Old 10-31-2016, 09:49 PM   #41
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Borrowed my friend's laptop/interface for a test.

I generated five white noise files: at 0dBFS, -0.5dbFS, -1dBFS, -3dBFS, and -6dBFS. I also chose two music files: one mp3 ("Mexico City" by Jolie Holland), and one wav ("The Dream that You Are" by Libby Kirkpatrick), all 44.1k. Noise files were mono (well, stereo with identical track on both sides, due to accident.)

Interface used was a Universal Audio Apollo Twin. Did an analog loopback via balanced 1/4".

Played from Reaper, recorded in reaper. Played from iTunes, recorded in reaper.

I had to adjust the input gain slightly on the interface when playing through iTunes, but it may have had more to do with the coarse-grained GUI for adjusting the input gain than anything else (I had to set it at the last "click" before clipping when playing the 0dBFS file... i.e. it might have been a tiny rounding issue or something and so I had to go to the next-lowest click for iTunes... not sure.). This resulted in a difference of 0.7dB between the reaper and iTunes results, but this 0.7dB relative difference was preserved exactly across all test results.

So, no real difference in levels. There was no difference in the stereo field, judging by "lissajous" vectorscope. There was no difference in long-term average EQ. There was no audible difference at all.

Short version: I could find no difference in the results at all.

So, with my friend's mac laptop and that interface, I found nothing to imply that iTunes was messing with the sound in any way.

I think the OP needs to do the blind testing and get back to us. :-)
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Old 11-05-2016, 10:18 PM   #42
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Thanks for taking time out.
I think what someone mentioned is probably what I was hearing... Some sort of EBU R128 thing, that would make sense as the CDs I've ripped are all normalized/clipped to -0.1dBfs source files. My last post I decided it was close enough to not be able to tells differences After I posted I realized that the reaper track I was comparing was the one that I had lowered the volume, applied slight compression and a ebur128 limiter. That I did in an effort to match what I thought the iTunes version sounded like. I forgot to bypass for my final analysis, hahaha.. so yes they did sound the same. Level wise, I'm not sure how one would test for ebur128 style compensation, it's not easy to test for but it is a real perceptible thing.

Regarding reaper's approach to stuttering... I often mix in ways that take my track count over 100 tracks. Stock plugins are usually fine, but when I use more interesting plugins my playback sometimes struggles. The problem is, it's not consistent, and not really predictable. Maybe playback fine during the mix process, say after 8 hours I'm happy and I call it a night planning to listen and bounce in the morning with fresh ears. The next day it stutters in one spot, and I have to bounce stems or restart, clear cache, change plugins, etc, etc,... the thing I don't like is I have to use my ears to listen for pops/glitches. There's no indication whether I'm in pure 24bit/48 mode or something drastically less, as heard during the stuttering. Sometimes it only happens once during the the whole bounce, and I have to listen with extreme focus to verify it didn't happen. Means mixing with an analog chain as a master bus isn't as simple as it should be.. should be a simple play-record. Then my head says, well if it can't play it back, can it even bounce it internally correctly??? Doubt creeps in. Although yeah I do a good job of saying "reaper rules.. who cares".. back of my mind the doubt always creeps back in like a weed.

Last edited by otb; 11-05-2016 at 10:32 PM.
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