based on my listening on Freya: Psvane CV181 TIII > Sophia 6SN7 ≥ Northern Electric 6SN7. The Sophia's excel at space and nuance. Northern Electric is very similar, which they should be considering they're very, very similar construction. From what I've seen, the differences between the TJ Full Music/Sophia/Northern Electric are minimal, if any at all. NE 6sn7 was a little more closed in, but this may be due to lack of break-in. I admittedly didn't spend much time with the NE 6SN7 since they seemed so similar, sonically, to the Sophias. edit: I'm also fairly certain the NE tubes are made in china by TJ Full Music.