OK, so after about 30 hours of constant run, the sound is still quite off. A few issues so far:
1. Left channel (with the tube containing high voltages) seems to have quite lower sound output (at least a ~10db diff, measured very unscientifically). The effect follows the tubes during a swap.
2. Overall gain is quite low, compared to my amp's built in phono-stage. Compared to a line in from a DAC, there's likely a gain difference of about 15db, maybe more. Is this normal? Will it improve as the tubes cook?
3. The sound can still be a little muddy, but I truly expect this clears up once the gain issues are addressed.
All that being said, I'm really happy I've been able to get it up and running. This was my first major electronics project, so the fact that I've even gotten this far makes me really happy.
For now, I'll continue to let it run, but if there's anything I should be on the lookout for, I'd love the advice.
thanks!
S