Sensei Caswell: "Our SEM is known as a 'Voltage Controlled State Variable Filter' because it provides simultaneous high pass, low pass, and band pass outputs, all with a 12 dB/oct slope. The notch is the inverse of the bandpass, achieved by summing the low pass and high pass outputs. This version is a combination of the original SEM filter and the newer design from the OBX, along with improvements by SE. It has a modest current draw, which it pulls evenly from the plus and minus rails."
Three attenuverter and four attenuation pots control the FREQUENCY, RESONANCE, FREQ CV 1, RESO CV, LP HP, INPUT and OUTPUT, delivering smooth, detailed, and complex expression.
Switch it Up
FULL and HALF strength filter frequency keyboard/voltage tracking, and BP / LP-HP modes.
Patch it Up
Seven patch points: 1 V/O, FREQ CV 1, FREQ CV 2, RESO CV, INPUT, BP LP-HP, and OUTPUT direct the deepest manipulation.
All Controls and Patch Points
- FREQUENCY – Adjusts the frequency, or cut-off of the filter.
- RESONANCE – Adjusts the resonance of the filter.
- FULL HALF TRACK – Switch between full and half keyboard/voltage tracking.
- FREQ CV 1 – Frequency control voltage 1 input attenuverter.
- RESO CV – Resonance control voltage input attenuverter.
- LP HP – Low Pass / High Pass attenuverter.
- INPUT – Adjusts the audio input.
- OUTPUT – Adjusts the audio output.
- 1 V/O – One volt per octave control voltage input.
- FREQ CV 1 – Frequency control voltage 1 input.
- BP OUT – Band Pass Output. No cable patched, BP passes through the mains.
- RESO CV – Resonance control voltage input.
- INPUT – Audio input.
- BP LP-HP – Switch between Band Pass and Low Pass - High Pass modes.
- OUTPUT – Audio output.
Size - 12hp
Depth - 39.7mm with ribbon cable attached
Power Usage - 32mA (+12 / -12)
BYSIB (Before You Send it Back)
This filter (and the SE88) can be "input driven" to the cutout/cutoff/blackout point, for angry, aggressive unpredictability, and staggered, shell-shocked recovery. We wanted it that way; it’s perfectly harmless OpAmp smashing, for smashing good fun. Think traumatic movie scene after which an actor’s hearing momentarily disappears (extreme wooziness overtakes the balance of his senses—and camera work), high-pitched sounds follow, and then blessed normalcy of awareness and sensory perception gradually, grudgingly return. That. No reboot necessary: just sweep the frequency counterclockwise until the SEM 'n SE88 snap back to their "right mind," and rein in the input and resonance levels—resonance levels below 9:00 are safe; unless of course you want "that" to keep happening. Taunting the edge is entertaining too.
* From 7:00 (0) to 9:00 our “Negative Resonance Saturation” adds beefiness, boosting the waveform amplitude and taming waveform transients (most pronounced in the 3003 filter): set to 9:00 to achieve the cleanest tone possible.