Dual Ian Fritz Threeler Filter

The Threeler filter has all the acid of a TB303 or MS20, but with a character all its own, and greater versatility via the Mode switch.

In Ian’s words:
This new filter design is different from the usual filters found in analog synths. It consists of three first-order filter sections that can be switched between either high-pass or low-pass response. A four-position mode switch allows selection among four different combinations of these responses. A voltage-controlled resonance amplifier allows operation of the filter well beyond the onset of oscillations. In this regime the circuit's nonlinearities provide a wide variety of phase-locking and chaotic outputs. Signals are available from all three filter sections to provide the widest variety of waveforms and filter responses.

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