I recently replaced the tubes in my Carvin Nomad from generic EL84's and 12AX7's to Groove Tubes EL84S quartets and ECC83S preamp tubes. This is a 9 tube change and it is great. It's a 1 twelve combo amp that now can kick a AC 30's butt with no problem. I love Vox sound but I didn't need another amp. Tubes and tech work came to about $235 bucks but it was well worth it. Chris Lewis and Jason have been super helpful with many projects of mine. Thanks guys.