I've given You a solution a few answers before ( TSR-1 ).The voltage dropped across the bridge should provide about 7.5V (roughly), which will go into a 7805.
That should keep it fairly cool. I have a LDO adjustable regulator (MIC2941A) which I'm going to set up for 3.3V.
Search in the Internet about MiDi Thru Box.I just don't feel comfortable with driving
the MIDI out with the pin from a CPU directly
You'll find some schematic how to interface a MiDi port.
As driver chips I would use 74HC... or 74HCT... Chips ( e.g. 74HC14 ).
They are faster then the old 40xxx one.