I have noticed a trend with NOS 6DN7 tubes being very noisy and needing run for hours before they settle down. What i am wondering if its just as simple as running the heater element to warm them up, or do they need current flowing through them to burn in? Basically i'm thinking of putting together a simple rig just to power up the heaters and bed them in. Has anybody tried this, or have any thoughts on the theory?
Cheers,
Mark