@charles1dad regarding light loading, which Roger felt benefited all of his amps. the following is taken directly from the Music Reference RM-10 manual:
"The amplifier is flat within 0.1dB and has low distortion of 0.3% when played below clipping on average level material. At the recommended bias current of 30mA/pair, the idling dissipation is nine watts or 75% of the tubes’ rating. I estimate tube life to be 5,000 to 10,000 hours. Although higher idling currents will reduce distortion, it can also be reduced by light loading. Basically, light loading reduces the output current demand on the output tubes, allowing them to be more linear. It also reduces noise, raises damping factor, reduces distortion by 78% and allows for 80% more peak current when needed. The only loss is about 20% of the power rating or 1dB."
In addition to some neat design features in the circuit, the way the output transformers were wound also contributed to the benefits of light loading as discussed in the manual. The only negative was a 7 watt loss of power, which is inconsequential if you also consider light loading doubled the class A range of the amp to a little over 20 watts.