Powering a car amplifier / subwoofer at home...


Ex. Club Member
Was viewing this forum of some people who have apparently used computer PSU's to power car amps...


and my neighbour just gave me his JBL active box:


and... I just so happen to have a power supply knocking about... which is rated 5-15v variable, 25-30A


Now... the JBL is rated 20A
So if I were to connect... would it be too much power from the PS?

Anyone else tried it? Or am I advised against it?
Come on experts...


Ex. Club Member
I am doing the same. What wattage is the PSU? What wattage is the amp, tell me this and I'll help you, lol.

Wattage divided by voltage = amps and if they work out the same you know you it'll work

The sub is only 16 amps so you should be alright as most power suplies are around 400w


Ex. Club Member
Your computer PSU will have a power rating... 350w is a common one, therefore trying to run a 1kw amp off it for example would cause trouble!

Your power supply sounds like its 450w (Power = Voltage * Current, in this case 15v * 30A = 450w)

So i'd find out what your amp is rated at wattage wise.
(which from your rating of 20A would make it 12 * 20 = 240.. so i'm guessing 240w?)

Your power supply should cope with that then...


King of Subsonic
If the JBL is fused at 20A then that PSU would be perfect. Set it to around 14v.

Whats all this BS with regards to 'the sub is rated at 16 amps'?!

No need to even comment on computer psu's as he has one which will be fine for the job. You 'can' use a computer psu if you want it, I've done it without problems. Its very rare, basically near impossible that the amp would do its rated power (for example 1kwrms) and you wont be running 1khz sinewave through it...

If the bench psu does 25-30A max at upto 15 volts, then it will be perfectly fine for running the car amp which is fused at 20A, as you'll likely never get near 15A, let alone 20.

Take 14.4v as the nominal voltage, set the psu output to 14v and enjoy :)

Edit: That active sub is rated at 100wrms, which I doubt it would even use, so do a quick 100wrms / 14v and you get just over 7 amps. Do 100 / 12v and you get 8.3 amps.

No problem with that, enjoy!


Fusion Motorsport
MSC Founder
Official MSC Trader
most amps are at best 60-70% efficient. So power/voltage may be inaccurate.


Ex. Club Member
Computer PSU's give out voltage closer to 12v so working out ampage from 14.4v is pointless, I used 12v so that's where I got 16amps peak from.


King of Subsonic
Computer PSU's give out voltage closer to 12v so working out ampage from 14.4v is pointless, I used 12v so that's where I got 16amps peak from.

You said 'the sub is only 16 amps' which doesnt really make any sense.

His psu does upto 15v. hence the suggestion of using more voltage.


Ex. Club Member
I meant absolute peak amps if driving it really hard at 12v (the sub is 200w peak) So 16 amps is well within the range of his power supply