I thought I'd bring all the Mk4 articles together into a new thread.
The Ultra-LD Mk4 is the latest version of Silicon Chip's low distortion 200W amplifier, with many improvements over past designs. They have designed out the now harder to find parts, further reduced the distortion vs Mk3, reduced the physical size of the board (using smd parts in the front end), and added additional features (clipping indicator leds etc).See the preview article for more detail on what has changed.
So far in the series :
Ultra-LD Mk4 200W Amplifier Preview - Silicon Chip July 2015
Ultra-LD Mk4 200W Amplifier PT1 - Silicon Chip August 2015
Ultra-LD Mk4 200W Amplifier PT2 - Silicon Chip September 2015
October issue will have the power supply article which I will post when I have it