This is by no means a definitive, scientific study on tube quality/reliability, but I have not had the best luck with the Gold Lion PX300B model tubes. My Canary Grand Reference amps takes a total of sixteen 300 B tubes. I installed a full set of these tubes about two years ago. Half of them have gone bad on me thus far. “Gone Bad” includes a run away bias that very well could have damaged the amp if not caught quickly, to completely dying, to not being able to hold a consistent bias.
The Canary Audio designer prefers Electro-Harmonix gold pin 300B tubes. I decided to give these a try and so far, so good. I have had them in for only about six months so time will tell, but I can generally say for sure, they hold their bias better than the Gold Lions did in this amp.
Electro-Harmonix is a brand under the New Sensor company, an American (Mike Matthews) company with its tube manufacturing facility in Saratov Russia which was formerly the Reflektor plant. Having owned many NOS Reflektor tubes, including the coveted 1975 “Holy Grail” 6N23P’s, I have confidence the facility is capable of putting out solid products. New Sensor also owns Sovtek, Tung-Sol, Svetlana S-Logo and Mullard.