both the power and pre amp tubes are fairly new although it's possible that they are already bad. the symptoms are: 1)when first turning on the unit i hear a crackling, static sound for about 5 seconds. 2)sometimes i will get the same crackling,static sound when playing as well 3)it may be my imagination but this only seems to be happening when using the inside 4ohm speaker output jack. i tested the cabinet with another amp and sprayed the output jacks with contact cleaner. any ideas?