Synthetic Sound Labs Steiner Filter (1 MU) - Model 1021

via Synthetic Sound Labs

Updated version of the model 1020 from 2010. You'll find some demo links of the original from 2010 on site.

"The SSL 1021 Steiner Filter is a 1 MU revision & enhancement of our popular but discontinued 1020 Steiner module, which was 2 MU. All the same crazy goodness is still there, plus a hidden feature that calms it down a bit without losing that wet, slippery sound everyone loves.

The Steiner filter is a unique filter for sound shaping that synthesists have long admired for both its warmth and quirkiness. Invented by Nyle Steiner in the early 1970's, this filter was used in Nyle's Synthacon synthesizer line and has been lovingly recreated and updated as part of our modular line.

At first glance, it may appear to be another 2-pole State Variable type filter with it's high-pass (HP), band-pass (BP) & low-pass (LP) outputs. But that's where things get turned upside down. The 1021 has HP, BP & LP inputs, not outputs. These allow for all sorts of CUTOFF (center frequency) controlled "mixing" of input signals.

Due to the unique way it's inventor injected the inputs into the internal signal path, they tend to slightly interact with each other and the control voltages, making the 1021 a bit more organic and unpredictable than many other synth filters. The RESONANCE also interacts with the CUTOFF adding an additional natural touch and warmth.

But if you really crank the RESONANCE up, you can make all that warmth go out the window because at or near oscillation, the 1021 starts to squeal and complain like a school girl tantrum.

There’s a hidden feature built into the Cutoff frequency knob. When pressed in, the 1021 switches to a “warm mode” that allows more subtle control over its settings. Pull the knob and you go right back to the original crazy Steiner – but watch your speakers and ears. Dogs run for the hills in this mode!"