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Help for hooking radio speaker to 3.5mm headphone jack

Discussion in 'General Electronics Discussion' started by Wader8, Nov 24, 2014.

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  1. Wader8


    Nov 20, 2014

    I have an old Nokia E72 phone with standard 3.5mm headphone/line-out/etc jack and I've like to hook up a spare external speaker I found from an old 220v FM clock-radio which got it's clock messed up so I put it away.
    I already detached the speaker from the radio, I thought it would work but I guess it needs external power,

    F - F
    0.5 W 8ohm

    and it has a yellow and blue wire.

    I do have a local special electronics shop not far that has all kinds of DIY stuff that big markets never have, like resistors, so I rather do something DIY with a battery

    But I have zero electronics knowledge, I have no idea what's the voltages, ohms, ampers needed, but I do have a small multimeter at home if needed so it should be easier.

    I do have 220-240v line at the location, but there's no any PCs so I would ignore the whole USB speaker thing that I just came across, I can also find an old phone charger to convert to a more managable voltage out of that i could crate a DIY setup.
  2. KJ6EAD


    Aug 13, 2011
    You have a few issues to deal with. The phone output is designed to drive two channels of a high impedance, low power load such as earbuds, not a single low impedance speaker. However, if connected correctly to one of the channel outputs, you should be able to hear a small volume of sound from your speaker.

    A set of amplified speakers such as are commonly used with computers would be ideal but if you insist on using the speaker you have, you need an amplifier. A circuit or kit that uses an LM386 may appeal to you.

    You will need to sum the left and right channels together to have both feed into a single amplifier channel and speaker.
  3. Wader8


    Nov 20, 2014
    Is combining left and right channels necessary? Because I don't need both.

    Do you have any idea on how much would this cost me approximately, for the parts I would need, to see if it's worth it.

    That said, I don't really know anything about wiring either, and what amplifiers are, so I would need a step by step visual tutorial unfortunately.
  4. davenn

    davenn Moderator

    Sep 5, 2009
    if you don't, you will likely notice missing sections of audio, due to a stereo recording often has different bits of the music coming out different channels
  5. Wader8


    Nov 20, 2014
    Oh yeah ofcourse, but I don't think the radio show I'm listening to has and special left-right channel stuff, unless they're playing an external clip but probably it goes through the systems to make it stereo if it's not, i don't know really, I might try it on the PC a few times to see if there's some missing stuff.
  6. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    The PAM8403 is an efficient stereo amplifier that can drive 4Ω loads with as much as 3W from a 5V power source. Available on a PCB very cheap on eBay.

    I've seen a comment that the PAM8403 is noisy - a constant background hiss. But at that price it might be worth trying.

    I agree with Dave that you should mix the two channel audio signals together if you have only one speaker.
    Frenoy Osburn likes this.
  7. BobK


    Jan 5, 2010
    Mixing the two signals simply means putting a resistor (say 10K) between each and the input to the amplifier, it is no big deal.

    KrisBlueNZ likes this.
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