[solved] Oscillater Phase Shifter?

[timbowek]

Been having trouble trying to do some exercises that come in the book i bought for sound design. There a point were it says , to sync 2 Sawtooth wave OSCthen only change OSC 2 to 90 degree Phase, and the other is the same process only with the OSC 2 Inverted I suppose it means 180 degrees????

Where do I change the Phase of an oscillator (Phase Int)???

Is there a way to only change OSC 2 Phase or even invert the OSC2??

The book is called "How to Make Noise" Simon Cann , I use a Polar.

[Timo]

Originally Posted by timbowek

Where do I change the Phase of an oscillator (Phase Int)???

Is there a way to only change OSC 2 Phase or even invert the OSC2?

I don't have a Polar, but on my old Indigo you can find Phase Init (the phase at which Oscillator 2 starts) in the Oscillator Edit menu.

A Phase Init value of 0 is totally free running. In other words, Phase Init is disengaged and therefore the waveform phase of Oscillator 2 is not sync'd to Oscillator 1 in any way.
Phase Init of 1 would start Oscillator 2 at 0° at key-on.
Phase Init of 64 would be 180°.
Phase Init of 127 would be nearly 0° again, as you've nearly come full circle (360°).

Given that it is linear, a Phase Init of 32 (a quarter of the available 127 values) would start Oscillator 2 at around 90°.

By the sound of it, you want Oscillator 1 completely out of phase with regard to Oscillator 2. However I don't believe you can't change the start phase of Osc1, so instead simply set Osc2's Phase Init to 64 (which would be 180°, as you mentioned) and you should get the same effect.

Phase inversion at 180° would only occur when you use oscillator waveforms that have orders of symmetry higher than 1 (such as sine, triangle, square, etc.). In this case, both oscillators summed will cancel each other out when using the same tuning.

To physically invert a saw wave or other complex waves, you could also try the TI's Wavetable PWM Oscillator. You should be able to physically modulate the "pulse width" of this oscillator too, rather than at key-on only.

[timbowek]

Thanks, Timo I thought that with the Phase Int you Shifted the Oscillator 1 but it makes sense it will change the second oscillator. So if i ake say Two Squares ut them in Sync mode then give the second Oscillator's and set its Phase INT to 64 (180°) will the sound completely cancell itself??

[Timo]

Nearly. You don't need Sync mode*, just Phase Init. But yes, two square waves (or sine, or triangle) at identical tuning will cancel each other out when a phase init of 64 (180°) is used for Osc 2.

Try it yourself.

• Load up the patch called -START- or -INIT-
• then change the Osc Balance knob to zero (the middle) so you can hear both oscillators.
• turn Osc 2 detune down to zero.
• change both Osc 1 and Osc 2 to Pulse waveform
• set Phase Init of Osc 2 to be 64.

Press a note, and you should be able to hear.. not a lot really. You might hear a click or pop as you hit a key but this is due to the Punch Intensity. You can turn Punch down to zero in the main edit menus.

You might hear it slowly phasing slightly but this would be due to fine detune values of Osc 2, or the analogue-esque emulation side of the Virus (subtle detune instabilities - if you want clinical waveform accuracy, turn up PureTuning to the max).

* Sync mode is a completely different function to Phase Init.

Phase Init merely starts Osc2 at a particular phase position - the oscillator is free to do whatever it wants thereafter, it's free running.

Sync mode, however, forcefully resets the phase of Osc2 to 0° everytime Osc1 completes its own phase cycle.

Graphic illustration of sync mode: http://www.infekted.org/virus/files/sync.png

[timbowek]

Thanks Timo for the help now how do i CHange the [Unsolved] to solved

[Timo]

Done.

I also edited/added in a bit more info to my last post, so you can follow it easier.