Tube rolling for EAR 912


Hi, i've just registered here but have been a passive read'er for a while, and learned a lot in different threads.

I have recently bought an EAR 912 tube preamp and i want to experiment with different tubes (not because im not happy as it is, i love it... but because i can :) ). So i wonder if anyone have tested 6N1P-EV tube in the 912? And how did it compare to the original? I got the following quote from wiki, regarding this tube: "... excellent low distortion and low noise characteristics."

I am also open for suggestion to other types of tubes, but preferably only tubes that someone has heard on the 912.

Note that i am completely green when it comes to tube amps and tubes, theEAR912 is my first one.
aboy
When I talked to Tim at the Anaheim Show in 2015, he told me his favorite tube brand was Mullard. The old ones, of course. Isn't is surprising how few audiophiles own, or have even heard, EAR electronics? Small number of dealers and pro reviews, no advertising, no frequent and regular model "updates" (Mk.2, Mk.2SE, Mk.3, Mk.3SE). 
I have an EAR 912 preamp and 890 power amp, as well as the HP4 headphone amp and the EAR Dac 4 (although I generally use my Chord DAVE instead). As soon as I got the preamp I started tube rolling. I tried Telefunken, Phillips and a bunch of other NOS 7DJ8s.  Then I tried some new JJ gold pin 6DJ8s. They all sounded awful.

I emailed EAR to ask why and Tim replied that he found it amusing that audiophiles thought they knew better than he did and tried to improve on his design by trying different tubes. I reinstalled the stock tubes - which I believe are re-branded Sovtek. You know what, it sounded amazing, much better than any of the NOS tubes I tried.

It may be that EAR carefully select the tubes they put their own brand onto. But it did teach me that sometimes it is best to listen to the person who designed the equipment.

Anyone want to buy a big box of preamp tubes?
FWIW this is my experience exactly on my EAR 912 - tried Telefunkens, tried Teslas, went back to the standard tubes. 
I have an EAR Acute which I use large O getter late 1950s Amperex.  They are superior to many of the more modern tubes I've tried (about 15 pairs).  Also, my older EAR 864 line stage sounded dull compared to the Mullard 12AX7 CV4004 and cleartop RCA 12AU7 in the line stage.  It became a different animal too, lush tonality (spot on), super dynamic, super deep bass, extended but sweet highs.  I keep it only as a backup because it did suffer from an opaque quality (not severe, just not high end), lacking air and openness of my current pre-amp.  Otherwise, what a gem to listen to at it's price.