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Phase Opposition (or phase invertion ?)

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JoPo

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Re: Phase Opposition (or phase invertion ?)

PostSun Jul 10, 2016 12:11 pm

Yes, W_ellis ! You're right ! Phase inverter in a mixer behaves like sync inverter module. When signal is above 0 (only positive, rarely goes under 0), it outputs the signal with its phase inverted uder 0 (only negative) and I'd like to obtain the signal with its phase inverted but remaining above 0... I konw it's weird but I have an idea and I'd like to see what it would result. :mrgreen:
My goal is to have the exact opposit on right & left pan. Like on the 2 jpg first curves but with any curve, like random lfo.

--> Shark --> is there a way to extract dc offset from a signal and use this dc offset continuous signal ? I just find dc filter (and SC dc filter outputs only 0 value, here), nothing that could extract the dc offset. If I was able to extract the dc offset, I would be able to achieve what I want to do.

sharc wrote:For a basic waveform like a triangle you can shift the phase 180 degrees using a comparator with a 1 sample delay on it's threshold input. This then acts as a peak detector which you can use to invert the original ie - sawtooth from triangle.

Ah... :| Ok... :shock: Can you show me how it would look like ? :? :mrgreen: 180 degrees is what I'm looking for ! :)

Thanks a lot for your help, guys ! I increase knowledge and this is my food.
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sharc

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Re: Phase Opposition (or phase invertion ?)

PostMon Jul 11, 2016 8:01 pm

JoPo wrote:180 degrees is what I'm looking for !


Yes, excuse me for responding without taking the time to check. The method I suggested will give you a 90 degree phase shift ;)

For 180 degrees you can use an Inverter Sync or Mix1 Bipolar. You just need to remove the DC offset first if there is one ...and then re-apply it
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sharc

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Re: Phase Opposition (or phase invertion ?)

PostTue Jul 12, 2016 7:10 pm

JoPo wrote:--> Shark --> is there a way to extract dc offset from a signal and use this dc offset continuous signal ? I just find dc filter (and SC dc filter outputs only 0 value, here), nothing that could extract the dc offset. If I was able to extract the dc offset, I would be able to achieve what I want to do.


Possibly with a contiuous waveform, but I can't think off-hand of a way you could do this in realtime with a DC offset on a random LFO.

If I remember correctly the DC filter module reduces the level of the input signal by a fair amount ...and is quite DSP hungry when used in multiple. I played around with it when I was working on the ADD16T modules before realising it wasn't needed in that instance. For those I ended up using Mix modules with a -ve constant val on one signal input to remove the offset of each harmonic. If you know the amount of DC offset as I did in this case then it's easy enough to remove it manually.

A mix module can both remove the DC offset and invert the phase.

For auto-removal you could try using a comparator + S&H to detect the positive and negative peaks in an offset waveform. This could then determine the value to remove the DC offset. This method probably won't work very well at all for random waveforms.

The delay method would work (again for continuous waveforms) but uses more DSP and gets more complicated if the source signal doesn't have a fixed frequency.
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JoPo

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Re: Phase Opposition (or phase invertion ?)

PostFri Jul 15, 2016 11:40 am

Houlala ! I have a lot of work ! :P

Thanks a lot, Shark for all those advices ! They help me a lot for learning !
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