I disagree about tetrode being "cleaner". No doubt that tetrode has an edge to it which triode doesn't, but I find that edge to be the grain associated with pentodes (or tetrodes) not true musical detail. Triode is indeed smoother and sweeter, but I find that its simple, pure sound to be more direct and cleaner, once the "razzle dazzle" tetrode grain has been eliminated.
With VTL I do prefer the bass in tetrode mode - seems like not enough feedback (my guess here) is available in triode mode (feedback drops when you throw the switch because the output tubes have less gain in triode mode)
With VTL I do prefer the bass in tetrode mode - seems like not enough feedback (my guess here) is available in triode mode (feedback drops when you throw the switch because the output tubes have less gain in triode mode)