200+amps on 12v

[EightySix Four]

I need about 200 or so amps on a 12 volt rail from a wall socket. Is there any possible was I can do it without breaking my bank?

 

[Mday]

200 Amps off a 12 V rail from a wall socket...

um, is this VAC or VDC? and what wall voltage is that wall socket at?

 

[EightySix Four]

It's a normal US wall socket, and I'll need the power VDC

So you know it's for car amps inside a house. The Sub amp draws 114amps and the other ~70amps.

 

[brentkiosk]

This is a lot of power - 2400 watts. Even at 100% efficiency, this translates to 20 A at 120 volts. So, when you get it done, you will need a 30 A circuit to run it. Starting from 240 VAC might be a better option.

DC power supplies in this range are possible, but it might cost a few bucks. This is the kind of power that might be used to run a 1 or 2 KW radio transmitter, so you might find further info in amateur radio lit.

 

[EightySix Four]

The other thing about it is I will probably never use full draw from the two... I just need a way to reliably power them with maybe half volume or so... 100 ampish

 

[Mark R]

A big car battery and a battery charger.

The battery will be able to produce large current surges for short periods, while maintaining a stable voltage. Use the charger to top it up when you are finished.

If your loads are enormous, and you will be running for long periods - use several batteries. One or 2 amps per battery.

 

[Calin]

And you might want (if you use very high current draws for very short periods of times) to add a big capacitor just before the POWER IN of the amplifier

 

[blahblah99]

I can design a multiphase 12V power supply for u, up to 8000W

 

[MrDudeMan]

Originally posted by: Calin
And you might want (if you use very high current draws for very short periods of times) to add a big capacitor just before the POWER IN of the amplifier

good idea :thumbsup:

 

[EightySix Four]

I have a 1.2 farad cap that will go inbetween the power and the amp.


blahblah99... how much ?

Also the car battery wouldn't last long before requiring a recharge would it?

 

[IamElectro]

There is probably no cheap way for you to do this. Have you ever seen the power supplies that car stereo shops have for powering amps behind the displays. Mind you that they only power one amp at a time.

It would probably be cheaper and less time comsuming to but a half decent power amp

 

[blahblah99]

Originally posted by: crazySOB297
I have a 1.2 farad cap that will go inbetween the power and the amp.


blahblah99... how much ?

Also the car battery wouldn't last long before requiring a recharge would it?

It'll be a lot more expensive than what you are willing to pay for it.

If you're looking into power amp for home use, you might consider getting a pro audio amp, as it'll be cheaper than trying to get or build a 12V 200A power supply.

 

[EightySix Four]

I have 2 amps very good amps, and I'm using these speakers indoors for a few months under the premise of breaking them in, so I honestly don't need that much power, just half volume to break them in while I wait to get the car I'm gonna install em in.

 

[f95toli]

Try asking at www.diyaudio.com.

Someone there will know the answer to your question.

 

[EightySix Four]

http://www.imagexoom.com/image.php?i=uploads/img_0439.jpg

It works, there's alot of background noise though, more than likely due to the small amount of power available to it. This is hooked up to the small amp, and it's powering one speaker okay. I'm gonna tie in a second psu and see how it ends up working... we'll see.

 

[Calin]

You should put every one of the PSU behind a diode that will allow only "juice out". You will need some big diodes, as the usual ones survives at only several amperes (and you have 10 times as much). And before you're asking (if you thought of that), you can't use several diodes in parallel, as they won't share the load (maybe if you use some kind of resistance in line with every one of the diodes)

 

[EightySix Four]

This amplifier uses 70 amps total, and this PSU is giving it about 20. Would that be the cause for all the noise?

 

[Calin]

The current the amplifier uses is dependent of the load on it. If you listen at low/moderate levels, it will use maybe a tenth of the max rated current.
Why the noises? A switching power supply can have noise on the 12V phase - as the only things that use 12V are CDROMs and hard drives (for their motors, so very clean current would be no problem) and voltage reduction circuits on mainboards (which have their sistems to clean the low voltage delivered to the processor).
One more thing you should take into consideration is that a switching power supply will give almost perfect DC voltage at very low load, and the deviations of output voltage (seen as noise or harmonics) will increase alot near max load.
If this is true, you could measure the frequency of the harmonics and add filters against them at the power entry point in the amplifier (use an oscilloscope). Or (but it won't be as good) you could use a big condenser.
Look at band-pass filters or low-frequency pass filters. These would solve that problem.

Another thing, try to separate the power supply from the rest of the system electromagnetically (put it into a aluminium hand-made case or something as to reduce the electromagnetic radiations that move out from the power supply.

harmonics... Let's say a switching power supply uses a oscillator at 5kHz to switch on and off the power (imagine the socket gives AC (220V effective), a bridge of diodes straighten it (310V max, but still 220V effective), then there is a transistor that switch on and off at 5kHz. You have a transformer that reduce it at 27V effective (with multiple exits at different voltages like 13.5 that would be ground, 13.5+3.5, 13.5+5.5), and then those voltages are straighten (and some of the voltage is lost in the process).
In an end, the output signal will contain harmonics (sinusoids) of 5kHz, 10kHz, 15 kHz, 20 kHz and so on. Those might be the noise you talk about

 

[EightySix Four]

Would the cap that I'm going to put on it help lessed the noise?

