The Polyphemus Optical Compressor is based on the Pigtronix Philosopher’s Tone, a vactrol-based compressor & overdrive first released in 2009. It’s known for its incredibly long sustain, and has a unique diode-clipping overdrive that can be blended in with the clean compressed signal.
The Philosopher’s Tone was designed by Howard Davis, the legendary inventor of the Memory Man and Electric Mistress when he worked for Electro-Harmonix in the late 1970s. Since that time, he’s designed several effects on a contract basis, and this is one of a few he did for Pigtronix.
After the original release, the Philosopher’s Tone underwent several revisions and new editions. The first was the “Germanium Gold” edition, which was in a gold enclosure and featured a single germanium diode in place of one of the silicon diodes in the clipping section (in other words, a marketing gimmick).
Later, the circuit was reworked into two new and slightly simplified pedals: the Philosopher’s Rock, which emphasized the overdrive component, and the Philosopher’s Bass, which was tuned for bass frequencies. These replaced the original Philosopher’s Tone.
Most recently, it was redesigned as a miniature pedal, once again using the original Philosopher’s Tone name. This version included an onboard charge pump voltage doubler, so it no longer needed its own 15V or 18V adapter. This is the only one currently manufactured as of this project’s release.
The Polyphemus is an amalgamation of all of these, primarily based on the original Philosopher’s Tone (which had more features than any subsequent versions) but incorporating various modifications and tweaks from some of the later versions, including the charge pump, germanium diode, and improvements to the sustain control.