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Powering Car Stero and amplifier

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guich

Sun Jun 01 2008, 07:22PM

Registered Member #1269 Joined: Sat Jan 26 2008, 06:22PM
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Posts: 9

iÂ´ve also a car amplifier in my room (i hope i will get my sub tomorrow) and this is my power supply: 37176578 3014

It was under 80â‚¬ an itÂ´s just a 12V transformer (40A) an two 35A rectifiers in parallel (ok you need a 1F cap)

If you use an ATX a capacitator WILL help you! The rms amps will not change but if the amplifier pulls over 20amps the cap will give him the current and the ATXÂ´s fuse will not switch down

FAKE ACOUNT

Tue Jun 10 2008, 12:55PM

Registered Member #1529 Joined: Tue Jun 10 2008, 12:50PM
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Posts: 2

PC Powersupply unit! Easy to get one cheap, but use one rated at about 150% of amp power so you don't overheat it

aonomus

Tue Jun 10 2008, 01:49PM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

PC power supply won't work, the rated power is spread across 3.3, 5, and 12V rails. The only way I really know how it would be practical would be to get a fixed 13v power supply charger, car battery, audio cap, and amp all wired together in parallel since a lead acid or AGM battery are the only things that can provide the absurd current draw for milliseconds. I would actually be very interested to know if you have a current measuring transformer for an oscilloscope and could take readings of current draw vs waveform....

Also, who let the troll in? Who also thinks the troll can't spell?

Tonskulus

Thu Jun 12 2008, 09:53AM

Registered Member #1223 Joined: Thu Jan 10 2008, 04:32PM
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Posts: 133

I had also car amp in my house. But i did not use 12V supply, instead of that I had 230V / 2x30V / 500VA standard 50Hz transformer in place of amplifiers original SMPS transformer. So goodbye for powersupply problems, this one was working like any real home/pa-amplifier. Modifications were also really small, I only had to remove original ferrite transformer from amplifier. So it was easy to put this amp back to car by changing transformers.

GeordieBoy

Thu Jun 12 2008, 11:16AM

Registered Member #1232 Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881

I'm suprised the output side electrolytics of the original SMPSU were sufficient to provide hold up for 10ms when the 50Hz transformer was fitted!

Dr Who

Fri Jun 13 2008, 09:12PM

Registered Member #1540 Joined: Fri Jun 13 2008, 08:49PM
Location: Chicago
Posts: 3

Are you looking to power your sub amp inside your house? Or are you trying to power it inside your car? The two applications have vastly different solutions.

And just some things to keep in mind...car subs are designed to take advantage of the cabin gain of your car. To use an auto system in the home requires one to use a different cabinet alignment. Also, car amplifier designs are heavily compromised to work on your 12V battery. Instead of rectifying your wall voltage down to 12V and then back up inside the amplifier doesn't make a lot of sense. And by the time you've got yourself a powersupply that can handle a few thousand watts at 12V, you might as well have just purchased yourself a dedicated amplifier designed to work off your 120VAC...something like a Behringer EP1500 might be along the lines of what you're looking for.

Also, computer CPUs aren't very good for step load responses (i.e. big bass hits), therefore, you can easily damage them.

Do you know why that is? I've heard it mentioned many times, but never any reasons provided...not that I doubt it, but I'd love to have a reason the next time I tell someone that.

Marko

Fri Jun 13 2008, 10:56PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

I'm suprised the output side electrolytics of the original SMPSU were sufficient to provide hold up for 10ms when the 50Hz transformer was fitted!

Do you know why that is? I've heard it mentioned many times, but never any reasons provided...not that I doubt it, but I'd love to have a reason the next time I tell someone that.

Read my post up in thread - simply said it's due to cheap design which lacks current mode control, and overall low power capability (Most cheap ~400W supplies don't usually provide more than ~16 amps on 12V line, and this still needs some underrating).

Lack of current mode control means that PSU can't tolerate voltage drop on it's output, and thus we can't use those large farad-range caps on the output nor draw high peak powers through the supply because in both cases it's overcurrent protection would trip.

waffle

Mon Jun 16 2008, 05:36PM

Registered Member #642 Joined: Fri Apr 13 2007, 10:19PM
Location:
Posts: 15

The down n' dirty way...An automotive battery charger. This one is good for 12 amps on the "high charge" setting. i bought it for $5 at a yard sale. It runs my 200 watt amp + 10" subwoofer well, although I draw close to 12 amps during the bass hits.
DSCF0375

So what is inside... It looks like a huge transformer and a diode. No regulation, no smoothing caps, and only half wave rectification. Interestingly enough, though, when I use it with my amp there is no 60hz hum... my guess is the amp has at least some internal smoothing caps...
DSCF0376

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