AB box VS ABY box

Discussion in 'Effects, Pedals, Strings & Things' started by reverendmando, Mar 6, 2015.

  1. reverendmando

    reverendmando Member

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    Ok, so what I think I've come to a conclusion about the two, and I just want to verify if I'm right:

    1. Loud noise or hum seems to be a problem with ABY switches bc the signal is being split and the culprit is usually a ground loop, non-isolation, and a myriad of other problems for splitting the signal.

    2. There doesn't seem to be much information online about just plain ol' AB switches. Is it subject to the same issues as an ABY? I've seen many AB switches on the market that feature no ground lifts & isolated transformers, so I assume they are indeed NOT subject to obnoxious hums.


    I currently use the Radial Bigshot ABY which works great between my Orange OR15 and Billm modded Blues Jr, isolation transformer and ground lift eliminate the hum, b/c there definitely was a loud piercing hum before. I find myself never ever ever using the Y, I just really need an AB (for the most part) and plan on getting one with a small footpring like the JHS mini AB, Loopmaster or Analogman, of course I'd keep the Radial, just in case.
     
  2. JerS

    JerS Member

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    Typically, hum is not an issue with an A/B box. They are usually passive, so not much to mess up the signal.
     
  3. gibs5000

    gibs5000 Member

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    I wouldn't say that ABYs make "loud noise" as you put it, rather that when used in "y" mode, and when they are passive (lack of a buffer) because they split the signal, you have to deal with a loss of output volume, but they can create white noise, passive and parallel do not mix with audio signals.

    Buffered ABYs on the other hand will work fine, without noise, however, you may need one with a ground lift, and phase switch, depends on the amps your using. I built my own buffered ABY, works great thus far, no white noise issues, and no volume loss.

    AB's are low noise, because there is no parallel connection in them. Just one or the other. Used one for a long time with no issues, ABYs are more for if you want to use 2 amps at the same time.
     
  4. blackba

    blackba Supporting Member

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    Only other thing I can add is that AB boxes typically ground out the output not being used to keep the noise down. I use an AB box to switch between the 2 channels on my silver face fender, works great and no added noise for the reasons others mentioned.
     
  5. stinkfoot

    stinkfoot Member

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    There are different problems that might occur. Hum is usually due to the signal to the two amps sharing a ground connection, so that can happen with AB as well as ABY boxes. The solution to that (if you experience ground loop hum) is to have a box where one of the outputs is transformer isolated.

    Signal loss due to passive splitting only affects passive ABY boxes (since there's no splitting in the AB). The cure to that is to make sure the box is buffered, or keep a buffered pedal in front of the ABY.
     
  6. reverendmando

    reverendmando Member

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    Thanks for all the info. I've been looking for an AB switch online and almost next to none mention if the unused signal is grounded or if there's an isolation transformer. Is it just assumed that the unused signal is grounded? The only one I've found that says so is a switch by Saturnworks.

    http://saturnworkspedals.com/product/ab-pedal/
     
  7. stinkfoot

    stinkfoot Member

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    Most of them are wired that way, yes. Transformer isolation is more rare, though. Thankfully, that's a big selling point, so you'll most likely know if it has it just by the description.
     
  8. reverendmando

    reverendmando Member

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    Anybody happen to know about a plain ol' ab switch with an isolation transformer built-in? Other than Lehle.
     
  9. stinkfoot

    stinkfoot Member

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    I was going to suggest Lehle, but... :)
     
  10. Monstercastle

    Monstercastle Supporting Member

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    Radial Twin Cities or even the Decibel Eleven Split Personality are the ones I'm considering.
     
    Last edited: Mar 7, 2015
  11. reverendmando

    reverendmando Member

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    Last edited: Mar 7, 2015
  12. stinkfoot

    stinkfoot Member

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    That one needs a serious buffer in front of it, due to the extremely low input impedance (10K in, 10K out). I'd look at the Suhr Buffer, GigRig Humdinger or Lehle P-split for a simple isolation device to hook up after an A/B (on either the A or B output).
     
  13. reverendmando

    reverendmando Member

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    Thanks for all your help everyone, it's much appreciated! So in conclusion, an A/B switch w/ground on unused signal and as Stinkfoot recommended a Suhr buffer (didn't know it had an iso output) running after channel A or B should do the trick.
     

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