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Old 18th August 2006, 05:53 PM   #1
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Default Sonic Impact Power

Can I use a computer power supply to power my sonic impact amp? The +12v on a computer supply varies from 4.5 amps to over 20 amps..... Will too much amps harm the amplifier? Thank you.
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Old 18th August 2006, 06:00 PM   #2
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No problem! The amp will only draw the current it needs.
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Old 18th August 2006, 06:06 PM   #3
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I'm not 100% certain of the theory or the realities, but if you have got proper voltage regulation, there isn't really such a thing as too many amps in a power supply. The amperage spec is really an upper limit, not a quantity that is guaranteed to push through.

Some power supplies put out more *voltage* if you're drawing far less current (amperage) than they're designed for. Voltage can kill chips.

I don't know exactly how computer supplies work, but I imagine that it wouldn't be too bad. Dunno how clean the power is, maybe there's interference on the rails. I'm rather inclined to think that the power is at least somewhat dirty.

Intuitively, think of a river. The max amperage is how much water can flow past in the canal, the current draw in use is how much water *is* flowing past, and the voltage is how hard the water is being "pushed" downwards. A low voltage, high-current situation might be seen as a shallow, wide river that you can stand and wade in. A high-voltage but low-current river is like ... well ... a river that's been put into a pressurized pipe in a hydroelectric dam Don't rely on this intuitive explanation too much though, as it's not exactly correct

There are forum posts about this subject here, actually. Search and ye shall find. People have also been using inexpensive LCD monitor power supplies to power T-Amps, and you can find posts on that too. Those are 12V with a ~3-5 amper max. Also, someone mentioned CB radio supplies. Those can be had down to 5-7 A max, or less, and are 13.8V, which could be good for more power to the speakers than a 12V supply can do. You'd have to be certain that it's well regulated, as getting voltage much above that will kill the chip. Dunno where the voltage "roof" is.

Hope this helps, and hope I wasn't telling you anything you don't know. Good luck
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Old 18th August 2006, 06:07 PM   #4
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Kent: Once again we see that there are so many ways to say basically the same thing
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Old 18th August 2006, 09:17 PM   #5
cpemma is offline cpemma  United Kingdom
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Quote:
Originally posted by kristleifur
Kent: Once again we see that there are so many ways to say basically the same thing
Or one can say, "You don't have any problems running a 60W light bulb or a 3,000W kettle from the same mains socket, do you?"

Luckily the load only takes the current it needs, or our electric bills would be very much higher in this nation of 13A sockets.
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Old 19th August 2006, 07:05 AM   #6
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Default A question of power

Ok, let’s rip it guts out and look at this thing! The sonic impact will rarely draw over 1 amp and for most playing much less than this. This means a 2 amp supply is overkill. And with a 2 amp rated supply a shorted component will be current limited to a reasonable value so probably no smoke and fire. This supply will probably have a noise spec of 50-100mv and this can be lowered with a bulk storage cap between it and the amp. So we have quiet power and full output capabilities. Now let’s look at the big supply; first we will be dealing with fan noise then dealing with output noise due to the fact it probably will be running in discontinuous mode due to such a small load. This is not only electrical noise but can be heard as a shrill screeching sound, not pleasant. So to get around this we add a bank of load resistors to force it into normal continuous operation. Now we have generated a mess of high current high frequency circulating currents to radiate electrical noise into everything close so we must separate the supply physically.
Opps! I just shorted something out and what happens? A ball of flame comes out of it and the amp is quickly reduced to a burning puddle of melted plastic. There is a very high maximum short term output with these supplies, probably in the neighborhood of 500 watts or more. This will raise a lot of smoke in a hurry.
I think you get the idea, the SMPS’s of 2-3 A @ 12v are real cheap if you look around at the surplus places. Some are easily adjustable and can be set to 13.5 volts with which the SI works very well. Clean, safe, cheap and quiet! And they sound good!
Roger
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Old 19th August 2006, 09:12 PM   #7
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I agree with Roger.
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Old 20th August 2006, 02:50 PM   #8
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Hi

Have been listening my new AMP6 for some days now using the computer smps,rated to 15A 12v .
What I have notised is the great amount of heat these make.The fan can't be disconnecteed.The fan keeps the smps cool when feed with only 5v.But I don't like the idea of using fan,considering the amp itself stays almost cool all the time.

So I have another SMPS from an old scanner,2A 12V.I suppose the recomended ap. 2A stays also for AMP6 with TA2020 chip,with moderate listening levels ?

thanks
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Old 20th August 2006, 05:12 PM   #9
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Default Supply sources

I do all my posts in word first then cut and paste, you still have to proof them as it won’t help with a wrong word!
I take apart printers and scanners too. A good source of good parts! Some of the little supplies are of exceptional quality and ready to be used. Over current, voltage, temperature and adjustability are pretty much standard with these. Use some care and common sense as the rectified line voltage stored on these bare supplies can do some serious damage!
I use an amp 3 for my computer sound and it is powered by a 1.25 amp supply set to 13.5 volts. Since the supply for this setup is remote in a separate box I use a large bulk storage cap in with the amp. I think it is 10,000uf @ 16V, been awhile, not sure. I have even used supplies as small as .75 amps and set to 12V it worked ok but set to 13.5V it would over current limit if you played loud stuff with bass in it. It would just cut off for a short time then turn back on, irritating but nothing was hurt except my ears/pride. Point is with SMPS’s you don’t need to go way overboard for some worthy sound.
Not too long ago you couldn’t use the available SMPS’s with amps at all as they couldn’t take the large load swings. Now most all the available supplies are rated to “zero” load and behave properly. An exception here is the larger supplies needed for high power amps. They can go into current limit/shut down charging the large caps on turn on. A cap change in the start up circuit will take care of this for most of them. Look up the control chip and research it’s applications for this.
Roger
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Old 21st August 2006, 10:46 AM   #10
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Default Re: Supply sources

If you are using a 12V SMPS with the AMP6, you are not getting much voltage to the chip - maybe 10V. Unless you have bypassed the bridge and regulator.

If you are using the AMP6 with all the parts in place, all you need is a ~15V transformer. 2.5-3A is big enough. No need for a DC supply. If you DO want to use DC, you will need at least 16V. 20-25VDC would be better.

Quote:
Originally posted by sx881663
I do all my posts in word first then cut and paste, you still have to proof them as it won’t help with a wrong word!
I do the same thing - and have the same problem!!
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