tube recommendation please

There is no best tube, only a best tube that will allow you to achieve the sound that you want. I would suggest living with the pre-amp for a while and then describe in detail what attributes you would like to improve. If you find that your current tube set up is too lush and warm you will get remarkably different tube suggestion if you had posted too dry and analytical.

Since you don't have a tester your better off buying matched pairs from one source not trying to match single tubes that have values from different testers.

Looking at the specifications on your amp it has a gain of 12db. That would point to the 12au7's being your signal tubes as you are calling them. Really they are the first tubes in the gain stage and the 12ax7's are used as drivers. Unless there is a way of drastically reducing the gain of the 12ax7's or they attenuated at the output, but I don't think so. They will both be important. The 5AR4's are rectifiers. They will make a difference but your right for trying the other four first.

I have Mullard 4004 and Telefunken ribbed plates. They both have attributes that I really like. But the tubes that stay in my set-up the most are Full Music 12ax7's. They are really nice tube. IMHO

I think I will give the Psvane 12ax7's a try next. Happy rolling!

RCA 12AU7A clear tops with side getters. You won't need another pair for many years to come. For less money, consider Philips JAN 12au7a.

Hi.

I just bought a Prologue 3 a little over a week ago. Unfortunately I haven't had as much time to listen as I want to. Kevin said to wait a a few weeks until the pre has had a chance to break in. I am trying to be patient, but have been contemplating tubes to roll. The stock tubes so far seem pretty good. Kevin selects the platinum grade tube for PL line, so they are screened to begin with. I am not sure which tube the x7 or u7 affects the sound more. I think I will shoot him an e mail. The rectifier tube used in the Prologue 3 have a good reliability record, so I am bit reluctant to change that out--but I probably will. The Mullard 5AR4 is expensive, you might want to look at the alternative versions listed in the manual.
If I may ask what is your amp and interconnects and speaker wire. These can greatly influence the sound stage etc.
Michael