Sound quality is subjective but also can be objective using properly designed double blind tests. I would be willing to wager that you cannot pick out a wav vs an itunes 256 kb AAC file using the double blind method. Objectively the AAC file is a smaller file size than the wav, but I would take issue with the fact that its sound quality is below a 30 year old compact disk (actually, since the CD went commercial 29 years ago, there actually aren't any 30 year old compact disks).

The wonderful thing about perceptual encoding is that you can get the SAME sound quality for a much smaller file size. With hard disks selling at the price they are, this has become less of an issue, but for moving data over the net, it has helped to get the $18 CD down to $10.

Respectfully, Mr. Del Colliano, please refer us to a controlled listening test demonstrating that CD is "anything but high definition audio". Two channel CD has been conclusively demonstrated to be audibly indistinguishable from SACD and DVD-A( and, by extension, Blu-ray ). See "Proven: Good Old Redbook CD Sounds the Same as the Hi-Rez Formats", http://www.theaudiocritic.com/plog/(posted Oct 17, 2007). CD is, and should be, the standard for 2-channel audio in the home. The crude, electromechanical, LP cannot compare in any way to the CD as a music recording/playback format. Unaccountable and unsupportable comments like "CD is anything but high definition audio" have no place in high quality audio journalism. Either put up( produce hard evidence supporting your 'claim' ), or shut up.

I meant to say "Two-channel CD has been conclusively demonstrated to be audibly indistinguishable from TWO-CHANNEL SACD and DVD-A( and by extension, TWO-CHANNEL Blu-ray ).

Multi-channel SACD, DVD-A, and Blu-ray beat 2-channel CD, but only because of the up to 4 additional channels they can accommodate, not because they are 'high resolution'( higher sampling rates and more bits per sample ).

I agree with Jerry, knowledgeable audiophiles with experienced ears can easily discern the difference between a CD and any file type, between a Blu-ray and any other delivery format of HD.
The difference is in the dynamic range and most consumers simply dont have the equipment required to experience the increased dynamics found on a Blu-ray disc. For those of us that do, this is a big thing. When using the HDMI connection in a protected interface, the studios have allowed a 1 to 1 copy of the master tape to be bought and owned by consumers for the first time in history. To say that SACD or DVD-Audio is its equal is sheer nonsense. Both are compressed and this compression limits their dynamics.

The larger point is still true. Downloaded content may be convenient but its not even close to being suitable for audiophiles and videophiles who have invested in the right playback equipment for the ultimate viewing and listening experience.

I agree with Jerry, knowledgeable audiophiles with experienced ears can easily discern the difference between a CD and any file type, between a Blu-ray and any other delivery format of HD.
The difference is in the dynamic range and most consumers simply dont have the equipment required to experience the increased dynamics found on a Blu-ray disc. For those of us that do, this is a big thing. When using the HDMI connection in a protected interface, the studios have allowed a 1 to 1 copy of the master tape to be bought and owned by consumers for the first time in history. To say that SACD or DVD-Audio is its equal is sheer nonsense. Both are compressed and this compression limits their dynamics.

The larger point is still true. Downloaded content may be convenient but its not even close to being suitable for audiophiles and videophiles who have invested in the right playback equipment for the ultimate viewing and listening experience.

Bobster, you may agree with Jerry, but you are both wrong. For the definitive test, see "Proven: Good Old Redbook CD Sounds the Same as the Hi-Rez Formats", http://www.theaudiocritic.com/plog/(posted Oct 17, 2007). You seem to have bought into the popular misconception that 'high end'( expensive ) electronics sound better than the everyday garden variety receiver you can get at Best Buy, and that if you own 'high end' equipment you have better hearing than the rest of us mere mortals. Sorry to burst your bubble, but every time a properly controlled listening test has been done, even leisurely trials conducted in the homes of the 'audiophiles' over months of trials, the 'golden ears' and their 'high end' gear have been indistinguishable from the garden variety. To quote Peter Aczel, editor and publisher of The Audio Critic, "In controlled, double-blind listening tests, no one has ever( yes, ever! ) heard a difference between two amplifiers with high input impedance, low output impedance flat [frequency] response, low distortion, and low noise, when operated at precisely matched levels( plus or minus 0.1 dB ) and not clipped". And again, "As long as they[preamps, CD players, and other line-level electronics] meet the fairly exacting specifications expected these days -- and most of them do -- they will sound the same, regardless of price." Or, as Aczel remarked in another context( posted April 13, 2006 ), "Of course, it[the truth] would be bad for business, at least for the business of Halcro, Mark Levinson, Pass Labs, et al., whose astronomically priced products sound the same as a $200 Pioneer receiver."

