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Oscillator dependency on midiDAC

Discussion and support for users and builders of Oakley Sound musical products.

Moderators: Kent, Synthbuilder

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Pav
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Oscillator dependency on midiDAC

Post by Pav » Wed Nov 03, 2021 8:25 am

Hi,
Today I was thinking about Oscillators and notice now (better late than never)
that your Oscillators have a resistor dependency on the version of midiDac.

To save folk time here are the two sections:

SVCO B 2.6 Builders guide is a tad too vague for my liking as it does not answer the question why.

Older Oakley/MOTM systems:
120K R12
Newer Oakley, MU and Synthesizers.com systems:
180K R12


Regular VCO v7.7 builders guide is better - being more specific about a dependancy -
* For use with an issue 4 or earlier Oakley midiDAC, R9 should be a 180K 1% MF resistor.
* For use with a standard build issue 5 Oakley midiDAC, MU (Dotcom and others) and any
Eurorack system, then R9 should be a 220K 1% MF resistor.

Are these options related to each other ?

Having a multi-midiDAC system with both one v4 and one v5 midiDAC , 2SVCO-B,1VCO, 1 ASV
I have previously assumed I can patch any Oscillators with any midiDAC, but now wonder if i should ?

I also mix Oakley eurorack dual oscillators with the 5U system occasionally
But any configuration was with a Yarns eurorack .. so im assuming i am in a complete mess configuration
wise and should do something about it .

Thanks
Pav
rgds Pav

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Synthbuilder
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Re: Oscillator dependency on midiDAC

Post by Synthbuilder » Wed Nov 03, 2021 8:44 am

The current version of the midiDAC allows, with the fitting of one optional resistor, compatibility with Synthesizers.com and Eurorack, that is midi note 36 (C2) producing 0.000V. Prior to that I did my own thing which was midi note 60 (C4) producing 5.000V. Although the two systems will have the same scaling, the absolute pitches produced by the VCOs will be different for the same CV.

The resistor changes in the VCOs were originally an answer to people building their modules in the MU format. It made sense for the latest version of the midiDAC to comply with these now more popular standards. See page 7 of the midiDAC's Builder's Guide for more details.

Tony

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Pav
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Location: UK Hampshire

Re: Oscillator dependency on midiDAC

Post by Pav » Thu Nov 04, 2021 10:05 am

Thanks,
it was the VCO options i was trying to understand.
Is there no modification for v4 MidiDAC to calibrate C2 = 0V?
rgds Pav

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Re: Oscillator dependency on midiDAC

Post by Synthbuilder » Thu Nov 04, 2021 11:44 am

Pav wrote:
Thu Nov 04, 2021 10:05 am
Is there no modification for v4 MidiDAC to calibrate C2 = 0V?
To do it properly you will have to add a 18K 1% MF resistor from pin 6 of U1 to pin 1 (square pad) of the INIT trimmer.

Recalibration of INIT will also be required.

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Re: Oscillator dependency on midiDAC

Post by Synthbuilder » Thu Nov 04, 2021 12:28 pm

As for the VCO options. Ultimately, which resistor you chose to fit into the VCO (that is VCO, ASV, & SVCO) will depend on your choice of midi to CV convertor, sequencer, or analogue output keyboard. If you want it to work with a more modern set up based around the current offerings in MU and Eurorack, or an issue 5 midiDAC with R2 fitted, then you will want the higher resistance of the two resistor values. However, if you have an pre issue 5 midiDAC then you should fit the lower of the two resistor values.

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