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#1
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Enabling LLM Reverses Output Polarity on 002R!!!
Hi, Digidesign and DUC folks. I've always had issues with the sound quality of having Low latency Monitoring turned on, so I decided to run some tests and try to see why the sound changes so much.
My signal path is: preamp-->converter-->002R digital input-->main output1+2-->002 analog input. I recorded the signal and sent it to main output 1+2 and re-recorded that on an analog 002R input. The signal is recorded on the first track with proper + polarity and after going out main 1+2 is recorded on a new track, also with proper + polarity. If I enable LLM the polarity flips on the main output.(and the second track being recorded) This is true on all buffer settings. I'm really in shock since flipping the polarity can cause such major monitoring problems, especially with vocalists. Anyone come across this? I'm currently running protools LE 6.9.2 and OSX 10.4.8 on a powerbook G4 1.5ghz. |
#2
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Re: Enabling LLM Reverses Output Polarity on 002R!!!
You do understand that LLM doesn't work with the Digital Inputs?
LLM works by passing the signal directly from the Input to the Output so it only works with the Analog connections on the interface. |
#3
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Re: Enabling LLM Reverses Output Polarity on 002R!!!
To clarify a little bit .... it LLM DOES work with Digital INPUTS .... but when LLM is checked the Digital OUTPUTS on the 002 do not work ....
Not really sure about the polarity question though .... |
#4
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Re: Enabling LLM Reverses Output Polarity on 002R!!!
Quote:
True LLM only works on the analog outs 1 &2 but that's not where the problem comes in. It does not work properly with the digitals inputs depending on what converters you are using to feed the 001, 002 etc. LLM has no way to compensate for the varying converter latency imposed by different converters. If all converters had a set latency amount it would work correctly, but since that isn't the case different converters give different result when fed to the LE with LLM turned on. I think the first time I saw this was using a Focusrite TTP w/the digital card on a Digi001 setup, at least the TTP had ways to route the signal for monitoring so i was able to get through the recording. |
#5
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Re: Enabling LLM Reverses Output Polarity on 002R!!!
This issue was fixed in Pro Tools 7.0.
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#6
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Re: Enabling LLM Reverses Output Polarity on 002R!!!
Quote:
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#7
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Re: Enabling LLM Reverses Output Polarity on 002R!!!
Well, I'm shocked this hasn't been discussed. I'm beginning to see why musicians often have monitoring problems on LE systems but not on TDM systems.
To be clear this is not a latency issue, the polarity of the track you are recording flips. If you are punching in on a track, the polarity can go from in phase then out of phase for the punch and back to in phase. This can be a real problem for singers using headphones. |
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