I've been searching for the magic tube combo to run in a '58 Champ clone that I built about a year ago. This is a class A single ended amp, meaning one power tube has to do the work of two. The kit came with a JJ 6V6 which is a good sounding, long lasting tube but I always like to experiment. Without going through all the details about trying different AX7s in the pre-amp (tested quite a few) The best combination I've found is a TAD 5E3 rectifier, a JJ 12AX7 short plate plain pin, and the Genalex 6V6 output. No info on lifespan of this tube but is was compared to a TAD 6v6(junk with the bottle attached to the base crooked and the bottle snapped off in my hand the third time I was installing it) and the JJ6V6S. Although the JJ is a fine tube(and I used a brand new one for test) the Genalex beats it in detail, clarity, tone, and extremely low noise. Harmonics are out of this world. I have 6 other amps, all of which are A/B and have 12" expensive speakers. Celestion Alnico Blues, Jensen Alnico, etc. The Champ has a little 8"Weber Alnico vintage in it and for quality sound and tone it can stand it's own against any of these other amps when armed with the Genalex output and JJ pre-amp. This combined with being small and light has now moved the Champ to my favorite go-to amp. Have ordered a matched set to go into my Princeton Reverb Ltd. Edition that has a 12" Jensen Alnico. Expecting pure bliss. If these tubes even last half as long in the Champ as the JJ did, then these will be what goes in it from now on even though they cost more than twice as much. I've never been able to get warmer, creamier overdrive out of anything else like this. Blues is my flavor and Genalex I favor.