Info on digitally stabilized oscillators? (looking for some)

Does anyone know of good resources for technical information regarding integrating digital stabilization and analog VCO’s?

look at the anushris schematics

In which way the problem you want to solve wouldn’t be solvable by DCOs? What do you want to achieve and from what kind of input (MIDI, CV)?

I am not sure how to exactly answer that question, so I Will use an example:

The original korg ms20 had a regular VCO in the signal path correct? now the mini being released has the “same” circuitry, but is not digitally stabilized. does that mean the Mini has DCO’s, or is it a digitally stabilized VCO?

It is very unlikely the MS20 uses DCOs (since DCOs pretty much exclude the possibility of having external CV control and doing FM).

I suspect that what they mean by “digital stabilization” is simply “digital tuning/scaling” - that is to say, the MIDI/USB/keyboard CV is continuously scaled so that the frequency measured on the VCO output matches the target note.

Would would be the difference in a VCO of old that drifts, versus new VCO’s that stay perfectly pitched and do not require circuitry warm up?

I think I understand more:
"“Digitally stabilized” doesn’t change the fact that MS-20 has a pure analog voltage controlled oscillator. It’s just taking care of the CV which controls the VCO BEFORE it hits the VCO, so things stay in tune."

But, I am curious how this is done?

> ““Digitally stabilized” doesn’t change the fact that MS-20 has a pure analog voltage controlled oscillator. It’s just taking care of the CV which controls the VCO BEFORE it hits the VCO, so things stay in tune.”

That’s the way I think it works but I’d love to be proven wrong on this - my understanding is that Korg tried to deviate as little as possible from the original MS-20 design but had more room to make improvements in the control circuitry (which wasn’t there to start with in the original MS20).

> But, I am curious how this is done?

There’s a microcontroller somewhere that receives the MIDI / USB data and converts it into data sent to a DAC (which eventually gets converted into a CV fed to the VCO). The data sent to the DAC is obtained from the MIDI note using a formula that looks like this :

dac_code = midi_note x scale + offset

The VCO output can be fed back to the microcontroller so that a timer can measure its frequency - “closing the loop”. This means that at each new note played, we can measure the deviation between the target frequency and the expected frequency, and deduce updates to the scale/offset factors (which we can make to slowly track the ideal values).

Now the thing is: how to make it work when other CVs (modulations, external inputs) are also fed to the VCO? I have no idea, the very first thing I would try would be to use a DAC to measure anything that gets fed into the VCO! Things like this are much easier to do on synths where all modulations are digitally generated.

Thank you tons for your time and info, always helpful

You need to read this.

http://www.electricdruid.net/?page=info.junodcos

Hmmm we’re talking about VCOs with some digital feedback loop. DCO are a different thing - there is no need for any stabilization since the starting point is a digital pulse wave.