A very likely reason two amps can sound different, yet measure similarly on the test bench, is that the measurements typically taken are not done under the real load an amplifier will encounter with a dynamic waveform. Secondly, I'm not sure the typical bench measurements are measuring the right thi...

I noticed that some 6SN7 tubes are quite valuable, and others won't get a bid. The Tung-Sols seem to command a premium price. Why is this? There must be millions of 6SN7's around as every TV in the 50's had 4 or 5 of them, so it must not be an availibility problem. I've thrown away a bunch of them t...