WAV vs. FLAC vs. AIFF

I just did an A/B comparison with Flacs and Wav of the same tracks in the same playlist, allowing me to switch. I heard no discernable difference.

When I first started with integrating computer audio with my audio system, I used an analog stereo to rca Y IC (audioquest) from my old laptop headphone jack to aux input on my preamp at teh time. I recorded several CDs of music with Real player. I since ripped these back to my current music server setup and play via Squeezebox Touch along with the rest. The sound quality after all that is still quite good but there is some noticeable deficiencies mostly in dynamics, compared to other very good recordings. Still "hi fi" I would say and quite listenable (nothing offensive, mostly just a bit of omission). I say its much better than most home cassette recordings I have heard over the years but not current SOTA. So in many cases with computer audio I think the glass is still significantly more than half full even in less than ideal circumstances compared to past options, unless something is flat out just not working properly as designed.

Excellent comments by all, IMO, on an issue that by its nature is highly speculative.

11-23-11: Dtc
I agree that networked solutions can provide better isolation that direct connections. Remember, I am not talking about audio streams in general, but the difference between FLAC and WAV files. I am not willing to say that computers routinely make computational errors when compressing and decompressing FLAC files and therefore WAV files are better. If people think they hear a difference, that is up to them. But I have yet to hear a detailed explanation of why that happens that makes sense.

What about my hypothesis, that differences in the processing that is performed when playing the different formats result in differences in when and how often "Speed Step" and related power conservation features are called into play (unless the user goes through the steps that are necessary to disable those features), in turn resulting in significant differences in computer-generated noise transients, in turn resulting in differences in jitter and/or noise coupling?

Even if an asynchronous USB DAC is being used, conceivably high frequency noise transients riding on the USB signal pair and/or the associated power and ground lines could couple past the DAC's input circuits to internal circuit points, where they could affect timing of the DAC chip itself, and/or subsequent analog circuit points. Galvanic isolation would help in that regard, as you noted, but it is not always employed, and who knows how effective it is in any given situation?

And then there is the possibility, perhaps somewhat more remote but conceivably still possible, of differences in rfi resulting from those format-sensitive noise transients, the rfi perhaps bypassing all of the digital circuits that are involved and coupling onto sensitive analog points elsewhere in the system.

11-22-11: Mapman
But the format itself does not correlate to sound quality in general though. Lots of other crap can go wrong and chances are it does so differently because of different hardware and software processing scenarios for different formats. The devil is all in the details. But not in the source format itself. If processed properly, the results are the same. That can be a big if though.

11-23-11: Mapman
Most general purpose computers have no business being connected directly to your high end audio gear! Think of this [network playback] as a form of isolation, similar to other steps you might take to isolate your rig from potential sources of noise.

Well said! Agreed 100%.

Best regards,
-- Al

Al - First, I agree that proper setup of the PC is necessary, including not letting the CPU performance fluctuate, as you point out. I should have added the caveat the the PC is well set up, which I agree is not always the case.

I agree that there is a potential for noise issues without isolation. That is why various isolation technics are being used. Any extra noise should not affect the left/right data bits. The amount of processing used to decode a FLAC file is really minimal. I just do not see that minor extra processing having much effect. When I compare playing WAV files to playing FLAC files I do not see any noticible fluctuation in CPU usage. It must be there, but it is pretty minimal, at least on my system., where usage is typically under 5%. As I said, if the async USB is doing what is advertised to do, then that noise should not affect the timing. If the noise interferes with the async USB circuits in the converter, then differences are certainly possible due to jitter. So fair enough, it is possible. I am just not sure there is enough noise from unpacking the flac to make an audible difference.

It seems that people using wireless solutions would not see the effects of this noise, unless it goes through the power cords.

I must say, it would be very difficult to actually measure any of these differences on the circuitry of the converters and DACs.

The 35 pound Hubbard squash is cooking. The French Canadian meat pies (Tourtier)are getting started, and the traditional home made vegetable soup for Thanksgiving lunch is just getting going, although we made the stock yesterday. Starting to smell good.

DTC, thanks for the good response, with which I am in essential agreement.

I would just like to make sure it is clear to everyone that under my hypothesis cpu utilization which is low but non-zero may actually be WORSE with respect to noise generation than, for instance, 100% utilization would be. 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.

That switching involves LARGE changes in cpu current draw, which happen quickly, although I don't know exactly how quickly. Current changes that are both large and fast = large noise transients.

For those who may be interested, utilities such as the Windows-based program CPU-Z allow those changes in clock rate and voltage to be observed as they happen. It should be kept in mind that cpu current draw is highly dependent on clock rate.

Happy Thanksgiving to you and yours!

Best regards,
-- Al