Better late than never I suppose from a hollow state man in a solid state world. I get a bit of a giggle out of that reply, musicians and audiophools love the mystique of British valves that in reality are simply equivalent to American tubes, there is NO difference. If you want tubes with a difference, use broadcast and industrial types such as the 7025 low hum and noise twin triode, a 12AX7/ECC83 in disguise. Then there is the 6146W "ruggedized" 6146 and the 6146B that the Yeasu FT-101 series hates, mind your interelectrode capacitances, but I digress.
Now finally to the point, back in the day American meant all American, the original tube(s) was were American, in this case a plain old 12AX7. Somebody stuck that ECC83 in there because it looked cool until the lid was closed. (;->) I leave you tube affectionados such as I with this to watch:
https://www.youtube.com/watch?v=-GgWIlvyEL8 an interesting video on how receiving valves were made by (not as tiny as Asian) dainty British women's fingers.