With the JJ/Tesla EL84 tube you seem to get a compromise between tone and reliability. Nice mids, sparkling highs and solid bottom end characterize this tube. From a construction standpoint I think JJ has hit the mark. As with any EL84 tube they can be prone to mechanical noise in combo amps. However, they seem to take the heat and vibration in stride without any negative tonal effects. In the AC30 the JJ/Tesla EL84 tube will really deliver the VOX chime with lots of swirl and shimmery harmonic content. In the little Pro Junior just crank it up and you get a great, nasty, overdriven sound.

These are the same tubes that Groove Tubes relabels as GT-EL84-S.