"perry mason" wrote ...
Hi, I'm building a power supply to run a 12vdc car stereo in my room.
The power amp is a 300w ADS Power Plate 300. At 12.5v I need a 24A
supply? This seems wrong somehow. I thought I'd use the xformer from
a surplus 12v battery charger with an LM317 but I have the feeling
something needs review here. I'd appreciate any observations others
may have. Thanks for your time, pm.

From what we can perceive as your understanding of
electronics, even if you had an adequate transformer (which
seems unlikely from your description), a proper schematic,
and a kit of all the components, you would still likely find it
very difficult to successfully build such a power supply.

Where did you get the 24A figure? What is the fuse rating
on the amplifier? 24A seems too low assuming the unit is
really 300W because it is very unlikely to be 100% efficient.