I've noted that some new production 6922 tubes die an early death, becoming noisy. As far as tube rolling, this should be a sticky (or redone into a one of my blog posts for easy reference: https://www.superbestaudiofriends.o...-other-glowing-delights.486/page-8#post-21818 Assuming everything works and specs won't cause long term damage, some things such as bias and voltages are left up to the designer. This will be dependent upon the tube type, the circuit, and could even be something subjective (oh how horrible, am amp designer also using ears to design an amp!). When we change tube types, we throw that out the window. ... One day, the GE JAN5670s will be rare. While some new production 6922s die early, there is no guarantee old stock 5670s will perform up to par. I bought a bunch of WE396a, and one-third of them I would not resell to anyone here on SBAF. They either have extreme gain mismatches between the triodes or have unacceptably low omissions. Basically, trash can or relegated to Vali 2 use. 10% are total trash can.