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modular phase distortion oszillator, is that possible?
MUFF WIGGLER Forum Index -> Modular Synth General Discussion Goto page 1, 2  Next [all]
Author modular phase distortion oszillator, is that possible?
lilakmonoke
phase distortion is really my favourite sound and it just so much cleverer than subtractive and sounds better to me than fm. i still dont fully understand it, its modulating the phase of the wave? that means the beginning of the wave shifts back and forth? modulated with what?

here is a question to the developers: shouldnt there be a phase distortion module and could this even be done in analog?
thermionicjunky
WMD and Wiard/Malekko have phase modulation oscillators. The Wiard is analog.
slow_riot
there was a phase distortion patch in MaxMSP.

Basically, you use a sawtooth wave to scan through a wavetable to get your waveform, for example a sine.

I believe in a phase distortion patch the initial saw wave is itself distorted.
thermionicjunky
Phase distortion seems a bit different and is used in the SSL Modulation orgy/Tap Tempo LFO (Electric Druid).
slow_riot
http://www.electricdruid.net/index.php?page=info.pdsynthesis
lilakmonoke
i mean the phase distortion that is in the casio cz synths. that of course is done digitally but im wondering if the same could be done in analog. or is it the same in the serge?
slow_riot
that is the phase distortion that I am referring to and have linked to an explanation of.

WMD have a modular version of this coming out soon.

Or else you could use something like the Miniwave or Piston Honda and something to distort or otherwise manipulate the sawtooth wave that scans the digital wavetable.
wavecircle
Phase Distortion could be done with a piston honda. If you had a sine wave selected in the PH and drove the sine wave using the external input with non linear functions, i.e. not a rising sawtooth as the wavetable address you would get casio type phase distortion.

I think with the CZ series you would have to study the waveforms and the non linear address functions that drove the waveforms specific to those machines. If I remember correctly the CZ series also had some kind of waveshaping after the phase distortion section.
lilakmonoke
ok i get it its basically just a distortion of the waveform along the usually linear time axis. but then how do you turn any waveshape into a sine in the end, because thats what it happening on the casio?

yes, the donut could do that, the e350 not. but what about pure analog?
wavecircle
I don't think you could do CZ phase distortion in analogue because you need to have a waveform in memory to be addressed. The "distortion" of the waveform comes from addressing it in a non linear fashion. Memory is essential to do this. Analogue phase modulation is certainly possible but I can't think of a way PD could be done.

I am guessing with the casio CZ, it returns to a sine wave because a sine wave is the reference waveform in the memory and the look up address eventually returns to a rising saw in a given time?
lilakmonoke
Quote:
The sine-to-ramp PD waveform on the Casio CZ is the same as applying a variable ramp-down/triangle/ramp-up waveform as a modulator to a carrier. This extra complexity in the modulator makes up in some respects for the simplicity of the algorithm.


seems more complicated than that but the secret is in the shape of the carrier. anyways i think its brilliant because it only works with carrier and modulator having the same freq so you are staying away from disharmonic territory. my casio cz-1 is by far the best digital synth i know. its beautifully low fi digital, if that makes any sense. i would love that in my modular.

besides anything can be done in analog i think, its just maybe very complicated to do.
nerdware
Phase Distortion was Casio's way of getting around Yamaha's patent on the FM technique used in the DX synths. Yamaha used Phase Modulation, so they could use modulation feedback without nasty frequency drift effects, but they called it FM. (Who knows why?) Roland took a different approach, which they called Linear Arithmetic Synthesis.
Navs
For analogue phase modulation, you could try the A-137-2. It's saws/ pulses only, but the principle is the same.

For analogue phase distortion, try audio-rate filter FM.
matttech
i thought the WMD Phase Displacement Oscillator was essentially Phase Distortion....

As soon as I heard the demos it reminded me of a plugin called "PlastiCZ" by RE-FX that I used to really like

here's a cheesy demo someone did on youtube:



the range of sounds you can get out of it is pretty impressive, and i'm sure i recognised some of this sound in the WMD videos (especially the rounded and warm bass tones). I'm thinking that the "CZ" in the name "PlastiCZ" must be a reference to the CZ family of synths


got to forget about it though, as i've got too many oscs already!
Why Adapter
matttech wrote:
I'm thinking that the "CZ" in the name "PlastiCZ" must be a reference to the CZ family of synths



Maybe it's from the Czech Republic hihi
wsy
Phase distortion isn't hard to fake if you have a delay line that can respond FAST
to changes in CV.

Just run the carrier in as a sine wave to the input, modulator to the CV delay,
delay time to something small (like 10 milliseconds) and the CV delay attenuator
to taste. ASSUMING your carrier and modulator frequencies track accurately,
that's all you need.

(and yes, I've read Chowning's papers and his patents; he really had to dance
a jig for the patent office to admit he had something there because if you don't
make it all digital then it treads perilously close to Armstrong's patents for broadcast
FM, which were about 70 years old back then!)

If you have a copy of Roads' Computer Music Tutorial (or a copy of Alsa Modular
Synthesizer on your Linux box) this is easy to work out.

