| Notes | The Moog 921A Oscillator Driver provides the control voltage, and the pulse reference voltage for the 921B Oscillator. It contains a control voltage summer and a switched frequency control for either semitone or octave. Module cabling is wired in parallel so that a single 921A can control up to three 921B modules.
The gain of the module is 0.5X so it outputs 0.5V per octave. Why 0.5V? The module is powered of +12V and -6V so the op amps can only drive to less than -6 volts. This module needs a range of +/-3V for the frequency control plus whatever voltages are added from the CV jacks. I suspect they simply reduced the gain to have adequate headroom with the restricted negative supply voltage.
The 921A Oscillator Driver is a very simple 1 MU wide module. One of the trimmers has been replaced on this module. |
