Mark Levinson No.53
The No.53 uses eight half bridges working synchronously to achieve a much higher Pulse Wave Modulation (PWM) switching frequency of 4MHz. The eight large air-coil inductors (four can be seen in the photos) allow the circuit to avoid the inevitable dead band time in the interval when the MOSFET switching devices hand over to one another. ML's engineers call this approach "Interleaved Power Technology."
I was shown the simple notch filter board which removes high frequency spurious distortion. The presence of the inductors greatly helps the filtering, avoiding the need for a brickwall low-pass filter. I understand that this amplifier is scheduled for review in our magazine. Stay tuned!