Nice thread and some very good points both pro and con. I like the sound of tube amp and the ease of a good sounding SS amp, I use both, but all of my SS amps lean toward the sound of tube amp. Since I also own the Mastersound 300B SE I am going to address your questions with this amp in mind. The Mastersound only has 6 tubes, 2 of which are the 300Bs so heat is not really much of an issue, compared to most tube amps this one runs pretty cool. My Mastersound amp is the higher output version which uses either the 32B or 300BXLS tubes and yes these tubes are quite expensive, probably around $625 for a pair of 300BXLS tubes, the 32B tubes cost much more. However, new regular 300B tubes can be found for around $150 for EH to around $350 for a pair of really nice Full Music Mesh Plates all the way up to very expensive Western Electrics with various price points all the way up. The other tubes, 5687s and 12au7s are very inexpensive, so overall tube replacement is not all that expensive or much of an issue.
Biasing the 300Bs will require a meter but those are cheap and biasing the output tubes only takes a few minutes. Once the tubes settle in I only need to check the bias about once a month and rarely do I have to make any adjustments. So overall the downside to this particular amp is very small in relation to the sound it produces.
Biasing the 300Bs will require a meter but those are cheap and biasing the output tubes only takes a few minutes. Once the tubes settle in I only need to check the bias about once a month and rarely do I have to make any adjustments. So overall the downside to this particular amp is very small in relation to the sound it produces.