Some BOSS pedals accommodate stereo output, but many like the CH-1, BF-3, et. al. have only ONE input. How would I use a 1 input/2 output pedal in stereo (connected to two different amps) through each amps' effects loop?
The simplest way is to make the a stereo pedal the unit which splits your guitar signal in the first place.
you can TRY putting Amp1send -> CH1input..CH1output1->Amp1Return CH1output2->Amp2Return
If your amps are happy about running a signal ONLY from the loop. Another option would be to rig up some kind of stereo mixer. FXSEND from each amp must become a single mono line - either a simple Y cable, or an actual device which will mix the two, then feed that into the INPUT of the pedal. Outputs run right back to the FXRETURN on both amps.
Is that what you were looking for? It's true, BOSS pedals aren't too accommodating for people who want to run multiple stereo units. Some kind of setup with a powerered distribution system could allow for multiple stereo fx to be used at once, but it might not be worth the effort. AND you have line level vs. instrument level to think about. I tend not to...
Verivorax pretty much covered it..used to run mine at the end of the 'board as the last pedal in the chain to my two amps,this is how boss used to recommend it's stereo chorus pedals to be used before it started the stereo delays,reverbs etc some players still do this like Daryl Stuermer from Genesis/Phil Collins Band who uses a CE-5 on one of his boards two two mesa boogie combos running clean and relys on his Tonebone or Fultone pedals for distortion/overdrive but since i got CE-2 i don't really need it anymore so i'm going to use a DD-3 at the end instead to split to the amps unless i see a DD-5 going cheap somewhere.....