In the interests of getting some varied and helpful information into the forum! Help appreciated. Please make replies as non-technical as possible. :) OK. I have a fantastic integrated Tube Technology Synergy amp. It has 12 x EL34's - new Electro Harmonix that came with the amp - 6 per channel, that are biased via an on board in built biasing meter. The meter shows an LCD reading and the bias is tweaked via some little pots. The manual advises setting the bias for 35. A couple of the tubes can't seem to reach 35 - more like 30 - I was told this is ok providing above reading is above 25. I also notice that the reading fluctuates slightly - gather this is normal. My questions are - does biasing need to be rechecked every so often. Are the tubes not giving 35 problem tubes or is it the amp? I am told that with a service the tubes should be rebiased by an external professional meter and would be better - is this bull? I am thinking of getting a full set of Svetlana Winged C, matched - told would make a significant improvement. Any views? :) Thanks guys.