Sine wave from Analog synth has extra partials?

[Tone Deft]

if you listen to it and it sounds like a sine then you can use it as a sine.

ark listened, and he heard more than a sine wave.

the more you know your tools the better of you are. also just learning how to investigate this stuff is a good thing to learn.

a dirty sine isn't unusable, you should just know that it's not a pure sine wave. or you can not know, use your ears and sculpt your sound in your usual way.

you don't have to know, knowing won't always help you, it will never hurt you, there's nothing to lose and sometimes something to gain.


the moral of the story is that "wow, Analog does not put out a pure sine wave." that is kind of surprising.



Operator has a pure sine wave but it also has other sine modes that add other harmonics. they changed this a bit in Live 8 (did they take out the dirty sines since they added the harmonic slider window thingy to Operator? I don't remember.)

[Tone Deft]

^ nice.

it's more obvious that what I expected. the partials were down at -48dB, quite low.

Spectrum isn't broken.

wanna share that m4L patch? I've been out of the loop (but I'm starting a 4 part class m4L class next week, gotta study up!)

[Tone Deft]

thanks for the file share.

all respect for doing the work of checking it out. sorry if I mistyped, long day at work (all that posting and shit.)

FWIW with the m4L patch my left and right 'oscopes' aren't showing data, I'm sure I can fix it (later, making choons now) just a heads up for others that might try it.

[Warrior Bob]

I was wondering about this myself just a few weeks ago. It's good to see it being discussed, as I was afraid that either Analog or Spectrum wasn't working correctly, and I was afraid I was relying on imperfect tools.

But it actually makes sense that Analog wouldn't produce a pure sinewave. It's a physical modeler, isn't it? Modeling circuits that were never mathematically perfect?

If this is true, then I think it'd be really cool to have an "impure" sine wave to play with, that I know has all these eccentricities that could be pulled out by using resonating filters, resampling, all that.

That, and I am a huge nerd and am curious how it all works.

[Synthbuilder]

No analogue synth can generate a perfect sine wave. As another poster said sines are normally generated from squashing a triangle wave, which in most cases, but not all cases, is generated from the VCO's core sawtooth output. The most accurate sines in synth VCOs usually come from triangle wave core circuits - which are normally used for LFO duties and not the main pitch output.

Various forms of 'squashing' exist but none of them generate sines of less than 0.5% THD as far as I am aware. Most are considerably 'worse' than this. There's usually a little trimmer inside the synth so you can get it as sinelike as possible. Normally, this finds a nice balance between the 2nd and 3rd harmonics.

Oscillating filters are more sine like, but these too show distortions and would not be described as pure either. The VCS3 or Synthi AKS (as pictured earlier) is known for its unlike sine wave output from the filter. Jarre's early albums are littered with this ethereal almost vocal like wail from the VCS3's filter. Assymetrical distortion caused by the VCA and output stages also have an effect on output quality.

Analogue VCOs also suffer from stray 50/60Hz (and its harmonics) pick up, as well as a considerable amount of FM and AM jitter introduced by noise in the CV pathway and the VCO core.

There is considerable debate among analogue synth fans about which VCOs sound better. That's not just the sine wave but all the other waveforms too. It's all very subjective too.

[3phase]

I see some wobble here and there,

The little wobble here and there is your partial..and it well can be in the -50 db area when a rough computer scope already gets it

[polkadotninja]

Seven years after the last reply to this post, I wondered the same thing. Thanks for the explanations!

(the haters wondering why a discussion on harmonics is interesting confuse me ... if you don't have interest in the details of sound, don't read posts on those details!)