WAV vs. FLAC vs. AIFF

My assumption is that with any of these formats, the bits being delivered are the same and timing is the real issue. I agree that in the past it was likely that a lot of activity on the PC could affect the sound, mostly because of timing (jitter) issues. But with the use of async USB the activity on the PC seems to be a real secondary issue. As long as the buffer is full and the activity on the PC is relatively low, it seems that the aysnc USB is the determining factor. I use a PC with a very low end processor, and running FLAC through J River, the CPU hardly goes about 5%. If the FLAC decompression is a problem on a system, it is probably because there are too many other things running. Although, as I said, using an async USB converter/DAC should minimize that effect. There can still be noise issues (like small ground issues) but that should not be affected by the minor differences in processing time to decompress files. I am of the mind that "everything matters", but with properly done async converters/DACs, it seems that the other effects can be extremely small. That said, there are always people who say they hear differences in everything. I would suggest converting a few of your wav files to FLAC and listening. dBpoweramp is a good converter and it has a free version.

What hardware/software are you using?

Although in principle any half-way decent modern computer should have no trouble de-compressing and processing any audio format, my suspicion is that a major reason for reported sonic differences between lossless formats relates to the fact that in modern computers the clock rate, voltage, and power draw of the cpu chip are usually dynamically varied as a function of the processing requirements at any instant of time. That is done for purposes of minimizing power consumption and heat generation, and in the case of laptops to prolong battery run-time.

That switching involves changes in current that are both large and abrupt, which can be expected to cause significant noise transients to propagate through a lot of the circuitry on the computer's motherboard. That in turn can be expected to contribute to jitter, or even outright mis-clocking and breakups, on the signals that are used to output the audio data.

See my post here for a description of how to disable that switching in Windows 7. That change did in fact resolve the audio breakup problem the OP in that thread was having. Some computer BIOS's also allow "EIST" (aka "Speed Step") to be disabled, which may accomplish the same thing. I'm not particularly familiar with Mac's, but I believe that third-party software might be needed to do this.

The sonic significance of all of this will obviously be dependent on the particular computer that is being used, on what kind of output is being used (USB, S/PDIF, Ethernet, etc.), and on the jitter sensitivity of the component to which the signal is being sent. Ethernet and wireless presumably have little if any sensitivity to these issues, because of the packetized and buffered nature of the data transmission.

None of this necessarily correlates with the resolution or quality of the audio system.

It would be interesting to know if those who report sonic differences between these formats perceive the same differences when these power conservation features are disabled, and the cpu is running at the same speed and voltage all the time.

Regards,
-- Al

Hi tom,
Maybe there are many reasons why one file sounds different on system than another.

I like to think I have a reasonable set up. The only differences I have heard between the same file is in the conversion. I.e coverting from 44.1 to 48k etc. Whether a WAV or Aiff they sound the same if taken from the same master file. While flac has some live unpacking it too sounds the same unless there is some terrible software being used.

If someone believes any different send me a PM with the original music file, and I will gladly convert it on professional equipment to whatever you fancy. WAV to AIFF or whatever & send it back to you. Then see.

Al - I agree that minimizing system changes is a good practice, as is removing unnecessary software and processes. I take a different route from many - I use a Netbook with Windows 7 Starter. There are very few processes running, not even virus software (which is OK because it is a dediated system and I almost never have it on the Internet directly). You can even turn off networking if you have the files local. I still think these tricks are less important with a good aysns USB converter/DAC. I use a async USB converter and a DAC that does its own reclocking, so hopefully I am immune to PC induced jitter. If you have galvanic isolation you can elimiate other types of noise also. Unfornately, when people hear differences it is very difficutlt to find out why.

Al:

Thanks for the clarification. I've read the same elsewhere and it seems to all boil down to the competition for power and the sound card that goes on inside of a computer. It is not optimized for music playback as currently set up. That's probably the reason why a third party add on like Bitperfect (for those of us with shallow pockets) dramatically cleans up the sound.

Once you have an optimized platform, like a well designed music server, then differences between files should be minimal, at best, when it comes to the better ones. It will be nice when some sort of standardization takes effect so makers can concentrate on perfecting software/hardware and we can just rip and download to our hearts content and sit back and enjoy.

I have yet to hear all that's out there so this is conjecture, on my part, but it seems to make sense.

Al the best,
Nonoise