Sine wave from Analog synth has extra partials?

[ark]

a sine on a classical analog has no partials..

Some classical analog synths have no sine waves available at all. I'm pretty sure, for example, that the Minimmoog D has only triangle, sawtooth, and square (with pulse width modulation). I do not think that the current Minimoog Voyager offers sine waves either. Even the currently manufactured Doepfer Dark Energy has only triangle and sawtooth available, at least as far as I can tell from the panel photos.

[ark]

No, I don't find it at all improbable that an analogue synth attempting to produce a sine wave will have overtones at -45dB. You'll note that OP says he sees it in the spectrogram, not that he heard it.

Actually, it is quite easy to hear it. Here's how.

Put an instance of Analog in a MIDI track (not a preset, but the Analog device itself, directly from the Instruments\Analog folder).

In the "Osc1" section, set F1/F2 to F1 and Shape to sine.

Turn on "Fil1" and set the filter type to LP24 and resonance to 80%.

In the "Amp1" section, set the Sustain to 1.00.

You now have a patch that plays a sustained sine wave going through a resonant low-pass filter. If the output of the oscillator were a pure sine wave, changing the cutoff frequency would change only the amplitude of the output, because there would be no partials to affect. However, if you change the cutoff frequency, you can hear the effect of the resonant filter sweep. This is how I happened to notice the anomaly in the first place.

This may be a geeky question, but I would think that understanding stuff like this thoroughly is an important step in learning about sound design.

[noisetonepause]

Yeah. I think your first guess was right.

[3phase]

a sine on a classical analog has no partials..

Some classical analog synths have no sine waves available at all. I'm pretty sure, for example, that the Minimmoog D has only triangle, sawtooth, and square (with pulse width modulation). I do not think that the current Minimoog Voyager offers sine waves either. Even the currently manufactured Doepfer Dark Energy has only triangle and sawtooth available, at least as far as I can tell from the panel photos.

a resonating filter should produce a pure sine wave

[contakt321]

I think its a great question and look forward to a serious answer

Same.

[Tone Deft]

a resonating filter should produce a pure sine wave

not true.

edit - ^ I'd like to play with that. I imagine it will emphasize a fundamental frequency until it stands out more than the others, eventually the others might die down.


I saw the same thing with Analog last night. it would be interesting to see the output in the time domain.

[ark]

I saw the same thing with Analog last night. it would be interesting to see the output in the time domain.

Create an audio channel and set its input to "Resampling," then expand the time line to look at the details of the signal. When I tried it, the signal looked like a sine wave; but of course the partials might well be too small to be readily visible.

[ikeaboy]

I am assuming that this is an artifact of Analog's attempt to simulate classic analog synths, flaws and all; .

that would be my guess

That would be mine as well. Barely perceptible imperfections add subconscious interest, that's my understanding of analogue synth appeal. Although at 45 dbs quieter I'm not so sure in this case. It would play a bigger part when it interacts with with distortions caused at later stages though, correct me if I'm wrong.

[Johnisfaster]

geekiest. forum post. ever

^^^ No offense but if that's the prevailing attitude then the ableton forum really isn't what it used to be! Asking questions like that has improved my production a lot.

Please explain how finding out if a sine has extra partials could in any way improve your production.

[Johnisfaster]

all this talk about sine waves out of analog synths has made me kinda laugh. I frequent another forum where everyone is obsessed with analog gear, many of whom own an assload of classic synths. There is a running joke on this forum where they tease anyone who's looking for a perfect sine. The reason being that you just aren't gonna find it in analog. This is usually because the oscillators are based on square or saw waves as the main oscillators while the tri and sine are usually just shaped versions of the square and saw. They can be very smooth but will always be imperfect to some degree.

[Tone Deft]

geekiest. forum post. ever

^^^ No offense but if that's the prevailing attitude then the ableton forum really isn't what it used to be! Asking questions like that has improved my production a lot.

Please explain how finding out if a sine has extra partials could in any way improve your production.

seriously? tell me how it hurts you. why would you not want to know how your tools operate?


there are times when I want a pure sine wave, usually for sub bass. there's one frequency I want to fill, or I just want a pure sine wave because of how it sounds.

other times you might want something with more character, something more full and rich, then you want something with more harmonic content.

[ark]

geekiest. forum post. ever

^^^ No offense but if that's the prevailing attitude then the ableton forum really isn't what it used to be! Asking questions like that has improved my production a lot.

Please explain how finding out if a sine has extra partials could in any way improve your production.

Easy.

The reason the issue came up in the first place was that someone was demonstrating to me a patch he had made. He started by calling up an instance of Analog, setting its oscillator to generate a sine wave, and then putting a filter on it.

I said: "That filter's not going to do anything unless you change the waveform." He demonstrated that what I said was not true.

At this point, there were two possibilities:

(1) The signal he was using was not actually a sine wave.

(2) My understanding about how filters affect harmonic structure was incorrect.

Surely it is useful to know which of these possibilities is the truth!

[SimonPHC]

Please explain how finding out if a sine has extra partials could in any way improve your production.

The theme of a creative work can be (pseudo-)scientific. This kind improvement might not be technical, but is valuable.

My guess is that the imperfect sine in Analog is by design, for reasons mentioned above. An emulation of an analogue oscillator should try to emulate the original and all it's 'defects' to the fullest. If you want a cleaner sine, use the digital one in Operator. It's digitally certain.

[Johnisfaster]

seriously? tell me how it hurts you. why would you not want to know how your tools operate?


there are times when I want a pure sine wave, usually for sub bass. there's one frequency I want to fill, or I just want a pure sine wave because of how it sounds.

other times you might want something with more character, something more full and rich, then you want something with more harmonic content.

I get that man, but if you listen to it and it sounds like a sine then you can use it as a sine. I don't see how finding out if there are imperfections there that you can't even hear could possibly change your production all that much. It sounds like a sine, use it as one. Or maybe any song up till now that used analog as a sine synth is completely flawed and sounds terrible.

[Johnisfaster]

At this point, there were two possibilities:

(1) The signal he was using was not actually a sine wave.

(2) My understanding about how filters affect harmonic structure was incorrect.

Surely it is useful to know which of these possibilities is the truth!

I'll give you that one, I like how you think. I just feel like "how could it matter?" is all. I mean I have a small modular rig with several analog oscillators. The sine on one of them has a ton of harmonics which I don't like but the other 2 are pretty clean, but the fact is I can filter any of them and they change. Does that mean they are unusable? nah, it just means they aren't pure, and they don't need to be.

But I can understand how you just wanted to expand your knowledge I guess.