# how to use pc power supply for 12v



## Jodean

what and how can i use a pc power supply to provide 12v for a car amp....

must be a couple wires you can jumper on the main atx plug to get it to turn on...

then is the hard drive cables red just 12v?? should i cut them and splice them all into one??


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## Jodean

well i came up with this

http://web2.murraystate.edu/andy.batts/ps/PowerSupply.htm#levels

and i used a 420w raidmax supply that i half melted the wires on.....cut those all off and am using the other 12v+

It works.....im powering a rockford 500w amp to push my Tempest X.....its working better than the old sansui 80w per channel.....or 160w with both voice coils

I wired the sub in parallel and bridged the amp

thing is when connected to the amp its only at 10.90 volts and drops to 9.9v under heavy load.....still louder and sounds better than the sansui though

What other cheap 12v power supplies are there?? Im really looking to get 14.4V to get the max out of the amp..

Joe


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## hddummy

Interesting concept. It seems a little too MacGuyver to me, but it's working...right. You are dropping in voltage because the amp is trying to draw too much power from the supply. You might try using one of those big capacitors that car audio guys use. It won't help your steady state voltage levels, but it should keep it from dropping during momentary high demands.


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## tonyvdb

Your best option is to buy a Car battery charger as thy have a setting that will give you plenty of Amperage at 12vDC (should have at least 20amps of output not a trickle charger) You can find them for less than $70 on sale and it is properly regulated as well. Your likely to overheat your PC Power supply at some point and could cause damage to your amp.


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## Jodean

ive already thought of the battery charger thing but most now adays are SMART chargers and wont output anything until connected to a battery.....dont really want a battery in the basement.

The pc supply isnt overheating its actually working quite well.....just wish it outputs 14.4v

Its 11.6v not connected to anything.....then drops to 10.9 when you connect something.

It must be providing enough power to the amp to outpower the old sansui's 160w so i must be getting 200 or 250w out of the amp.....the tempest is moving another half inch both directions so i know theres more power there now.


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## sparky77

I would suggest something like this.

http://www.mfjenterprises.com/Product.php?productid=MFJ-4035MV

Or if you have somplace locally that sells amateur radio equipment or maybe even a comercial radio supplier should have something similiar and can possibly get something used for much cheaper.


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## Jodean

well that would be counterproductive....i could probrably buy a descent sub amp for that.


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## tonyvdb

This is what you need here











Go here to order one they only cost $42


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## Jodean

tonyvdb said:


> This is what you need here
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> Go here to order one they only cost $42


dont think that will work.....its 4 amp....my pc supply is doing 13-14 amps

and judging by the two 30 amp fuses on the fosgate amp i think i need MORE POWER!!!!

funny how a power supply costs as much as a amp itself......going by that rate the car amps should be free!!!!


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## tonyvdb

You wont be getting anywhere neer 14 amps with a pc power supply unless you have rewired it with 12 gage wire directly to the circuit board in the PS. Your lucky if your getting 2 or 3 using the wire that is already there. PC power supplies have several 18 or 22 gage 12volt wires in that bundle and you would have to at the very least tie them all together to get enough wire to allow for that kind of current.


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## Jodean

uhhh.... the wires are just fine being 6" long.....no need for huge wires.

pretty sure im getting somewhere around the 14 amps as this huge tempest is floppin all over the place....my alpine amp in my car has a built in amp meter and it reads 12 amps when driving very hard. the alpine is only 175w and this fosgate is 500w

i am using the two largest yellow wires from the 2x2 connector. 

If its not then why does it say 15a on the 12v+ right on the power supply??


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## sparky77

uh, fosgate, your wasting your time, I ran two 300 watt pioneers in my pickup with two 2 farad caps on 60amp fuses and I fried the fuses on more than one occassion. Car audio is one thing, where you never reallly need to use more than about 50 watts where you aren't likely to use more than 10 amps at the peak with the whole system, compared to my pro audio system that draws over 160 amps from the bank of sub batteries yet still manages to pound with 16 guage wire from an outdoor outlet. I've pullled over 2,000 watts peak from a single outlet and have never blown a fuse or tripped a breaker, and being a licensed electricitian, I can tell you that that is about the limit. Above all else I'm an amatuer radio efficianato, and I've used PS's to power amps, and you will likely need at least a 15 amper to cover what you want to do, if you have all the wires from a pc PS tied together, theoretically it should do the job, but a few "lightening caps" sure wouldn't hurt.

My entire system is powered off a bank of solar panels that charge an array of sub batts that runs at 24 volts and then is re-converted to 120v ac pure sine wave, which produces a lot of heat in the basement. Mostly the power from the solar cells, and batteries powers our dryer since we have 16 people living in our house, but for the most part, it works pretty good, our electric bill is less than 300/month. Come July, it'll actually be lower even with the higher temps in ND, but with more solar hours the batt's charge more that they get discharged, even running the 6 AC units.


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## Jodean

ok, im not going to war over car audio brands..... but pioneer?? ill stick with fosgate since it was free...

I never thought of a cap.....do i have to ground it out every time i turn it off or was that just the old style caps...

Im pretty sure im getting somewhere near 14 amps.....but thats if i had 12v and since its dropping to 10v im probrably only seeing 10-12 amps.

ok now im interested in the solar panel thing....

but first how are you getting a $300 electric bill?? I know i dont have 16 people living here but that seems awful high....my heat pump in ac mode only costs me $20 a month in august and i leave it cranked down to 72 since its so cheap. 

Im kinda thinking you wasting money on solar panels and using energy robbing appliances.....maybe not but theres no way i can force a $300 electric bill. I have all twist bulbs for lights and almost all new appliances and the heat pump.

oh....im a civil eng (contruction management) and was EE so i do play around with wiring and also wired my new house under my own permit.


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## tonyvdb

Jodean said:


> If its not then why does it say 15a on the 12v+ right on the power supply??


Its like trying to push a softball through a hole the size of a quarter, There is no way you will get a current of 15 amps at 12 volts DC through a 22 awg wire. The power supply is capable of 15 amps but thats at the circuit board before it splits the power over 5 or so wires going to different pins on the connector. If you run your amp for a long time this way you will eventually over heat the wire and probably melt the coating on it and could cause a fire.


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## Jodean

tonyvdb said:


> Its like trying to push a softball through a hole the size of a quarter, There is no way you will get a current of 15 amps at 12 volts DC through a 22 awg wire. The power supply is capable of 15 amps but thats at the circuit board before it splits the power over 5 or so wires going to different pins on the connector. If you run your amp for a long time this way you will eventually over heat the wire and probably melt the coating on it and could cause a fire.


Im not using one wire.......and there is only 4 12v wires coming out of the power supply.....all others are 5v and 3.3v

the two wires i had there were not hot after a couple of hours of use....you have to keep in mind its only 6" long.

i did put all 4 wires together now but it probrably wont make a difference.....

your looking too far into this...

its almost like your mad that it works for me....


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## Jodean

LOL!!!

finally figured out how to do amps on my test meter....

its pushing 13.4 amps to the rockford.

I like how people join in and dont know anything about the subject but reply with info they dreamed up..........thanks for the help......at least now i know im getting 13.4 amps but at 10v

For those who really want to have knowledge on this subject here it is. 13.4 amps out of a supply rated at 14 amps max. this is a true 420w supply and not a generic.

I hope this helps anyone needing 12v suppply and most stuff wont require 14 amps so you could use an old throw away pc supply if needed.......very straight forward and simple all you need is a wire cutter and one small wire nut.


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