Can remember first power supply I built.. on a breadboard.. it was stepped-down, full wave bridge rectified, filtered, and regulated. Remembered burning my finger on the original Rs I had installed in the regulator section, until I scavenged a similar value resistor that could handle more power. On that same board, I installed a push-pull audio amp to drive a loudspeaker. (holy shit I just realized I can re-size the comment box on accident.. though I digress..) Glued that board, with all it's line voltage stuff exposed, to the speaker. Ended up removing the AC/DC section when I bought my first used car, and used it to drive my car's speakers with one of those cheap first generation MP3 players. Only 10w, so wasn't very powerful.. but it seemed to impress friends.