Nord's classical Virtual Analog Synth Nord LEAD 1/2/2x/3/4/A1 and Nord Rack versions

Different phase when selecting patch

Postby linusminus » 09 Jun 2021, 18:53

I've made a bass sound with a square and sawtooth an octave above (unsynced). The fine tune is at 0. Sometimes when I select the patch, the sound is different. This seems to happen especially if I play while selecting, but I'm not sure. Most of the time it has the very same sound that I want. How does the phase work on the Nord Lead 2X? Is there a way to assure it will sound the same each time I open it?

Also, two times in a row when recording the bass into a 3-minute song, it did this thing at the end. The phase seemed mostly unchanged until that point.I understand that since it's unsynced the phase will differ, but I found it strange the way it happened.

Image

Some insight into how the oscillator phase works on the NL2X would be very helpful.
Last edited by linusminus on 09 Jun 2021, 18:54, edited 1 time in total.
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Different phase when selecting patch


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Re: Different phase when selecting patch

Postby CountFosco » 10 Jun 2021, 13:15

Specifically to your question I don't think I have an answer. But I don't see how, what looks like a complete cancellation, could be caused by phase issue between square and sawtooth waves an octave apart. As their shapes and frequencies are quite different, even a random coincidence of phase should leave plenty of uncancelled energy. Can you zoom in on your waveform plot a little? On this view, it doesn't strike me as an issue caused by a gradual drifting of relative phase. More like something quite sudden and intermittent.
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Re: Different phase when selecting patch

Postby linusminus » 10 Jun 2021, 13:36

CountFosco wrote:Specifically to your question I don't think I have an answer. But I don't see how, what looks like a complete cancellation, could be caused by phase issue between square and sawtooth waves an octave apart. As their shapes and frequencies are quite different, even a random coincidence of phase should leave plenty of uncancelled energy. Can you zoom in on your waveform plot a little? On this view, it doesn't strike me as an issue caused by a gradual drifting of relative phase. More like something quite sudden and intermittent.


Oh, sorry! The empty area doesn't show cancellation--there just wasn't any notes played at that section. I agree, it's definitely not gradual shifting of relative phase. It's odd that the patch sometimes sounds different when selected.

This is the end of that section where it drifts

Image

This is before drifting

Image
Last edited by linusminus on 10 Jun 2021, 13:43, edited 1 time in total.
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Re: Different phase when selecting patch

Postby 23skidoo » 10 Jun 2021, 15:25

The Nords do not provide a feature (to my knowledge, at least on the models I own and have owned) to reset the osc phase on gate (keypress), which is what you need. As a result the oscillators "free run" in the background just like normal analogue ones do. So the phase relationship will vary over time due to ordinary drift. In addition, digital tuning has very small rounding errors in it so perfect frequencies are not always exactly mathematically perfect multiples of each other so even something as "stable" as an octave relationship will cause frequency drift. Add to that minor pitch variations (pitchbend, any pitch modulation, etc) and the dispatch timing of frequency changes between the oscillators and you'll rapidly lose any accidental sync you had. So yes, they'll freewheel phase-wise against each other continuously as you play, and not in any predictable or necessarily obvious manner.

Yes, this does mostly affect the sound of bass patches. No, there's nothing you can do about it. Many old analogue synths which don't have a phase reset have this same problem with bass (it's well understood), which is why bass synths became a genre, in fact - they provide specifically this feature, so you can get a perfectly reproducible phase-locked attack on every note.
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Re: Different phase when selecting patch

Postby CountFosco » 10 Jun 2021, 15:29

Ah, yes, playing and not playing notes can be one cause of dropouts in the waveform! ;)

Edit: Cross posted with skidoo, you're in better hands with him.

But skidoo, the DC drift that can be seen at the end of that waveform. You think that can be caused by a slow phase shift?
Last edited by CountFosco on 10 Jun 2021, 15:31, edited 1 time in total.
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Re: Different phase when selecting patch

Postby maxpiano » 10 Jun 2021, 18:55

23skidoo wrote:The Nords do not provide a feature (to my knowledge, at least on the models I own and have owned) to reset the osc phase on gate (keypress), which is what you need. As a result the oscillators "free run" in the background just like normal analogue ones do. So the phase relationship will vary over time due to ordinary drift. In addition, digital tuning has very small rounding errors in it so perfect frequencies are not always exactly mathematically perfect multiples of each other so even something as "stable" as an octave relationship will cause frequency drift. Add to that minor pitch variations (pitchbend, any pitch modulation, etc) and the dispatch timing of frequency changes between the oscillators and you'll rapidly lose any accidental sync you had. So yes, they'll freewheel phase-wise against each other continuously as you play, and not in any predictable or necessarily obvious manner.

Yes, this does mostly affect the sound of bass patches. No, there's nothing you can do about it. Many old analogue synths which don't have a phase reset have this same problem with bass (it's well understood), which is why bass synths became a genre, in fact - they provide specifically this feature, so you can get a perfectly reproducible phase-locked attack on every note.


+1 I observed the same phenomenon that the OP is reporting on a NS2 patch (I could get 3 random "flavours" of it) and came to the same conclusion: free running digital oscillators with no phase reset.
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Re: Different phase when selecting patch

Postby linusminus » 10 Jun 2021, 20:40

Thank you so much for the answers! I just wanted to make sure it wasn't my synth that was acting up. Knowing this, I'll probably record shorter sections of the track and copy/paste throughout the song rather than one take.
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Re: Different phase when selecting patch

Postby 23skidoo » 11 Jun 2021, 19:13

CountFosco wrote:But skidoo, the DC drift that can be seen at the end of that waveform. You think that can be caused by a slow phase shift?

Yes, absolutely. You can try it yourself with any two oscillators - try various combinations of pulse and triangle or saw waveforms. Modulate the pitch of one slowly compared to the other, that will create phasing that makes it very easy to see.
Last edited by 23skidoo on 11 Jun 2021, 19:14, edited 1 time in total.
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