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aRt

New Member
hi everone

i was wondering if anybody knows how big of a power supply do u need to power up a 600watt car amplifier in your house?
 

Scubasteve

New Member
A car amplifier requires 12Vdc, which an ATX power supply does produce. There is one problem though, which is the current requirements of the amplifier. If it puts out anything significant, then don't expect the power supply to produce enough current.

If you get it working and have problems with the bass overloading the amp, put some large capacitors (over 12V rating!) in parallel with the connection. This may be able to regulate it enough.

steve
 

Kingpin094

New Member
I am currently using an ATX 230Watt power supply to power a 2Chx100Watt amp. driving 2 6.5" speakers. The PSU that I am using is rated to put out 6Amps. at 12V so it provides more then enough for my needs. It all depends on how much power you want to try to pull from the supply and how much you want to drive from the supply.
 

Scubasteve

New Member
Kingpin094 said:
I am currently using an ATX 230Watt power supply to power a 2Chx100Watt amp. driving 2 6.5" speakers. The PSU that I am using is rated to put out 6Amps. at 12V so it provides more then enough for my needs. It all depends on how much power you want to try to pull from the supply and how much you want to drive from the supply.
How is it possible to put out 200watts of audio with only 72watts of input power? You cannot be loading the amplifier enough to notice there isn't enough power for the amplifier.

Steve
 

bogdanfirst

New Member
i am not sure i have seen some ATX psu's that can get you 600W....
but considering that the suply doesnt handle sudden changes of current very well, you should put some large filtering capacitors.
you can power the 200W amp from then 72W PSU, but you will either overload the suply and maybe burn it, or you will not get enough power to the amp and have a lower power then you expect with distorsions, or maybe both.
i think that if you go to an audio store you will find power suplies like you need. i know i saw a 12/40A suply intended for audio aplications. i think it was switching too, but as i saw it has like 2 10000uf caps for filtering plus a dozen or so 100n caps.
 

stevez

Active Member
As others have observed - 600 watts/12 volts is 50 amps. If the output is really 600 watts and it's continuous then you need the 50 amps plus something to account for efficiency. If the amplifier were 75% efficient then the power must be 50 amps/.75 = 67 amps continuous.

When my son was fooling with this stuff the ratings were peak, not continuous and few people actually run them at 100% output. The capacitors store the energy then give it up on peak demand. The capacitors can make up for the inadequacy of a power supply (or voltage drop on cable) but only for a moment.
 

Gene

New Member
aRt - Is the 600 watt number the output wattage to your speakers or is it the input power requirement?

If the 600 watt value is the output to your speakers, it has little value in determining your power supply requirement - although it is related. To determine the requirements for your power supply, you will need more input information (i.e., input watts or amps).

Forget about using a wimpy power supply from a computer (like an ATX) - you are talking about a serious power supoply here.
 

Kingpin094

New Member
Just to clear things up, almost all 100W or greater amps. use 12-14Volts as the input but then the step up the voltage to between 25 and 35 volts. You will almost never find a car amp that runs directly on 12V. Therefor an amp running at 30V * 4Amps = 120W. But you still have to take into account that the output power of an amp is usually rated about 130% of what it actually produces. The rated output of an amp. is measured at ideal conditions in order to get the absolute maximum from the amp.
 

Scubasteve

New Member
Yes Kingpin is right.. Audio amplifiers always step up the voltage to a + and - voltage greater then 12V (usually 30-80V) by means of a switching power supply internal to the amplifier. You can see how this increased voltage potential forces more current through the speaker coil, therefore increasing power!

The losses of the switching supply, amplifier, and wiring can take a toll on overall efficiency. Good amplifiers rate their output as measured, not inflated. A lot of crappy brands inflate their ratings by 50% or higher..

Steve
 

Gene

New Member
and . . . if the 100 watt (rated) amp actually produces 77 watts and the rater was considering 2 ohm speakers. What happens when you connect a pair of 8 ohm (house type) speakers? I'd say about 20 watts out.
 

Madmartin

New Member
If you only want to power up for some measurements except full load test, then a 4 A 12 V supply might do. Big amps tend to have quite a nice quiescent current, I observed. PC power supplies can't do a lot af amps at 12 V , but they did it at least sometimes for me. Watch for your pc-power supplies needs. As almost all switching designs, they need a minimum load. I went good with a 12V / 50W bulb over the 5V rail when drawing maximum power out of 12V. Maybe your supplies are better and don't request such loading, but some do. ATX p/s are AFAIK switched on by pulling the PS-ON pin to GND.
You can, regarding the available output current of your power source, not expect maximum output of your amp.
Also watch for high curents when connecting your amp. It might fill its internal caps with quite some amps during the first few seconds. Many workbench and also pc power supplies trip out, then. Simply reset the overcurrent trip quickly several times.
 
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