The 3rd module i built.
This Dual VCO is based on the Moog Rogue oscillators and
Two wide range VCOs
Saw and Varable PW
Using the tempco option i found it hard to get the VCO stable
though. Tuning the VCOs turned out to be difficile too,
for once you tune one VCO the other gets untuned.
Additionaly, if you tune up one VCO for a 5th sound,
i.e., the other VCO gets inluenced too. These are not two
Enough causes to build some more VCOs: Ray Wilsons MFOS VCO,
Ken Stones B-N-Tic Filter and two SSM2044 Filters (tempco
regulated and usable as VCOs, i hope) are planned for the
Each oscillator provides three trimmers for calibrating the tune
and the scale. For the 1st oscillator T2 (init), T1 (scale) and
T3 (high scale), for the 2nd oscillator T5 (init), T4 (scale) and
T6 (high scale).
For a accurate calibrating a frequency meter would be recommendable.
i used a freeware oscilloscope:
first connect your 1V/oct source to the first oscillator and
connect the output to the frequency meter.
1) feed the module with 2V (C2) and adjust T2 to read 130.813 Hertz
on the output
2) feed the module with 4V (C4) and adjust T1 to read 523.251 Hertz
3) again feed the module with 2V (C2) and adjust T2 to read 130.813 Hertz
4) feed the module with 4V (C4) and adjust T1 to read 523.251 Hertz
5) feed the module with 6V (C6) and adjust T3 to read 2093.005 Hertz
on the output
each trimming action will affect the whole calibrating so repeat
steps 1)-5) until the oscillator is calibrated. then continue with
the 2nd oscillator. after that go back to the 1st oscillator and check