The tubes that I was referring to were JJ tubes, which I've had a great deal of reliability issues with (only with EL84 tubes). So it's possible that one of the tubes was faulty instead of simply being overly mismatched.CurtissRobin wrote: As to "mismatched" tubes harming an amp, nonsense. Assuming tubes of the same type, at least one of the tubes would have to be faulty, not merely different in transconductance from the other(s) to cause harm.
I have read a lot though about the tubes being too far out of balance causing trouble. I don't personally lean one way or the other. Like I said, I think the people that push the need for extreme tube matching in guitar amps are the people making the tube matchers or offering the tube matching services, much like DeBeers did with the diamond in the 1930s.