VAC Vintage Mk II - Manual (Page 10)

GE EL34/6CA7 (applies to those manufactured in USA by MPD):
Robust tube with bass similar to better solid state amplifiers. Overall a bit wooly
sounding. This is one of the large bulb variants of the EL34, and is actually a beam
power tube.
EI EL34 (Yugoslavia):
Similar to the East German tube, but inferior in most respects. Has unique exhaust
tip on the top. Not recommended.
Chinese EL34J (available from Penta, Gold Aero, Richardsons, & others):
Good detail and very liquid sound, this tube may seem a bit soft and bright in some
systems. We have been unable to confirm rumors of unreliability.