Schematics / VCF
VCF by Nyle Steiner ,as part of the Synthasystem Modular Project ,visit the page here http://user.xmission.com/~dingebre/Project.html for detailed information , construction and calibration tips and pcb's .
From the Synthasystem manual:
The filter is a sound modifier capable of passing certain audio frequencies while attenuating others. All STEINER-PARKER filters are capable of three modes of operation, namely low pass, band pass, and high pass.
The filter also has a variable resonance (Q) knob which will produce a resonant peak at the center frequency. The height of the peak depends on the setting of the resonance knob.
The center frequency of the filter can be controlled by a knob on the front panel and or by control voltages fed into the control voltage inputs.
The filter has three inputs which are automatically mixed in equal proportions before being fed on into the filter. The filter is made to operate in the low pass, band pass, or hi pass mode by turning the mode switch to one of the three positions marked L.P., B.P., or H.P.
The filtered signal comes out of two jacks in parallel marked Sig Out.
The filter can be calibrated by feeding white noise into a signal input, turning the resonance high, plugging keyboard voltage into the VAR jack and adjusting the V.C. Var trimmer until the his pitch shifts one octave when an octave is played on the keyboard.
Figure 4A contains some drawings of waveform envelopes that serve to illustrate the filter's pass characteristics.
Use of the filter involves feeding audio signals into one or all of the filter's input jacks and taking a signal out of one or both of the output jacks.
A keyboard, sequencer, envelope generator, or any control voltage producer can be fed into the V.C. input jack to control the cutoff frequency as well as using the front panel knob for this purpose.
visit the Synthasystem subforum for more details : http://electro-music.com/forum/index.php?f=189