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msharpe 6th May 2006 07:06 AM

Powering car amps with power supplies
I am designing a home system based on car audio components. I planned to use 12v power supplies to run the amps. I'm curious as to how powerful the power supplies need to be. I'm assuming that they need to have a wattage rating equal to the wattage of the amps, or could they be of lower power?

DigitalJunkie 6th May 2006 07:13 AM

The power supply needs to be *atleast* as powerful as all the equipment it's running..

Say it's running 2 amplifiers with 20A fuses,and a CD/Radio deck,with a 10A fuse.. Ideally you'd want a supply with atleast 50A capability..but you could probably get by with a bit less,if you don't crank the volume up alot.

Of course,you could always make your own..
Monster MOT supply

msharpe 6th May 2006 06:13 PM

OK that makes sense. Well in that case I could use some more advice. What would be the best way to get a power supply(s) with a max power of 2800W :D ?

sr20dem0n 6th May 2006 07:38 PM


Originally posted by msharpe
OK that makes sense. Well in that case I could use some more advice. What would be the best way to get a power supply(s) with a max power of 2800W :D ?
Your money would be much better spent just buying home amps, it's going to cost you many hundreds of dollars to buy 12v supplies that can feed that much power. If you buy them they're almost $200 just for 40 amps (around 3-400 watts worth, depending on what amp you're using).

edit: I see you posted max power, max power is worthless (especially with these brands out there like Pyle and Dual who slap retarded numbers that have no ties with reality all over their products), what's the rms power you plan to use?

Perry Babin 7th May 2006 06:35 AM

I agree that it would be better to use mains powered equipment.

If you already have the amplifiers, you may be able to find a used switching power supply on eBay. I've seen several 5v/200 amp supplies. You could use 3 in series (each set to 1/3 of the desired output voltage). At 2kw+, you're going to have to power the supply from a 230v outlet.

The following page has a calculator to show you the size supply you'll need for car audio amplifiers.

msharpe 9th May 2006 07:40 PM

Well, I decided to go with the Ebay route (that's where I was buying everything elsew from anyway :D) I managed to snag 2750 watts worth of power supplies for about 80$. This should be way more than enough. The subs are 500watts RMS total for the pair and the other four speakers are "500 watt" 4-way coaxials. Is it a fair estimate to say they are probably about 200watts RMS? I should know for sure when they get shipped to me though. And another question, the subs I bought are by Coustic and the other speakers are by TNT. Are these brands any good? I did buy them for their cheapness I'll admit. And if they are bad, I'll probably try and upgrade to better units later.

I'll probably have some more questions when I start building this beast.

sr20dem0n 9th May 2006 10:33 PM

The power handling of the speakers doesn't matter, how much power will you actually be sending them?

As for the speakers, the "500 watt 4 way coaxials" are probably around 30rms, they fall under the Pyle and Dual category that I was referring to earlier.

And no, Coustic and TNT are not good brands

space 10th May 2006 06:27 AM


The power supply needs to be *atleast* as powerful as all the equipment it's running.
It would be a good idea, but not entierly nessesary. Because of the crest factor (peak/avg. power) of music and theather sound, the RMS-value of the suplies can be smaller. Some powersuplies can supply peak values beyond the RMS-value. Others tough don't.
If one has some way of storing energy for times when the power needed peaks beyond what the supply can deliver, one can do with smaller supplies. The key here is battery(ies). They can deliver wast amounts of energy if called upon. The powersuppply/charger only need to supply the effektive RMS value. If one chooses to go with battery(ies), one of course needs to make other choises on what kind of batteries/charger. One other thing one need to take into acount, is that batteries have a more limmited lifespan.


beppe61 10th May 2006 02:23 PM

Dear Sirs,

please excuse me if I jump in this extremely interesting thread with a question maybe a little off-topic.
I have found a huge 2kVA - 12VAC toroid and I would like to use it along with an also huge diodes bridge and suitable smoothing caps.
After the caps the the voltage would be around 17 VDC, if I am not wrong.
In general could it be too high voltage (i.e. 17 VDC) to power a car audio amp ?
I cannot find in the specifications the admissible voltage supply range.

Thank you so much again.
Kind regards,


msharpe 10th May 2006 06:20 PM

Well, I'm certainly no expert, but I do know that most car amplifiers should be able to handle at least 14.4 volts DC, as this is the fully-charged voltage of a 12 volt car battery. I would image that running one off of 17 volts would present no danger. If anyone else has anything to say on this matter then please do. I'm just making an educated guess here essentially. So, unless someone says that I'm totally wrong, then I would say at least experiment with it.

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