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Caustica
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Joined: 05/14/2017 - 05:23
Pulsating PadSynth Problem

I've been showing PadSynth some attention lately, but I've come across an issue, one I'm unsure about.  I'm either doing something wrong, it's a bug, or it just needs a little Rej-Tweaking.  There's a pulsation issue going on somewhere.  I noticed it after realising it was impossible to get a pure, non-pulsating tone out of it, or any non-pulsating tone out of it.  This is odd because being an additive synth, it should be easy in PadSynth to get perfectly smooth, non-pulsating tones out of it due to the harmonics being built-up of sine waves.

Try it, leave everything off, no LFO, no anything, and no matter what you do, there's always a slight pulsating effect when holding a key down.  I've literally given-up trying.

One of the beauties of additive synths is they don't suffer from pulsating effects that, for example, sample-based synths often do, so if anyone knows what's going on here, I'd love to hear what it is.  I was going to put this in the bug section but thought I'd check first just in case there was something I'm not aware of that is switched on and causing it.  Basically, just try to get a pure, non-pulsating sine wave out of it if you can, and if you manage it, please share the preset so that I can look at it, see what I'm doing wrong.

 

paulovski
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Joined: 09/19/2012 - 06:13
Have you tried the smear

Have you tried the smear control all the way down? (The far right slider)

Caustica
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Joined: 05/14/2017 - 05:23
Tried it on both harmonic

Tried it on both harmonic sets, the smear set minimum and with the blend hard-left, hard-right, and central.  The pulsating can even be seen in the level meter of the instrument, but really it should be a steady tone with no fluctuation.  I noticed it changes speed depending on pitch as well, so maybe the sine wave the synth is using is based on a sample and is not quite a sine wave shape.  Just guessing, obviously, but it does seem to point to that as being the issue.

Do you get the pulsating effect on yours?

 

paulovski
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Joined: 09/19/2012 - 06:13
Bear in mind that it is a

Bear in mind that it is a wave table synth. It is playing a sample. I'm not in a place to go test right now, but if I just bring up one or two harmonics i hear a perfect tone

Caustica
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Joined: 05/14/2017 - 05:23
As right, so it is based on

Ah right, so it is based on samples then.  That would definitely explain the problem and I suppose an updated sample would fix it.  Not sure how you're getting a constant tone out of it though, lol, I wish I could!

Anyway, thanks for the feedback, I'll stick it in the bug section.

 

paulovski
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Joined: 09/19/2012 - 06:13
Stick to even harmonics in

Stick to even harmonics in the editor.

You might want to read this

http://zynaddsubfx.sourceforge.net/doc/PADsynth/PADsynth.htm

Caustic Song file (optional): 

Caustica
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Joined: 05/14/2017 - 05:23
Still the same issue, even if

Still the same issue, even if I use just a single harmonic from either odd or even, the pulsating is still there.  Your demonstration of using various harmonics that are either odd or even appears to be rectifying something.  If I use just one harmonic, no matter whether it is odd or even it should be a completely pure, steady tone.

The sine wave used in SubSynth for example is perfectly fine, no pulsating at all, it should be like that, but that's not the case when using a single harmonic in PadSynth, not even with the smear set to minimum.  Thanks for looking into it though, and I've added it to the bug section so hopefully Rej will take a look some time.

 

paulovski
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Joined: 09/19/2012 - 06:13
I'm not using odd harmonics.

I'm not using odd harmonics.

It's not Rej's algorithm. He can't really do much about it.

Caustica
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Joined: 05/14/2017 - 05:23
I never said you were using

I never said you were using odd harmonics.  I said no matter whether I use all odd or all even, I still get the same problem.  Not sure why you're talking about algorithms, it's an additive synth, kinda like a simplified Kawai K5000.  On additive synths, the sound is built-up in an additive fashion using sine waves, so if the basic building block of the synth, the sine wave, is fluctuating as it is in PadSynth, then it's not going to work properly.  Like I said, one of the beauties of additive synthesis is it doesn't suffer that pulsating effect, or "beating" as it's sometimes called.

Have a play with Harmonaut (Free VSTi Additive Synth) to see what I'm talking about:
http://vst4free.com/free_vst.php?plugin=Harmonaut&id=1668

Anyway, like I said, I've added it to the bug section so hopefully he'll take a look at it some time.

James
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Joined: 01/21/2013 - 07:09
The reason Paul is talking

The reason Paul is talking about algorithms is because the C++ code that drives the Padsynth was written by someone else, and that someone else describes it as the 'PADsynth algorithim'.