Does the airport express have an audio *INPUT* ?

The audio port on the AirPort Express (AX) is for audio output only. Audio streams are input to the Express via the AirPlay protocol. There are no physical audio input port(s) on the device. Sorry!

For the AX, audio input is primarily provided by iTunes. Of course, it can also get input from other sources like Rogue Amoeba's Airfoil.

iTunes does most of the work. When iTunes plays back standard audio content (AAC, MP3, audiobooks, Internet music streams, etc., it decompresses those file formats and creates what's essentially a raw, uncompressed audio stream. That stream is compressed using Apple's Lossless Compression (via a QuickTime codec), encrypted, and then, streamed (via AirTunes/AirPlay) to the AX. The AX decrypts the stream, decodes it, and outputs it in either analog format or as a digital PCM stream.

If iTunes is playing back a digital multichannel file format like AC3 (Dolby Digital) or DTS, those bitstreams (like the lossy formats) are wrapped in Apple's Lossless compression, encrypted, and then, streamed to the AX. In these cases, the AX would first decode the stream, and then, output the raw AC3 or DTS stream via its optical digital audio port.

Get a dac that has an tos input. Plug the tos cable from ax to the dac then to the audio equipment. There is so many types of dacs. I have been using the one from radio shack due to being inexpensive.

Then you can play aiff files from itunes via computer or ios and airplay or there is a few apps that will play flac files.

Or convert all the lossless audio to aiff and get like pogo plug or a nas

Not sure why you responded to my post. The OP was looking for a means to input audio into the AirPort Express. Your solution is still relying on the AirPort's audio output port to send a digital audio signal through an external DAC, and then, on to an audio receiver.

That WAF is always the killer when wanting to get the cool stuff.

My set up is 1 AirPort Extreme, 2 airport expresses, 1 Apple TV. With this I can intercom my kids room in the morning to wake up for school if he is not up yet (or play music).

The Apple TV and one of the ax's are next each other because when I watch movies I want to use the Apple TV to be both the sound and video going into receiver. If I want to listen to music I will use the express and use the tos to the dac (I wanted a more expensive dac, but the WAF was unacceptable)--the radio shack supports 24 bit 192 hz it just doesn't have the little indication lights telling what it is getting.

I don't think having video going from one device and then Airplaying to another for sound would be solid yet. Ape doesn't give us the ability to change the lag times to sync up voice and data in the ios devices. We do have that ability in itunes. I haven't messed with it though. Depending on your home network your voice may lag behind the video. If we could add QOS to the packets streaming audio it may be possible. When you stream to one device and that one device controls both hand off's to tv for video and receiver for sound that one device is buffering them together. When you mix the routes you have two devices buffering sound and video separately.

The only exception to this is when you try and play movies on a windows pc the sound still lags. But then we can adjust that in itunes.

Sorry macobs30 I was responding to Tielor1223 not you. I understand what you are attempting to do and just wanted you to be sure how the AX worked so that you can make an informed decision.