Update on the rolling of Amperex 12AU7 Mullard, Blackburn, Lancashire factory tubes (orange world, mid 70s vintage):
I've got a good 12-15 hours on the tubes now. The high end is more extended than the Primaluna 12AU7s and it is certainly clearer.
The bass has come on nicely; there's plenty of it and it matches the Primaluna 12AU7s in quantity and has better defined form.
The tubes sound warm enough, strong and detailed. I surely prefer them to the stock ones.
One thing that has proven interesting with them; with these tubes I like streaming via Tidal to my DAC better. Everything sounds crisper and more alive, and they closed the distance between my vinyl rig and digital. Vinyl is still preferred and better overall to my ear, but digital is definitely more tolerable. So, this makes the investment all worth it. I'm excited to hear streaming music whereas before I hadn't used it very much over the last 6 months because vinyl was upstaging it significantly. I think I'd have buyer's remorse or felt I learned a tough lesson if the NOS Amperex didn't sound as good as what they swapped.
Oh man! I'm now a curious tube roller.