Primaluna signal tube replacement

Primaluna’s stock tubes in the outer positions are fine. I have been running vintage Amperex "Bugle Boys" in the gain positions with great results. On the power amp I run A-matched EL-34's from Sophia Electric - also outstanding.

All great advice. Thanks.  Especially the “reseating” comment.  I think I’ll work the originals back into those slots and see what happens.  I tend to overlook the simple stuff sometimes.  I sure love this amp.  

I would replace all the stock 12AU7s with NOS or UOS RCA or GE tubes. 

and you can sub in the 5814As which are electrically the same but are lower noise tubes. Have owned 7 of the PL amps. One of the biggest improvements I got was pulling all 6 of the input tubes and replacing with RCAs. They are not expensive either, tons and tons of 12AU7 and their variants were made. 

If the filament supply can handle extra current, and if the filament voltage is 12V (not 6V), then a great upgrade from the 12AU7 and its congeners is the 12FQ7.  Even as a cathode follower, the 12FQ7 can be heard to be an improvement on the 12AU7.