EFM Dual VCO 3D
The 3rd module i built.

This Dual VCO is based on the Moog Rogue oscillators and features
Two wide range VCOs
Saw and Varable PW
Syncable

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 independent VCOs!

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 2nd cabinet.
Setup procedure: 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 once more
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 the values.
Visual Analyser (Sillanum)
trimming sequence OSC 1: T2 - T1 - T2 - T1 - T3 (repeat several times)
trimming sequence OSC 1: T5 - T4 - T5 - T4 - T6 (repeat several times)
last update 11 JAN 2012
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