This article describes how to build such a device:
http://www.frontiernet.net/~rlsnuffy/db50xg/index.html

Unfortunately the PCB isn't made any more as far as I can tell and it runs off the mains (there is a transformer included on the board) so unless you have experience building mains powered kits I'd suggest giving it a miss.

How about this: http://www.heise.de/ct/artikel/MIDImal-285418.html

This is probably what you are looking for:

http://www.joebrown.org.uk/wp/?p=3124

thank you guyz, unfortunately they still look much more complicated than i expected, so i would have to give it up. 🙁

hi

a simpler but less general purpose solution could
be to utilise the computer's PSU. this could be
like in the case of some older ANTEC PSUs
which present a 4 pin molex connection or via
a bracket as found for ESATA.

simpler logic could also be used if you omit the
steps in creating the current loop and opto-
isolated detector and just took the midi signal
(TTL) direct from a gamport/midi socket.

in the above you would pretty much do what the
onboard waveblaster header does on a card.

bye

There are some very small micro ATX psu's that still have 4-pin molex power connectors - you could stuff one of those in a small component enclosure.

Those wavetable boards require -12V so you can't run it off an external molex or ESATA connector alone. The micro ATX PSU is a good idea though.

hi

i would expect the +/-12v rails to be purely for
the analogue section and probably not require
much in the way of current. someone can check
that out and the 5v rail would be the
main requirement. in this scenario a simple
DC-DC converter would be the only component
necessary for this design which can provide
+/- for the analogue section. i suspect anything
over +/-8v would suffice of around 100ma but
i have not investigated this.

bye