I finally got around to a quick test of this, because tomorrow night is my big comp: V3 A/D vs 722 A/D.
so, I want the levels to be right on. I just did a minute long test in front of my home stereo.
V3 > S/PDIF > HD-P2
and
V3 > analog > line-in 722 (-5 dB)
both recorders at 24/96.
after transferring the files to my computer, I went into WaveLab and trimmed the start and end of the two files so that they start and end at the same point. I then did an analysis to see how the levels turned out.
here are the results:
HD-P2 levels:
and
722 levels:
so, if we look at the average RMS values, the left channel is within 0.04 dB between the two recordings, and the right channel is within 0.06 dB between the two recordings.
I am thinking that this is
very good level matching between the two recorders, and that my full-on comparison tomorrow night will be a wonderful comp between V3 A/D section and the 722 A/D section.
but I was still curious about the tiny discrepencies. I
think this is the reason: because I did not use wordclock to sync the two files, even though I trimmed the two files to start and end at the same place, the files from the 722 was actually slighty longer, as evidenced by this shntool output:
from that, we can see that the file from the 722 is 0.003 seconds longer than the file from the HD-P2, which is roughly 288 samples at 96 kHz. so, it is entirely possible that the very slight level variations are from the different number of samples being analyzed between the two files. unfortunately, I do not have a BNC > BNC connector, otherwise I would run word clock out from the V3 to the wordclock input on the 722 (my V3 is not an opti-mod).
anyone have any other suggestions as to why the levels are
slightly off. (of course, with levels that close, I don't think people will really be able to detect that small difference, and that won't affect what people think of the comp.)
BUT, I think my comparision will still be valid, even with the different digital clocks. it looks like the levels will be spot on, and I have no intention of ever mixing the two sources, so the slight time drift will be a non-issue for me.
so, this brief test of mine indicates that the published output levels on the V3 and the published input levels on the 722 are spot on.
and as a side bonus, this was the first time I ever used the analog outs on the V3. by running from both the analog and digital outputs, I was able to verify that Grace did indeed fix the polarity of the digital output relative to the analog outs. not that I ever doubted it after getting the unit back from them, but it's nice to see right in front of me that the two files were of the same polarity