"perry mason" wrote in message
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.
-----------------------------------

perry mason:
You will very likely need a hell of a lot more amps than a LM317 @ 1.5A can
deliver. Also it is very unlikely that your surplus 12 volt battery
charger can deliver enough current to be useful in building the kind of
heavy duty power supply that is certainly going to be required for your set
up....... 24 amps at an absolute minimum with an actual requirement of
almost double that if indeed your 300 watt amp can really deliver 300 watts
RMS ... and that you intend to run it at high volume levels and are
expecting clean performance.
To build a safe and proper 12 volt power supply that can deliver enough
current for your apparent needs is not going to be an easy, novice task, nor
will it be cheap.
Do a search on the internet for power supply and electronic equipment
suppliers and most certainly Ebay for power supplies that are already built,
you can most probably buy something cheaper than if you built it.... and if
you purchase a quality built unit it will likely include important safety
shutdown features to protect your stereo equipment, your home and the power
supply against over-voltage and fire starting short circuits.... very
important when dealing with this kind of metal melting current.
A possible low-tech solution for you would be for you to use that 12 battery
charger that you have to keep an automotive battery continually topped
off.... then you can run your high power stereo system through a suitable
fuse directly from the battery. If the charger is an "automatic" type that
will reduce to a trickle charge when it senses that the battery reaches a
fully charged condition you can leave it hooked up all the time whether you
are using the stereo or not. The main drawback to all of this would be
that if you intend to run your stereo at very high volume levels on a
continuous basis the battery may run down after approximately an hour or so
unless you give it a chance to charge up with the stereo shut off or turned
down to easy listening levels.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


..
..