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Author	Topic: phase offset
keph Member	posted 20 March 2004 18:59 i am struggling with creating a dynamic phase offset for an LFO. i desire to send one LFO to two different hotparameters but offset one slightly from the other. easy enough to do with a delay with zero feedback, but i thought it would be nifty to offset in terms of degrees and have the phase offset adjust based on the frequency of the LFO. i think this would also be a delay that adjust the delay based on the frequeny of the LFO. however, i can't get seem to get it right. any ideas? IP: Logged
KX Member	posted 21 March 2004 17:20 If the delay is set to 1/LfoFrequency it will offset by 360degres (if my maths are OK). So 1/LfoFreq divided by 2 should offset by 180degres, by 4 offset 90 etc.. IP: Logged
SSC Administrator	posted 21 March 2004 18:14 How about if you click frequency modulation, use a Constant as the modulator, and set the MaxMI to: Float pi * 2. In the Value parameter of the Constant, you could use: !Degrees / 360.0 to control the phase offset in terms of degrees. IP: Logged
keph Member	posted 21 March 2004 19:01 quote: Originally posted by SSC: How about if you click frequency modulation, use a Constant as the modulator, and set the MaxMI to: Float pi * 2. In the Value parameter of the Constant, you could use: !Degrees / 360.0 to control the phase offset in terms of degrees. ah, interesting. thanks. using the delay always ran into the problem of a built in maximum offset (LFO freq under the 0.25 range was problematic). i post some results to tweaky shortly. IP: Logged
KX Member	posted 21 March 2004 19:12 Simple (!!) and very effective. I was looking for this kind of offset for LFO. thanks I'll try that for each partial in additive resynth... Could you explain in a few words how this "Float pi * 2" works? IP: Logged
SSC Administrator	posted 22 March 2004 09:28 Float pi * 2 sends the message "pi" to the Smalltalk class "Float" to return a constant that is an approximation of pi. Then it is multiplied by 2. IP: Logged
KX Member	posted 22 March 2004 10:43 quote: Originally posted by SSC: *Float pi 2 sends the message "pi" to the Smalltalk class "Float" to return a constant that is an approximation of pi. Then it is multiplied by 2.** I understand that part; I'm wondering how freq mod can success as a phase shifter (delay). Is it smalltalk-specific? IP: Logged
Bill Meadows Member	posted 22 March 2004 19:34 2*pi radians is the same as 360 degrees. So modulating the frequency between 0 and 360 degrees accomplishes the same thing as phase shifting the signal that amount (since it is periodic and infinite). IP: Logged
KX Member	posted 22 March 2004 21:26 So the frequency is NOT modulated when the unit is degree; the wavetable index is simply offset, right? IP: Logged
pete Member	posted 23 March 2004 04:24 Thats right, it's realy phase modulation as is both the the DX7 and the Synclavier II. None of them are true FM, they should realy be called Phase modulation Synths. If these Synths were realy true Frequency modulation types, the results would be just the same except that the oscilators modulation would be 90 degs out of phase (which wouldn't sound any different) and the FM effect would be very very small if the mod input was high frequency, and very very large if the mod input was low frequency. A true FM synth would be uncontrolable and not very user friendly. By the way it's always Phase modulated wether the unit is in degrees or not. [This message has been edited by pete (edited 23 March 2004).] IP: Logged
KX Member	posted 23 March 2004 16:16 quote: Originally posted by pete: A true FM synth would be uncontrolable and not very user friendly. Even PM is not that user friendly! I knew DX is PM... I'm still trying to figure how a phase shift can change the pitch I think I should do some drawing to see the problem... IP: Logged
keph Member	posted 23 March 2004 22:52 quote: Originally posted by KX: Even PM is not that user friendly! I knew DX is PM... I'm still trying to figure how a phase shift can change the pitch I think I should do some drawing to [b]see the problem... [/B] this may be usefull as well: http://www.analoguesque.com/modsynthesis.htm (scroll past the book adverts at the top.) IP: Logged
pete Member	posted 24 March 2004 05:36 Try thinking of it this way. The world is rotating once every twentyfour hours. If a person stays in London for exactly one week he will see seven days and seven nights. Some one else who was staying in New York for the same time time would also see seven days and seven nights all be it in a different phase to the chap in London. Both these people will see the days oscilate at seven cycles per week. If yet another person was to take a cruse around the world (ie changing his phase) for the same weekly period he would see eight days and nights or six days and nights depending on which way round the world he went. His days would oscilate at eight cyles per week (or six cycles per week). You can see from this that a continuse change in phase will alter the frequency. You should also see that if the phase changed one whole cycle every second it would either add 1hz or subtract 1hz from the original frequency. Does this make sence? Pete IP: Logged
KX Member	posted 24 March 2004 12:26 Thanks! now it' clear IP: Logged
KX Member	posted 26 March 2004 00:55 I enjoy to see advanced users being so patient... thanks all! [This message has been edited by KX (edited 26 March 2004).] IP: Logged

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