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How to convert stereo into mono ?

Discussion in 'Electronic Design' started by SA Dev, Oct 6, 2003.

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  1. SA Dev

    SA Dev Guest

    Hi,

    I am going to be using an amp from
    http://www.canakit.com/Contents/Items/UK193.asp. I am taking a line output
    from a PC sound card and wish to power one speaker with it. My questions
    are:

    1. How can I combine both the left and right channels from the sound board?
    Can I just connect them together?

    2. How does input sensitivity work?

    Thanks,

    Alan
     
  2. No. Think about what happens in that case when the signals are different:
    each output is trying to force the other to be something other than what it
    wants to be. Depending on the sound card, this could cause damage.

    Connect the grounds all together. Then connect the hot lead from each
    channel to a 4.7k resistor, and connect the other ends of the resistors
    together, and connect *that* to the input of the amp.

    Or, if your software permits, mix to mono in software and then just use one
    channel.

    That kit says it's specced at "100mV/47k". That means that the input
    impedance is nominally 47k ohms, and that 100mV signal is enough to drive it
    to full output (if the volume is all the way up).

    By the way, before you go taking the 22W rating of that kit too literally,
    you might want to dig up the spec sheets for the TDA2003 (the chip it's
    based on) and seeing what kind of power, distortion, and frequency response
    you can actually expect.
     
  3. SA Dev

    SA Dev Guest

    Walter,
    Thanks, I found this page today:

    http://www.hut.fi/Misc/Electronics/circuits/linesum.html

    It recommends using 10k resistors. Would both work equally well? Would the
    4.7k's you suggest work better for the amp I plan to use?

    Thanks a bunch for your help,

    Alan
     
  4. 4.7k or 10k will work equally well. This creates the classical Summing amplifier input.
    You may notice some volume differences between the two, So you might want to experiment with your
    particular setup.

    Cheers
     
  5. Active8

    Active8 Guest

    you'd use a summing amp, i'd think. if your sound software doesn't
    support mono, you could try the Creative Lab's SB -- some abbrev for
    Sound Blaster Hardware Programmers whatever. you can get the C code to
    code your own stuff. the sample code had a recorder/player with the mono
    option.
    you stick your hand under running water and turn up the temp until it
    hurts.

    input sensitivity of what? you need so much input signal to acheive a
    given S/N ratio, basically.

    summer below.

    hope this helps.

    mike
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    GND
    created by Andy´s ASCII-Circuit v1.22.310103 Beta www.tech-chat.de
     
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