Running a 12V car amp from the mains

[SamJUK]

Hi all, what a fantastic comunity you have here.

 

I have come up against a little problem this morning regarding a project I am working on and was wondering if anyoe here could help.

 

Our project is a 50" touch screen table and it's been decided to put speakers and sound into it. We need to have a 4chnl amp in it so we could drive each speaker seperatly if needed. After a bit of research I bought a kenwood KAC-6404 car stereo amp but now have to trouble of powering it.

 

All the 12V transformers I have found won't put out more than 6amps and I need 19...

 

Short of putting a car battery in the base of the table I am out of ideas.

 

We have made 5 of these tables and so I have 5 of these amps to power.

 

Thanks in advance guys and girls,

 

Sam

[Simon Lewis]

Hi, Sam,

 

A suitably sized computer power supply should be able to do this.

 

Simon

[MarkPAman]

Simon's beaten me to it, but here's a link to one that will do it:

Click me!

[SamJUK]

Thanks chaps,

 

I've only just found this place, love it.

 

Sam

[Stan Hope-Streeter]

You won't get 12V at 19A from a standard PC power supply without rebuilding it. The 12V output is normally rated for a lot less than this.

 

The necessary modifications are widely available on the internet but you need to be an experienced electronics constructor to do it.

 

If your amplifier is only ticking over and not drawing anything like its full rated current, then you "might" get away with an unmodified ATX supply - just be aware that you will need a dummy load resistor on the 5V supply to make the regulation work properly. Worth a try if you have some scrap PC's lying around that you can raid for the PSU's

 

Try looking for the power supplies sold for ham radio equipment - most of this runs from 12VDC and 20 or 25 amp regulated supplies are readily available.

[timtheenchanteruk]

please dont forget a car amp is not designed to run peak at 12V, but 13.2-13.8 (ie the charging level of a car electrical system)

 

the HAM option seems the best IMO, if its like the ones u used to have for my CD, they run at 13.2V, around 20A stablised.

[ramdram]

Years ago I used to be into slot car racing. The emporium in Hammersmith used car batteries with a trickle charger across them. Some of the 16D Mabuchis would take 30A up the straight, so I cannot believe you would be under powered, ie the technology works.

 

Instead of a car battery with acid and consequent H&S worries, ** laughs out loud **. you might consider the Yaesu kit which is a gel type battery. You could google and see if there is a Yaesu battery charger which might fit the bill???

 

HTH

[MarkPAman]

You won't get 12V at 19A from a standard PC power supply without rebuilding it. The 12V output is normally rated for a lot less than this.

The one I linked to seems to say that 20A are available at 12V - unless I'm reading it wrong :D

[callumb]

These cheap PSUs may state they will provide 20A but when you get close to those loads they go all funny voltages fluctuate then go pop (well more explode!) with some nice blue smoke! If you want ones that provide what they say you need like likes of ones from OCZ, Antec and Corsair. Decent branded supplies. They cost far far more but do what they say with out little fuss!

[Simon Lewis]

They cost far far more but do what they say with out little fuss!

 

Hence my comment about a "suitably rated" psu. Some are 20A across dual 12V supplies etc., but tere do seem to be a number that will produce well in excess of the 19A asked for.

 

Of course, the actual current draw is likely to be far less than this.

[Robin D]

You could just use a good quality car battery charger rated at 20A or more. If you are concerned about smoothness of supply, put one of those 1Farad capacitors so loved by boys with self drive mobile sound systems! :D

[Simon Lewis]

You could just use a good quality car battery charger rated at 20A or more. If you are concerned about smoothness of supply, put one of those 1Farad capacitors so loved by boys with self drive mobile sound systems! ;)

 

The battery chargers that we "reverse engineered" for teaching purposes had no smoothing or voltage regulation of any form whatsoever. Putting a capacitor across the load will help to some extent (but is not the complete solution), but it is no match for the smoothed and regulated output of a switch mode power supply.

[savage1]

the PSU in my pc can chuck out over 50amps on a single 12 volt rail IIRC it was just over £60 so there are definatly cheaper options but 19amps on a single rail isn't that much for a modern PSU

[Paul TC]

Some of these computer PSU's may omit some of the mains filtering components to save the maker a few pence per unit, even if the circuit board has provision for them.

Has been found to cause issues in some applications.

[bassnote]

After a bit of research I bought a kenwood KAC-6404 car stereo amp but now have to trouble of powering it.

Car amps are notorious for bad power consumption. And for a reliable end product I would probably advice aganist usign a car amp off a PSU as it seems a long way around a problem.

 

How loud do you need each speaker to be?? The KAC-6404 gives 40w at 4 ohm per channel. Would something less powerful work ok? world replacing the 12v stuff to 240v stuff be an option?