The PRM2 is a passive Dual Ring Modulator. At it's core it is a standard ring modulator utilizing audio transformers with balanced Primary and Secondary impedance and a 4 diode "ring". 2 switches per ring modulator (Amputate) are added in line of 2 of the 4 diodes. These switches remove the diode from the circuit, creating a +/-/half wave rectifier between the carrier and input. This configuration can lend to complex rhythmic and unbalanced modulations, depending on the frequencies of both the carrier and input. The PCB was designed to hold either the audio transformer that ships with all kits, or a Hammond 107N. Aside from being a higher end transformer, the primary and secondary are drastically different (10k Primary, 600 Secondary Impedance). For standard ring modulation, the input can be attenuated with the trimmer to better match the secondary, or, for the reason I originally started designing this circuit in the first place, was how awesome it sounded with the input over-saturated by the transformer. Unfortunately this transformer does not work well with the +/- rectification as it results in either the carrier or the input dramatically overpowers the other signal and it's not useful at all. I opted to keep this option in the design, so if someone wanted to take advantage of it, they could build one of the ring modulators with the 107N transformer and skip the Amputate switches. Also, they are extremely expensive ($18+ a piece!).
