Here's a Single Ended Stereo Power Amp I made from the remains of an antique Sony Reel to Reel Tape recorder.
As much as possible is made from the original tape recorder -- even brackets and screws. The AC cord gromet was one of the old motor vibration dampers.
It's litterally a breadboard project, as the base used to be a polymer cutting board. The back panel (dark plexiglass) used to be a sliding door from a (cheap) piece of furniture. The mesh cover is cut from a what used to be a waste basket.
Other parts, including the bridge rectifier used in the re-engineered power supply (original power transformer), and the speaker terminals, are from a circuit board found in a garbage pile.
It uses 30M-P23 (Japansese version of 30A5) output tubes and 6267 input tubes. The original Reel to Reel had transistors for the 1st stage of the tape head pickup, but that end of the PC Board has been sawed off as a line input is more than enough to feed the 6267's through added coupling capacitors.
30M-P23/30A5's are often found in hot chassis designs, and while this does have a proper power transformer, one end of the 30M-P23's heaters are connected to the AC line. Everything else is powered from isolated windings of the transformer.
30M-P23/30A5's are rated for 7.5 to 8 Watts, and it has plenty of horsepower for it's intended use as a PC speaker amp. I'm especially impressed with the low-end response.