[serengetiplains]

Ok, I'm late to this party, but I think I've learned more of the ropes of computer playback and have some observations to share.  I recently discovered PC playback, to my ear, sounds better than Mac.  I now have a slightly more nuanced perspective regarding this matter.  Until quite recently, I assumed the playback software (iTunes, Foobar, whatever), unless otherwise asked (via checkboxed DSP, or something), *didn't process the signal.*  What a mistaken assumption, geezus.  Nothing about computers is straightforward, is it?  Ask just for the bits (those things many an audio engineers would say are just bits)---"just give me just the bits, please"---is met, in reply by the computer, with something other than just the bits. 

Here are my findings:

1) In some respects, hardware matters.  I've compared desktop to laptop to desktop plugged into massive AC power conditioning.  When I ran this comparison, I listened through iTunes, and comparisons were all done on Mac machines.  I noticed obvious differences in sound: to my ear, massively AC conditioned desktop play was best, followed by laptop, followed by grunge-fed desktop.

But note:

2) In some respects, hardware doesn't matter.  I compared Foobar to iTunes on: my wife's PC laptop (Windows Foobar vs. Windows iTunes), on my Mac desktop running Windows (Windows Foobar vs. Windows iTunes), on my Mac laptop running Windows (Windows Foobar vs. Windows iTunes), and on my wife's laptop + Desktop + Mac laptop (Windows Foobar, Mac iTunes, Windows iTunes).  The result?  Foobar wins every time with clearly audible differences.  iTunes is soft, lacks resolution, is not as dynamic---is overall a little less on most audio characteristics I can name.  Windows iTunes sounded, to my ear, identical to Mac iTunes: soft, rounded, veiled, blah blah.

So maybe my assertion in 1) that "hardware matters"  reduces to: hardware matters only when its processing bits, which is seemingly always.  The sonic differences I noted in changing power supply methods possibly attribute (mostly attribute?) to those parts of the computer hardware processing the bits.  That would make sense to me as a starting point for further investigations which, parenthetically, I'm completely incompetent to undertake.

[IronLion]

Maybe I'm not reading your post carefully, but I can't seem to find if you indicate anywhere in it how you are getting your sound off the computers you tried.  This is in my view the a critical part of computer-based playback, equally if not more important than hardware and software.  Explaining this would give more insight into your experiences with different results in computer-based audio. 

[serengetiplains]

"Bits" are transmitted via a USB cable to Steve's Spoiler DAC. 

[serengetiplains]

I should also note that my sonic observations above hold whether Foobar and iTunes output 44.1KHz "bits" or upsample them to 96KHz.

[bigamp]

I concur.  Software does make a difference.  Like all aspects of audio, there are different strokes for different folks.  I like JRiver using DirectSound at 16/44.1.  IMHO, this changes the bits the least and lets my upsampling DAC do its magic.  In my system, I found that using an ASIO driver and/or SRC provided less detail than DirectSound.  Others prefer Foobar with ASIO and SRC upsampling, which gives a more holographic sound.  However, IMHO this changes the bits.  But if they prefer the sound, go for it.  Its not unlike picking tube gear vs. solid state for the sound difference.  My approach is to get the most untainted bits possible to the DAC and let the audio equipment do its stuff.

There may be ASIO drivers out there that don't change the bits, but I don't know which ones don't.  I've tried several and they all sound different from each other (therefore likely changing the bits).  JRiver claims their ASIO driver doesn't change the bits.  If you use Steve's new driverless firmware, I would guess that you don't need an ASIO driver.  Most SRCs also change the bits (if you upsample and then downsample the resulting bits in the file are not the same).