The AJH Synth Ring SM is three modules in one: a ring modulator based on an analog transistor core design, a sub bass generator that creates tones 1 and 2 octaves down which morph from a trapezoidal wave (a softened square) in the lowest registers to a sine-like wave in the higher registers (so its harmonics don’t compete too much with the original sound), and a 5 input mixer based on the classic Moog CP-3 design. This mixer is used to combine the original inputs, ring modular, and sub bass sounds; you can override them by patching in alternate inputs. The inclusion of an integrated mixer will occasionally leave you saying “Why can’t I hear this? Why am I hearing that instead?” until you get used to changing its levels as you move between different processings, but in the end it allows you to create a much thicker, complex sound with just one module.

The Learning Modular Synthesis: Eurorack Expansion course covers all three of these sections. The movie below focuses on using the ring modulator section, showing a few different applications (including processing a sawtooth from the Moog Mother-32 with a sine wave from the Expert Sleepers Disting) as well as really focusing on the waveforms and harmonic spectra it creates so that you better understand how a ring modulator works:

I’ve also written a post and released a video where I used the Ring SM alongside an AJH Synth Sonic XV filter to show how complex you can make a single oscillator sound. Click for the detailed post+video.