Problem of voices inconsistency with REV2-16 but only when mixing both osc

[Pl@ton]

Hello,
I've checked old threads but I haven't found the same problem.

On my brand new REV2-16, when I listen to oscillators individually, everything looks good, but when I mix them together the sound changes almost at every note.

I know REV2s have subtil differences between voices, but what I encounter is not really subtil. It sounds like each voice is set on a different level of shape mod. Some have more bass than other, and/or more harmonics.

Of course I've made resets, recalibrations, and even reset of calibration in the debug menu, followed by many recalibrations, but this happens everytime.

Again, what is really strange to me is that if I listen to just one oscillator at a time, I don't have this problem. As far as I hear, both oscillator sound the same and pretty solid individually.

Both examples attached were made after initializing the pach.
First example is pulse wave on both oscillators, 50% shape mod, and oscillator mix at 64.
Second example is (the same but with) sawtooth, 50% shape mod, and oscillator mix at 64.

Could you please let me know if this happens on your REV2 too please?

Thanks in advance !

[timboréale]

Yeah you're hearing the usual beating of the oscillators against each other, that's normal for all free-running oscs and is considered a feature, not a bug. If you want the onset of every note to be more or less identical with multiple oscillators, set the Osc Reset to ON in the misc params menu for both of them.

To get into the details: when you mix pulse signals at not-exactly-identical-frequencies, you are effectively cancelling portions of the wave with the phase relationship between the two. A similar but less-obvious effect occurs with sawtooth or other waveforms - but pulses show it the strongest since the negative portion of one cancels out the positive portion of the other - you end up with a multi-level output that has a widely variant duty cycle, causing some cycles to sound richer and some to almost disappear (if the phase during that cycle is fully out of phase the cycle will be totally silent, even!). This is just a principle of physics and is mentioned in almost every bass tutorial out there that uses more than one oscillator because the effect is so strong that it can often ruin a good pulse bass patch - so synths with oscillator reset are particularly important for that type of patch sound since the attack is fundamental to the sound. For poly stuff, it can be a good thing to have such a wide range of attack variances especially for sounds like strings as it adds a shifting richness similar to PWM without burning up an LFO.

[Pl@ton]

Indeed, oscillator reset ON fixes the "problem". That's great !
Thanks a lot Timboréale !!!

[creativespiral]

As a general sound design principle, I recommend never equally mixing two oscillators of the same shape, that are tuned exactly the same... always mix one at a higher level, and one lower.  ie:  if you have two saws at C3, keep one of them at a higher volume than the other... then you can still get the interesting detuning/phasing between them if you offset their fine tune, but you won't "lose the fundamental" if the two oscillators are in opposite phase... either it will appear to go up an octave, or you may loose significant amplitude, if they are equal volume.

As timboreale mentioned, in extreme situations (ie: using a sine, or even triangle), with free running oscillators, destructive interference at 50% phase can cause the sound to audibly disappear when both oscillators are tuned the same and have same volume and shape.   

If the two oscillators are in separate octaves, or of different shapes, then its not as big of an issue and you can mix them more equal.  I will usually never mix two equal osc at more than 60/40% ratio.   

[Pl@ton]

Thanks for the advices Creativespiral. I take good note.
And by the way, congrats for the vcm patches !