I'd been casually playing electric guitars with solid state amps for 20 years before I finally got a tube amp about six or seven years ago. As to be expected, my primary feeling after playing it for a short time was "whoa, why did it take me so damn long to get a tube amp!". I might get poo-pooed for it not being a true tube amp because what I picked up, after reading a bunch of reviews, was a little Fender Super Champ X2 combo. Anyway, fast forward a bit and I've had a lot of fun with this little guy. I just play at home or out with friends with a full band at a house sometimes and this amp fits my needs perfectly. It has a lot of tonal options with the modeled amp "voices" and lots of on board effects, plus it has the clean channel that sounds primo and is a great pedal platform. But I digress...it just has three tubes, a 12AX7 preamp tube and two 6V6 power tubes. It was all good for probably four years and then one day it just died, no sound. Ended up being the 12AX7, replaced it and was up and running again for another year before it started sounding weird again. I picked up another matched 6V6 pair and all was good for another 6 months...until last night. Never had it biased, just went for another 6V6 matched pair similar to the original ones. I'd been hearing a bit of a ringing sound at times lately and had a feeling something wasn't right, but when I powered it up last night, after a few minutes I got the dreaded snap, crackle, and loud pop! The first thing I tried was another 12AX7 I had because the power tube pair was only six months old. No go, kept popping. Next I tried the original 6V6 pair because I wasn't sure they were totally gone. Flipped the power switch and got a loud, "BUZZZZ!!!" that caused me to shut it down quickly. I put the other 12AX7 back in and that was also a no go, still popping. So I had basically tried all combinations and figured I was screwed and needed another pair of 6V6s. Then I had the thought of mixing the 6V6 pairs up and after a little trial and error, I was able to isolate the two bad tubes, one from each 6V6 pair, and now the amp is working great. The funny thing is, one 6V6 is Chinese and the other is Russian, they look very different physically, and are obviously not a matched pair, but you know what? The amp sounds pretty damn good! I'm a relative tube-noob, clearly, but I was surprised that this unmatched pair of 6V6s from different countries that look so different, sound so good together. We'll see what happens, but I let it rip for a couple hours last night and it sounded great. For you tube amp veterans out there, is it common to mix what should be matched pairs or quartets and hit pay dirt tone-wise? I was kind of surprised it worked out, but time will tell I suppose.