Triangle wave looks more like a square wave

The Dave Smith Instruments Prophet-12 Analogue Synthesizer

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erpione
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Triangle wave looks more like a square wave

Post by erpione » Tue Nov 26, 2013 3:29 pm

Happy to be back here as a new owner of a P12!

I looked at the different waves with an oscilloscope and it seems that the triangle is more like a square wave. Do you have the same result?

Thanks!
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Bald Eagle
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Re: Triangle wave looks more like a square wave

Post by Bald Eagle » Tue Nov 26, 2013 10:37 pm

This is the stereo signal my P12 sends out for its triangle. It's from an initialized patch with the only change being setting oscillator 1 to a triangle wave form.
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BobTheDog
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Re: Triangle wave looks more like a square wave

Post by BobTheDog » Tue Nov 26, 2013 11:48 pm

Those are pretty strange triangles!

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geoscience
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Re: Triangle wave looks more like a square wave

Post by geoscience » Wed Nov 27, 2013 12:09 am

Strange indeed. What is going on here?
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erpione
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Re: Triangle wave looks more like a square wave

Post by erpione » Wed Nov 27, 2013 1:14 am

Thanks Bald Eagle!

I would love to know if we both have an odd triangle or it is by design.

pelican
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Re: Triangle wave looks more like a square wave

Post by pelican » Wed Nov 27, 2013 2:23 am

Looks like a triangle to me. No waveform is perfect

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Re: Triangle wave looks more like a square wave

Post by erpione » Wed Nov 27, 2013 5:31 am

Dear Pelican - please find below examples of what a triangle wave should look like. I would really appreciate if you cold post a snapshot of the triangle wave on your P12.

The examples below are triangle waves from other synths, both hardware and software and both analog and digital (VST's and modular). None of them looks like the triangle of the P12. Waveforms are somehow "different" as you can see from the variety of snapshots that I posted but as a matter of fact a triangle wave looks and sound different than a square wave because it simply does not have the same partials. I may post a series of spectrum shots later but I am pretty sure that the P12 triangle is not strictly speaking a triangle wave.

If your P12 triangle wave looks like the other examples below, I will know that my P12 have a technical issue and will have to return it for repair. This is not a critic I would just like to know why the P12 triangle is the oddest triangle wave I have encountered. Sure it sounds good but not as a triangle wave.

Thank you very much for your help.
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Fuseball
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Re: Triangle wave looks more like a square wave

Post by Fuseball » Wed Nov 27, 2013 8:32 am

The triangle from my Prophet 08 looks like all those examples you gave from various soft synths (ACE, Massive etc.) so I think it's fair to say that a hardware synth's triangle should at least resemble a triangle.

The triangle from my Prophet 12 looks exactly like the triangle from erpione and Bald Eagle's synths. It's clearly a trait of all Prophet 12s. The square wave doesn't look much like a square either, but at least it sounds like one. The triangle is more problematic, as I don't think it sounds like one. The initial upward slope of the waveform is too steep and gives it a buzzy quality that isn't part of a triangle wave's natural sound.
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Re: Triangle wave looks more like a square wave

Post by Pym » Wed Nov 27, 2013 8:35 am

Try changing the shape mod to get it smoother
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jasonswe
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Re: Triangle wave looks more like a square wave

Post by jasonswe » Wed Nov 27, 2013 9:06 am

I noticed this earlier on when I heard the waveform using higher harmonics, but I figured this was the flavor of tri for the P12. Adjusting pulsewidth or symmetry of the wave doesn't really give more of a characteristic triangle. I think it sounds 'best' in its centered position. For FM purpose it is good with a clean triangle. Clean was a bad word... Maybe I meant 'ideal' shape. Considering these are algorithmic-ally calculated Osc.

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Re: Triangle wave looks more like a square wave

Post by Tomavatars » Wed Nov 27, 2013 11:02 am

Chris, do you plan to work on the waveforms, on the calibrate of the osc ?

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Bald Eagle
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Re: Triangle wave looks more like a square wave

Post by Bald Eagle » Wed Nov 27, 2013 11:15 am

This is very odd being that the oscillators are digital. Unless there is a bug in the algorithm there must be some other hardware problem.
pelican wrote:Looks like a triangle to me. No waveform is perfect
No matter how much I squint and turn my head sideways I don't see a triangle in there.
pym wrote:Try changing the shape mod to get it smoother
That doesn't help.

