Is there any 50W 300B SET monoblock out there?

Charles, it was using the Sovtek 6A3 which is the tube that comes stock with the amp. The driver tube was the 6ER5.

You can push an individual 300b to 15-17 watts but now you're simply stressing the tube and diminishing its inherent sonic attributes.

Not necessarily true as regards to diminishing sonic attributes.

My SET is 8 watts, probably 80-85% of the time with my listening levels(75-80 db range) I'm using only "fractions" of 1 watt of power.

It is nice to see someone that understands the correlation between their listening levels and the power output of their amplifier. I wish more people would understand this.

How hard does this amplifier(power output) run the 300b? Are you familiar with amplifiers that maximize the 300b power curve and sound good doing so?

Our circuit puts 500V on the plate. In addition to other circuit design features this allows us to get 12 very clean watts (low IMD and low IMD rise) out of the tube. As the output transformers are specially wound for a Class A3 circuit, we see negligible increase in stress on the tube.

Designer Kevin Hayes has indicated to me and others that a truly WE-spec compliant 300B will have no trouble in these amps. As he has indicated, though, and as "Raquel" has emphasized in a number of past threads, a number of 300B reissues from contemporary sources do not meet those specs, and can turn this particular series of amps into popcorn poppers.

Thank you for bringing this up Al. As a former owner of VAC Auricle Musiblocs I have great respect for Kevin Hayes and his designs. These are the types of tubes that we recommend in our amps as well. The "new production" faint of heart tubes need not apply. If you can't get a nice set of NOS 300B tubes we recommend the current production of the Sovtek 6A3, which is not really a 6A3 at all if you look at the specs. It is reliable and works very well in our circuit.