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  #1  
Old 01-02-2005, 10:15 AM
rageagainst rageagainst is offline
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Default Phase shift

Could someone tell me how you would go about phase revsering in protools.

sorry for the noob question
cheers, R
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  #2  
Old 01-02-2005, 10:29 AM
danickstr danickstr is offline
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Default Re: Phase shift

mixing boards have buttons (good boards) for phase reverse, but since you also said phase shifting, i wanted to mention that i had seen a plug-in that had 360 degrees of phase shifting but i was thinking that this is not possibly accurate unless the signal is a continuous wave.

just for thought.
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  #3  
Old 01-02-2005, 10:40 AM
PTUser NYC PTUser NYC is offline
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Default Re: Phase shift

You can invert the polarity of an audio track several ways. Here's a few:

Destructively, you can use the RTAS plug "Invert".

Or you can use DSP for real time audition-able, automatable, and non destructive polarity inversion. Many plug ins have polarity switching options. I'm not in front of my PT rig right now, so I can't give a list, but it shouldn't take too long to find a plug in that has a polarity switching offered as a parameter. Try the EQs?

Anyway, keep in mind that while DSP processing is non destructive, and offers other options, unless you have Automatic Delay Compensation running on your rig, using DSP to invert polarity will result in a short delay (latency). While it might not change much in the pocket of a guitar track, for example, usually people are inverting polarity on tracks that have some audio coherence with another track, (like another part of an M/S signal, or acoustic leakage from a source which was close miked on another track, etc) with which they are hoping the inverted track will interact. In that case timing is critical, and the small delays that result from (non ADC aligned) DSP processing must be addressed.

Since polarity inversion is a simple "flip", I don't feel badly about using an RTAS plug in several times on the same piece of audio. I wouldn't, for example, boost 2kHz +3db on an RTAS EQ, decide I didn't like it, and then RTAS a 3db cut at the same frequency to get rid of it it - I'd just undo the original - something you can't always go back and do easily an hour later. With a polarity inversion, I feel OK about flipping it over rather than undoing it. Not convinced? Then get the original out of the audio bin! The point is that polarity flipping is a process for which I consider RTAS' "invert" to be a good candidate.

By the way, the reason I'm being picky and saying "polarity inversion" rather than phase, is that phase is variable in more ways than simply "180 degrees out" (polarity inversion). If you're talking about a two state "phase" control (like the button on a console) its really a polarity inversion switch, which is only one of many ways to manipulate phase.

I hope this was helpful.
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  #4  
Old 01-02-2005, 11:15 AM
rageagainst rageagainst is offline
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Default Re: Phase shift

so if i wanted to create this efect, what would you suggest.


http://www.recordingeq.com/rw/tip7.html
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  #5  
Old 01-02-2005, 11:40 AM
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allstaar allstaar is offline
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Default Re: Phase shift

Insert a Digi one band eq on the track you want to invert the polarity ("phase") on.

Click the button that looks like a zero with a diagonal line through it . If your track's stereo, click both buttons so the two sides of the stereo signal are in phase.

That's a simple answer, PTUser NYC's reply is worth taking the time to fully understand though.
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  #6  
Old 01-02-2005, 11:45 AM
Greg M Greg M is offline
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Default Re: Phase shift

rageagainst,

I have used the technique described by your link. It can sound pretty good. Record then pan exactly as the link directions say. Then, on the distant mic panned right, put on an RTAS 1 band eq and push the phase button.

Greg
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  #7  
Old 01-02-2005, 12:00 PM
rageagainst rageagainst is offline
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Default Re: Phase shift

cheers guys, that really helped.

RA
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  #8  
Old 01-03-2005, 06:08 AM
frenchman frenchman is offline
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Default Re: Phase shift

Time adjuster does it (polarity inversion) with a minimum of 4 samples delay.
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  #9  
Old 01-03-2005, 06:42 AM
TCDet TCDet is offline
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Default Re: Phase shift

Quote:
...i wanted to mention that i had seen a plug-in that had 360 degrees of phase shifting...
Is there an OSX plug-in for this? (Not for modulating, although a side-chain CV input would be nice.)
There is a hardware "Little Labs" box (IBP).
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