I recently bought a Boogie SOB off someone on this board. Great amp, just like I remembered them to be from the mid-'80s. While these amps don't seem to appeal to some people, I like it for its blues tones. This one has the 100w option, reverb, and the Limit circuit (that some people don't like). A friend of mine had one in the '80s that had Simul-class, reverb, and the Limit control and his amp simply ripped a hole in anything that we put next to it. Anyway, here are my questions: Much seems to be made of the idea that an amp needs to be properly matched to the load. Mesa states over and over in the manual for this amp that impedance matching is not critical and that the user should experiment with mismatching. Why the divergence from general opinion especially coming from the manufacturer? Can you remove the two inner power tubes if running the amp in the 60w mode? This amp was built in 1985 or so. I would assume that it needs a cap job, but it seems that the caps used from the '80s onward did not dry out as quickly as the ones used in the '50s and '60s. So, is a cap job really needed? (No hum.) When I got the amp it had a set of JJ 6L6s in it. They were only warm to the touch after the amp had been on for quite some time which leads me to think that they were biased too cold. I replaced them with a quad of new GT 6L6s I've had on the self for 20 years that are rated H4. These warm up much like they should and sound good too. I know a measurement is a better technique though. Can I use a set of Yellow Jackets in this amp? Is there an attenuator that seems to work well with Boogies? Just to knock it down a little in 60w mode. (I don't hear much mention of people using them with Boogies.) Here is a copy of the schematic for this amp. Can someone tell me what the Limit circuit does and why it seems to be replaced with a Presence control on many of these amps? http://www.schematicheaven.com/boogieamps/boogie_sonofboogie.pdf Thanks for any help.