So I popped open the back of my Sunn just to see what tubes were in there because I was bored. I'd never checked before because it sounded so good, I didn't wanna question what was in there. But I was bored, so I popped the back off and pulled them out. Wow! First surprise was a pair of RCA 6550s, which usually go for quite a bit on eBay. Then I popped out the phase inverter. A mullard 6an8! Holy shiza! Those are supposed to be like the holy grail! I then checked the 12AX7a, which happened to be an Amperex, another nice find. Then in the reverb slot, a Fender rolleyes: ) Groove Tubes 12AX7! IIRC, there's supposed to be a 12AT7 or 12AU7 there, so I figured that's why the reverb was always distorted and howling. So I replace it with an EH 12AT7. There was less noise & howling, but it was still present. Maybe i'll try a 12AU7 when I get some spare change. I've heard the reverb ain't the best on these amps, even though the tremolo is excellent. It's ok though, the reverb channel is great for when I wanna screw around with microphonic feedback and getting my signature "elephants humping" sounds, as well as divebombers, bombs exploding, sirens screeching, etc. just tons of freakin noise. It's alot of fun. Still, to find tubes in it that are worth more than what you payed for the head is quite cool in my book. I feel as though I ripped speddling (James Hart) off, even though he bought it for half what I payed him for it.