It`s a "primitive" 3-way "Y" cable, the resultant sound can be "big and full", but ground-loops problem I never resolved. I had even the "guitar rack" full of everything and once blowed brand new "Drawmer" compressor...there are some sophisticated ways (signal "splitter"/booster/mixer), but I forgot almost all about it:-) In rarely occcasions when I play the guitar, I use just the "blackface" Deluxe Reverb (in the last 10 years). And yes, I used with good results M.Boogie "Studio" preamp for that "stereo" things - 2 output for two power amps and two guitar boxes. Try and see, the same power outlet for all amps and check for possible AC difference between the "masses" of the amps...