At a high level sending music to another room with an Airport Express and iTunes is quite simple. (Assuming the Airport Express has already been physically connected to a DAC or AV Receiver via an optical TosLink connection). First configure the Airport Express to allow AirTunes, configure iTunes to look for the Airport Express, select the Airport Express as the output device for the music and that's it. Music will now be sent to the audio system connected to the Airport Express and the digital output will be bit perfect.
At a more detailed level sending music to another room with an Airport Express and iTunes is just as simple once you know what you're doing. Here are the steps to get everything working, followed by a video that shows each step in sequence. It really is simple and incredibly inexpensive. The Airport Express is only $99 and outputs bit perfect audio!
01. Open the Airport Utility (Applications >> Utilities >> Airport Utility)
02. Select the Airport Express on the left side of the Airport Utility
03. Select Manual Configuration
04. Select the Music tab in the main Airport Utility window
05. Check the box to Enable AirTunes
06. Click Update to restart the Airport Express (optional - check to see that the box is checked upon restarting)
07. Open iTunes
08. Select Preferences form the main iTunes menu (iTunes >> Preferences)
09. Select the Devices tab
10. Check the box to Look for Remote Speakers Connected with AirTunes, and select OK
11. In the lower right corner of the iTunes window select Computer >> Multiple Speakers
12. Select the Airport Express check box and click the X to close the popup window.
13. Music will now play via wireless on your remote audio system
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