Excuse me,
beardedalbatross , but I think that there is an exception - If using an iPad, I believe that there's an optical TOSLINK output in the same socket as the headphones plug into. If you buy an adapter cable, you can plug digital TOSLINK output from the iPad into any outboard USB DAC. But I might be mistaken...
If you can't get digital from the optical connector, then here's two other ways:
Another thing to keep in mind is that you can easily, through 2 different methods, output a standard digital s/pdif signal from an Ipad.
This means you can pipe the raw digital sound data straight to an outboard D/A converter of your choice, or a digital input of your receiver if it has one, and at that point the Ipad's D/A converter and sound circuitry is not factored into the equation at all.
Method 1 (wireless)1-Purchase an Apple Airport Express ($100) and connect it to your home's existing wi-fi network
2-Use the "airplay" function on the Ipad to wirelessly pipe the Ipad's audio signal from the Ipad to the airport express. This function is system-wide so it will work with any audio app you are using on the Ipad
3-Connect an optical Toslink cable, from the optical output of your Airport Express, to an optical input of your D/A converter.
This method is handy because it's wireless. I have an Airport Express hooked up to the input of my Onko Home Theater Receiever, and can sit and read on my Ipad, while at the same time piping audio from Pandora or a Google Play Music App, wirelessly to the stereo.
Another bonus is that on any mac laptop running system 10.8 on up, it can also pipe the audio from the laptop to the same airport express. So a mac laptop can also be a wireless sound source as well, not just the Ipad. Iphones too. On the Windows side, the Windows version of Itunes can play audio out to the airport express.
Method 2 (Wired)1-Purchase a $30 "Ipad Camera Connection Kit", which connects to the Ipad's connector, and gives it a standard full sized female USB port. For newer Ipad's and Ipad minis there is a newer version of this accessory that connects to the lightning connector.
2-Purchase a "USB Audio Class" class compliant USB audio interface with a s/pdif output. This is basically a driverless computer audio interface that connects to the USB port of the above accessory, and offers a s/pdif output. One mainstream $30 option is the Behringer UCA202
3-Connect the s/pdif output of your audio interface to the s/pdif input of your D/A converter or Receiver. The Ipad will automatically output it's stereo signal out of the s/pdif connector of the attached interface
Of the two connections, I like the wireless option better (even though it costs a bit more) because:
-It's wireless, which is always a more flexible solution. You can actually sit and use the Ipad for other functions, from another spot in the room, while it is sending audio to your converter.
-This solution does not tie up the Ipad's connector, which means the connector is free to eventually recharge the Ipad. With the wired solution, once its time to charge it the music would have to stop.
-The Airport Express can be useful for other things since it is also a general purpose travel sized wireless router
-With the "airplay" function, other devices like mac laptops and iphones, and the Windows version of Itunes can all send audio to the airport express connected to your stereo.
All of the above functions have been tested, by assorted folks out there, to be bit accurate.
Thanks!
