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Old 5th February 2006, 08:53 PM   #1
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Default increasing current(amps) by splicing wires

hello, everyone. this is my first time posting, so i'm sorry if i sound like an idiot (which isn't far from the truth).

i was wondering if it is possible to take a computer power supply and somehow splice the wires on it to increase the the current (amperage). i have a PhoenixGold XS4300 amp from my car and would like to use it as my home audio amp, so i need to simulate a car battery, and ignition wire. the problem is that the amp draws 35 amps of continuous current draw at full power, and peak current draw of 50 amps. most power supplys that i could find on the net seemed to top out at around 20amps on the 12V wire. i appreciate any help on the matter. thanks.

oh yeah, on the site(or a site i can't remember) someone had suggested using a car batter charger to do the job. however, that will probably be more expensive though, and i'll still need to think of something to use to hook up the the amps remote/on wire on the amp, or it won't turn on.

-ivan
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Old 6th February 2006, 01:15 AM   #2
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I am not sure about the computer power supply route...as they may not be able to put out enough current fast enough
(I don't know much about computers)

most car amps need a good bit of power to perform there best.

when I bench test amps I use a large 12v DC power supply
(you can find some beefy power supplies on ebay at a fair price)

car battery chargers will power it but in most amps you will get ton of hum,and it is very hard on the charger.

as for the remote wire all you have to do is send a small 12vdc positive(+) signal to it
you can rig up some sort of on/off switch to the remote wire to fit your needs.

hope that helps some
welcome to the site!
I'm new here also you will find a lot of good info here if you look around.


!~mike~!
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Old 6th February 2006, 01:28 AM   #3
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12V*35A=420W
probably more than 60% will be transformed to speaker load (4ohm, yes?).
this is huge continous power, I think you won't need it, maybe only for short momemts during listening to music.
Unless you heavily overdrive the amp the mean current will be probably less than 4A for really loud music. Give a 10-22mF electrolytic cap across 12V supply, mind the polarity.
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Old 6th February 2006, 03:44 AM   #4
Stocker is offline Stocker  United States
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A word about the big cap: some PC supplies will see a big capacitor on the output as a short-circuit and try to protect themselves by shutting off....

And that kind of power is literally at ear-splitting levels. Try a regular supply without modification beyond a jumper on the green wire to a black wire (so it will turn on at all) and see if it gets loud enough for you.

PC power supplies can be wired in parallel with a few external components, but try one by itself first.
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Old 6th February 2006, 08:45 AM   #5
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thanks for the help guys. i really appreciate the input.

i was looking at the 12vdc power supply to just hook it up to. what i was thinking though, in order to get the amp to turn on, everyone says to bridge the + on amp to the remote, and that makes sense. the only thing is that concerns me there is when i look at my amp specks is that, "Input Sensitivity: Line level inputs = 100mVRMS to 3VRMS; and Hi-level Inputs = 1.75VRMS to 35VRMS" My electronics knowledge is limited, but i'm thinking that the "line level inputs" must be the remote-on thingie for the amp and the "hi-level inputs" is for the power cord from what should be the battery. i don't know if it would be bad if i just bridged it, but i fugure that for that part, worse comes to worse, i'll just pull out the power supply out of my old computer and use that 12v+ for the remote-on cause that one isn't for much amps.

darkfenriz>>regarding my speakers, i haven't bought any yet, so i can use whatever, but i was figuring on 4ohms.
>>regarding the amp. it's pretty strongs, so it like a lot of juice. it's rated at 14.4VDC at 4ohms 35Watt RMS X 4 channels.>> so if i understood right, you're saying that even though the specs on the amp say that its drawing 35amp continous and 50amps peak, that is if it's turned up REALLY high (which i don't really care about). if you really thing that the amp will only draw about 4amps of current or so, then a PC power supply should work, as i found ones that top out at a max of 20amps for pretty cheap.

I was also wondering, if it's ok to bridge the wires to the remote-on and the possitive on the amp, then can't i put two 12V+ wires together and increase the amperage as well. Cause i can find a PC power supply with 2 12VDC+ power wires, and just use that. However, I don't know if by splicing 2 12VDC+ wires will change the voltage, or something else that might be bad.

again, thanks for all the info guys. this site rocks. i've found a lot of info, but sometimes it's hard to filter through all of it. i appreciate your input.
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Old 6th February 2006, 08:45 AM   #6
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great, thanks for the info. i'm gonna pick up the powersupply tomorrow, and i'll let you guys know what i come up with. hopefully, my hair won't be standing straight up, with a little cloud of smoke rising from it.
-ivan
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Old 6th February 2006, 04:31 PM   #7
Schaef is offline Schaef  United States
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Just a couple of notes on the PC power supply....

What you propose, probably won't do what you think. The PC power supply has a couple of ratings on it. The 12V rating is the TOTAL power draw for the 12V line. In other words, its not 20amps per 12V line, but 20amps total for all 12V lines combined.

Also, the cheapie supplies may claim they're rated to that level, but they may not actually reach that level. There have been tests done on PC power supplies, and generally the cheapies never reach their rated outputs.

Next, if I read one of your other posts correctly, it sounds like you're going to blow up your amp. Input sensitivity is for the incoming signal, not the power!!! The high-level input is if you're running the speaker out from your car stereo, as opposed to a line level out from it. DO NOT HOOK POWER UP TO EITHER OF THESE!!!! There should be an input somewhere else.

Hope this helps you some!
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Old 8th February 2006, 01:41 PM   #8
Stocker is offline Stocker  United States
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nonono this is a misunderstanding! the 'remote' lead is switched by the head unit... when the head unit comes on, 'remote' goes high to 12V. When the amp sees the 12V on the remote lead, it turns on. +supply to the amp is also the same nominal 12V, but this is where the current is really being sucked through.

Good point about 'all' the 12V wires. you might want to splice *those* together so the wire doesn't get too warm. Depending on the power supply you may also need to load the +5V output a little but try it without first to see if it is 'good enough'.

high level input = speaker wires going in
low level input = RCA jacks
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Old 9th February 2006, 06:15 AM   #9
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Default NO NO

By the time you go through the grief of getting the amp to work in the home, you would be better off just to build an amp operating off the AC mains.

Or you could run the amp on 12V and measure the supply rail voltage. Then just buy a power transformer that will deliver that much voltage and swap it out so that the line operated transformer's secondary is connected in place of the DC-DC inverter transformer in the car amp.

However, considering how crappy most car amps are, you would still be better off with a decent used home amplifier.
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Old 10th February 2006, 02:44 AM   #10
Stocker is offline Stocker  United States
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??? splice together 15 or so +12V wires and you have a high current supply. jump the 5VGood and you turn it on. How is that difficult?
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