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In Reply to: OK, I can agree with that, but that's not what I said posted by bwb on February 18, 2012 at 11:34:37:
You don't have to agree with me. I agree with you. :-)
(My comment about the sound differing each time was the most obvious example of how correlation might not be causation. Many reports of "differences" fail to deal with the most basic cause of audible differences, namely varying moods on the part of a listener.)
What does matter is the buffer size and buffer load strategy. This determines the period and duty cycle of the bursty buffer loading processing, which translates into periodic power supply load and thereby periodic jitter. If this periodic jitter is of very high frequency it will be out of the audio range or filtered out by the PLL in a DAC. However, an attempt to run with very low buffer sizes won't work unless latency is low enough, since otherwise there will be buffer underruns. It's conceivable that changes in actual latency will affect the timing of several levels of processing in the computer and hence the waveform imposed on the power supply rails, even if the buffering parameters are unchanged. This will affect the spectrum of jitter and hence potentially the sound. However this will be a third order effect (jitter itself is already a secondary effect due to some degree of reclocking at the DAC). Given that the advocates of low latency have not listed all the variables they are investigating and how they are controlling for them there is no reason to pay much attention to their conclusions. However, the observations are often interesting.
Some people have measured spectra of the analog output of a DAC that shows jitter induced sidebands whose position varies as the buffer reload rate in a computer based transport vary. This effectively puts the lie to those know-nothings who claim "bits is bits". If one creates periodic (deterministic) jitter one can use synchronous detection and measure jitter artifacts that are well below the noise floor of a DAC (and associated measurement equipment. One can also put a scope on the power supply rails in the computer and observe how the waveform varies as the computer configuration changes. It is possible to get to the bottom of these issues if one is so inclined. I'm not, because I am happy with how my system sounds as is. I was willing to spend perhaps 100 hours setting up my speakers and room, a task that resulted in a dramatic improvement in the fraction of recordings that were enjoyable and IMO a much more useful task than further reduction of latency.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
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Follow Ups
- RE: OK, I can agree with that, but that's not what I said - Tony Lauck 02/18/1212:12:20 02/18/12 (1)
- Amen brother Tony! /nt - bwb 13:07:24 02/18/12 (0)
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