Do you wait until they're warmed up before playing music? My McIntosh has about a 30-second "tube-warmup" before it'll play. It literally display "tube-warmup" on the front LEDs. My Cary 120S manual says warm-up time is 3 minutes. The tech at Cary Audio said it was ok to start playing pumping music through as soon as the amp is turned on but I take his technical advice with a grain or two of salt.