A ring modulator multiplies a sound with a modulation signal, typically a sine wave. The result of this ranges from tremolo-type effects at low modulation frequencies to bizarre-metallic sounds at high modulation frequencies.
Multiplying two signals is a trivial task in the digital domain. The RM-1, however, does not do this. Instead, it implements analog multiplication, and thus works in the same way classic analog hardware does. In an analog multiplier, the input signals interact in a highly nonlinear manner. As a result, the output signal gains new harmonics not present in the inputs. The effect of this is an audible and very musical sounding saturation. Its character depends on the level of the input and modulation signal, which can be controlled using the Drive knob in the RM-1.
Analog multipliers have one major downside- the circuits cannot be tweaked such that they offer a perfectly symmetric, balanced multiplication. As a consequence of this, the modulation signal is always audible, and often needs to be filtered out using a gate following the ring modulator. This is fortunately not required in the RM-1, which employs a symmetric network. So only the desirable properties of analog multiplication are modeled.
Parameters of the RM-1 include the aforementioned Drive knob, a modulation signal generator (sine) and a dry/wet control. The modulation signal generator can be replaced with a mono or stereo side-chain signal, allowing to multiply arbitrary signals. The AM/RM switch allows to toggle between amplitude modulation (also known as 2-quadrant or unipolar multiplication) and ring modulation (4-quadrant or bipolar multiplication). All parameters of the ring modulator can be modulated using the CV Inputs on the backside of the rack extension.
