Vox AC10C1 - have used Tungsol ei84s.( very nice tubes)....T.A.D. el84str's (nice tube but a bit 'sterile').....and now the Preferred Series 7189. The PS-7189 lives up to its billing\reviews. I am very pleased with this tube. Since getting these valves a week ago I haven't used my 2x10 external cab once as the Vox on it's own is sounding Better than Ever! Thanks Tube Store..This was my 4th order from the Tube Store and once again am Very pleased with service and products.