'Muddy' sound is one of those subjective things that mean different things to different people. To me, all 6L6 amps sound a bit muddy. And 5881's have so much mud on 'em they blow bubbles, IMO. Other folks love 'em.

Anyway, this looks like a job for an experienced tech. Tube amps operate with voltages that can [u]KILL YOU DEAD!!![/u] :eek: (I hope I got enough emphasis on that).

The transistor/tube debate has raged ever since transistors became commercially available. If you use the search button at the upper right of this page, you can tap into dozens of threads on this topic. (I oughtta know, I was ragin'n'ranting along in most of 'em)! :D