....and by box I mean car, but here is a good place to start.

 

In one of our wedding rooms here, we've installed an amp so that people can turn up with music. We have to cater for most sound sources (USB, CD, SD, iDevice, Droid etc). With this in mind, I'm looking at using a car head-unit to do the job, as they're compact and tick the boxes. Obviously I don't really want to have it wired to a car battery sitting in the corner, so my question is: does anyone know of a good AC to DC supply system for a car stereo? It won't be driving speakers, just connected via the pre-amp, so it shouldn't need a huge current supply.

 

Cheers

Personally I would be a bit worried about doing that if its used by the general public, as if anything went wrong it could come back and hit you.

 

At work where we build custom test equipment we have to do full PAT tests and comply with 61010 safety assessments to ensure that the equipment is safe for any person to operate it. Because if we didnt and something went wrong, we would be liable.

 

Buying something of the shelf would be the easier and probably safer (legally) then DIY.

 

If you go down the avenue of purchasing a Car stereo, i would make sure it has some ability to switch off the main outputs and  to act as a "preamp only" as im not sure about car stereos but normal Hifi can be damaged if they are turned up with no speakers attached.

 

I would say getting it on a bench power supply and testing how much current it draws and then choosing a safe limit above it would be the best bet. This is because to predict you would need to know how much Quiescent current it needs (just to sit at tickover) and then how much it is delivering to the load and how efficient the amplifier is itself.

You can buy 13.8v power supplies. You would be sensible to get this tested, as suggested, but since the output is much lower voltage, the radio part would be running at safe extra low voltage (as far as I know).

 

CPC is a good source. Something like this ought to do if you aren't running speakers:

 

http://cpc.farnell.com/_/in06007/power-supply-bench-13-8v-3a/dp/IN06007

 

but as suggested probably best to find out what the unit draws before buying.  I regularly use my 3.5A unit for testing radios even with speakers attached, though without turning up the wick.

 

Most aftermarket head units, and therefore probably most in general are OK without speakers attached as they are designed for all options. For example many will run with only two speakers even though they have four outputs. Also, if they have line out, then they probably expect to be connected to external power amps instead of directly to speakers.

 

It's something I've done myself, albeit only at home. A car head unit, connected to the input of a hifi amp. Worked fine for me.

Update:

 

I was bored and started looking around for power supplies, and searched, by error, YouTube. In there is a guy who has setup a car head-unit driven off the mains...........via a PC power supply. So, I dug out a PC PSU (300w), picked up an ISO connector and a fan connector for a PC, wired the red and yellow from the head-unit to a yellow from a HDD connector (and black to black), and Bingo! I now have a head unit driven off the mains