I own an '80s (I think 82) JCM800 1987 (the non-master version), and it has 4 inputs. Now I generally jumper the bottom left input into the upper right one and plug my guitar into the top left one. Today I found this video on youtube, where the guys splits his signal into the top left and bottom right input of his Marshall (don't know which version). [ame=http://www.youtube.com/watch?v=fPTL9wS5XQE]Using an A/B/Y Box with a 4-input Marshall - YouTube[/ame] Is there a significant change in sound/volume with both inputs? I can't seem to find evidence that he uses an extra pedal in one of the chains, so it should be direct signal. At this point I'm splitting my signal to the JCM800 and a Soundman amp but this might be interesting! I haven't been able to test it because the amp is at the rehearsal room..