Lamm ML2.1 popping noise?

Please help! The left channel has developed one or two popping noise coming form the speaker at times, not too loud but frightens me! I checked the bias of the output tubes and it is 0.34v with music. I that too high! Have anyone had this problems before? thanks.
Hi Luna,

my ML2.1 run line a Swiss watch, never had such a Problem,. But reduce the bias to 0.29-0.31 without music (0.31 is the maximum).
But it can be possible that one of the tubes is going weak...
Check the small tubes one may be going bad
Thanks for the responds, I have since set the bias down to below 0.31. So far no pops and fingers crossed. I think I should change the 2 small tubes too as they have been there for many years!