Your belief that DTS-HD Master Audio and/or Dolby TrueHD sound better than CD, SACD, and DVD-Audio is without foundation. Find a properly controlled listening test that supports your belief and I will agree. Absent that, you have no evidence or basis for your 'belief'.

"To say that SACD or DVD-Audio is its[Blu-ray's] equal is sheer nonsense. Both are compressed and this compression limits their dynamics."

No. First of all, you are confusing data compression with dynamic-range compression. None of the lossless digital formats require dynamic-range compression, and in practice, all( CD, DVD-A, SACD, and the lossless BD audio formats ) provide more than enough dynamic range to accomodate any recording without audible clipping even on high performance( distinguished from 'high end' ) audio playback systems. It is true that DVD-A and SACD are data-compressed, but the compression in both cases is lossless compression, which on playback is identical to the uncompressed recording( before compression was applied ).

"Downloaded content may be convenient but its[sic] not even close to being suitable for audiophiles and videophiles..."

Mostly agreed and very sad. Most people seem to prefer convenience to sound quality, but you don't need 'high end' electronics to hear the difference. And it is possible to download lossless audio files now( though most downloaded music files do contain lossy-data-compressed content ), and eventually, when higher bandwith becomes cheap enough, movie downloads may equal BD; there is no theoretical limit on the quality of downloaded content.

Focusing for a minute on just the video component of downloading vs Blu-Ray here are my observations. I own media from VHS to SD to HD-DVD and Blu-Ray and I also get Netflix streaming videos, via my Blu-ray players. When I started using the Netflix feature, the streaming video varied from extremely pixellated and fuzzy (reminiscent of VHS quality) to near SD quality with no upscaling video. In the last year or so, the quality has noticeably improved. Now I would say it's between SD quality with upscaling to something a bit under Blu-ray, but quite acceptable. Most of the variation depends on both your local wireless connection speed and the network traffic of your neighborhood ISP. One fairly easy way to see the improvement over SD with upscaling is to watch a foreign film with subtitles. Even the best upscaling processors render the subtitles with noticeable pixellation, whereas the best examples of Netflix streaming provide very smooth fonts, approaching that of a Blu-ray. I am planning to continue both buying and renting Blu-ray discs because the overall quality is still the best and you also get extras, which are not available in streaming format. I will also continue to use Netflix streaming for TV series and films which don't warrant buying for whatever reason.

If you can't honestly tell the difference between even 320kbs and CD quality, something is not right with how you are listening to the music. While I will agree that with certain types of music it can be a little less disputable, such as todays generation of hiphop, and some techno music. Anything acoustic like Eric Clapton, and very transparent like Diana Krall sound radically better on CD. Hell ACDC sound overwhelmingly better on CD.

Now I am not disputing your opinion, or you ears. And I have no idea what you have for equipment, but I have a very fine hometheatre put together comprised of Paradigm Studio speakers and NAD processor and power. I have spent hours upon hour of listening. I have gone to such an extent of listening and being disappointed with all the MP3s I have accumulated over the years that I have spent an equal amount of time tracking down and ripping CD quality (WAV) files for almost everything I had. Most made a incredible difference, a small portion only made a small difference, and and handful I couldn't tell the difference.

Specific areas that you (or I for the purpose of what I am writing) can tell the difference is the depth and more importantly the quality of bass. Even high quality MP3s lack bass punch and can make the sound very muddy. Also, the soundstage become less of a wall of sound, and more like I am listening to 2 speakers.

If you listening to music via earbuds, then of course you aren't hearing a difference. But if you have any have decent quality to your system (even much less that I have) you should be able to tell the difference.