DT50 212 --- amp went out on me after about 2 months, a quick gurgle as tubes burned out ... then nothing. Thusly, I looked at the tubes ... the EL's were glowing bright, 12AX7's were out. Went to Guitar Ctr and after being assured they'd work, I got the Groove Tube russian brand. I would avoid chinese brands also. Russian just seems better sounding to me. Easy to replace and took about 1 minute of careful pressure to install. Unplug too ... duh?! LOL.
I immediately noticed that the factory 'hiss' was nearly gone (like 90%), and the sound was more colorful. I looked online and noticed the EH stock brand was much cheaper than the GT brand.
As well, each topology was more defined. 3 and 4 are now my fav's. Wonder how the sound will be if I replace the EL's with a high quality brand?