I'm very much enjoying this tube! I have an AC30VR model, which used an 12AX7 as a preamp tube. While the amp sounded great as it came from Thomann, no mods made, I always found that when using more grit on your guitar it was very harsh on the ears and it really started to tick me off. Especially when you really dug into the strings. (cheap Chinese tube was to blame) Having had enough of that I ordered this tube because of it's description, I was willing to pay a bit more then the other alternatives.
This does exactly what it says! That top end harshness is gone completely, the amp is more responsive, sounds better, warmer and cleaner even when used with an overdrive pedal. At this point my AC30VR sounds incredible. Like a proper VOX AC30! I will buy this again.
I have no negatives to add about this tube. So far I've found it to be everything I was looking for! Having read the other reviews I see that most of us are having the same experience with this tube! So buy one, you won't be disappointed!