21
8. Voltage Controlled Oscillator / Waveform Generator
The voltage controlled oscillator section uses a unique VCA saw core oscillator circuit to generate a full range,
temperature stabilized, analog saw wave. Frequency is variable from sub
-
audio, low frequency oscillator range to
ultrasonic allowing the oscillator to function as an audio source or modulation source.
The waveform level siders set the output level of the oscillator waveforms. The output of each waveform level
slider is patched internally to the input of the binary filter using switched jacks. Patching into any of the individual
waveform jacks will remove it from the input of the binary filter. The mixer level slider will still control the output
level of the waveform.
The oscillator frequency can be modulated using the pitch and FM inputs. The pitch input uses the 1 volt per
octave standard for stable pitch tracking. The pitch input is internally patched to the midi pitch output. This allows
the octave up(31) and octave down(32) buttons to be used for transposing the oscillator range up and down.
The FM input utilizes exponential pitch modulation to create everything from subtle to extreme frequency
modulation.
Voltage Controlled Oscillator Patching Notes
•
The oscillator does not have a coarse frequency control by default. To add a coarse frequency control,
patch the output of the inverting mixer / splitter / offset (137 or 138) into the pitch input (110) of the oscillator.
With nothing patched into In A(135) or In B(136), the In A Level(45) trimmer becomes a coarse frequency
control by sending –
5
v to +5v DC into the oscillator core.
•
Patching into the pitch input (110) of the oscillator removes midi pitch(104), octave up(31) and octave down
(32) button control.
•
Patching the output of the sine wave(114) into the timbre modulation input(113) creates an interesting
waveform.
Summary of Contents for Microvolt 3900
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