JTM45 was perfect, now has a can a bees

[chrisrbr]

Hey all,
subject kind of says it all.  I built a JTM45, fairly stock, but did put in a switch to go split cathode on V1.  Amp was sounding great, then turned it on last night and there is a "can of bees" distortion flavor to it know.  And it appears that the low end has diminished a bit.  Tried swapping every tube, that wasn't it. 
puzzled?? kind of just appeared out of no where. 

any ideas??  amp is only a few weeks old.

thanks
Chris

[plexi50]

Go back over the cathode switch and wiring to confirm nothing has come loose and that they are all making contact within and through the switch