Zesto Andros PS-1 Tubes

Is this the model which uses 12AU7s and 12AX7s? There has been a lot written in general about rolling those 2.
If it's the Phono Stage then certain commonly tried substitutions may not work. The switch I am thinking of in particular is using in 5751s instead of the stock 12AX7s. In a Phono stage, the loss of gain using 5751s may not be desirable. That does not preclude many other common rolls. If you like your sound clean and strong then vintage Telefunkens might sound good. If you want a rich full sound then older Mullards might do the trick, but they are getting truly scarce. The current production Gold Lion 12AX7s have been prized for their rich full sound.
A really special 12AU7 sub are the uber expensive Amperex Heerlen production 7316s. The Stock tubes are pretty good BTW they seem to like the current JJ803S replica, for their 12AX7.

You shouldn't hear any additional gain from brand to brand. The eletrical parameters should be the same no matter which brand you choose. The sound however does change in terms of tone, extension and imaging, amongst other things.
Pops are you suggesting we build our own tubes? I doubt you meant that, many of us, including me, don't know how to build a component from scratch. The one thing I can modify quickly, without soldering in most cases, is a tube switch. It affects im the sound in very obvious ways in most instances. It is a rare case that stays unaffected by a tube roll. It is easy and rewarding.

I don't think I have ever rolled tubes in a component without listening to it first. There are some tube which I know I like the sound of and therefore have a low threshold for rolling a tube of that type. For instance I have tube power amps which use 6922s in the input stage. Current production work of course but just don't seem to sound nearly as good as my preferred NOS/OS tube of this type a Mullard CV-2493. In addition, I have made a hobby of collecting tubes of certain types as well, so I like to experiment with them when I get the chance.

I thought you said it was autobiased. If you change the output tubes on an amp and it is manually biased ,that is when you need to bias the tubes. I never heard of anyone biasing small signal tubes. (I am sure there is an exception out there ...)
So are you happy? It sounds like the tube rolling addiction might have gotten to you. Be careful it is a slippery and steep decent. Best and good luck-

The Teles are very durable they seem to last forever. Did you get your ECC83 12AX7 = M8137 equivalent NOS NIB. If so it should also have a long life. I am wondering why your Brimar gave out so quickly even if it had a limited lifetime by measurement.
Did you try the New Sensor Gold Lion ECC83? I heard they were sort of Mullard like, sweet and melodious If you don't need all the gain of the 12AX7 you might want to try a 5157. I like them a lot, and now that the NOS and OS (Old Sh*t)12AX7 are getting hard to find.