Also, my plan overall is to use 3 PSU's in a 1U rack mount and run it from inside the case to the amps. That should be enough seperation to get rid of all the noise the PSU's put out. Put the cap and a fuse or two insde the case between the PSU and the amps for protection. You think with those all together is should reduce noise well enough?

 

[Mark R]

The PSU will do fine, unless you overload it. In practice, you'll probably overload your ears before you overload the PSU. If you do overload the PSU, it'll probably just shut off, but you may get some distortion on the bass before it does shut down.

The big capacitor is a good idea. Bear in mind, that it is possible that the PSU won't be able to start up with the cap connected. You may need to connect the cap via a resistor, and have a switch to bypass the resistor once the PSU has got going started. You'll have to try it though - it probably will work fine, but electronic PSUs can get upset when connected to a massive capacitor.

You will also need a better connection to the PSU. Connect all the black wires together and all the yellow wires together - and connect both big groups direct to the amp/cap (before you do this, see the note below). One of those little wires won't cope with 20A, it'll overheat, if you run the amp for any length of time.

Important: If the PSU has dual 12V rails - then don't connect both rails together. Use one rail for one amp, and the other rail for the other amp - you'll need to check the manual for which wires are connected to which rail.

Similarly, if you are using multiple PSUs - do not allow power rails from different PSUs to be connected to each other. This is really important. (Trying to power one amp off 2 PSUs is an absolute no-no). You could have serious problems with power imbalances or the PSUs fighting each other, because they are all set to slightly different voltages. If you are running a different PSU for each amp - then you should connect the grounds together. Having different grounds for each amp, could potentially cause problems with hum.

 

[EightySix Four]

Hmm, how could I possibly make use of all 3 PSU's power... if I can't connect all the rails together? None are dual rail PSU's... but I was hoping to combine all their power.

 

[bobsmith1492]

You probably don't need 200 amps. Where did that number come from? If it is from the fuses, they're always way higher to absorb the initial current inrush.

One option would be to build a huge switching power supply, at least for the subwoofer amp as you can filter out the switching frequency with a low-pass filter and still let your bass through. There're some good sites about them.

 

[Mark R]

I'd just use 2 PSUs - one for the midrange, and one for the sub. Use the cap on the sub amp.

You won't get full power, but then you're unlikely to need it. I would set up the system as I've described and see if it is satisfactory. If not, only then would I think about more expensive options.

If you *have* to have full power - then the only affordable way of doing it is with car batteries. The power from car batteries will also be much cleaner than that from a PSU which has lots of high frequency noise in it.

 

[EightySix Four]

I got the numbers from the amplifier spec sheets from infinity, and infinity is known to underate all there stuff.

 

[bobsmith1492]

Ah, I see the one amp draws 114. I was gonna say, I don't know man; 200 amps is pretty rediculous. But, 114 is somewhat more reasonable. Definately don't try to power them together on the same line.

Truth be told, you'll never hit the maximum on that. The numbers are maximum, which mean peak power. That can only occur when you have probably a 2 ohm speaker hooked up (what's yours?) on each channel (how many are there, and are you going to bridge them?) and playing a huge bass hit. That's really the only time it will hit anywhere close to its peak power. With a big cap right by the amp, I'm sure you could get away with something like a computer power supply (of ~30 amps) and still get a load of power. When I was testing out this 460 watt amp my brother brought home from somewhere, it had like 40 amp fuses on it. I hooked it up to a 20A power supply I have, no caps, and could crank it up all the way without any issues. I hooked up a meter to measure current, and it only hit about 4A. Granted, the gain controls on the amp are broken, so it wasn't putting out as much as I'm sure it could have, but it was rumbling the house quite nicely on cheap, dual 12" subs.

Anyway, point is you don't need a 200A supply to run that thing. Try just a hefty 12V transformer (maybe a 12-0-12 with the two sides in parallel) into a bridge rectifier with some caps. That can give a lot of power assuming you can find a decent transformer. This is all it takes to make one: http://sound.westhost.com/p68-f2.gif Just wire the two sides of the transformer up in parallel instead of series like that shows since you don't need +/- 12VDC.

The transformer is the expensive part (well, that and the caps.) You'd need something like.....
http://www.surplussales.com/Transformers/PowerTra.html
That might work; you'd have to look around really.
Actually, this would be better: http://www.newark.com/NewarkWebCommerce...aSearch/partDetail.jsp?SKU=95B5032&N=0

If you have to buy a supply, something like this would work: http://www.newark.com/NewarkWebCommerce...caSearch/partDetail.jsp?SKU=89F683&N=0
That would supply a lot of power.

In the end, it's going to be expensive; that's a lot of power. Maybe a car battery would be cheaper?