AC/DC for a sub. No, wait...
August 24, 2010 1:30 PM   Subscribe

My son wants to DJ using a conventional amplifier and speakers, but with his car amp (Pioneer GM-D7400M) powering an 800 watt sub-woofer. This requires a 110 volt wall outlet converted to 12 volts. Can he use a battery charger, or does he need a larger, non-pulsing DC source, like an actual battery or DC power supply? Any other options/wiring tips? TIA.
posted by weapons-grade pandemonium to Technology (9 answers total)
 
You'll need some sort of power supply. Here is a video doing this with a PC power supply. It might be easier to just pick up a regular amp.
posted by sanko at 1:46 PM on August 24, 2010


Can he use a battery charger

No, probably not. And you're right that he'll want a clean source.

The issue here is one of current. Can whatever he's using to power the thing safely source as much current as the amp is drawing?

My guess is that lots of stuff designed to run most car accessories is going to fail miserably at delivering that much current.
posted by Netzapper at 1:47 PM on August 24, 2010


You are going to want a good power supply. You can find larger ones at amateur radio supply shops. They will supply good clean power. You would be better off buying a new amplifier.
You will probably get hum from a battery charger.
posted by Climber at 1:54 PM on August 24, 2010


800 Watts into a 4 ohm load is about 14 amps. It's quite unlikely that you're going to find a DC power supply that can supply 15 A continuously.

The 'cleanliness' doesn't matter at all -- the B+ rail in a car with the alternator and ignition running is about as noisy a power source as they come so the amplifier has sufficient input filtering to deal with it.
posted by Rhomboid at 3:55 PM on August 24, 2010


(Er, scratch that.. it's 14 amps at the load but more like 66 amps from a 12V source, assuming it uses a dc-dc converter to get more than 12V required to put 800W into 4 Ohms.)
posted by Rhomboid at 4:01 PM on August 24, 2010


With Rhomboid's calculations, I found a 75 amp continuous output power supply. At $450, you are better off buying a nice QSC RMX amplifier. My 2450 works great. Overkill for what he is driving though. The 1450 would be a better fit.
posted by Climber at 7:07 PM on August 24, 2010


This (or something along similar lines) should do the trick.
posted by InsertNiftyNameHere at 1:45 AM on August 25, 2010


25A at 12V is 300W, which is a bit short of enough to power a 800W amp.
posted by Rhomboid at 2:08 AM on August 25, 2010


Rhomboid: "25A at 12V is 300W, which is a bit short of enough to power a 800W amp."

You are correct of course, sir. I saw your 12 volt @ 14-15 amp comment and jumped the gun.
posted by InsertNiftyNameHere at 2:45 AM on August 25, 2010


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