Actually I'll go one even further and say that over the course of the last 16 years of researching tube factories - as more often then not, most tube companies had on an average 2 - 5 different ones producing tubes and some were much much better then others as far as resolution and fidelity goes.
I'm more inclined to say one should learn how to combine said factories as a collective means of voicing ones tube components - as I'm very very very fond of the following combination of signal tubes on my main tube integrated, I can only state what works for me, so here goes.
[1]
NEC ( Japanese Grey Long Plates NOS 1950|59 ) 12AX7|ECC83 or Tungsram ( Hungarian NOS 1953 Silver Plate ) or CSF - Thompson 12AX7|ECC83 ( Grey Plate NOS 1960|67 France ) x 2 as Phase-Splitters.
[2]
Along side a single NEC 12AX7|ECC83 or TEN Kobe 5715 ( Japanese tubes ) as Preamp Tube.
[3]
And these combined with either Mazda 12AU7|ECC82 ( Grey Plates - Solid Box Plate NOS 1956|62 France ) or Siemens 12AU7|ECC82 ( Silver|Chrome Plate Germany ) x2 as Input Tubes.
All of these are of course voiced to be used along side a Quad of Telam|Polam EL84s ( Warsaw | Poland NOS 1960|68 ) in which again, I must stress is about how said combination of tubes are used together to create an end result that suits ones ears|system|senses correctly.
And said combinations bring out the very best in multiple genres of music and are extremely well matched for highlighting the best in vocal based music, as well as allowing me to dig even deeper into instrumental type recording and allowing every strand of the notes to be rendered in a manner to which I find very addictive, so much so that I tend to hoard only these tubes that to my ears|senses have taken me to that magical point in life where I no longer think about pursuing different components just for the sake of change, and am quite content where I'm at system wise.
Odd changes are, but I'm going to throw one at some of you whom mightn't have thought of this before - but combine say a Telefunken 12AX7 ( Flat Plate - not Smooth Plate ) with a pair of Sylvania 12AU7 ( Long Black Plate - Square Bent Getter NOS 1952|57 ) and tell me what you think of said tandem?. I think you're in for quite a surprise, but as with most items in our shared hobby, it's all subjective.
But give it a shot none the less.
Happy Rolling.
scar