This is SSM2164 based dual state variable filter module. 2 filters are tuned with same knob, and CV, but can be
detuned with either a knob or CV.
- Q pot:
- controlling Q or resonance (whatever name you like) of both filters
- MODE switch:
- choose filter response: 2x LoPas, 2x BandPas, 2x HiPass, LoPas HiPas, LoPas BandPas, 2x Noth
- TUNE knob:
- tuning in range of +/-5 octaves
- 12/24 switch:
- choose between paralel and cascaded configuration of filters
- COUPLING switch:
- bypass capacitors at filter signal inputs (AC/DC)
- OUT2 switch:
- routes output signal from 1st or 2nd filter to OUT2 jack. Usefull in cascaded configuration
- DETUNE knob:
- tunes 2nd filter's corner frequency according to main tune in range of +/- 5 octaves. (In human language:
detunes the filters)
- DET. CV knob:
- simply attenuator for DETUNE input
- CVQ knob:
- attenuator of CVQ input (controling resonance)
- CV1, CV2 knobs:
- attenuators for CV1 and CV2 inputs accordingly
- DETUNE, IN1, IN2, CV, CV1, CV2, CVQ
- OUTPUTS: OUT1, OUT2.
- Frequency range:
- 0.3Hz-30kHz using knobs and external CV
- Self oscillation:
- from 0.3Hz with lower output level, high distortion above 10kHz. All this with one filter.
Cascaded configuration makes distorted sine
- Output level (at high Q):
- 10Vpp around center GND
- Temperature drift:
- it's not stabilized, so it should be as SSM2164 data sheet specify (havent measured this) which is about 0.5%/C
- Center frequency:
- 500Hz at no CV applied (Tune in the middle)
- Power Supply:
- +/-12V at 30mA
The panel is made of 3.5mm thick aluminium plate powder painted to "computer-grey" color. All pots, switches and jacks are attached to it. This way pots had to go through shaft-cutting operation. Panel writings are made in PCB software and transfered to the plate in small print house.
The PCB houses all circuitry and pots, so the wires go only to jacks and unfortunately to the switches, because I don't know any switch to fit my idea of making modules. Along with isolating plate the PCB is attached to panel only by pot's and switches' nuts. A lot of less work than with quad vco and dual ADDSR.
It's single width (12TE or 2.4''), fits into 5U 19''rack frame.
bare PCB top
bare pcb bottom
short sequence 1.1MB: 1st track of the sequencer controls cut off frequency, 2nd track - detune, 3rd track - resonance. Single non-modulated saw oscillator used as only audio source, recorded straight from filter output. No edditing except cuts from longer recorrding.