Apple Airport Express Very Cool Product

The optical digital output can be modified to be a S/PDIF coax output fairly easily. Same modification that I do on the M-Audio Transit to change from toslink to coax.

Steve N.
Empirical Audio
Manufacturer

"Is this modification necessary to go from Airport Express via iTunes to an external DAC connected to my stereo system?"

If you want S/PDIF coaxial (the lowest jitter option) to go to your high-quality DAC, then yes is the answer.

Transit does not upsample to 48 kHz. I can program Transit to do 44.1 or 24/96 and it passes iTunes, MP3 and AC3. It uses a custom driver that bypasses Windows Kmixer.

Transit is probably not the best solution for iMac. I have heard that the drivers are not realy optimized for iMac. A modified Edirol with coax S/PDIF out is probably the ticket. It uses standard drivers - you dont need to install any.

The Airport express would probably make a good adapter if the wireless network solution was buffered well and isochronous. I'm not convinced based on what I have read.

Yes, Toslink is inferior. That's why I mod all of these converters to have a coax S/PDIF output, with a short cable attached.

If the Airport Express output wired USB, then you would still need a USB to S/PDIF wired converter. The main advantage of the AE is to eliminate the USB cable and have music throughout the house.

Steve N.
Empirical Audio
Manufacturer

Here are the guts of the AirPort Express. I have started modding it:
http://www.audiocircle.com/circles/viewtopic.php?t=14992

Actually, converting the toslink to coax eliminates a few components at both ends, reducing the jitter....