RF leak thru power cord depends on the type of power supply. Rowland's supplies have zero current switching and power factor correction presenting load similar to resistive. No narrow current pulses. Ref1000m, a second generation uses also power factor correction. In contrast linear power supplies are, in reality, a very primitive switchers operating at 120Hz. They produce a lot of electrical noise since switching is done at max voltage (producing narrow current spikes of high amplitude). Higher switching frequencies of SMPS are easier to filter. Linear supplies in power amps require a lot of capacitors not only to filter out 120Hz but also to reduce voltage drops since they aren't regulated (line or load). For that reason Jeff Rowland uses zero current switching (+PFC) supplies operating at 1MHz, even in class AB amplifiers (Models 625, 725).
One comment on Damping Factor. Speakers are mostly resistive meaning that 4ohm rated speaker will measure likely 3ohm with DC ohmeter. This resistance is in the circuit limiting effective DF to less than 3. Adding 1/10 (0.3ohm) equivalent to DF=27 should not affect the sound. Above that it is only spectmanship. In class D amps very high DF, especially for low frequencies, is caused by the fact that one of the output switchers (Mosfets) is always connected to low impedance point (GND or Vs), making low output impedance to start with. Feedback reduces it even further.
Also, transition from A to B in class AB is audible - it is only matter of extend. It is because trans-conductance (Iout/Vin) is different for one transistor (class B) operating at given time vs two transistors (class A). It is called "gm doubling" and it adds to distortions in class AB amplifiers. It is also the reason why extending area of class A operation (increasing bias) increases distortions.
One comment on Damping Factor. Speakers are mostly resistive meaning that 4ohm rated speaker will measure likely 3ohm with DC ohmeter. This resistance is in the circuit limiting effective DF to less than 3. Adding 1/10 (0.3ohm) equivalent to DF=27 should not affect the sound. Above that it is only spectmanship. In class D amps very high DF, especially for low frequencies, is caused by the fact that one of the output switchers (Mosfets) is always connected to low impedance point (GND or Vs), making low output impedance to start with. Feedback reduces it even further.
Also, transition from A to B in class AB is audible - it is only matter of extend. It is because trans-conductance (Iout/Vin) is different for one transistor (class B) operating at given time vs two transistors (class A). It is called "gm doubling" and it adds to distortions in class AB amplifiers. It is also the reason why extending area of class A operation (increasing bias) increases distortions.