Double Penetration (DP) Filter

The Moog transistor ladder and the EMS diode ladder mated: the diodes and transistors of the ladders are replaced by opto-isolators, so the audio fed to the diode ladder crosses to the transistor ladder as infra-red light and turns on its transistors; the transistor ladder needs no audio input and does not work by itself, while the diode ladder can be used on its own. In general use, feed the diode ladder's inputs and most settings give filtered signals at all four outputs: each filter's own, their sum and their difference, the difference quite unique. The transistor ladder's input (FM) puts an FM effect on the diode ladder's signal; a signal there of a similar frequency gives filtered harmonics. Each filter's cutoff and resonance are set and modulated on their own; the Q PATH switch swaps the resonance feedback paths between the filters, which tends to make things go a bit nuts.

Key features

• Diode ladder: two inputs, CV1 and CV2, its output; res, freq and cv1 knobs
• Transistor ladder: FM input, CV1 and CV2, its output; res, freq and cv1 knobs
• Sum and difference outputs; the Q PATH switch
• 12 HP; Nonlinearcircuits publishes no current draw, depth or assembled price (it sells the DIY PCB and panel), and ModularGrid lists none