Dave Sloven
Ambassador of DOOM!
The Chinese tubes are the best for high-voltage settings, such as the power tubes in the Peavey 6534+ and the cathode followers in the preamp of the 5150/6505 series. They have thicker glass and are simply built more sturdy. Sure there are some duds but that's why I always bought 'select' Shuguang tubes that have been through more testing by Ruby or Tube Amp Doctor.
I had two Tung Sol 12AX7 tubes fail in my 6534+
Tung Sol and JJ are fine in the Ultra series amps (Triple XXX, JSX, etc) but those amps show a strong preference for balanced Sovtek 12AX7 LPS (long plate) tubes for the phase inverter. I find JJ ECC83S tubes sound good in V1-V3 of the JSX, whereas I use JJ 5751 tubes in V1 and V2 of my 3120 to give more useable gain controls. I am pleased with the JJ KT77 quad in the 3120 and the Tung Sol 6L6GC-STR quad in the JSX.
I had two Tung Sol 12AX7 tubes fail in my 6534+
Tung Sol and JJ are fine in the Ultra series amps (Triple XXX, JSX, etc) but those amps show a strong preference for balanced Sovtek 12AX7 LPS (long plate) tubes for the phase inverter. I find JJ ECC83S tubes sound good in V1-V3 of the JSX, whereas I use JJ 5751 tubes in V1 and V2 of my 3120 to give more useable gain controls. I am pleased with the JJ KT77 quad in the 3120 and the Tung Sol 6L6GC-STR quad in the JSX.