I've had a 15w Egnater Tweaker Head for around 5 years now. About 10 years ago when these were first released they had an almost BOSS Katana like following across many gear forums and IME they are an excellent low cost mid powered tube amp with a whole lot of versatility built into them. There are switchable internal modules that control the gain structure and tone stacks for US (Fender type), AC (Vox Type) and Brit (Marshall type) amps along with other mini switches to control sag, bright/normal, tight/deep, normal/hot gain, a 3 band EQ, and both gain and master volumes. Aside from this though I tend to be an explorer and a tinkerer wanting to learn as much as I can about how different components impact tonality and output in both guitars and basses and in my amps as well. If something can be improved in a cost effective manner I'm typically all in for it. A 15w Tweaker has 3 preamp type tubes (preamp, effects loop, and phase inverter) and two power tubes with a pair of 6v6s stock. But the amp which is cathode biased will accept any octal power tube so for me that's an invitation to tweak away with various tube compliments both preamp and power. I want through several different types of power tubes finding out that EL34s work best with the Brit setting but not the US or AC. 6v6s worked well for those but a pair of NOS Tung-Sol 5881s worked even better. More clean headroom and a deeper more spacious 3D tonality. So they stayed. Then I worked my way through the front section trying various 12ax types before settling on a Tung-Sol 12ax7 for the effects loop, and NOS Sylvania and GE 5751 grey plates for the preamp and phase inverter roles. These improved the overall sound a bit more but I wasn't done. Some reading about others experiences prompted me to go searching for an RCA Blackplate 5751 for a preamp tube and one of several JAN 12at7s for the PI. It took awhile to find some at prices I was willing to pay but I finally did and installed the RCA 5751 and a JAN Phillips 12at7 last night. Amp guys have always claimed those old RCA Blackplates 12ax7s and 5751s are kind of a Holy Grail tube in V1. Until last night I didn't believe they could possibly make that much difference but they sure as hell did in my amp. As good as it sounded before the whole amp came more "alive" with more presence and clarity than I'd ever heard before. Even the effects loop seemed to be impacted in a more positive way. Now, after 5 years, I finally have the head just where I want it. So when I hear some of the amp and tube gurus out there saying tubes can make a huge difference they're not just blowing smoke. Each minor tweak made changes, some good some not so good, but this last one pushed it over the top for me. A V1 tube can be a real difference maker.