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midiDac calibration with precalibrated vco
MUFF WIGGLER Forum Index -> Oakley Sound Systems  
Author midiDac calibration with precalibrated vco
Hi again,
I have a functioning MidiDac with midi-in and midi-out working and the oakley bus is doing its job.

When I calibrated the VCO (using Mutable Yarns for midi )..I tuned the Coarse knob so that 12 oclock pos gives me C4 .

When calibrating the midiDac with the aforementioned VCO .. I put the Tune control on midiDac to 12 oclock, but then had to turn the vco coarse control fully CCW as the two appear summed together.

Should I have left both controls at 12 and use the INIT control on MiDAc to get me C4? No mention of where to leave the Coarse setting of the "master VCO".

I had Tiptop Z3000 and a korg prophecy as audible references to help me.
As well as a Freq Meter (2 dec places of accuracy).

Already expecting a second round of calibrations for all modules...but its time to enjoy wiggling with it.

This can be a bit of a minefield. There is no accepted standard for what voltage creates what frequency. And adding unlabelled coarse frequency controls simply adds to the confusion. So I understand your frustration.

The tune pot on the midiDAC covers only a small range so it should be left in the centre for all calibration purposes - both for the VCO and the midiDAC itself. Use the INIT trimmer on the midiDAC to bring it into alignment with Yarns if you want them to behave similarly. That said, Yarns probably works on a different range since it only has a +/-12V supply and can't produce the whole midi range when the lowest note is 0V.

I choose to make my VCOs produce middle C (C4) at their typical settings when the 1V/octave input is at 5.00V. Thus, I would expect the 2U VCO to be producing 261.6Hz when the KeyCV input is 5V, the coarse tune pot is set to slightly above the minimum and the fine tune pot in the middle - these are the default positions. For the SVCO-B I would expect it to be producing 261.6Hz when the KeyCV input is 5V, the frequency pot set to 12 o'clock and the octave in the 8' position.

So the idea is really to get your interface to produce 5V and then tune the VCOs using their tune trimmers to match the above. With the midiDAC playing a C4 note this should be well within the movement of the midiDAC's INIT trimmer. I don't know whether Yarns and the midiDAC can be made to match octaves exactly.

Thanks Tony,

More puzzled than frustrated.

I have Mother32 also where oscillators set 12 oclock as the C4 so i was trying for consistency where i can.

Im torn between consistency with my mates Oakley and my own eurorack. He followed the instructions explicitly and i was initially puzzled with his VCO coarse range when not under keyCV control. Have since read your user guide.

I will re calibrate the VCO as you suggest.
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