Makning an A/B box that is "not noisy" for a friend. Can they actually be noisy?

[rosssurf]

I have a friend that has an a/b box but he says it is "noisy". The a/b box is simple hardware, can one actually be noisy?  Can anyone steer me toward a good box that is quiet and doesn't pickup any "buzz" or anything like that.

[stumper1]

The a/b box on Fulltone's site works great.  What kind of noise is your friend getting?  If it's from the unused amp - the Fulltone one should work great and is cheap to build.  If it's a ground loop issue, look at the GEOFEX a/b/y/ at General Guitar Gadgets.  I'm not sure if that one shorts the unused output or not but it does isolate the gounds between the two amps.

Good Luck.

-The box itself should not be picking up any "buzz".  Generally the problem is either from the unused amps input being left "floating" (like when you plug a cord in with no guitar connected to it) or from a ground loop caused by connecting the grounds of the 2 amps.

[Mark Hammer]

I'm with Stumper.

If your friend uses electronic-switched boxes after the A/B box (for instance, to select between this series of effects going to this amp/channel and that group of effect going to the other one), the A/B box will be "pop-ey".  Typical Boss/DOD-type boxes have an input buffer that assumes you will plug into the box ONCE, and all subsequent bypassing will happen electronically internal to the pedal.  Of course, anyone who uses such pedals can attest that if you have one plugged into the amp and THEN plug your guitar into the pedal, there will be a pop/thump at that point.  Though there is no real noise contributed by a simple mechanical switch functioning well, or by straight wire, there *are* circumstances where an A/B switch can mimic what happens when guitars are plugged/unplugged and perhaps that is the "noise" your buddy hears. A potential solution is simple to straddle each of the A and B the output jacks with a 2.2meg resistor.  This will allow the caps at the front of the effects pedals after the A/B box to drain off, without loading them down.

Alternatively, is it possible there is a shielding issue?