ABY with no switch?

Discussion in 'Burnt Fingers DIY Effects' started by KeithJ, Nov 26, 2016.

  1. KeithJ

    KeithJ Tele-Meister

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    I want to build a really simple A/B box so I can run two guitars into one amp. What I'd like to do is just wire up 3 jacks in a Y with no switches or LEDs or anything. It seems easy enough, but i can't find any examples that this had been done. Could this cause any problems with the amp, or is it pretty safe to do?
    Thanks!
     
  2. Guitarteach

    Guitarteach Poster Extraordinaire

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    Why no switch? Might have noise or loading issues.

    Are you planning to mix or use the volumes on the guitars?

    It's easy enough to try.

    Metal box. Two mono jacks one side, one on the other.

    Solder the earth tags together. Solder the two tips tags on one side that carry the hot signals to the tip tag on the other so then are combined. Check there is no connection between the three tips and the earth tags / box with a meter.

    You might find the guitars interact with each other differently but I am not sure.
     
    Last edited: Nov 26, 2016
  3. luckett

    luckett Banned

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    You don't want to make this passive. Wire it up with a separate buffer on each input and a single buffer for the output. Just like a simple splitter but with the direction reversed.
     
  4. FenderLover

    FenderLover Poster Extraordinaire

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    Copy the input circuit from just about any 2-input amplifier schematic you can find. It's not really an ABY circuit, it's just a passive mixer.
     
  5. ebb soul

    ebb soul Poster Extraordinaire

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    You'll most likely need buffering.
     
  6. FenderLover

    FenderLover Poster Extraordinaire

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    The input resistors in the amplifier circuit provide isolation between inputs. I think it is generally sufficient. Many commercial circuits passively split and combine signals in the same manner, using just two resistors for isolation. If buffering is a concern, running either guitar through a buffered pedal first would do the trick.
     
  7. KeithJ

    KeithJ Tele-Meister

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    Thanks everyone! I kinda figured it would need buffering of some kind. This is for a friend who uses two different guitars on stage (different tunings) and wanted a really fast way to change between the two. I was thinking a super simple Y would be the fastest: just set one down and pick up the other. I guess I'll just wire in a 2pdt in there, but maybe skip LEDs. Thanks again!
     
  8. jddub440

    jddub440 Tele-Holic

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    I can't think of any reasons this would cause a problem for your amps, effects or guitars. It sounds simple and fun....I've been building a lot of utility stuff like this in the last month or two for my friends. I haven't put any buffers into any of my builds so far and I have not had any issues and neither have my buddies!
    I recommend just trying it....and try to do it as cheap as possible just to start and see if you want any improvements like a buffer (because they do require power and it seems like you want this to be the simplist/plug-in-and-play type of utility box).

    Plus I believe you can avoid any crosstalk between the two guitars if you just turn the volume down on the guitar you're NOT using.
    Please note that I could be very wrong about that but in my mind how is there going to be crosstalk if one guitar ain't talking??
    Good luck with it....keep us updated on how it turns out please
     
  9. reddesert

    reddesert Tele-Meister

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    Just using an unbuffered Y parallel connection with no switches isn't likely to cause a problem in the sense of breaking anything, but it has the potential of not sounding good. The reason is that the signal would go from the played guitar into both the amp input and the other guitar's volume pot in parallel, and so the volume and tone settings on the unplayed guitar will affect the sound. In an extreme case, if you turned the volume on the unplayed guitar to 0, you'd also get no volume out of the played guitar.

    (There is an exception to the rule about that nothing will break but just sound bad: if both the guitars had active preamps, connecting their outputs could conceivably damage them. It's relatively unlikely.)
     
  10. Guitarteach

    Guitarteach Poster Extraordinaire

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  11. KeithJ

    KeithJ Tele-Meister

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    This is really interesting, I hadn't thought about that! Oddly, the two guitars are almost identical, just stock SGs, but in different tunings. Pretty sure he, like most guitar players, just leaves all the controls turned up to 10 on all his guitars, so this might work. We'll have to experiment with it.
     
  12. luckett

    luckett Banned

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    Leaving the guitar on stage with the volume turned to 10 is a feedback generator waiting to happen. You would have to damp the strings somehow, which kind of defeats the facilitation of a quick change. It also has the potential to introduce unwanted hum if there is any EM interference on the stage.

    Just add a switch or make it buffered and all those problems go away.
     
  13. kennl

    kennl Tele-Afflicted

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    I have seen a number of players doing the multi-guitar switch with a volume pedal.
    1) back down volume
    2) unplug current guitar
    3) grab next guitar & plug in
    4) ramp up volume pedal
    Looks visually effective to the audience and works flawlessly
     
  14. FenderLover

    FenderLover Poster Extraordinaire

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    That's the reason for the mixing resistors, to provide isolation between sources. It also allow you to turn either guitar to zero. See post #7. It's done commercially all the time.

    That's the one I built too. Simple, flawless.
     
  15. FenderLover

    FenderLover Poster Extraordinaire

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    The guy that warmed up for Jeff Beck last October in Minneapolis did this. He looked frantic and uncomfortable. Frankly, it looked a little unprofessional. Far easier to step on a switch (A-B) or just pot up a guitar (mini-mixer).
     
  16. Doorlord

    Doorlord Tele-Meister

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    This works for me, except I use a Polytune to mute instead of a volume pedal.
    I use 3 guitars (Std, Open E, and Open F with high action for slide). If I used a switchbox I'd tangle cords and trip myself.
     
  17. Daddy Hojo

    Daddy Hojo Friend of Leo's

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    Or just use just about any tuner. They almost always have a "mute" option that would allow you to switch guitars.
     
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