Moog Music MF-107 FreqBox - Manual (Page 23)

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pulse-width modulation or PWM. The rest of this setup is the basic sync
setup, the PWM adds a cool shifting, swirling sound to the VCO.
W/ Voyager/VX-351
Many folks will want to use the FreqBox as an extra oscillator in
their analog setup, such as a Voyager with the VX-351 CV Expander.
The Freq control input is set at the factory to change the VCO frequency
one octave per volt change at the input (commonly called 1V/Octave).
This means a 1V/Oct signal generated by a keyboard would allow
the keyboard to control the frequency of the VCO. Figure 18 shows
a diagram of such a setup. Set the External Audio In switch of the
Voyager’s Mixer to ON, and turn the External Audio level up to mix the
FreqBox VCO signal with the Voyager oscillators. Tune the FreqBox
VCO frequency in relation to the Voyager’s Oscillator 1.
Figure 18 - Using the FreqBox with a Voyager/VX-351
There are some technical considerations for using the FreqBox for
this and similar applications. First, the FreqBox VCO is a descendent of
the Voyager VCO, but is not exactly the same. It will not have exactly
the same sound. Second, FreqBox VCO is subject to oscillator drift
with temperature change. In many situations, such as studio settings
where the temperature doesn’t vary, the FreqBox will be tuning stable,
but in situations where the temperature can change drastically, you may
find that the FreqBox VCO drifts somewhat in frequency. Finally, the
linearity of the FreqBox CV response is good in the lower and mid-
range frequencies, but may not be perfectly linear at higher frequencies.
These considerations aside, a wide range of musical usage is available
to the analog musician using the FreqBox as an oscillator in a voltage
controlled system.