DAC for iTunes?

Yes, but it's at least good enough to pass CD-quality resolution.
No. Soundstage is influenced by three things:
1. Speakers.
2. Room.
3. There is no Number 3.

I believe the Airport Express is limited to 16/44.1 CD resolution, so any high-res files will be converted to that format when played. Other airplay devices like the Apple TV upsample to 48khz to account for dolby digital tracks being played through it for TV/Movies etc. IMO cd resolution is plenty good.

Wel, no, if you didn't change speakers in the store, then it wasn't the speakers. But you also didn't change DACs. But you did change program, and on top of that one program had been compressed, and the other hadn't. If I were to add a #3 to my list above, what I'd add is the quality of the recording. They can vary a lot. So what you heard isn't really a mystery. Unfortunately, for any given recording, we are usually limited to one recorded version of it, so it's not something we can control, unlike our speakers and our room.

how did you change the playback?

Depending on how compressed your earlier rips were, using Apple Lossless will help at least a little. Adding a DAC will not.
None at all.

Whatever sonic improvement you're seeking, a new DAC is not the solution.

I'm wondering if you would benefit more from adding a DAC in line to your system or just upgrading the speakers? Have you checked out the Peachtree audio gear? Integrated amplifiers with the ESS Sabre DAC in there which is supposed to be one of the best for computer audio conversion. Of course, as stated above, quality of the recording makes a huge difference as well. I have no experience with this, but have you checked out amarra or pure music software?

For converting digital to analog, of course!

But I suppose your real question is, what good is a separate DAC when you've already got DAC chips in your computer sound card, your Airport Express, your AVR, your CD player, your DVD player your BR player, your TV, and lord knows what else. The answer is that DACs can vary on a technical (i.e., measurable) level, but even really cheap chips are so good your ears usually can't tell them apart. Still, people want to believe that they can get better sound just by adding another piece of kit, and the industry is happy to oblige.

From a technical standpoint DACs are probably going to improve in terms of measured performance for the foreseeable future. However, the dirty little secret that the DAC manufacturers don't want you to know is that the law of diminishing returns applies to DACs just like it applies to everything else.

For example, the big problem with trying to use an external DAC to try to improve the sound quality of an Airport Express is the already entirely sufficient quality of the DAC that is already in the Airport Express.

The myth is that the higher the sample rate, but better the sound. Reality is that the law diminishing returns is alive and well in that arena as well.

So true...the law of diminishing returns is very prevalent in the audio business. I can't tell you the number of set ups that I have heard at trade shows that were in the 100k and above range... Did they sound good? Yes, most of them really did. (strangely some really didn't) But, of those systems that were 100k, were they 95% better than all of my setup? Not a chance. To my ears that extra 5-10% of quality increase costs exponentially more expensive and isn't worth it. I think cars is another area where the law of diminishing returns is rampant, but still status and want vs need play huge roles in those decisions. Is a Lamborghini worth 150k more than a Subaru Brz performance wise? Enough people think so I guess.

Have you tried just switching your music player and getting better content like Flac? Maybe just give foobar a try and see if that makes any noticeable difference? I'm assuming you already have a huge library of music, so starting over on high resolution digital audio is probably not the best route either? In my experience the two biggest factors to improving audio quality is the room quality/placement and speakers. After that it's electronics....recording quality being a given..good in-good out!

If it's limited to 16/44, you are best not to make any volume adjustments via the airport express (you really want 24-bit if you are changing volume digitally) but there's no loss from the 44.1 output.
It's not even diminishing returns at this point - we can't hear over 20kHz so 44.1kHz (which can represent signals up to 22.05kHz perfectly) is more than enough to cover the entire range of human hearing. 16-bit source files are plenty as well, because 96dB of dynamic range is more than enough to damage your hearing, and most music only uses about 1/3 of that dynamic range anyway.
On Windows, the best player is JRiver Media Center. But if you have your system audio output set to 24/44.1, and your player set the same way, you are pretty much guaranteed bit-perfect output these days.

JRiver and other players make this easier by using WASAPI output, which takes control over the sound card and sets it to 24/44.1 automatically, but it is not necessary. Even iTunes has sample rate options now.

