PWMing sound examples?

Discussions about anything analog, digital, MIDI, synth technology, techniques, theories and more.
User avatar
Zamise
Supporting Member!
Supporting Member!
Posts: 2351
Joined: Wed Oct 20, 2004 2:41 am
Gear: Rollhand P00
Band: Quantum-Source
Location: DenverMetroUSA, Quantum-Source.com
Contact:

Re: PWMing sound examples?

Post by Zamise » Fri Sep 10, 2010 12:51 pm

Its not processed to high quality yet, and I sound like total gimboid trying to hold a camera, mic, and play the crud too, but here is my dabblings. AG is going to kill me.

<ZQS> [....<OII>.....soundcloud player v2.42.....................link]

User avatar
Solderman
Supporting Member!
Supporting Member!
Posts: 1799
Joined: Sat Nov 17, 2007 5:43 pm

Re: PWMing sound examples?

Post by Solderman » Fri Sep 10, 2010 2:41 pm

I'm not sure what is missing, because I would get something very much like PWM when I had a Minikorg 700s and used the sawtooth for Osc1. Osc2 can only be an inverted sawtooth on the 700s.
As far as creating a pulsewidth of varying duty cycle from sawtooth or any waveform really, you would just need a comparator in the correct place in the oscillator circuit, which is how the Akai AX60 does it. The Roland Alpha Juno is doing it differently, I believe. PWM is generated before the waveform is transformed from rectangular into a sawtooth in its case.
I am no longer in pursuit of vintage synths. The generally absurd inflation from demand versus practical use and maintenance costs is no longer viable. The internet has suffocated and vanquished yet another wonderful hobby. Too bad.
--Solderman no more.

User avatar
Zamise
Supporting Member!
Supporting Member!
Posts: 2351
Joined: Wed Oct 20, 2004 2:41 am
Gear: Rollhand P00
Band: Quantum-Source
Location: DenverMetroUSA, Quantum-Source.com
Contact:

Re: PWMing sound examples?

Post by Zamise » Fri Sep 10, 2010 3:54 pm

I think I'm getting it now, maybe... I tone generated a perfect saw, then inverted it, and then mix pasted the two together and they cancel each other out. If I change the width of one of the saws after that then do a mix paste I get squares/pulses of different lengths and widths like shown in the SY77 manual.

Seems to generate fine on computer now, it makes sense, but when I get the opposing saws in my sampler, they do not cancel out when I play them at the same time. I also no longer have a perfect saw when I record one back on my computer from the sampler, it is more of a sine.

I noticed opposing sines will cancel when mix pasted, but when offset they never seem to generate a square/pulse, for the most part just getting louder or quieter in amplitude and still all curvy, so not so much noticeable PWMing, actually no squares at all are generated.

I think that may be what is happening inside my sampler since the saws nor the squares are perfect and look more like curvy wobbly sines with a sort of saw like shape to them. So I might as well just be using sines which are c**p for noticing the PWMs.

The CS-15 saw I sampled was more of curve on one side then sharp drop than a perfect saw which probably didn't help much either on my first attempt at it.

Probably too much BS to make heads or tales of what I'm trying to get done now :? So I won't go into the strange sounds I heard when I played 3 offset saws together on my sampler :? :? :?
<ZQS> [....<OII>.....soundcloud player v2.42.....................link]

User avatar
pricklyrobot
Synth Explorer
Synth Explorer
Posts: 1742
Joined: Sun Feb 19, 2006 6:37 am
Location: Austin, TX

Re: PWMing sound examples?

Post by pricklyrobot » Fri Sep 10, 2010 7:33 pm

So, you're reinventing tremolo, via phase cancellation? #-o
Arturia MiniBrute -- bits o' Euro -- Sammich SID -- E-mu MP-7 -- Korg ER-1 -- Thingamagoop

User avatar
madtheory
Supporting Member!
Supporting Member!
Posts: 5155
Joined: Mon May 01, 2006 12:45 pm
Real name: Tomas Mulcahy
Gear: Flangebeast Mk1, Plonkotron, Morovdis Arpeggiator, Maplin My First EQ, Jeff Wayne Thunderchild rack, Thermostat, Buck Owens' Moog.
Band: Minim
Location: Cork, Ireland
Contact:

Re: PWMing sound examples?

Post by madtheory » Sat Sep 11, 2010 12:00 pm

Stop using "ing"! What you're saying is "Pusle Width Modulationing" which makes no sense. It's not a verb. And don't say "the PWM" either, it's not a noun. It's a description of an action (I think that's called an adverb, but check with AG ;) ). I think that will help you to understand how it works.

Three offset saws is just a form of detuning. As suggested earlier, get the Novation demo, and hook it up to a scope. Educational, and it's also a very cool synth.

User avatar
Zamise
Supporting Member!
Supporting Member!
Posts: 2351
Joined: Wed Oct 20, 2004 2:41 am
Gear: Rollhand P00
Band: Quantum-Source
Location: DenverMetroUSA, Quantum-Source.com
Contact:

Re: PWMing sound examples?

Post by Zamise » Sat Sep 11, 2010 1:42 pm

If one is adjusting the Pulse Width Modulation (PWM) then they are Pulse Width Modulating (PWMing), one becomes a Pulse Width Modulator (PWMor), eh???

To be correctlitudliest, should I be saying that I want to hear some Pulse Width Modulation Modulating (PWMMing) sound examples?

Whats the Novation Demo? Is it freeware?

I just got the Schope VST mentioned in another thread , quite a bit better and faster using it than recording, zooming, and scrolling through the waves on a sound editor.

I was getting what sounded like resonance sweeping with 3 sampled saws, one being inverted the other two identical on my RS. It didn't sound like detuning or trem really, but hey yeah I am probably reinventing something dumb, but I figure sampling the waveforms turns them to crud is my big problemo. I'm thinking what I'm wanting to do using samples to PWM, would just be 100x easier just to sample an already PWMMed wave. There are already PWM voices in my RS too, but I'm thinking it is a static PWM. I'm wanting to hear PWM movement.
<ZQS> [....<OII>.....soundcloud player v2.42.....................link]

User avatar
aeon
Moderator
Moderator
Posts: 881
Joined: Sat Apr 02, 2005 8:18 am
Location: a lily-pad in the pool of my mind.
Contact:

Re: PWMing sound examples?

Post by aeon » Sat Sep 11, 2010 9:10 pm

The summed-saws trick works a treat when you introduce gentle pitch-mod to one of them - you get spectral movement a la PWM, but if you have serious mod control, a la E-Mu Command Station engine, you can get all kinds of Brownian/semi-random PWM spectral movement.


cheers,
Ian

User avatar
Zamise
Supporting Member!
Supporting Member!
Posts: 2351
Joined: Wed Oct 20, 2004 2:41 am
Gear: Rollhand P00
Band: Quantum-Source
Location: DenverMetroUSA, Quantum-Source.com
Contact:

Re: PWMing sound examples?

Post by Zamise » Sun Sep 12, 2010 1:11 am

Pitch modulation hmmm... well I don't know if I am still fully understanding yet. But when I am pitch modulating one of the two sampled opposing saws then to me that is where I can not tell the difference from simple detuning of one of two normal saws being played together and supposed sample based PWM. This is where my confusion lays, and I wonder am I really doing PWM via playing two sampled waveforms?

Last night I retried the sampled saws a little difrently than what I was doing, I put one opposing saw on left channel and the other right played them together expecting to hear tone, one in left and one in right, I heard tone like expected, then I processed the two opposing saw samples within my RS to make the L&R in to a mono. Guess what? They canceled each other out and I got no tone. So the samples them selfs are not c**p, they are good saws. So I am thinking, the reason why PWM doesn't work using samples is I am thinking the waveforms have to be summed together at an earlier stage and that waveform played instead of having the two playing together.

Not sure it makes a whole of sense why it wouldn't work the same either way, but the only analogy I can think of to help myself somewhat understand is:

If you have two lights and you are pulsing the electricity to them in opposite phases you are still going to be lighting up your room, they don't cancel out keeping the room you are in dark. Correct? This represents playing the two opposing samples from sampler to a speaker. However if you combined the electrical signals or summed the pulses of electricity before they get to a light, then it is doing Pulse Width Modulation and if you had opposing, or inverted, or phased 180 electrical signals, they would cancel each other out, the light would then not shine and you'd be in the dark.

If anyone is still reading, would that be a proper analogy to what is going on with sound? Is there a name or technical term for what I'm talking about?
<ZQS> [....<OII>.....soundcloud player v2.42.....................link]

User avatar
Solderman
Supporting Member!
Supporting Member!
Posts: 1799
Joined: Sat Nov 17, 2007 5:43 pm

Re: PWMing sound examples?

Post by Solderman » Sun Sep 12, 2010 3:12 am

Did you remember to detune those sawtooth waveforms slightly before mixing them to mono? The movement is created by the beat frequency of them a few semicents apart. It's easier with analog because they are never actually perfectly in tune.
I am no longer in pursuit of vintage synths. The generally absurd inflation from demand versus practical use and maintenance costs is no longer viable. The internet has suffocated and vanquished yet another wonderful hobby. Too bad.
--Solderman no more.

User avatar
clusterchord
Active Member
Active Member
Posts: 742
Joined: Sun Oct 02, 2005 8:35 pm
Real name: Tomislav
Band: Nimbus Dei
Location: Zagreb, Croatia
Contact:

Re: PWMing sound examples?

Post by clusterchord » Sun Sep 12, 2010 3:25 am

here's a cpl of examples:

sh2, first one then two oscillators, introducing PWM, switching octaves, and finally tweakin filter cutoff:

http://www.babic.com/SYN/SH-2/clc_SH-2_ ... pwmseq.mp3

slow PWM on trident mk1, w filter env:

http://www.babic.com/SYN/TRIDENT/Tri1_ResoPWM-Strgs.mp3

fast PWM on OBXA, almost canceling out at extremes:

http://www.babic.com/SYN/OBXA/OBXA_lfo-pwm-ddl.mp3
Image

jupiter · oberheim · prophet · sh · moog · andromeda · ppg wave · vs · waldorf · yamaha · eii · casio
rhodes · solina · acetone · eurorack · system100 · förster · lexicon · eventide · space echo · svc350 etc

User avatar
Zamise
Supporting Member!
Supporting Member!
Posts: 2351
Joined: Wed Oct 20, 2004 2:41 am
Gear: Rollhand P00
Band: Quantum-Source
Location: DenverMetroUSA, Quantum-Source.com
Contact:

Re: PWMing sound examples?

Post by Zamise » Sun Sep 12, 2010 3:29 am

@ solderman - Nope I didn't detune. I can detune one while playing them together which to me I don't think is producing a true PWM by playing them together on my sampler, it sounds like normal detuning between any two indentical sampled sounds. What I've been doing is phasing the cycle on the inverted sample so it has the same cycle time which isn't detuning as far as I know, it should still adjust the percentage of the pulse width but not the cycle length. Or something like that, Right-O-chaps?

Listing to those examples now clusterchord...
<ZQS> [....<OII>.....soundcloud player v2.42.....................link]

User avatar
Zamise
Supporting Member!
Supporting Member!
Posts: 2351
Joined: Wed Oct 20, 2004 2:41 am
Gear: Rollhand P00
Band: Quantum-Source
Location: DenverMetroUSA, Quantum-Source.com
Contact:

Re: PWMing sound examples?

Post by Zamise » Sun Sep 12, 2010 6:33 am

Those are awesome examples clustershord, thanks! I think I can more distinctly here the PWM doing its thing on those and I don't think I am really getting quite the same thing out of using samples. But maybe I am, and I just don't know it. The second example, the Trident, I've always liked the sounds on those for some reason and don't know why exactly, I don't think the Tritons at least not without a Moss board would soud like your demo. Maybe I don't know what I'm talking about still, but something about the Trident sounds tho, I need to look more in to those some day.
<ZQS> [....<OII>.....soundcloud player v2.42.....................link]

Mooger5
Expert Member
Expert Member
Posts: 1459
Joined: Tue May 06, 2008 5:11 pm
Location: Lisbon

Re: PWMing sound examples?

Post by Mooger5 » Sun Sep 12, 2010 4:30 pm

Zamise wrote:@ solderman - Nope I didn't detune. I can detune one while playing them together which to me I don't think is producing a true PWM by playing them together on my sampler, it sounds like normal detuning between any two indentical sampled sounds.


He´s right. If one of the waves is slightly detuned it won´t sound the same as normal detuning of identical waves. Both will still be out-of-phase most of the time, not cancelling out completely since they´re running at different cycles, but attenuating/deattenuating each other progressively. That´s what gives movement. And when both meet in-phase the audible result is a pulse with constantly varying width. It sounds very very close to a normal PW slowly modulated by a triangle wave LFO, although without any sort of control over modulation amount or PW starting point. I´ll try and post some audio examples.
What I've been doing is phasing the cycle on the inverted sample so it has the same cycle time which isn't detuning as far as I know, it should still adjust the percentage of the pulse width but not the cycle length. Or something like that, Right-O-chaps?

Listing to those examples now clusterchord...
That´s a clever idea. That way you can determine a "static" duty-cycle for the pulse. Some samplers provide dynamic sample starting points but I´m not sure if the resolution is enough to shift them with LFOs or EGs at will.
Herrare umanum est.

User avatar
madtheory
Supporting Member!
Supporting Member!
Posts: 5155
Joined: Mon May 01, 2006 12:45 pm
Real name: Tomas Mulcahy
Gear: Flangebeast Mk1, Plonkotron, Morovdis Arpeggiator, Maplin My First EQ, Jeff Wayne Thunderchild rack, Thermostat, Buck Owens' Moog.
Band: Minim
Location: Cork, Ireland
Contact:

Re: PWMing sound examples?

Post by madtheory » Sun Sep 12, 2010 7:06 pm

Here's the Novation V Station plugin, it's cool:
http://www.novationmusic.com/support/v_station
Zamise wrote:If one is adjusting the Pulse Width Modulation (PWM) then they are Pulse Width Modulating (PWMing), one becomes a Pulse Width Modulator (PWMor), eh???
No, and furthermore you've not had a need (nor will you) for any of those contractions.

Mooger5
Expert Member
Expert Member
Posts: 1459
Joined: Tue May 06, 2008 5:11 pm
Location: Lisbon

Re: PWMing sound examples?

Post by Mooger5 » Sun Sep 12, 2010 8:39 pm



0:00 - Synth1 square wave
0:03 - selecting various pulse widths
0:09 - PWM by LFO
0:18 - saw wave
0:20 - two identical saw waves in phase
0:23 - two identical saw waves in phase, one detuned by 3 cents
0:30 - two identical saw waves out of phase, one detuned by 3 cents
0:42 - two identical saw waves out of phase, the starting point of one being randomly shifted
Herrare umanum est.

Post Reply