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PSU Can you daisy chain PSUs?

Discussion in 'Hardware' started by Wicked_Sludge, 31 Aug 2012.

  1. Wicked_Sludge

    Wicked_Sludge My eyes! The goggles do nothing!

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    my home theater system consists of automotive stereo amplifiers powered by old ATX PSUs i have laying around (dont judge, the price-per-watt for automotive amps is way better than that for home theater amps. and i already had all the stuff laying around so for me it was free. on top of that, as ghetto as it is, it works really, really well!).

    earlier this week i acquired a 3rd amp to add to the two i already had in use. this means i need more power from my PSUs. i have several <200watt OEM PSUs laying around that if added together would give me enough juice to run the amps. unfortunately due to the output of the PSUs and the different requirements of the three amps theres no way for me to power each amp by its own PSU.

    so my question is this:

    can i daisy chain the PSUs and amps together?

    that is, can i connect the 12+ and common leads on up to four PSUs of varying wattage ratings together and then connect the daisy chained PSUs to the amps?
     
  2. Bladesingerz

    Bladesingerz Minimodder

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    So you want to put multiple PSU's in parallel to feed everything? That would be possible yes, allt of people use multiple psu's for big pc's and servers.
     
  3. Wicked_Sludge

    Wicked_Sludge My eyes! The goggles do nothing!

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    you got it. i want to connect the PSUs together in parallel and then connect them to the amps (which will also be in parallel. but daisy chaining amps is common and im not worried about that end). this way the amps will all be drawing from a single large "pool" of watts coming from several small PSUs.

    ive never daisy chained in a PC. i thought you usually used one PSU for, say, the mother board/CPU. and then had your second one to power off-board items like HDDs, optical drives, fans, and that kind of thing. that way the PSUs never really "see" each other.

    or am i way off?
     
  4. Big Elf

    Big Elf Oh no! Not another f----ing elf!

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    You'll need a cable to start up the 2nd PSU
     
  5. Wicked_Sludge

    Wicked_Sludge My eyes! The goggles do nothing!

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    no, big elf. these PSUs arent anywhere near a PC. ive cut all the connectors off, hot wired the PSUs to be on constantly, and ive soldered heavy gauge wire to the 12+ and common outputs on the PCBs. they are connected directly to the amplifiers. ive got them plugged into a common power strip and to turn the amps/PSUs on and off i just flip the power strip on or off.
     
  6. Deders

    Deders Modder

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    Electricity fluctuates and if 2 currents meet each other when they are out of sync then you'll get pretty lights but only for a second or so.

    I've tried this myself. Graphics cards are designed so that each power connector powers a different circuit so if a PSU actually does have separate rails generated from separate components, and not one big one divided into several like most are, it won't explode.

    Everything was fine when I had one PSU powering everything except the 4 6-pin sockets (SLI) , and the other PSU just powering them. As soon as I tried to power a disk, the fluctuations between the signals coming from the molex and the IDE connector blew one of my PSU's with sparks and everything.

    There is a way to sync up the signal from the PSU but I don't have time to google it right now, just don't cross the streams!!!
     
  7. Wicked_Sludge

    Wicked_Sludge My eyes! The goggles do nothing!

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    i assume youre referring to the ripple coming from the rectified dc power source. i hadnt thought of that....but does it really present a problem? i would think that even if the peaks of two ripples line up the worst you would have would be 12v+12v in parallel, or, 12v.

    not trying to discredit you, but youre SURE it was the two ripples from the two PSUs that caused your problem?
     
  8. Boscoe

    Boscoe Electronics extraordinaire.

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    Or use diodes in series with each PSU so if you do get any large fluctuation between rail voltages you'll be fine. Use big diodes, foreword voltage on a typical diode is 0.7V with 200W PSU at 12V roughly 20A so 20A X 0.7V = 14W max dissipation.
     
  9. Deders

    Deders Modder

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    I did read somewhere that even a slight difference in signal, (I imagined it like 2 waveforms not quite meeting at the right point) can be a bad thing, there was an additional (apart from the green) wire that needed to be connected, this was several years ago and at the time I didn't want to cut into any wires as I was waiting for a new PSU to arrive soon.

    It might have been because I didn't connect the earths, but it was fine until the moment after I switched on with my hard drive connected to the other. Luckily only dodgy PSU's were harmed in the making of this discovery.
     
    Last edited: 1 Sep 2012

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