HM VCHM VCO_75O (Hearn Morley Voltage Controlled Oscillator) is an analog VCO made to give classic four waveforms (sawtooth, pulse, triangle and sine) in a narrow 6HP width. It features counting 10-turn “Tune” knob, where each turn corresponds to 1 octave of frequency range. Thus manual frequency sweep range is 10 octaves: staring from 16 Hz and up to 16 kHz, and this single “Tune” knob covers duties of the commonly used separate “Coarse” and “Fine” tune knobs. The saved panels space is then used by “FM” knob, which provides exponential Frequency Modulation, taking the Modulator’s signal from the corresponding “FM” jack. There is no linear FM present, because we highly recommend to use our FM AID module, which perfectly couples with HM VCO to give the user many different flavors of linear frequency/phase modulations. The “Tune” dial has a handy lock, so you can lock in the knob from accidental moves and keep the exact frequency setting unchanged.
There are also:
– standard “1V/oct” input jack for over than 7 octaves of perfect tracking;
– “Sync” input for hard syncing to the Master ocsillator;
– “PWM” input for Pulse Width Modulation.


Tune: 16 Hz … 16 kHz

outputs level: -5 … 5 V

outputs impedance: 1 kOhm

module depth: 5 cm or 2 inches

width: 6 HP

power consumption: +46 mA / -46 mA at +/-12 Vdc