The What Compressor is a simple, stereo compressor circuit inspired by a Joe Meek optical compressor.  It includes a couple of unique features: a built in low-cut filter in the sidechain, and a resistor that blends in some of the dry, uncompressed signal.  The designer David B. Thomas offers instructions, a bill of materials, and schematics–as well as the charming story of the compressor’s origin–on his personal website.

Notable Features:

• Optical compression element
• Only two knobs: compression and output gain
• Stereo or dual mono
• Built in 3db/octave sidechain filter
• “April” resistor sets wet/dry ratio for built-in parallel compressor

Price: No products offered

For more information, see David B. Thomas’ website.