[ EDIT: I just tested this, and it works just as expected. Of course, if you over
modulate the CV so that the delay line delay becomes negative (ie. it's outputting
voltages that haven't yet arrived) you get some nasty noise, but other than that,
no surprises ]

- Bill
lilakmonoke
the delay version is probably similar in sound but not really what i would use seriously. i think PD has a bad reputation because its connected to the casio name and thought of being "plasticy". thats not what i am hearing from my cz-1. if you combine it with an analog bass its really an awesome sound machine.

here is an epic track im working on that is mainly the cz-1 and a roland sh-09 for the bass and a few effects. go hear for yourself:

http://tindeck.com/listen/qkyg

i think even an updated digital version of a pd oszillator with higher sample rate and better converters would be great. sort of like the difference between an 80s wavetable synth and an e-350 module. so instead of the next ms-20 filter can somebody please develop this? ;-)
felix le chat
lilakmonoke wrote:
the delay version is probably similar in sound but not really what i would use seriously.

It is not "similar", it is exactly the same provided your delay line is completely neutral sounding (easy to do with DSP). But of course, analogue delays color the sound a lot.

And as far as I remember, in digital audio, FM and phase distortion can produce exactly the same sounds.

Flc
lilakmonoke
in PD you are distorting the wave shape with a modulator while keeping the frequency the same. depending on the modulator you can get very different results. with a delay all you can do is manipulating the time axis while at the same time introducing a second frequency, that of the delay. so from my understanding it cant be the same.
wsy
lilakmonoke wrote:
in PD you are distorting the wave shape with a modulator while keeping the frequency the same. depending on the modulator you can get very different results. with a delay all you can do is manipulating the time axis while at the same time introducing a second frequency, that of the delay. so from my understanding it cant be the same.


I think you might be right. Phase distortion =/= phase modulation, and I think I mixed the two up. Phase modulation is what the digital delay would do. Phase distortion may well be like what the SSL tap-time LFO (and it's smaller twin, the Modulation Orgy) do.

I never owned a Casio synth (but did have a DX and wrote all of the original patches for a band back in the 80's that was heavily DX-based.) If the SSL TTLFO is genuinely the same as the CZ phase distortion, then you would just need to use a pulse wave frequency modulator, phaselocked to the carrier.

Same setup as before (carrier into the DDL audio in, modulator into the DDL CV delay in) but use a PWM wave as the modulator and phase lock it to the carrier (hard sync will work fine); vary the PWM width to vary the amount of phase distortion. No, that's not quite right; you still need to maintain balance between the first and second half of the wave.

That's the trick, I think. Not just phase speed, but maintaining a total of 360 degrees of phase at the desired frequency even though the nominal 180 degree point is getting shifted back and forth.

This is a good puzzle!

- Bill
nikmis
I have a cz-3000. That's the same type of synthesis as the other cz synths, right? There is a lot of menu selecting and I sometimes forget which is which. The envelope step button vs the value button always gets me. It is a lot of fun, though. It can do very unusual sounds, especially in the strange bells/music box/toy piano realm.
felix le chat
(please delete)
felix le chat
lilakmonoke wrote:
in PD you are distorting the wave shape with a modulator while keeping the frequency the same. depending on the modulator you can get very different results.

This is not phase distortion but wave shaping. For example, wave folders like the TWF and basic tube overdrive digital emulations use this.

Actually I was talking about phase distortion, which is distorting the phase of a wavetable oscillator (not the output of the oscillator).
For example, take a sine wave period stored as a digital audio sample. If you read the whole sample periodically, obviously it produces a sine wave tone. For doing this, you would use a periodic ramp signal that goes from 0 to 1 (kind of sawtooth), multiply the ramp value by the size of the sine wave period and connect it to the "reading point" input of the sample player.
Now if you use some processing between the ramp and the player, like adding a wave shaper or whatever else, then this system does not produce a sine wave anymore, but a tone with more harmonics instead. This is what phase distortion means for me. Perhaps I am wrong, but anyway I was talking about this.

Another implementation is using a free running sine wave oscillator and a variable time delay line. If the delay time is constant, you get a sine wave. As soon as it is modulated, some harmonics appear.

I don't see why both these techniques could not produce the same sounds as 2-oscillator FM (carrier, modulator).

That said I guess each of this techniques is best suited to a particular range of sounds.

Flc
ndkent
Looks to me from the diagrams that phase distortion is a wavetable beiing read in a not constant rate with a secondary envelope fading to zero at the end of the cycle so the wave maintains a correct pitch even if the shape is quite messed with.

I think people are confused with phase modulation. Still wanting to study it further since Wiard has it as well as the Fenix II to some extent. In analog you can modulate the phase in relation to it unmodulated. I would think any time it's being modulated the wave gets stretched or compacted,right? So that would mean a temporary frequency change. Correct? Most any significant change at an audio rate means a different timbre.

Regarding a synchronized delay of some sort, I guess that could displace a wave but when you modulate that's certainly a frequency modulation since the wavelength changes with a varying delay time change.
frijitz
Doesn't sound to me like it would too hard in analog. FM at the same frequency will give a phase-distorted waveform. It could also be done with a 4Q multiplier (ring mod) using a signal that gives the same waveshape as the desired phase distortion does.

Ian
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