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Can crossfeed cause elevated peak levels?

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DaveA:
On Sansa Clip Zip, I was playing some tracks with the peak meter enabled with an upper limit of 0db, and noticed that the tracks would sometimes clip, at least as far as the peak meter was concerned.  I didn't notice any audible clipping.  These were FLAC files with ReplayGain peaks calculated equal to or less than 0dB, although I had ReplayGain turned off when listening.  Meier crossfeed set to ON; equalizer OFF.

As an experiment, I turned off crossfeed and the tracks no longer would clip on the peak meter.  I then turned crossfeed back on, and once again they were shown as exceeding 0dB.  I then applied a precut of -1dB, and this also kept the peaks under 0dB.  My questions are:

a) Is it possible that crossfeed is slightly elevating the track peaks?  The results with crossfeed on vs. off seem to suggest this.

b) Is this something to be concerned about?  Given that a precut of -1dB seemed to prevent the 0dB threshold from being exceeded, maybe such a small elevation above 0dB isn't that much of a problem or something I should correct for?  Or is it?

Thanks for your help.

saratoga:
Since its adding a time delayed version of one channel to the other, I don't see why the amplitude would necessarily be less than the version without crossfeed. 

DaveA:
True, I wouldn't expect that the crossfeed version would be any less, but I hadn't really considered that it might be greater than the non-crossfeed version either.  But it makes more sense now.  Since the replaygain calculated peak is with no effects applied, that peak wouldn't necessarily be guaranteed with something like crossfeed applied.

My main concern really is exceeding the 0dB reference by some amount.  Is there any danger in going over that number by 1 dB or less?  I know the volume control goes up to +6dB, I'm just not sure how much 0dB can be exceeded without running into problems.

saratoga:

--- Quote from: DaveA on April 09, 2014, 01:34:10 AM --- Since the replaygain calculated peak is with no effects applied, that peak wouldn't necessarily be guaranteed with something like crossfeed applied.
--- End quote ---

Yeah, replaygain assumes that you do no other processing.


--- Quote from: DaveA on April 09, 2014, 01:34:10 AM ---My main concern really is exceeding the 0dB reference by some amount.  Is there any danger in going over that number by 1 dB or less?  I know the volume control goes up to +6dB, I'm just not sure how much 0dB can be exceeded without running into problems.

--- End quote ---

I'm not sure how much head room is built into the DSP, but in theory you could probably design a signal that did not clip, but that when feed through the crossfeed gain 3dB of additional volume.  This would not be likely in practice however.  I probably would not worry about it, the occasional clipped peak is rarely audible except in extreme circumstances or with massively compressed audio. 

FWIW, the +6dB is for the volume control, which is all analog.  That basically just means you're telling the gain on the amp to make up for an input signal that is less than full scale. 

DaveA:
OK, this makes sense.  Thank you for your insight, saratoga.

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