6V is surely enough. Stays between +/-5%. Some say don't go to the edge of spec like 5.7V which is -10% because cathode poisoning may happen. And don't go 6.9V which is +10% for life shortening may happen. Others say the getter material is going to expire before the filament anyway. But nobody ever said 6V-6.6V is bad.
Tomorrow I will adjust the other current regulator and left as is. Not sure if tomorrow finally can listen the 6V6 because at the afternoon plays R. Madrid vs F. C. Barcelona the Supercopa final.
Football time to relax. Those tubes you got show very good Vh consistency on same current anyway.
Has the right gain for your application on the other hand. No excess gain means less non necessary noise so there's an upside also.
But a lot of times when listened systems with NFB the sound become less warm and more unnatural.
You will listen soon. I tried it and has good bass, midband legibility, not shrunk image. You can argue cleaner for colder.
I don't use the Folded Simpilistic Fono but listen every day the Valve Itch. With FSF I listen more information but with VI is a lot more emotional the sound I know less information but for me is more important the emotional sensation.
Also sold Audionote DAC PCM63 top of the line. PCM 1704 with EB IV & discrete analog output stage. Now listening noDac with passive 4th order low pass filter, the others more information and less noise, noDac more noise but a lot more emotional.
