Matching of tubes is important, or not, more often depending on the design and type of amp, and the tubes you choose. A perfect example of shooting the matching theory in the head just happened to me. I have finally broken in my Wolcott Presence amps, and last week, I installed all the NOS Mullard EL 34 output tubes I could find (Circa 1960's). The sound is so much better with three quarters of the tubes as Mullards and the remaining as stock Sovtecs, that I can hardly believe my ears! This is not to say that 100% Mullards will not be better, it simply points to the fact that there is no absolute rule, especially if the quality differences are vast. As far as tube bias, I had to switch some tubes from socket to socket to get them all to bias, and where this is far from a ideal situation, it produced the best sound I have ever heard from these amps, and perhaps as good as I have ever heard in any amp.