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Re: Triangle wave looks more like a square wave

Post by Fuseball » Wed Nov 27, 2013 11:54 am

The Prophet 12 triangle looks like a slightly smoothed variation of the Prophet 12 square. Hold down a note and switch between triangle and square and you'll see what I mean on the scope.

Changing the mod shape is a simple pulse width change in both directions (identical to the square behaviour). It certainly doesn't smooth the waveform or get it closer to a traditional triangle.

The Prophet 12's sine at Shape Mod +63 is the closest I can get to a traditional triangle.

Whilst I can see that the Prophet 12's "analog" waveforms are useful in their current state, I would have liked to have seen something closer to traditional triangle, square and sawtooth in there too. I, perhaps naively, expected them to be modelled on the waveforms produced by the Prophet '08. It partially explains why the P08 can sound both sweeter and more biting than the P12 if you wish it to.

edit: FWIW, the saw and square waves from the digital half of the Evolver also look and sound (aliasing aside at higher pitches) like traditional analog wave shapes too.
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Re: Triangle wave looks more like a square wave

Post by erpione » Wed Nov 27, 2013 4:50 pm

Thanks for your comments. I am glad I am not the only one!

I completely agree with you Fuseball. Using the shape mod does not "soften" the triangle it is just like a PWM. Your idea of Sine Shape Mod at +63 is the closest of a true sine wave that we can get on the P12 but unfortunately it is still not a triangle wave. It baffles me that the P12 is not able to have such a classic shape of wave.

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Bald Eagle
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Re: Triangle wave looks more like a square wave

Post by Bald Eagle » Wed Nov 27, 2013 9:58 pm

I hope we get a more official explanation than "Try changing the shape mod to get it smoother". Is this a bug or is the P12 really designed this way? I would expect that the P12 would be able to generate the classic analog wave forms more accurately. If this is by design then a set of "classic" analog wave forms should be added in addition to these interesting variations.

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Re: Triangle wave looks more like a square wave

Post by Mefistophelees » Fri Nov 29, 2013 1:19 am

I'm guessing the basic waves on the P12 are based on real old synths.
A pure triangle is quite boring, sort of like an enhanced sine.
This triangle at least sounds more interesting.

Remember, it's not how it looks. It's how it sounds.

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scottrod
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Re: Triangle wave looks more like a square wave

Post by scottrod » Fri Nov 29, 2013 12:48 pm

Right. It's not a function generator, it's a musical instrument.

Don't understand why anyone would care about this unless the triangle is being used an lfo source, then it's important for sure.
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Re: Triangle wave looks more like a square wave

Post by jasonswe » Fri Nov 29, 2013 7:53 pm

A smoother, more ideal triangle should be a possibility by emmploying FM, because the OSC can modulate themselves for finer tweaking. I may try later. Not easy since OSC frequency is given as note value and not ratios between operators.

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Re: Triangle wave looks more like a square wave

Post by Fuseball » Sat Nov 30, 2013 5:53 pm

Mefistophelees wrote:I'm guessing the basic waves on the P12 are based on real old synths.
A pure triangle is quite boring, sort of like an enhanced sine.
This triangle at least sounds more interesting.

Remember, it's not how it looks. It's how it sounds.
Yes. I agree up to a point. The traditional triangle may not be the most exciting of waves but it absolutely has its uses. The Prophet 12 triangle both looks like and definitely sounds like a slightly filtered square wave. It sounds nothing like a traditional triangle and can't be used in the same way.

The P12's square wave doesn't look much like the ones output by my other synths, particularly on lower notes, but it sounds close enough, if a little clean. PWM is pretty close to my P08.

The P12 sawtooth is maybe a little soft by comparison but a little bit of drive (<10) seems to give it a touch more bite. Again it doesn't look that close to a straight sawtooth, such as the P08 produces, but it sounds good.

It's only the traditional triangle that's currently unobtainable (sine at shape mod +63 is closest but still not quite there). The P12's triangle feels quite redundant as a waveform. I can get exactly the same timbre by using the square wave and closing the filter a little. That's not as useful to me as a standard triangle.

In an ideal world we'd have both. :wink:
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Re: Triangle wave looks more like a square wave

Post by Bald Eagle » Sat Nov 30, 2013 6:37 pm

I also agree with the arguments defending the P12 Triangle up to a point. But a synth in this class should also be able to produce the classic analog wave forms in a manner that is a bit more familiar. There should be no reason why they can't be added with an update. I think we still deserve an official statement from DSI either stating when they will be added or an explanation why not.

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