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Mono'ing walkman + balance

Discussion in 'Electronic Basics' started by All, Jul 26, 2004.

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  1. All

    All Guest

    Hi
    I want to take the output from a walkman and put both channels into a mono
    guitar amp but with a pot to adjust the balance.
    Any ideas?
    I'm not looking for any fancy cct's it is for monitoring purposes only.
    I thought of running both o/p's to a pot and taking the wiper to the amp but
    not sure what value to make the pot and whether the walkman would object to
    having left and right joined even though it's via a resistor.
    Any help appreciated.
    B Bear
     
  2. As for joining two channels, I have an IT guy brother-in-law who just flat
    shorts left and right together all the time. He, too, plays guitar, and
    is the lead "singer" for a garage band named "Green Apple". Anywhoo, he
    does that all the time with no problems, I assume, because he still does
    it.

    Still, I don't know what your amp is designed for, but my brother in law's
    guitar runs at approximately microphone-level voltage, and your walkman's
    output is closer to line-level voltage. Guaranteed clipping.

    I have a radio transmitter here that takes microphone level monaural
    input. I fitted two resistors, one on each stereo leg, and tied the
    opposite ends together to make it one channel -- works fine, and barely --
    just barely -- fits inside a 1/8" stereo plug for use with whatever I
    like. The resistors are both standard 1/4-watt carbon film,
    red-purple-yellow-gold, so that's what, 270 kilohm, 10% tolerance. Works
    GREAT for *my* needs.

    Now, you want some kind of pot to do the "balance" thing, and your idea of
    using the slider as the amp-side should work fine, in my non-expert
    opinion. If you want roughly 270 k-ohm for each, then that's about 540
    k-ohm total. You probably won't get that, but you might be able to get a
    1 megohm to work. Problem then is the volume might be a little low when
    it's centered, and with ANY pot, when you put it hard over left or right,
    you'll wind up with NO resistance on that "channel", hence clipping. So
    you might want resistors inline with the pot. Perhaps a 100K-ohm pot,
    with 120k resistors on either side?

    I don't see any way to /simply/ cut out either channel without some volume
    problems, though. If you wanted to make a simple mixer, it's very easy.
    Just need a few pots, a few discrete resistors and caps, and a couple very
    inexpensive (<$2.00 each) IC chips. Then, you CAN cut out either channel,
    you CAN combine each together without hurting your walkman in the
    slightest, AND you can vary the output to be useful with your amp or even
    small speakers/headphones. You could also add a very simple "monitoring"
    circuit. But, it's up to you.

    Hope this helps at least somewhat...

    CJ
     
  3. burbeck

    burbeck Guest

    hi
    it is not a good idea to short out a stereo output in this way,
    possible damage to output chip, much better to mono the outputs with
    resistors at least 1k per channel.
    i have posted my solution to alt.binaries.schematics.electronics
    'walkman to mono with balance'
    regards
    bob
     
  4. dB

    dB Guest


    Yes, a pot will work fine. Anything from around 10k upwards. (Too
    high a value will attenuate the signal by divider action in
    conjunction with the input impedance of the amplifier.) You probably
    know, but it's worth saying, use a linear pot otherwise the "balanced"
    position will be towards one end of the pot's adjustment.
     
  5. Bob Masta

    Bob Masta Guest

    If you just take the wiper from the pot to the amp, the
    amount of balance adjustment will depend upon the
    input impedance of the amp relative to the pot. If your
    amp has (say) 50K input impedance and you use a 50K
    pot, then when the pot is all the way to one end the
    other channel will only be down by half. If you want more
    relative balance than that, make the pot bigger than the
    amp input impedance... but don't make it much over (say)
    500K or you will start having hum pickup problems.

    Won't hurt the walkman for any reasonable pot value.
    A 1 ohm pot might be a problem, but 1K or more is fine.
    But you probably want it to be at least as big as the
    amp impedance anyway.




    Bob Masta
    dqatechATdaqartaDOTcom

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
     
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