Originally Posted by Downunderwonder
If the ampeg is tube you can't A/B/Y it.
Note that ABY is a dangerous business at the best of times. One messed up connection smokes both amps instantly. Also, some are only meant for instrument signal, not speaker current.
while it would certainly work with the right AB Box, it is as Downunderwonder says - kind of dangerous, having a setup that can cause serious harm to your equipment with a single flip of a switch at the wrong time.
I'm using two heads into a stack of two cabs frequently,
but i use one speakercable and one powercable. when i switch heads, i just change those two. It's done in a few seconds and nothing can go wrong.