Toslink optical digital output

Try connecting the toslink cable first, then power down your system. Power up the modem first, then the router, then the Express and finally your computers to see if that will help.

The Express should automatically sense the optical signal. There is no adjustment for this.

It is very possible that the problem is not the Express, but the cable or TOSLINK adapter. I strongly suggest trying another one that you know that works.

Have you considered that you may need to select or activate that Toslink input on your receiver?

Ok, thanks for verifying that the TOSLINK cable is working properly. It is quite possible that the "digital part" of the AX's audio jack or the audio circuitry (that passes thru the digital signal) itself may be faulty.

I suggest that you plug a pair of headphones in to the Express or connect the Express up using your analog connection cable. Verify that iTunes is playing something and that you can hear it OK using the analog connector.

Remove the headphone jack or the analog cable and look inside the audio port on the Express. If the optical signal is working, you will see a red light inside the device. If you don't see the red light, then it's likely that you have a defective AirPort Express there.

If you do see the red light, I'm not sure what to suggest at this point as this would indicate that the optical signal is working. There are two types of digital audio connections used on most amplifiers, Co-ax and toslink. I assume you have the right input and connectors selected.

FWIW. iTunes uses a QuickTime CODEC to convert audio files to Apple Lossless, and then, uses AirTunes to send them to the AX. In turn, the AX uses built-in software that converts the Apple Lossless to an Encoded Digital Audio format. From there, digital audio is sent to a optical transceiver to convert the electrical signal to an optical one before sending it to the innermost part of the audio port. For analog, the AX has a built-in DAC to convert the Encoded Digital Audio to Analog which is sent to the same audio port.

Since, you are getting a good analog output, you know at least the DAC is working properly. Unfortunately, it does still sound like there is something amiss with the optical transceiver in the AX ... or the calibration of the digital signal between the AX and your stereo. If your stereo has multiple digital inputs, I would suggest (if you haven't tried already) is to use a different port.

... and you may still want to try another cable. I had a similar issue between my MacMini and Logitech speaker system that perplexed me until I tried another TOSlink cable. Trust me, I triple-checked the original cable, which did work with other equipment, but just not between these two.

It turned out it was a combination of cable used and device receiving the optical signal. The cable was one made by Monster with a little adaptor at one end to fit it into the airport express. Switching this cable for a different Toslink cable (also Monster) where the connector was built in fixed the problem. These cables are not expensive ($1 plus S&H on Amazon). Also, feeding the signal using the bum cable through an M-Audio CO3 and then on to my Mark Levinson DAC fixed the problem as well.

So, to summarize, using a different Toslink cable fixed the problem, which in my case was caused by a defective cable introducing signal degradation which gave certain DACs problems locking on to the edge transitions. I'd add that Toslinc connectors are fragile in general and one should avoid sharp bending which can create hard to identify problems, including sound dropouts or poorer quality sound if your DAC does not do a good job of locking onto and de-jittering the degraded signal.

After months of trial and error I too have narrowed down my dropout problems to signal path of AX Optical Output > Toslink Mini Adapter > Toslink Cable > DAC.

The DAC I'm using is built into the Peachtree Amp that I am thrilled with, so I hope that the new cable idea works.

Thanks for this discussion. Extremely helpful.

I had some success last night finally by setting a crossfade between songs. The crossfade I setup was relatively small, but at least then there is a continual signal going from the AEX to my receiver so there's no dropouts.