Which way to go? Airport Express or USB interface

Correct - once you connect the DAC it's all the same thing. Airport Expresses will lose connectivity if there's a microwave or 2.4 GHz cordless phone in the vicinity, but that's about it. Just make sure your DAC has jitter correction circuitry and you'll be fine.

If you store your files in the Apple Loseless format it won't make any difference between USB or Airport, but if you don't use any file compression, then the USB connect has the potential for better performance since the Airport will convert everything to Apple Loseless.

Thanks for these responses. It's now clear re the difference between USB and Airport. So, if I go via Airport Express, should I connect an outboard DAC to it and then to my amp? Or is it possible to do without the outboard DAC? The files I have now are compressed, but once I learn more and perfect the links, I may store files uncompressed.

Before going with Airport Express, please check out Squeezebox and Soundbridge first. I bet you'd be a lot happier with either. Follow the link for a review of the latest Squeezebox.

http://www.enjoythemusic.com/magazine/equipment/1205/slimdevices_squeezebox.htm

Read these two links:

http://www.positive-feedback.com/Issue22/nugent.htm

http://www.wavelengthaudio.com/usbdac.html

and tell me if you still want to go with an Airport Express. If it's convenience you want, go with the Airport Express. If you want hi-fi performance from your Mac G4, get a USB-coupled DAC from someone like Wavelength Audio, Apogee Electronics or Ack! Industries (when their new USB option for the Ack! Dack! comes out).

There are a few shortcomings of the AE not yet mentioned. The DAC in the AE (which you would be using if you went straight from the AE to your preamp or integrated amp) is mediocre in comparison to a decent outboard DAC (at least that is the case in my system). Alternatively, with the AE, the ONLY way you you can connect to an outboard DAC is via a Toslink (optical) cable - actually it's not an ordinary Toslink, but one with a special mini-connector on one end. Toslink/optical seems to be the least desirable of the means of digital connection, with Coaxial methods being preferred by many as the better way to stream digital info. Indeed the USB route is limited to 16 bit (redbook CD). But then again some of the best DAC's are designed (intentionally) for 16 bit so I would not concern yourself over it.

If distance is not an issue (from your computer to your system), I'd suggest a USB DAC like the Benchmark, or use a USB convertor like the Waveterminal U24 which hooks up to your computer via USB and goes to your DAC via a coaxial connection. I use this solution and cannot tell it from my transport.

Marco

Some misinformation appears above...

the USB connect has the potential for better performance since the Airport will convert everything to Apple Loseless

Apple Lossless is exactly that - lossless. There would be ZERO performance gain or loss. Both 802.11g and USB 1.1 have enough bandwidth to stream cd-quality audio so this is not an option. If anything, the Airport Express has an 8-second buffer that USB does not so there's additional protection against network dropouts if you're streaming audio in from the net.

Indeed the USB route is limited to 16 bit (redbook CD).

Neither USB nor 802.11g is limited to 16-bit/44.1 KHz. Both can handle increased bitrates, should that ever become important. It has absolutely no relevance in today's world, as the high definition formats are completely encrypted all the way to the DAC. That means there'll be no digital streaming of SACD or DVD-Audio anywhere!

some of the best DAC's are designed (intentionally) for 16 bit

Actually, all of the home/hi-fi DAC's are designed primarily for 16-bit input (even the dCS). It's only in the pro world where you would need to handle 24-bit streams.

Coaxial methods being preferred by many as the better way to stream digital info

With jitter correction circuits you won't notice the difference. I've tested USB into an M-Audio Audiophile through a $100+ Chord Prodac vs. the Airport Express and the Monster Cable optical and can't tell the difference.

I'd suggest a USB DAC like the Benchmark

The Benchmark DAC-1 doesn't have a USB input, and when I asked them about this earlier in the year they had no plans of adding one. I'd bet their space in that case is too cramped to add any more boards.

The bottom line is that the quality of sound you get out is in direct relation to the quality of the DAC. Everything else in the middle is pretty much irrelevant except when it comes to convenience.

I have been using the AE and loving it. I use a optical connection to my DAC in my BK Reference 20 and am quite please with the sound quality.

Ghunter's post has some useful clarifications. Also, Airport Express does not "convert everything to Apple Lossless." iTunes converts everything to Apple Lossless, _if_ it is being used to wirelessly stream audio data to AEx. But this is kind of academic, since, as Ghunter says, AL has been shown to be a true lossless format.

"Coaxial methods being preferred by many as the better way to stream digital info"

With jitter correction circuits you won't notice the difference. The bottom line is that the quality of sound you get out is in direct relation to the quality of the DAC. Everything else in the middle is pretty much irrelevant except when it comes to convenience.

I think the wireless technology combo of AEx and Apple Lossless works great. The ergonomics/convenience of using iTunes and being wireless is terrific, so that's where my vote goes. I did become curious about whether the optical feed from my AEx to my DAC was a weak link. I ended up purchasing a Monarchy Audio Upsampler DIP, which of course goes way beyond just substituting a coax feed for the optical. The results are noticeable and worthwhile, even though I am using a good quality DAC (Northstar Model 192) that is supposed to have very good jitter reduction circuitry of its own. It makes sense to me that jitter reduction can be a cumulative endeavor, and I think if you are using a modest source (AEx, DVD player, midfi CDP, and I would imagine devices like Squeezebox and Waveterminal), lightening the jitter-reduction load for your DAC by using some kind of anti-jitter box before the DAC can be worthwhile, especially given how inexpensive some of these anti-jitter units are on the used market. However, I don't want to sound like one could not possibly be happy without making this extra investment. I was very pleased, very satisfied with the sound from my AEx running straight into my Northstar, before I added the DIP. It sounded great; I didn't find it deficient at all. I just got curious.

If you are using a Northstar DAC, you should try an Empirical Audio Off-Ramp I2S. This is a USB to I2S converter. Simplest way to get data and clock to the DAC chip. The RJ-45 connector should be compatible. Do you want to be the guinea pig?

I use the AE with a Theta DAC. With a quality DAC I use an external HD with music stared at 320 ACC just for entertaining and back ground music when I am pre-occupied with other things. I still like to use transport and DAC when I want to sit down and listen. The AE works great and with a good D/A converter most people I have listen to it can't tell the difference between playing through the transport or the AirPort. I can still tell, so when they go home and I want to sit back and enjoy what I am listening to, I use the Disc. The AE and Mac are great though for random play list!