On OS X, tools like Amarra just handle sample rate switching (my understanding is that there is no equivalent of WASAPI on OS X for the player to easily take over the sound card) and adding transcoding of unsupported formats to iTunes. Amarra is ridiculously overpriced for what it does.
"HD" files are a rip-off, taking advantage of the uninformed consumer.

Here's a "24/96" recording from a limited edition package that was not cheap:


Low-pass filtered to 24kHz, so it's clearly a 24/48 file that has been upsampled. Oops. (not that it matters to those of us with human ears)

And a 24/352.8 DXD master which is 330MB for a four minute track:


This is actually a very good sounding, high fidelity piano recording. But all the music is basically under 15kHz, with a couple of peaks extending to 20kHz. (that are probably below the threshold of hearing) Then, as you extend upwards, you see a gradual increase of noise above 70kHz - you actually want to filter this out. If this track was a 16/44.1 file (or 24/44.1 if you like) it would sound exactly the same.


What makes a recording sound "high fidelity" is the quality of the mastering, whether the track has compressed dynamics due to the "loudness war" or not.
It may be that companies selling you 24/48 audio and beyond are paying more attention to the mastering of their files, but you don't need anything more than 16/44.

Great info, thank you! I to have use Jriver and liked the layout and flexibility of it over other players, but it doesn't support Airplay I think as a requirement for ambesolman.

Do you think audio master is a dying art?

Chronoptomis, how do you listen to music?

Thanks!

Hey, just curious, have you tried comparing your music while listening through an external DAC to see if it makes a difference to you? I even though I believe the data above, I have heard some super high resolution songs from a Mac through asynchronous DAC and it definitely sounded impressive, but I didn't do any comparison. Through that same system I did compare some standard MP3 and High Resolution of the same song and that was noticeably different. All part of the fun!

iTunes should be fine really. If you are outputting via your computer, you need to take a little care to get bit-perfect output (set the system & iTunes to 24/44.1) but if you're using AirPlay, it's just streaming the file so you don't have to worry about that.
I think the engineers still know what they're doing, but the artists or the label are forcing them to do bad things to the audio. (such as compressing the dynamics to make it sound loud)
Right now there isn't much particularly interesting about my setup. I spend a lot more time with higher-end headphones than speakers though. (which I find can be a lot less forgiving than speakers)
Well MP3 is less than CD quality. 320K MP3 is probably indistinguishable from CD to most people though. But once you are at CD quality, you aren't really going to get much better (audibly) than that.

I think the Airport Express only supports 16/44, so it probably just sends that out to it.

Changing the local playback settings won't make a difference to streaming audio, only playing music directly on the computer.

Absolutely, but my question is if you listened to the same track, one straight from your PC soundcard to your system and the other run through a DAC. Any noticeable difference?

As for headphones, what do you recommend? Do you use a headphone amp or...DAC? Probably best for another thread? Thanks again!

Possibly, but it won't be because you need a better DAC. It will probably be because of noise/interference n the analog side. An inexpensive USB DAC will solve that problem, if you have it.

Yes, but even the 1st generation was pretty darn good. It's gotten better, if anything.
No.

Well a soundcard basically is a DAC. But on-board sound cards tend not to have great signal-to-noise ratios so there can be some background noise/hiss with playback, and they often don't have a completely flat frequency response.

So an external DAC, or even just a better soundcard can help.
Right now I have the top-end Sony monitor headphones, which I'm pretty happy with after going through a number of lower and higher-end headphones. (Grado, AKG, Sennheiser, B&W etc.)

Low impedance headphones usually don't have a problem going loud enough, but they often need an amplifier because the headphone jack on a lot of devices has a high output impedance, and you ideally want the output impedance to be 1/8th or less the headphone impedance. So if your headphones were only 24 ohms, then the output should be 3 ohms or less. A lot of devices such as AV amplifiers have an output well above 30 ohms, if they even specify what it is. So in that case, a headphone amplifier would make sense.

If you have high impedance headphones, the issue is more about whether or not they can go loud enough, than them sounding bad. A pair of 600 ohm headphones only needs the headphone jack to have an output of less than 75 ohms, which is fairly common.