Power supply question..

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I have a class D car amplifier that produces about 1200wrms, (1 Ohm , mono) now have a wife = no car stereo any more so i would like to use it in a home system. So my question is what sort of transformer/ torroid etc do I need (240v Mains)??
TIA, Beau.
 
if its a really 1200w mono... u need hell lotsa power even if it was 99% effiecent. i think the average class D puts out about 30% of heat.

so....

1200/70 * 100% =~1714w

u need about 1714w.

1714w/12v = 142 Amperes

u need 12v at 142 Amperes. good luck at getting a power supply to suit ur requirements.

on the other hand, i doubt the amp is 1200w RMS. i bet is a mini 100w.....

u`ll do ok with a pentuim4 psu.
 
Beau said:
I have a class D car amplifier that produces about 1200wrms, (1 Ohm , mono) now have a wife = no car stereo any more so i would like to use it in a home system. So my question is what sort of transformer/ torroid etc do I need (240v Mains)??
TIA, Beau.


hacknet said:
if its a really 1200w mono... u need hell lotsa power even if it was 99% effiecent. i think the average class D puts out about 30% of heat.

so....

1200/70 * 100% =~1714w

u need about 1714w.

1714w/12v = 142 Amperes

u need 12v at 142 Amperes. good luck at getting a power supply to suit ur requirements.

on the other hand, i doubt the amp is 1200w RMS. i bet is a mini 100w.....

u`ll do ok with a pentuim4 psu.


it says 1200w at 1 ohm. he wont be using 1 ohm speakers.
 
Beau what brand of amp is this>???

And since it is a class D amplifier they do not draw near as much as a regular car amplifier....I know this because we did extensive testing on some comp. sytems when we were designing them
Multiple batteries are necessary and premature alternator failure was always a problem until a 200 amp custom wound was utilised


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hacknet said:
1200w on 50db/w speakers....

plus... do you trust those labs... at 1200w. the internal smps has to be hell of a chunky... i don`t think so...

50dB/w speakers? Show me!

And of course you are going to put in those multi-farad capacitors to take care of the current peaks so your smps only needs to be rated at a couple of 100 watts continuously, tops.

Jan Didden
 
1200W/1R=34.64V RMS=48.98V PEAK

These are usually bridge amps and run on a maximum of 60V DC, just build a 60V supply for home use.

"And of course you are going to put in those multi-farad capacitors to take care of the current peaks so your smps only needs to be rated at a couple of 100 watts continuously, tops."

AFAIK a 1F cap can only supply 1A for 1Second.

Bass in modern music has close to a 50% duty cycle, so 1200W out means 840W in, and that's driving a resistor with a 100% efficent amplifier.

I would probably use a 42-0-42V 1KVA transformer, 60KµF or so, and 60A rectifiers with a soft start.
 
hacknet,

I believe he was suggesting building a simple unregulated power supply and then run that into the amplifier . bypassing the switching power supply thats already in the amplifier.

question for you. you seem to be very skeptical about car audio amplifiers, have you tested some yourself or what ? Not all car audio amplifiers are junk, look around.
 
Beau said:
And the amp has been independantly tested, it came out at 1232wrms AT 14v, 1%distortion.
The clue is in the distortion figures. At 1% distortion I guess almost any Class B amp with a rail voltage over 50V can deliver 1200W into 1 Ohm. Clipping will be included, but only will occur on the peak of a sinus cycle.

The trouble starts to deliver this amount of power at a distortion of less than 0.01%.

BTW this amount of distortion would be nice in a tube amp, running 90W Class A or so. Which might produce 720W of heat (@12.5% efficiency) (per channel).
 
li_gangyi said:
Get a couple of car batteries...charge them up and listen to em?? Guess you would need a hell lot of charging...just to listen to some songs...try a few PC PSUs...down here in Singapore...you can get a scrape NEW one for 5 bucks...10A...so 10 ($50) should give you at least 40A...enuf??

Nice idea: use a car-battery from a diesel engine and a serious charger. I've no idea how much noise this would generate, but a bulky choke and some of those MultiFarad caps might help.
 
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