A really neat added value benefit of using Tung Sol valves in your amp is their low microphonics.  During testing at the factory Tung Sol Valves are tested on a vibrating table to ensure they are not microphonic.  Of course this extra testing adds a little bit to the cost. I first witnessed this benefit in my own original silverface Fender amp. Ever since it was new way back in 1970 the amp was always