This board is a generic audio controller with decent sound. It was designed for an ipod but can be used with other devices. It can be used to connect an ipod to a car or home hi-fi for example. There is space on the board for: line preamp (adjustable gain via multi-turn trimmer) to get the ipod line audio level up,  differential (balanced) audio driver for interfacing to some car amplifiers, 5V charging supply (sufficient for ipod, and probably tablets because it can supply up to 2A), microcontroller, relay switching of audio and other ancillary stuff (the board has 12V inputs to the microcontroller [e.g. for buttons] and 12V switched outputs, and also an I-Bus interface. Not all needs to be populated of course. The entire thing is quite small and can run off an unregulated supply of 10 to 16V. This is the preamp portion:

This is the entire circuit (large zip jpeg image). It works well (been working for over two years in cold and warm conditions).

This is the board assembled (100mm x80mm size).

It is a slide-fit into this enclosure (Farnell order code 1418583).

There are a limited amount of unpopulated boards for sale (30USD or 20GBP plus £2 or $8 postage), they are expensive because they are 4-layer boards with analogue ground plane. If you are interested, please contact (without the spaces or the character X)  “s X h X a b a z _ y X o X u s a f @ h X o X t m a i l d o t c o m” quoting ‘ipod controller PCB’. All parts available from Farnell, and also probably Digikey.

This is the top and bottom layout. All parts are hand-solderable.