“The Steiner filter is a unique filter for sound shaping that synthesists have long admired for both its warmth and quirkiness,” notes SSL’s Doug Slocum. “Invented by Nyle Steiner in the early 1970’s, this filter was used in Nyle’s Synthacon synthesizer line.”
The 1021 has HP, BP & LP inputs, not the outputs that are typical of 2-pole State Variable type filters. The inputs on the 1021 allow for all sorts of CUTOFF (center frequency) controlled “mixing” of input signals.
Due to the unique way its 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.
Increasing the resonance to at or near oscillation, the causes the 1021 to start to squeal and complain like a school girl tantrum. A new hidden feature not on the original 1020 is 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 Steiner – but SSL advises to watch your speakers and ears in this mode.
LP, BP & HP inputs are series normalized for convenience. There is an input for standard 1V/Oct (approx.) and a separate CV input with attenuator.
Lighted sliders for most functions provide flexibility and space savings, and the center frequency is controlled by a more traditional 1” fluted Moog style knob. Top quality 1?4” enclosed jacks permit smooth, effortless patching. Quality SMD components, fiberglass-epoxy printed circuit boards and meticulous USA hand-crafted assembly assure years of trouble-free service.
Here are audio demos, via Ron Sunsinger: