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The Buchla 100 series' sharp cutoff filter (1960s), two panel units wide, drawn in its Buchla Associates panel: "voltage controlled highpass and lowpass filters with 24 db/octave slopes. Cutoff frequencies are variable from 5 cps to 20 kc with no range shifting. Also functions as a bandpass filter with voltage controlled center frequency and bandwidth" (the 100 series catalogue). Each FREQUENCY CONTROL and the BANDWIDTH CONTROL is set by its knob or, by its switch, by the voltage at its black input; FREQ. MODULATION inputs and knobs, a MODE knob (independent or bandpass) and two uncaptioned red push buttons. The photograph shows the third FREQUENCY CONTROL without its knob, and the left FREQ. MODULATION knob's index outside its travel: it is drawn at its nearer end, max.

Key features

• Lowpass and highpass filters, 24 dB/octave, 5 cps to 20 kc
• Bandpass mode with voltage controlled centre frequency and bandwidth
• External or internal control of each frequency and of the bandwidth