Tinnitus FX - Schumann PLL

Phase-locked Loop Synth / Fuzz

The PLL is an analog harmonizer that turns your input signal into a square wave and then has a multiplier and divider that adds intervals to your note.
Two harmony notes are controlled by the loop function which controls how it tracks your original note.

makes one note into a chord
make any triad out of one note
makes it sound like there's someone else playing along with you
set the loop control to decide how it follows your playing
the three notes are a three-channel mixer that gets into a master volume
uses a +12 -12 bipolar power supply
Comes with the MOMENTARY switch accessory. This lets you mute the two harmony voices momentarily or turn them on momentarily.
The PLL Multiplier, Divider, Loop controls...

Some comments about the PLL:

it's not easy to explain everything it does but put most simply, it's a square wave generator that's controlled by an input signal (guitar, synth, drum machine, etc). the 'signature' of the sound ultimately lies in the tracking circuit which is of itself an amazing thing. from my experience, most analog tracking circuits of this nature suck (MS20, sherman filterbank2, analogue systems pitch-to-CV) but the PLL gives unprecedented control over how accurately or inaccurately you wish it to track a signal, and can cause wonderfully lively twitches and bumps of the pitch (if you want). and though it can become chaotic, it'll still be in key (or not, if you want). i'd describe the sound it generates as highly shapable harmonic-specific distortion. germanium overdrives act upon the squarewave and it's multiplier and divider to add 'beyond fuzz factory' fuzz. the overall tone depth is determined by the levels of the square wave (root) and harmonics (mult and divider). the post-mix waveshaper does alot to tone-down or amp-up the front egde of the sound after you get your harmonics dialed in. there's still other stuff you can mess with to alter the sound (like playing your instrument) but that's it in a nutshell. -- scott m.

https://schumannelectronics.com/pll.html