The VM901ABBB is an oscillator bank that replicates the unique oscillator controller/slave arrangement of classic modular synthesizers. The concept is that the the Oscillator Controller module sets the overall coarse tuning as well as rectangular wave pulse width for the three slave oscillators. In the original hardware modular systems, the oscillator controller and slaves were connected internally. Any number of slave oscillators could be used, but the "one+three" combo was common, and we felt it represented a good compromise of utility and size. Though these have the appearance of four individual single-width modules, VM901ABBB is a single quad-width module. If for you need something physically narrower, use the VM901 oscillator module.
901-A Oscillator Controller
The oscillator driver is the "master control" center; all of its control settings will affect the three slave oscillators. Changing its Frequency setting will equally offset all three slave oscillators, for example.
Inputs, Outputs, and Controls
Fixed Voltage Control- Sets the range down five octaves or up six octaves.
Frequency Range- Sets the coarse frequency range to sub-audio or standard audio ranges in standard organ footages. Use the Lo setting when using VM901 as low-frequency modulation source.
Fine Tuning (0/1/2)- Allows continuously variable tuning down (0) or up (2) one octave.
Width Of Pulse Waveform- Sets the width or "duty-cycle" of the rectangular (aka, pulse) wave. It has no effect on any other waveform. Its default setting of 50% produces a perfect square wave, rich in odd-order harmonics. Moving the knob left or right narrows its width as well as the thickness of sound until it almost disappears at its extremes.
Control Inputs jacks- These are 1V/octave exponential inputs. They're used for pitch CV as well as modulating the oscillator frequency. All three jacks are the same; signals received will be summed and are multed to all three slave oscillators.
901-B Slave Oscillators
As mentioned, 901-A oscillator driver settings equally affect all three slave oscillators. Conversely, settings on individual 901-B slave oscillators are independent and have no affect on the adjacent oscillators.
Inputs, Outputs, and Controls
Frequency Range- Sets the coarse frequency range to sub-audio or standard audio ranges in standard organ footages. Use the Lo setting when using VM901 as low-frequency modulation source.
Frequency Vernier- Allows continuously variable tuning down or up by about one octave and a major third.
Sine/Saw/Triangular/Pulse output jacks- Outputs for the sawtooth, sine, pulse, and triangular waves, respectively.