I own the PL Dialogue Premium Integrated amp and experienced something similar but not the same. It DID turn out to be a bad 12AU7. PL suggests a specific process in my manual. When I first switched a few tubes it wasn’t in the logical process PL laid out.
My problem was at startup, just before the protection circuit clicked in. Low hum rising in volume until there was a pop. No damage to the speaker. After that, no problems listening.
Following the PL process, the problem switched to the right channel, I marked the tube bad and ordered another. All is good now.
Just sharing an experience. I hope your problem is as simple.
Primaluna is an outstanding amp. BTW, I’m running Spendor A6, not super efficient, but PL drives them just fine.
My problem was at startup, just before the protection circuit clicked in. Low hum rising in volume until there was a pop. No damage to the speaker. After that, no problems listening.
Following the PL process, the problem switched to the right channel, I marked the tube bad and ordered another. All is good now.
Just sharing an experience. I hope your problem is as simple.
Primaluna is an outstanding amp. BTW, I’m running Spendor A6, not super efficient, but PL drives them just fine.