An FYI for mesa amp owners:
My always dependable (& discontinued) Basis M2000 stopped working last week, after 6 straight years of faithful service. Well, the valve side went completely down, and the SS side went to 1/2 power...everything was still powering up, but I still thought I was screwed - since trying to find someone to repair this behemoth of a bass amp would be a major pain unless I took it to Denver, 60 miles away.
I happened to have a Mesa Dual Rec I was troubleshooting for an injured friend. (I am a layman, I was just looking for the obvious, stupid stuff) and then I came across this video:
http://mesaboogie.com/news/2010/11/mesa-amplifier-tube-troubleshooting/
It turned out the Dual Rec's fuse visually looked completely fine, but it was toasted. 1 - 4amp slo-blo fuse and a Duet of 6l6 GC Str 440's (to replace a pair of Str 430's) and my friend's amp was back firing on all cylinders. I was pretty bummed about my M2000, while I watched the Mesa troubleshooting video to the end. Then I decided to try the test the tech used on the Dual Recs preamp tubes.
A simple tap of a pencil against the preamp tubes (while listening for any out of the ordinary noise) revealed a bad preamp tube. I swapped one of the dual rec's preamp tubes out into my M2000, and everything was as it should be. I'm so relieved....even tho I have been playing my Marshall Superbass(s) lately, experimenting with dirtier, grittier, overdriven tones.
Mesa's are bulletproof with the right care and service. This M2000 replaced my 400+ (which was sorta problematic)...but I'm very glad I stuck with Mesa.
I won't say they are the best amps...but they are the best amp for me, even tho the M2000 has been relegated to a backup amp at this point in time.