Phono preamp tube rolling.

When I Tube Rolled 6SN7 and Variants of this Tube.
I did this without support or loans of tubes from experienced owners.

In comparison to other Tube Rolling experiences, it proved to be the most difficult to make a selection, as some tubes choices, once with a little run time sounded like competitors to go on to a Short List.

When longer evaluation periods were used for the tubes, certain tubes became very different in their SQ and had to be removed, as the deterioration was very obvious.
There was a concern that the tube was developing a fault. 

I would say best to stick close to the advice of others with worthwhile experience as the selection for the initial investigations.
A Benchmark can be set for any other experiences to be had down the line.

@pindac
no questions, advices of others with worthwhile experience is very valuable and of course could be implemented, but my senses and fillings r more important for me. You know it’s like advices from others which women is better for you… you listening to that advices but using your fillings in the first place. 

I have a Zestos Andros Deluxe 2 that I've done a fair amount of tube rolling in.  The Zestos has two 12AX7s in the "primary" spot, and an interesting pair of 12DW7s (one triode has an 12au7 like mu, the other having a 12Ax7 like higher mu), which according to Zestos drive the dedicated output transformers.  I've rolled both positions, the 12 DW7 makes only a slight difference in clarity.  I've tried Mullard 12DW7s, some American NOS ones... not much difference to be honest.  I put in some NOS Orion DW7s (made by Tungsram) cause they look the coolest and I convinced myself they sound the best.  : ) 

The 12AX7s do make a pronounced sonic difference though.  In lieu on the stock JJs,  I've tried several NOS including: Telefunken smooth plates, Tunsgram 12AX7, RCA black plates, Mullard longplate square getters, Amperex long plates D getters, and Tesla E83CCs.  Long story short, the best sound came from the Teslas and the Telefunken in terms of clarity, bandwidth and detail.  Close behind were the Tunsgrams, which although deviating from neutral, had a seductive bloom to them.  The RCA black plates fared surprisingly well with a punch and clarity that I could've lived with.  The Mullards sounded like a wet blanket over the speakers, and were not suited for this phono amp usage.  All tubes were very quiet.  I'm leaving in the Teslas.  BTW, I love this phono amp.  It frankly far surpasses the Pass XP15 that preceded it in all areas.  The Zestos is completely quiet, with no overt tube noise.  It's end game for me.

gakerty
Mullards have never lasted too long in a phono stage or any other application here, for the reason you colorfully cite :)

The Zestos looks lovely and its use of an asymmetric dual-triode is very interesting! Use of output transformers is cool, too. I'd love to hear one some day. 

Certain Tubes can be quite expensive and tube rolling can generate a considerable outlay for the items to be compared.
I shared the pitfalls I had with the 6SN7 when I went alone on the subject of rolling these.
I have 5 out of Seven Pairs of NOS and New 6SN7 Tubes that are rejected.
A few of these pairs I will not sell on as they are not something I would like another to experience, I have no intention to reproduce the stress and the concern the use of them can inflect.

My later experiences where support from experienced individuals was at hand and the offer to assist accepted proved to be much more successful, and the choices made by myself have been keepers.

Ironically two friends that were consulted with,  for advice on other Tube Models are also agreeing and promoting the same 6SN7 I have chosen as their preferred tube.
One friend also thinks I am with a very good 6SN7 Tube and would like me to try the ECC33 once I have the approval of the Power Amp's Designer/Engineer to use it. 
The ECC33 was a Tube I was not even considering.