Andreas Stemmer's entry 74 on digital I/O added

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@3728 a1c6a512-1295-4272-9138-f99709370657

docs/FAQ

@@ -676,3 +676,46 @@ A73: Yes, the recorder can crash when you copy several gigabytes of
      * Use USB 2.0. Transfers will be much faster.
      * Copy incrementally. With fully charged standard batteries it
        should be capable of sustained copying for 2 - 2.5 hours.
+
+Q74: There's a digital I/O connector on my jukebox. What is it good for?
+A74: The Recorder models have a connector for digital audio output using the
+     common S/PDIF standard (Sony/Phillips Digital Interface). This jack is
+     not present on the Studio/Player/FM Recorder models. By using the digital
+     output in combination with high class external equipment, you can get
+     much better sound quality out of your jukebox, because you can use better
+     DA-converters and better amplifiers.
+
+     The Recorder and the FM Recorder models are able to record from digital
+     sources, too. The digital inputs don't have the 15kHz lowpass filter like
+     the analog inputs and you are sure to minimize the noise floor.
+     Generally, S/PDIF can be an electrical or an optical signal and there are
+     many devices that support both. There are even small 3.5mm sockets that
+     can take either an optical or an electrical cable. But the socket on the
+     jukebox is for electrical signals only!
+
+     If you want to connect your amp with digital input (RCA type) to the
+     output of your Recorder you need an adapter cable (3.5mm stereo jack to
+     dual RCA jack). Plug the 3.5mm stero jack into the digital I/O socket of
+     your jukebox and the red RCA jack (right channel) into the digital input
+     socket of your amp and that's it. You don't have to enable the digital
+     output. The sound settings on the digital output are always flat, your
+     volume, bass, treble, bass boost, loudness settings won't have any effect
+     here.
+
+     For recording digital signals on the Recorder, use the white RCA jack
+     (left channel) and plug it into the digital output of your CD player, MD
+     player or whatever. Don't forget to select digital input in the recording
+     settings. Note that there exist some adapter cables with different color
+     coding, so if output doesn't work the red jack try the white RCA jack,
+     too. The tip of the 3.5mm jack is the digital input, the ring is the
+     ouput.
+
+     For recording digital signals on the FM Recorder, you need a special
+     4-pole 3.5mm plug (shaft = ground, tip = left channel analog line in,
+     first ring (next to tip) = right channel analog line in, second ring =
+     digital in).
+
+     If you want to connect devices with optical inputs/outputs, you need a
+     small converter box which converts your signal from electrical to optical
+     (for digital output) respectively optical to electrical (for digital
+     recording).