An overview of five balanced-, or ring-, modulators: the Intellijel μMod, Makenoise ModDemix, Fonitronik mh-31, Doepfer A-133 and Cwejman VCO-2RM.
RingMod Roundup by navs
These modules have a different approach, feature set and, as you can hear, sound. The Cwejman is a classic two-input, one output affair and I included it as a reference as it has good rejection and headroom.
On the face of it, the additional features offered by each manufacturer set these modules apart. However, given that the basic concept is the same, these differences might not be that wide. The μMod's 'Q' function, for example, seems to be a bipolar offset, something that could be patched externally with the Cwejman or by increasing the manual gain on the A-133. Similarly, the auto-AM/ pseudo-SSB modulation offered by the ModDemix's normalizing could also be covered by a dual module like the Doepfer. Incidentally, it's a shame neither of these dual modules can be used as a mixer out of the box. Pre-patching a signal to one of Maths' attenuverters and using the uni-polar OR output as modulator would yield a function similar to the μMod's rectification switches. The mh-31 utilizes rectification as part of its 'RM' process which might explain its characteristic sound.
Two technical points to note: when used as a VCA, the μMod I tested displayed a small amount of carrier bleed (audible in the example above), but I'm sure this can be corrected by calibration of the 'Q'/ offset. The A-133 suffers bleed too, but this is understandable due to its lack of centre-indent pots. At low 'strength' amounts, the ModDemix displays an unusual response - the processed waveform seemed more typical of AM than the 'attenuated' RM I'm used to from the A-133. Both the Makenoise and Doepfer are DC-coupled, so I wonder if this difference is down to the circuit employed.
In terms of sound and function, I saw the closest parallels between the VCO-2RM & μMod one the one hand, and the Doepfer & Makenoise ModDemix on the other. The mh-31 is the most unorthodox design and doesn't easily fit in either camp.
To my ears, the Cwejman and Intellijel have the cleanest tone, with the Makenoise and Fonitronik well-suited to more abrasive timbres. While not as transparent as the VCO-2RM or μMod, the A-133 can be both clean or driven to distortion.
Thanks to Schneidersbuero for the loan of the Intellijel & Makenoise modules.