when you run the 4cm you eliminate the preamp onboard the amp. I am using my amps just for the power amp. i disagree with you on the power amp changing the tone. ive played the same preamps through different tube power amps and there is almost notice. im not asking for a amp theory here. I was just looking for more advance signal routing that hopefully wouldnt cost much. I know the headphone will work in a pinch. I know the other output will work as well. I liked your idea of the blubox. but im not buying a 300 load box. i cant use the left unIR because thats going back to the amp.