I have a set of both, and in my amp I can't tell them apart. I took my amp in for a simple repair and somehow the characteristics of the sound has never been the same. EL-34's all sound like crap in it. (that includes a very expensive pair of NOS') I just recently put a set of Electro-Harmonix big bottle 6CA7's in it and they sound far better. I have a pair of JJ KT77's on order to try out also. It's very frustrating because I have lost the sound I once had with this amp and have been experimenting with every combination and kind of 12AX7's and
power tubes in every slot to re-capture it. I am close but no luck so far. I have had this amp for 35 years, and it always sounded better than anything else I've tried. It was in the shop half a dozen times trying to bring it back. So far I have about $1700 into a $500 amp trying to get it right, so my advice is be careful who you let work on it. The upside to this is I can now bias my own amp and I am now somewhat expert ton tubes, having spent countless nights researching on the web. Here is one last fact, every tube will sound different!! I don’t care what they are or who makes them, no two sound exactly alike. Hell, just rotating the 12ax7's around in your amp will make it sound different.
