I've installed 3 new Sovtek pre-amp tubes in my Fender Hotrod, to replace the old Fender branded Sovtek tubes.
Out of the 3 tubes I received, 1 sounded much darker than the other 2, when in V1 position. So the quality can be inconsistent.
Fortunately, Thomann was so kind to send a replacement tube free of charge.
So, thumbs up for Thomann service!