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Very easy audio switch box?

Discussion in 'Electronic Basics' started by jdonnici, Jul 15, 2003.

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  1. jdonnici

    jdonnici Guest

    I've got an idea for a very simple project, but have been unable to
    find some info for it online... before I make a go of it "blind", I
    figured I'd post for some ideas.

    Basically, I've got 3-4 audio devices in my office and one set of
    speakers. All the audio devices have 1/8" stereo jacks for ourput
    while the speakers use a 1/8" stereo plug. Currently, I unplug and
    plug those speakers as needed, but it can be unwieldy. What I'd
    like is a simple little box with some switches so that I could
    quickly switch between source devices. I don't see a need for
    having more than one device selected at a time.

    Radio Shack makes a simple little "stereo audio source selector"
    switch box, which would be perfect, but all the I/O on it is RCA
    phono. By the time I buy it and all the little adapters to go from
    RCA phono to 1/8 jack/plug, I could probably do it cheaper on my
    own... or at least have more fun with it by the time I'm done.

    Now... is it safe to assume that I can just buy a small project
    box, some jacks and some switches, and wire it all up inside the
    box? Or will I need to do something with resistors or other
    components to not screw up the sound quality (and/or the

    I know very little about the inner workings of electronics, but I'm
    happy to learn and this seems simple enough. I do own a soldering
    iron (from a project waaay in the past), as well as other various
    tools... and RS is right around the corner. :)

    Any insights or pointers to relevant URLs would be most
    appreciated. I tried googling on all sorts of combinations of
    "stereo audio switch box", etc, but mostly seemed to find amp-
    related projects.

    Thanks in advance for any help,

  2. A simple switch is all you need; no terminators or mixers. RS sells a 2
    pole, 6 position rotary switch.

    There is one possible problem, though - a ground loop. If you get AC
    hum, you'll need a 3 pole switch so you can switch the ground too. Some
    electronics stores have switch components so you can build any custom
  3. dB

    dB Guest

    You can do it with a two-pole rotary switch with the number of
    positions corresponding to the number of audio sources you have - or
    maybe one or to more to allow for future additions.

    You will need to decide how to connect the sources to the box, (1/8"
    stereo jacks and leads with a plug on each end, for instance.)

    The "ground" side of each of the inputs need to be connected together
    and to the output "ground".

    The left channel "hot" inputs each go to a switch position on one
    section of the rotary switch, the right channel "hot" inputs to the
    corresponding positions on the other switch section. The switched
    (moving) contact of one section goes to the left connection on a 1/8"
    output jack, and the switched contact of the other section ...... you
    can guess the rest.

    If you have a choice between a "make before break" and "break before
    make" switch, choose the latter.
  4. Hello,
    This is a very simple project, and all the parts needed are available
    at Radio Shack. And you won't need any resistors. I recommend using an
    aluminum box for shielding purposes, and the common ground connection
    can be made through the box itself by simply mounting the jacks on the
    panel, so you'll just need two wires from each jack going to the
    switch. Here's a parts list:

    2 pole 6 position non-shorting rotary
    P/N 275-1386
    (This switch has 6 positions which is more than you need, so you can
    leave the other positions unconnected, or use 6 jacks for future

    1/8" 3 conductor open circuit chassis mount
    P/N 274-249
    $2.99 / pkg. of 2

    P/N 270-238

    Of course, you'll also need some wire, rosin core solder, a drill and
    bits for making the holes, pliers and wire strippers, and a knob if
    you want. Here's a crudely drawn wiring diagram that should get you
    through. If you're using a text-only server, you can get the diagram
    from my site at

    While you're there, you might check out the very cool Honda ad at

    Good luck.
  5. DarkMatter

    DarkMatter Guest

    Hey dumbshit! Do NOT post binaries into non binary groups!
  6. You still can't do it. Most news servers filter out binaries from text
    groups. Some people also run bots that cancel binaries in text
    newsgroups. Whatever the case, it never arrived here.
  7. Not more complex but, potentially, a problem for the devices. Multiple
    simultaneous loads might exceed the capability of your source device.
    It also makes it possible for their to be nothing connect although
    this is less of a problem in general.
    Stick with the diagram/circuit you have.
    Vide supra.
    Intentionally. You cut off as much as necessary to make it work.
    Vide supra.
    Vide supra.

  8. Well, he could do this, he'd just need to buffer it with an op-amp or
  9. He's having technical difficulties wiring a switch; why advise him to
    start messing with buffers?

  10. jdonnici

    jdonnici Guest

    Fair question... and not to worry -- I'm going with the nice simple
    rotary switch. ;)

    I picked up a couple of 'build it yourself' kits the other day, as
    well as a book called something like 'electronics projects for
    musicians' -- in the hope of learning more about this new world.
    I'm a software developer by day, so I'd love to start learning
    something about circuits and hardware logic.
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