Just rolled in NOS GE 12AU7 and Sovtek 12AX7WXT....
Initial impression of the combination is that tone is much rounder, a LOT less harsh in the top end than the chinese stock tubes, vocals are more lush - much more air so to speak. The bass is good and tight, and the mids are more present than ever.
Just like the stock chinese, the 2 pairs gave no hiss or hum. Dead quiet.
The Russians though, are more prone to microphonics than both the chinese and the NOS GE. A little tap proves this.. hehehe
I wasn't able to try the tubes one at a time, because the combination was done out of excitement, so I wont be able to give insights on the sound of the individual tubes.
Overall - These tubes really complimented each other, and safe to say - This combination will BLOW away the stock chinese 12AU7 and 12AX7 in every way.
I will give my more detailed insights on the said tubes once the tubes have settled in, I will give it 50-200 hrs to burn in, just in case there will be noticeable sound difference.