My three channel crossover is developing crackling sounds that seem to be tube related. I ruled out bad resistors. The reason I ask is the crossover is at the top of a forced air thermal thermal chimney in a rack three KT88PP and three 6V6PP amps under it. To spite that heat the crossover tunes directly under two biscuit blower fans are abnormally cool - no heat to the touch.
Can tubes start to fail from being too cool?
P.S. the bottom of the chimney has a small furnace blower feeding it. There is plenty of airflow, perhaps too much>
