When I replaced the set of valves in my amps recently, I was surprised that there didn't seem to be an immediate improvement. Previously, an output valve had been going down in one amp.

A week or more later, and the sound from all four sources, RADIO, CDP, VINYL and TV has improved.

I'm fully conversant with cable burn-in and s/s amp. burn-in, but valves?

Anybody have any views?