I tend to believe modern amps are designed around run-of-the-mill Russian or Chinese tubes, and that putting NOS in a modern amplifier won't yield significant results but tonight I was experimenting with tube-swapping in my Fender Blues Junior amp (with Cannabis Rex speaker) and the best tones I've ever heard come out of the BJR were with an Amperex 5751 and also with a no-name (the brand rubbed off a long time ago) NOS 12AT7 in V1. Those tubes completely changed the dynamics and tone of the amplifier and are stellar tubes compared to any modern tube I've tried. I think modern tubes are fine for less tone-shaping tube positions. I'll be leaving the NOS 12AT7 in V1 in BJR, the Amperex tubes are going in my Bassman. I haven't even experimented with NOS power tubes yet, but I'm already excited about the significant difference of having just one NOS preamp tube, so I may try NOS power tubes in the future. Is anybody else using NOS tubes in a modern-day amp? If so, what tubes and what amp?