimmers with a voltmeter, without iteration.

6 16 LED's gain reduction meter.


What's in the kit?

Absolutely everything!

  • Passive components (resistors, capacitors, inductors),
  • 2 Cinemag transformers
  • Active components (diodes, transistors, LED's, IC's),
  • Pre assembled and tested Discrete Op-Amp,
  • Front panel elements (switches, potentiometers, knobs),
  • Connectors, relay,
  • PCB's,
  • Front panel and side panel,
  • All hardware.


You bring the solder (use good quality solder, 1mm diameter max) and the Lunchbox.


Difficulty level

The CP5176 kit has an medium difficulty level. Nothing very difficult but a rather large number of components.

The setup is simple but require using a good quality AC voltmeter.


Technical specifications


Measure Conditions Value
Idle supply current No input signal V+ : +70mA
V- : -65 mA
Input impedance f=1kHz 13 kΩ
Maximum input level defined by input transformer +20 dBu
Maximum output level before clip f=1kHz +27 dBu
Minimum gain - ∞
Maximum gain +42 dB
Frequency response Deviation=+/-1dB 6 Hz - 27 kHz
Total harmonic distortion (THD) f=1kHz without gain reduction < 0.05%
with gain reduction < 0.1%
DIST Button ON 3%
Attack time from 20 us to 20 ms
Release time from 50 ms to 1.5 s


Technical documents





* API is a registered Trademark of Automated Processes Inc.