WAV vs. FLAC vs. AIFF

"The noise transients I am envisioning are associated with the abrupt SWITCHING of cpu clock rate, and in some cases voltage as well, that unless disabled by the user will occur as processing tasks intermittently start and stop."

Huh? There are certainly differences in power in the computer when there is highly CPU intensive calculations ocurring, but as noted, we have not seen this in the CPU usage numbers.

Has anyone looked at the CPU usage graphs while running .wav compared to FLAC?

Steve N.
Empirical Audio

If flac or any format encoded + decoded produces different results than original, assuming same resolution applied throughout then there is either a bug or defect in the system somewhere or a decision was made to sacrifice detail rather than implement a robust design. Like I said, things like bugs and defects can and do happen.

But if it is done correctly format encoding to and from at same resolution should produce the same results. IF not the case, please offer a more specific example of why.

ANother reason to go with devices explicitly designed to retain sound quality in a high end system. Real time compression/decompression, encoding/decoding is easily achieved with readily available modern processors. It is not rocket science to do right. But it still has to be done right......

Steve,

I don't necessarily disagree with any of your comments, and I don't assert that the hypothesis I offered is anything more than speculative, but the "huh" in your last response tells me that my hypothesis may not have come across clearly.

The OP in the thread I linked to early in this thread was using a newly purchased Windows 7 laptop, and experiencing severe distortion, and also intermittent skipping, when outputting audio via USB into a DAC. The same setup had worked fine previously, with a different laptop running XP.

The problem was fixed when at my suggestion he changed the power management settings within the Windows 7 control panel such that the MINIMUM (as well as maximum) "processor state" was set to 100%, instead of the default 5%.

That change in effect disables SpeedStep, causing the cpu to run at its maximum speed all the time. As I say, it fixed the OP's problem with distorted USB audio. Therefore it seems to me to be at least a semi-plausible hypothesis that SpeedStep could, with some computers and in some setups and with some DAC's, cause noise and/or jitter issues that would be sensitive to processing requirements, and therefore conceivably to data format. Particularly if those processing requirements load the cpu lightly and therefore intermittently.

Again, that is just a speculative hypothesis, but in the absence of evidence to the contrary one which seems to me to have at least some degree of plausibility.

Best regards,
-- Al

Al - Just another datapoint telling us that the CPU execution is having an effect on sound quality.

This is why I recommend only Mac, and only Amarra 2.3.x. This combo is simply killer. My PCs are not even close.

There are still SQ obstacles even with Mac, but they are minor IMO.

Some improvement can be had by using SSD rather than hard disk for instance. Also better power supply for a Mac Mini seems to help. I dont know why... The mach2music.com works well if you dont want to fuss with it.

Its good enough stock though, that I have not bothered with these tweaks yet. I use a 2009 Mini with Snow Leopard on it.

Its much more important that you use a good USB interface with good clocks.

Steve N.
Empirical Audio

Steve, I don't understand why SSD could be better. Music data on HD does not contain timing information. As for transfer rate required (1.4Mb/s for 16/44.1) it is a tiny fraction of the slowest HD interface. Also, compressed files would transfer approx 2x faster. The only possibility, IMHO, is lower power of SSD and therefore lower electrical noise in general.

Wireless devices like AE not only separate noisy computer from the Audio System but also have own separate Codec and clock. I store music in ALAC since that's exactly the format used to transfer data to AE (no conversion necessary). Jitter on AE digital (Toslink) output is respectable 258ps according to Stereophile measurements, that also confirmed it being bit perfect. On the top of it my Benchmark DAC1 adds big jitter suppression.