Is there any way to sync two VCOs that don’t have the facility built in?

I’m asking more in hope than expectation.

Does one of the VCOs have a reset trigger? (Much more common with LFOs). If so, you can wire up a zero-crossing detector and do a pretty credible hard sync.

AFAIK, the various flavors of soft sync typically require more complex access to the oscillator core(s).

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Credible but probably with a ton of aliasing?

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A lot of the Surge XT VCOs have a reset so I will try to make that work.

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oh for sure!

Here’s a (very early) discussion of that if anyone’s interested (@Squinky , I’m sure you know this one):

This video outlines a cool method for smoother sync using multiplication of two signals to create windowed syncing i think…

Im pretty sure this would work for what you want but it may not??

Good luck


Extremely cool video, thanks for linking! If I understand the technique it depends on sync already being implemented (and I haven’t checked what it would do with non-sine oscillators) but it might have a positive effect on a naive sync implementation. Definitely worth experimenting with!

I think windowed sync is in that paper, also a great link. Its been a while since watching that video, but i feel like sync is not a prerequisite to that technique.

IIRC it uses the “phase?” Of one oscilator and fills in the window with the other. If the two are detuned from eachother you should be able to hear both the fundamental from the main and new harmonic content from the windowed. Like i said its been a while i could be off

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ah–maybe he’s using the sync input on VCO2 as a convenience, not because it’s necessary. Looking forward to messing around with this when I get a moment! Really great video series, I hope he starts making them again

Yeah regardless this technique makes some nice sounds. Worth playing with for sure :wink: good luck op

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I am in the home stretch of creating a Venom Oscillator, and all anti-aliasing is done with oversampling, so it works well for pretty much all waveforms and modulations, including hard and soft sync. All the inputs can be modulated at audio rates, and almost all inputs (including the sync) have the option to be oversampled.

Yes, I am in a dilemma with this one. I am implementing the soft sync option similar to the VCV VCO, where soft sync reverses the waveforms, and a button switches between hard and soft sync modes.

If I have a hard sync voice for use with a keyboard, I can get consistent sounds with each note strike as long as I reset the syncing VCO with each note gate. But that does not work well with soft sync because the synced VCO never gets reset. The soft sync sound changes depending on the phase relationship with the note gate. To get consistent sound the synced VCO needs to be reset at the same time as the syncing VCO, separate from the soft sync.

I can solve this easily by using two dedicated sync inputs, one for hard, and one for soft. But adding one more input will really disturb my current faceplate design, and I really like what I have so far. I keep on vacillating between leaving it as is with inconsistent soft sync, or biting the bullet and adding yet one more input :frowning:

so have the user pick hard sync it that’s what they want. What’s wrong with the choice? why get so worked up about it?

If I want soft sync sound, but I want the start of each note to sound the same, then I need soft and hard sync to be independent.

The sound of soft sync can vary significantly depending on the phase relationship of the sync signal with the underlying synced VCO. The variation might be just what the doctor ordered. But perhaps I don’t want the variation. Perhaps I want the sound to remain consistent as I repeatedly play a C note for example. In that case each gate should trigger hard sync for both VCOs. Then the soft sync will have a consistent phase relationship for each note instantiation.

I think I will simply swap an input for my current soft sync button - problem solved.

Hitting the surge vco reset with a trigger at audio rate would have one good outcome which is it would make you understand in a visceral way why squinky always talks about aliasing. But I don’t think it would be useful in any musical setting :slight_smile:

That reset is really meant to allow some modicum of phase alignment on a trigger into a gate. It’s a non alias suppressed reset

That being said we made these modules so people can patch around and find out, as it were, so you might get some interesing sounds depending on what you want. Just not a clean hard sync!


and then ppl say “but what If I want the sound of aliasing”? And so it goes…

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What about using a phase locked loop? There’s one in the library or you could patch your own with an XOR and a slew. Hope I helped!


Ppl r incorregible aren’t they? thx