Everybody loves the Moog ladder filter, right? TB-303 etc….. And everyone loves the EMS diode ladder, the Pink Floyd characteristic synth sound, yeh?
So what happens when we mate these two filters? No, I don't mean what are the offspring like Lets just see them in coitus!
This circuit replaces the diodes and transistors of the ladders with opto-isolators. The interesting effect is that the transistor filter does not need an audio input, The audio from the diode ladder is sent across as infra-red light and turns on the transistors.
There are outputs for each filter, plus summed output and a difference output. The difference output is quite unique, never heard anything like it.
There is a switch to swap the resonance feedback paths between the filters which tends to make thing go a bit nuts.
update 31/1/2019 = out of stock. planning to develop a new PCB with no wiring
Techniques for using this module