I have the MB-125's and the biasing procedure is exactly as Zaikesman has described. Straightforward, easy to do, not particularly time consuming, and except for the one time cost of a $20 - $40 meter (mine's from Radio Shack and works like a charm), it's a no brainer. The replacement tubes are reasonable (your favorite brand of El-34's) and once you set the bias there's rarely much drift if any for long periods. - I check mine about once a month or so... and usually find just the slightest of drift now and then which takes a brief moment to "touch up". It's a beautiful thing. By the way, the amps themselves (besides being a DELIGHT to own) are absolutely wonderful. I've already mentioned their ease of use, the reliability has been exemplary (no problems at all in almost 3 years of use) and the sound IS fantastic. 3D like only tubes can really do, dimensionality, finesse and upper extension but with a bass control that not only belies tubes but sounds way more potent than 125 wpc ever had the right to. Throw in the tetrode/triode switch for whatever music delivery suits your mood or listening choices for the particular session.... and the only thing I'll ever consider trading mine in for would be a move to a much bigger room and the need for even more power. The MB 450's are on my long term wish list. Anyway, I'm gushing here and that's not what you were asking about but, nothing against ARC at all, the VTL's really do "make tubes user friendly", and well worth doing. Good luck.
