Headphone Jack - 8ohm Speaker

Discussion in 'The Projects Forum' started by Dalaran, Aug 31, 2011.

  1. Dalaran

    Thread Starter Active Member

    Dec 3, 2009
    168
    0
    I am looking for a circuit which I can use to connect a simply 8ohm speaker to a headphone jack connection.

    Does anyone have one that they have used before or could point me in the right direction?


    Any help is appreciated!
     
  2. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
    193
    Dalaran,

    I assume you're talking about a standard 1/8" headphone jack? What you going to plug it into?

    If you just want to connect an 8 ohm speaker to a standard 1/8" headphone plug, the simplest is to get a cheap headphone cable, preferably a mono, cut off one end and connect the ground/braiding to the negative (-) speaker jack and the center wire to the positive (+) speaker jack. If you use a stereo cable, there will be two center wires. Use a meter to determine which one goes to the headphone tip and use that one to connect to the + speaker terminal.

    Alternately, you could buy a headphone connector at RadioShack or online and solder two wires to it. Be sure to twist the wires along the entire length of the wire though.
     
  3. Dalaran

    Thread Starter Active Member

    Dec 3, 2009
    168
    0
    Thanks for the reply.

    I was under the impression I would need some sort of amplifier inbetween to not only boost the power (headphones don't need as much as a stand alone speaker) and also to ensure a low resistance 8ohm speaker can be connected.

    I will be using the headphone/speaker connection of a standard PC. I have built an arcade machine using a PC as its base and would like to use normal speakers instead of PC speakers for the sound.

    Thanks again.
     
  4. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
    193
    Ah, in that case, I'm not sure. If the speakers are small, you should be okay to just connect a cable and see if the output is high enough - this shouldn't damage anything, but I cannot guarantee it. If the volume is too low, you'll need to add an amp between the speakers and the PC. You'll probably need to do this anyway if you really want to get some sound out.
     
  5. wayneh

    Expert

    Sep 9, 2010
    12,100
    3,034
    There are such things as impedance-matching transformers that are used for this. It would give efficient power transfer from the device into the speaker without overloading the output. But it won't solve the problem of minimal power being available at that port.

    The good news is you can buy computer speakers for next to nothing, and these include a cheap built-in amplifier. I have some based on nothing more than the LM386 IC, which you might want to learn about. Of course you can spend as much as you need to, to get the quality you're after.
     
  6. ElectroDFW

    New Member

    Sep 2, 2011
    15
    1
    Dalaran,

    Depends on if you want to go with a cheap and difficult method, or a more expensive and easier method. Since my time is always worth less to me than my money, I can give you advice on the cheap, difficult method:

    The way I would handle this would be to get a pair of powered speakers second-hand. Ones with a separate on/off switch would be best, and an adapter supply rather than AC cord (to reduce hum). And if you're so inclinded, gut them to where you just have the speakers, control board, and misc. interconnecting wires.

    I would wire up the power switch to the main power switch of the arcade unit. Take off whatever speakers came with it, and resolder back on whatever speakers you are wanting to use. As long as they're somewhat close in spec, it shouldnt be a problem. Reattach a new pot to the volume control to be able to mount it in a convenient location for the user. Then just mount the board to somewhere in the cabinet away from other wiring.

    You're more than likely using a power strip inside the case for the monitor, PC, etc. so it'd be a good place to plug in the adapter for the speakers.

    Good luck to you. This sort of thing is a huge undertaking. I myself am planning something similar, but never seem to get past the 'planning' stage, ever. If you need clarification on anything I mentioned, please let me know.

    --Electro--
    aka David M.
     
Loading...