Info om Airport Express

K

KindOfBlue

Gjest
Fant dette mens jeg søkte etter data om AE:

From this discussion, and very recent: http://discussions.apple.com/message.jspa?messageID=7075423#7075423



I found yesterday an interesting article, maybe somebody is interested on that information too: http://www.stereophile.com/accessoryreviews/505apple/

First, it is important to note what the AE doesn't do. Whether you own a PC or a Mac, the AE works only with iTunes v4.6 or later and is limited to music files that iTunes can read; ie, 16-bit data only.(*) These data, though, can be in any file format that iTunes recognizes, from lossy MP3s at the low-quality end of the spectrum to Apple Lossless and lossless AIF or WAV files at the high end. It is also important to note that the AE functions only at a 44.1kHz sample rate. When you play 32kHz or 48kHz data, iTunes sample-rate-converts the data in real time before sending it to the AE. I tried using the Nicecast utility for OSX ($40) to feed iTunes with 24-bit data and 88.2kHz data from the inexpensive but excellent Amadeus audio-editing program for OSX. High-speed files were played back at half speed and hi-rez data were truncated to 16 bits, according to RME's useful DigiCheck utility for the PC.

Some audiophiles have dissed the AirPort Express on the grounds that its digital output is not bit-accurate. However, I found that this was not the case, that the data appearing on the AE's digital output were identical in the original file. To check this, I compared a WAV file with a duplicate that I had captured on my PC from the AirPort Express's S/PDIF output. I used iTunes on my PowerBook playing a version of the file encoded with Apple Lossless Compression to feed data to the AE. The files were bit-for-bit identical, proving that the AirPort Express is transparent to the music data (as is ALC, for that matter).

One operational glitch that didn't affect my system to any significant extent but did do so for some readers was the fact that, as the AE doesn't have a local clock circuit, when the incoming data is interrupted, as it is when you change songs in iTunes, there is no longer a digital output to feed the DAC, which loses lock as a result. Both the Levinson and the Benchmark DACs that I use deal gracefully with the lost lock and are quick to unmute when the new song is sent to the AE. I therefore missed the fact that with some other DACs, the first seconds of a song might be cut off.

(*) I have used Airfoil to send music from other programs, such as browsers, VLC, etc.
 
Topp Bunn