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Power supply help...

Discussion in 'Power Electronics' started by Liamborgini, May 5, 2013.

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  1. Liamborgini

    Liamborgini

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    May 5, 2013
    Hey there!

    I am relatively new here (about 5 mins) and I only joined to ask a few simple questions...

    I have a speaker project and I need to find out the power supply needed as the amp I am purchasing (http://www.ebay.co.uk/itm/2-1-Chann...nd_Vision_Amplifier_Parts&hash=item3a67699170) as it does not come with a supply...

    It says nothing about power apart from "18v-28v" dual AC... I was told by my granddad (REME - Electronics engineer) that I should use a step down transformer or laptop supply but I can not find a supply giving off 24v and (since I will be using 3 channels) I've estimated about 3amps per channel so 9A... I can not find any power output or step down transformer that has this power output...

    I am wondering (because they do produce 24v but not the right amps) if I can replace the fuse inside to give a larger current...

    Any help will be deeply appreciated! :D

    Thanks :)
     
  2. davenn

    davenn Moderator

    13,833
    1,950
    Sep 5, 2009
    you need either a mains transformer that has an output of 18V-0V-18V AC as a minimum and up to 28V-0V-28V AC max
    Or a 9V-0V-9V AC minimum up to 14V-0V-14V AC

    the supply comment in that advert doesnt give real clarity

    But going by the info in the datasheet its the first choice, else it could never supply the rated output power.

    so you want a transformer ( NOT A PLUGPACK) that has your local mains input voltage 240/110VAC... whatever in your country
    with an output tapings of say ... lets pick middle of that range, 24V-0V-24V AC and it should be rated at ~ 10 Amps


    NO putting a larger fuse in doesnt increase the current, the current available is a limitation of the transformer used.
    Also, for clarity, if a bit of gear is designed to draw 3A at 12V then it doesnt matter if the fuse is 3A, 5A or 25A, the unit is still only going to draw 3A.
    The fuse is there for protection .... that is... if the unit goes into fault condition and tries to draw more than 3A, it will blow the 3A fuse avoiding total destruction. But if you had a 5A or 10A fuse in there, and the power supply was capable of supplying that much extra current, then the unit would continue to draw excess current till it smoked and self destructed

    Dave
     
    Last edited: May 6, 2013
  3. Liamborgini

    Liamborgini

    5
    0
    May 5, 2013
    Thanks for all the help :)

    I can not find a step down transformer for 24v 10A AC anywhere, or anything near it...

    Any help on where to find one?

    I really need help trying to find a power supply for this... Thanks.

    Thanks for the help though :)
     
  4. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    Now you know why you can get 320W of audio power so cheaply. The transformer is going to cost you at least 3 times the price of the board. Look for toroidal transformers. I can find them on EBay U.S. for about $100., though not exactly the one you are looking for.

    Your best bet may be to find a broken receiver of similar power output for cheap and hope the power supply is working.

    Bob
     
    Last edited: May 6, 2013
  5. Liamborgini

    Liamborgini

    5
    0
    May 5, 2013
    Hi

    Thanks all for the help, after having a phone conversation with my granddad I understand that I only need 3A... I didn't ask why but apparently it will go into 9A when into the circuit?

    I've been looking for 10A power supplies :')

    Oh well. Anyway just want to clear some things up that he said...

    1)Do I only need 3A 24V
    2)It will work on DC yes?
    3)Will the 3A power supply triple to 9A when entering the circuit due to me driving 3 channels?

    Thanks :D
     
  6. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    3A at 24V will give you only 72W of power. How can you power two 80W and 1 160W amp from 72W? And you need a dual power supply. i.e. +24V and -24V, each at about 7A. If you don't intend to use all that power, you can probably get away with 3A each, but your power supply might not last long.

    Bob
     
  7. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
  8. Liamborgini

    Liamborgini

    5
    0
    May 5, 2013
    Ok

    Thanks for all the help but I was told that dual AC means it will work on 110/240v but I have no clue.

    I have no idea how much a "dual AC" power pack will be...

    Also I was told it will work on DC, can it?

    Also if I do need a power supply that isn't a power pack (DC) but a transformer, what will the cost be like? I'm looking at spending £20 max on a power supply...

    What are your recommendations?

    Thanks
     
  9. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    Here is a line from another listing for the same board:

    I Think that says it all. You DO need the heatsink, as I said before, unless you want to run <10W total power, and that might even be too much. And a new transformer is going to cost you more than you want. Your best bet is to find a take-out from a scrap amplifier or receiver.

    You could use DC but you would need + and - supplies, or two isolated supplies, again with about 300W capability.

    Here is a listing for a hink sink that I think is for that board:

    http://www.ebay.com/itm/1pc-Aluminu...?pt=US_CPU_Fans_Heatsinks&hash=item3cc4bd2846

    Bob
     
  10. Liamborgini

    Liamborgini

    5
    0
    May 5, 2013
    Hi

    Ah ok, I get it now, yeah I know about the heatsink, amplifiers get very hot...

    I'll probably get a home HIFI or receiver then, much more simple...

    I thought a transformer would be a lot of money.

    Thanks :D
     
  11. davenn

    davenn Moderator

    13,833
    1,950
    Sep 5, 2009
    Did you not read anything that I told you in my post earlier ??!!!

    I told what the dual transformer was.
    I told you that it will NOT be a plugpack

    Bob filled in the gap about why I told you you need a 10A rated transformer

    Dave
     
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