Car Stereos: Standalone system., sculpture piece, functional sculpture

Question
G'day Mate-

Sam from australia here-

Im currently working on a stereo system that will use a kenwood headunit and 4 six inch speakers-it will be a sort of functional sculpture piece.

I have already made the box our of wood and fitted the unit but a power source has become and issue.

I would like to either run it directly from mains power (240V AC reduced to 12V DC via use of a transformer).

I guess my biggest issue at the moment is that with all the previous headunits i have installed in cars the earth is grounded to the chasis- not the negative of the power source. If i use a normal transforer to go from 240vAC to 12v DC do i need to put in a resistor between the ground wire and the negative terminal to simulate the resistance of the chasis?

Any suggestions would be great!

Answer
Hi Sam,

There's no need to make things too complicated with the power supply; to operate the head unit, you just need between 12 and 15 volts DC between the black ground wire and the red and yellow power wires.  I'd suggest using a power supply with at least 7 to 10 amps of current capacity, which rules out most of the "wall-wart" type of power transformers.  Many people have modified old computer case power supplies for this purpose.

The reason electrical components in vehicles are grounded to the vehicle chassis is simply to save wire.  The negative battery terminal is also connected to the chassis, so the metal chassis is simply a convenient conductor that eliminates the need to run separate ground wires all the way back to the battery.  The resistance between the battery terminal and a chassis ground point isn't usually significant, and there's certainly no need to simulate it with a resistor.

Hope this helps!

Brian