Using an SMPS for audio amps

Ignoring the improper diagram for the rectifier, can anyone help me comprehend what is happening at each stage here. I'm interested to see if I could diy implement this, or atleast simulate in software, but it's a bit hard for me to comprehend. I can only understand the rectifier part. I have no clue what's inside the MCPS block. I see the pulses are possibly due to the transistor switching but I don't know how the sawtooth waveform came in (is it current or voltage waveform I don't know either). Also I remember seeing some LDO or something in the burson chassis, no clue where it'll fit in the schematic.

 

Looks like a DC-DC boost converter.