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DP Filter


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


Power draw:



Known modifications?


Techniques for using this module

Examples (Audio/Video)

modules/dpfilter.txt · Last modified: 2019/01/31 11:46 by donald_dasher