In Reply to: Charles, Please tell me if this makes sense. posted by Jim Austin on May 31, 2017 at 20:21:45:
I realized that I was unclear with how I presented the plot I posted above--not just with AA readers but with myself. I made that measurement a while ago and had not recently thought much about exactly what I'd done. I decided to revisit the issue. With a bit more confidence--not to say understanding--I compared Tidal files: the MQA file (decoded) and the CD-res file, with the MQA decoder turned on--but this of course is not an MQA file, so that shouldn't matter. This is the first track on Beyonce's Lemonade, which is available on Tidal in MQA (44.1/24 decoded) and regular CD resolution.I repeated this several times, carefully. Spent 2 hours recording three minutes of music, over and over, being very careful not to get the files confused. I'm confident of the result. There are two spectra in the chart below: MQA is red (although you can hardly see it), CD-res is yellow. These are Tidal files delivered bit-perfect to the converter--the Mytek Brooklyn--via Roon. The Brooklyn's MQA converter is turned on.
The two spectra--44.1 MQA, decoded, and CD-res--are identical, to within small fractions of a dB.
What's the nature of the ultrasonic information then? Upsampling? Aliasing? I don't know. But while I haven't ruled out the possibility that the Mytek DAC's MQA filter could be involved (since it could still be active even with non-MQA data), this does not appear to be an MQA phenomenon.
Edits: 06/05/17
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Follow Ups
- To clarify ... - Jim Austin 13:06:30 06/05/17 (14)
- Something seems very wrong here - Charles Hansen 16:06:39 06/05/17 (13)
- RE: Something seems very wrong here - Jim Austin 18:08:50 06/05/17 (12)
- Hmmm... - Charles Hansen 19:31:32 06/05/17 (11)
- RE: Hmmm... - Jim Austin 19:37:30 06/05/17 (10)
- Something still seems wrong here - Charles Hansen 22:40:21 06/05/17 (9)
- Let's go back to Beyonce - Jim Austin 07:47:16 06/06/17 (8)
- OK, now we are on the same page - it is aliasing *and* it is a bug. - Charles Hansen 13:47:03 06/06/17 (7)
- On a different, yet related topic - Charles Hansen 14:54:02 06/06/17 (0)
- RE: OK, now we are on the same page - it is aliasing *and* it is a bug. - Jim Austin 14:34:09 06/06/17 (5)
- Aha! - Charles Hansen 19:01:41 06/06/17 (4)
- Interesting - Jim Austin 19:22:14 06/06/17 (3)
- Agreed - very interesting! - Charles Hansen 22:08:13 06/06/17 (2)
- RE: Agreed - very interesting! - Jim Austin 04:50:06 06/07/17 (1)
- Thanks - Charles Hansen 12:42:23 06/07/17 (0)