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PYE Module Building Guide

PYE compressor module is our take on the rare vintage PYE compressor that is famous for its unusial gain control element. It works based on the PWM (pulse width modulation) which is basically the same way that light dimmers work. Audio signal is chopped at the very high frequency and thus the controlled amount of audio energy is removed.

We preserved the original design and even made some improvements. Here is the list of what was changed:

  • Increased the PSU voltage in order to improve headroom.
  • Improved output drive capability.
  • Increased the ouput stage gain (for unity gain insert conditions)
  • Other minor changes that do not affect the compression circuit.

We were able to recreate the transformer of the original blocking oscillator. The details of this transformer are provided in the Guide. This oscillator is an essential part of the PYE compressor. Yes, it can be replaced with a simple 555 IC based solution, but the sidechain and metering will behave differently with 555 oscillator. Currently, we do not recommend using this type of oscillator, but we provide a separate plug-in board for it in case you want to experiment.

Here are the features of our module:

  • Increased power supply voltage for better headroom (can be reverted to original 16V if needed).
  • Original blocking oscillator with inductor details revealed!
  • Correctly coupled stepped Threshold control instead of input and output potentiometers.
  • Improved output drive capability.
  • Unity gain (zero insertion loss).
  • Both hard and soft bypass.
  • Improved and stable link facility for stereo operation.
  • Original HF filter.
  • Ratios: 1:1, 1:2, 1:3, 1:4, 1:5, Limit.
  • Output and Gain reduction LED metering.

We highly recommend that you get a good scope for this build. Otherwise it may be quite difficult to check the module for correct operation.

PLEASE NOTE: complete building Guide will be available after purchasing of PYE module PCB set.

Here is the rough estimate of costs of the PYE compressor module:

Electronic parts (Mouser, US pricing) 190$
Audio transformers 108$
Front panel, PCBs, mounting brackets 60$
TOTAL (shipping not included): 358$

Approximate build time - 6 hours.

GroupDIY support thread here.