Originally Posted by TrollDragon
The best thing then would be to just let the other triode float unless is caused hum, then a ground would be needed. The ones with a center tapped heater would be better as well IMHO as the other triode would stay cold.
Definitely a better idea over the long term (and you get that free NOS triode after a few years when the first one weakens, not a leftover "poisoned" triode). I'll actually give that a whirl when I'm done with this ECC88 test.
Besides, that one 12Ax7 tube I tested, even plugged with lengths of Schiity aluminum cables, actually sounded pretty good. And these tubes could be interesting to use in parallel too. A 12AX7 has very high mu but low gm, so a paralleled 12AX7 would still have the same mu, but -supposedly- more gm and less noise (but more "Miller capacitance" or something, don't ask, I'm doing my best here).
Again, lads, let's get this stuff tested! A few different shops -in the US- that sell fairly cheap adapters/testers have been mentioned in this thread. All this stuff requires is a pair of adapters (or a DIY adapter made with a chopped up tube base) and some tubes.