i need about 100amps at 12 volts

[anwaypasible]

Originally Posted by aardvarkash10

why are you trying so hard to make your life miserable?

Its a car amp - so emulate whats in a car.

Get a battery (not a pissy little one - get a 17 plate commercial vehicle one) and a (say...) 25A continuous battery charger.

Done.

Now go "oonst oonst" yer heart out....

i am trying so hard because when i had this amp connected in the car.. the little clip light kept coming on far too early.
i can only imagine that the amplifier was being starved of amperage.
the car has a stock 120amp alternator and a regular platinum duty cycle battery.

i dont want to run the subwoofer with a bunch of square waves.. i'm looking for sound quality AND spl - not just spl.

[anwaypasible]

Originally Posted by russo

As said before, the car amp as an SMPS that takes the 12v input and convert it to 60-0-60v or more to feed the amplifier, so why don't you just open the amplifier, disconnect the smps from the amplifier and use a centertap transformer rated for the current and voltage supplied by the smps originally?
Would be easier and a lot cheaper than your initial idea.

i thought about this when i first read it.. and i would like to bring the amp back into the car some day.
besides, if the amp fails.. i would need to re-configure for a new amplifier.

[event horizon]

What would most likely happen is that one PSU (if in parallel) will supply all of the current until it reaches it's current limit, at that point the output voltage will drop until it reaches the preset output voltage of the second (slightly lower) psu.

Obviously this is undesirable as it means one of them will always be flat out if the load is high, it won't last as long! This is why current sharing is better than redundant supplies.

If you series connect 5V supplies then you only need the diode accross the outputs to protect the supplies in the unlikely event that one goes down on you! They'll all supply the same current which the load demands, as long as they are set to the same voltage then it should be reliable.

Yes it'd be great if the PSUs could be syncronised, though in certain respects it's better if they aren't as any switching RFI is spread over wider band of frequencies rather than being lumped at a single frequency. It's nothing to do with the 60Hz mains but down to the switching frequency of the PSU itself, this is likely to be over 25KHz.

[chris661]

Surely, someone else has spotted things like:

POWERCOOL|PC850AUBA|PSU, 850W 80+ DUAL 12V V2.2, POWERCOOL | CPC

[event horizon]

Originally Posted by anwaypasible

this makes me think that the step down transformer drops the 110v down to 5v or 3.3v and then uses another step up transformer to provide the +12v

am i speculating different design options here?

No, what happens is the same as a normal mutitapped transformer The secondary windings on the SMPS PSU will have multiple taps for each voltage, these will be fed through different rectifiers for each voltage & then into an inductor. The inductor will have the same kind of turns ratio as the transformer to keep all the supplies as closely regulated as possible. Ok, it might have 3 or 5 times as many turns but the ratio will be kept the same.

As an example say your 3.3V has a single turn on the TX & 4 turns on the inductor, the 12V will likely have 4 turns on the TX & 16 on the inductor..It's a way of keeping things stable compared to each other & really helps with the output regulation

[aardvarkash10]

Originally Posted by anwaypasible

i am trying so hard because when i had this amp connected in the car.. the little clip light kept coming on far too early.
i can only imagine that the amplifier was being starved of amperage.
the car has a stock 120amp alternator and a regular platinum duty cycle battery.

i dont want to run the subwoofer with a bunch of square waves.. i'm looking for sound quality AND spl - not just spl.

OK, just for reference, your car battery (even a small one...) is capable of in excess of 400 amps at dead short. And 100 amps is an arc welding rating, so your cables need to be appropriately sized. Use that imagination of yours.

If you had a clipping problem, it wasn't due to supply current unless your cabling was substandard. Otherwise, your car would have stopped every time the amp clipped....

[fff0]

Originally Posted by anwaypasible

i am trying so hard because when i had this amp connected in the car.. the little clip light kept coming on far too early.
i can only imagine that the amplifier was being starved of amperage.
the car has a stock 120amp alternator and a regular platinum duty cycle battery.

i dont want to run the subwoofer with a bunch of square waves.. i'm looking for sound quality AND spl - not just spl.

I think there is a few factors causing this clip led to come on.
One is the gain or source problem/factor.
Two is the amp has prob
Three is the heat, not enough ventilation.
Four is the power cable used is too small. Min 4 AWG for a sedan like Altis (from Bonnet to Trunk length)

I strongly believe its not the power problem. As power delivery problem will cause the bass to sound blurry, lack of power and recovers when there is a few seconds break, not clip with proper tuning as far as my experience tells me (I used to play SQL = SPL + SQ with Audison VRX).

Btw, have you tried to ram your engine to 3krpm and see if the clip prob still exist? Its because at 3~4krpm, most car alternator will then only give out its max rated power.

I just had quick glance at the current Hifonics amps, It seems to me most of them are Class D amps not AB or A which lowers the possibly of power delivery & heat problem. Unless you have an old Skool hifionics (>10yrs old) then its a total different story.



My 2 cents
Ps: Sorry guys, I know its not a car or ICE forum but I feel bad if i dont chip in to help threadstarter.

[fff0]

Originally Posted by aardvarkash10

..... your car would have stopped every time the amp clipped....

Heehehee.. done that clipping with too loud vol & too high music recording level, my aircon and car engine, still running.

[thermal runaway]

Just find some surplus SMPS units on ebay , there are generally a number listed. Select ones that have variable voltage and those that can be mastered and slaved if you cant find one that will supply all the amps on it's own. Most of the more recent types can be used on any supply from 110 to 250 volts and frequency from 40 to 400 Hz.
Just out of curiosity I have one big Farnell lab supply that's rated at 0-30 volts upto 100 amps !! But , even if you could find one it weighs 90 KG with a Tx that has to be seen to be believed !! Actually , I have 2 of them and 2 of it's smaller brothers , they are 0-60 volts upto 25 amps. They can be master slaved in parallel or series and programmed for almost any application. They are a pre-regulator design that reduces the voltage drop across the series regulator to minimise dissipation. Great nerd candy

As your in the USA , look for surplus Kepco stuff on ebay , they also do some heavy amp stuff similar to Farnell.

[anwaypasible]

Originally Posted by aardvarkash10

OK, just for reference, your car battery (even a small one...) is capable of in excess of 400 amps at dead short. And 100 amps is an arc welding rating, so your cables need to be appropriately sized. Use that imagination of yours.

If you had a clipping problem, it wasn't due to supply current unless your cabling was substandard. Otherwise, your car would have stopped every time the amp clipped....

my car is a uni-body (without a frame)
so the jigsaw pieces of metal are welded together.. but i think the weld they used is a rubber glue (or otherwise a terrible conductor)
i had my positive ran from the battery and then tried to ground the amps in the trunk.

yes, i consider the wiring substandard thanks to the unibody skeleton of the vehicle.

i had ground noise.. which they say is because the voltage at the amplifier is different than the voltage at the radio.. another indictator of the amplifiers not getting the current they needed.

i had multiple things happen over and over.. so i couldnt buy new/more power wire.
i just put the whole project on hold, because i said i wanted to do it right with some kinetik powercells.. and then just run the system for an hour off the batteries (rather than try to run the system off the stock alternator)
i'd just use the stock voltage system to re-charge those batteries.

well..
the project was out of my price range with the amount of money i had to play with.
now i am looking to hook the subwoofer up in the house to kill some time.
i'm thinking it will be cheaper than finishing the install in the car.. and my home theater is missing an amplified subwoofer, so i need a power supply in the house anyways to fill the gap in my home theater.