"Gainclone" or "digital" switching amp using pre-fab amp modules would be very simple. Just do a google search for "gainclone" or DIY audio and you will likely find a wealth of information to get yourself started. AudiogoN'r "Rawsonte" builds and sells lots of simple gainclone and other type DIY amplifiers. Maybe you can ping him and he will send you some links to sites that have information about do-it-yourself amps.
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