Phono preamp tube rolling.

@tvad
Lot of useful info. Thanks, tvad. I wasn’t familiar with this one.

@tomwh 
I don’t understand why you guys so desperately want to analyse some thing,  give a suggestions or answer some questions. It was no questions in my post. I just wanted to hear other people experience and stories rolling phono preamp tubes. Again my post did not contain any questions. 

@lowrider57 

OK then. Phono preamp is an extension of cart, arm, table. I'm sure you will be asked this question again.

Totally agreed with first part of your statement, but no offence, I’m pretty sure I will not ask any questions, cause I like my own experiments and conclusions. Just wanted to hear other people experience.

@tvad 
Joe mentioned Mullard CV4003 box plate as the best of the rest…. Did you personally tried that tube?

@lowrider57 

My experience was good.

What kind of tubes did you rolled? Components? plz..
outcome on best choose?

@lewm 

it almost certain that you will be certain you hear differences

 :))))))) that is funny one. 
In fact I could hear the difference almost right away, however to realize which one is better to my ears take some time. Could be several days.  

By the chance, did anybody tried Japanese stuff? ….Hitachi 12AX7, NEC 12AU7, Toshiba 12AX7 or Matsushita 12AX7 ?

@lewm 

NOS vintage tubes sold these days are very likely to be fakes

Fakes, you mean like really fakes, made faked under popular brands and models or just low quality NOS described as something very special?
Yes, testers gives you basic useful info, but of course not guaranteed that equipment won’t change tube function right after a tube being installed. Common vacuum leak could happen too specially during vintage NOS installation. 

lewm, I know that tricks with re stamped tubes… they use acetone to tear off original stamps and than put on a new signs. About five years ago I bought NOS rectifier MULLARD GZ34 from eBay faked like that :) fake signs just smeared off right away right in my hands after opening. So, no eBay that for sure…
I do trust Upscale Audio and TubeDeapot….
regarding Chinese tubes, I had pretty good results with Sophia Electric Blue Glass 6SN7 using them with my preamp…never tried others.  

tomwh, I tried to replace 12AU7 with 12AX7 ones, and it gave me a little bit more gain, not significantly, but noise increased too.. so SQ didn’t benefit from that switch. 

@mulveling 
thank you… it’s a quite impressive experience. What was following upgrade replacement for your Ares?

tomwh, it’s not odd to me…12AU7, 12AT7 and 12AX7 are pretty much the same tube with a little different gain settings. 

@mijostynit 

is always best to use the specified tube.       

Could be exceptions, but I general you right…. I always return to specified tubes. 

@tomwh The ares manual suggest that switch between 12au7, 12ax7 and 12at7 in case to play with the gain…. I did it successfully with no any problem.
My priority is listening to music and I’m not really interested in deep technical details of the tubes, it’s required lot of time. maybe I’ll explore this when I’ll retire… for now I just want to listen and roll, listen and roll :)…to figure out what I like the best…when I’ll be interested in tech questions I’ll post that… my current post is about something else as you could see. 

@chakster 
thank you for a lot of useful info.
You right that Japanese tubes are not discovered well. It wold be interested to hear from people who tried them.  

@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. 

pindac, what’s your 6SN7 keepers ? For what preamp ?

@mulveling 

Melz 1578 OTK, Russian military

The stamp of “OTK” is not about the brand or any tech spec… at old Soviet and Russian manufacturing “OTK” means Department of Technical Control passage. Usually checked and ready to ship products was stamped with OTK stamp. 

@lowrider57 

The OTK stamp meant it went through quality control and met the highest specs

You right about passing through quality control… but too optimistic about highest specs…all Soviet NOS has to be carefully checked before using…we have to be specifically careful with tubes made in USSR in 80s - 90s cause quite control of this period was much lower than 60s - 70s.