I’m trying to DIY class D audio amplifier. I had a question about the design though. Since this is a single-supply class D amp, what does the low-side switch do? When the high-side is on, the voltage potential is VCC to ground, but low side just connects the speakers ground to the MOSFET ground instead of to a negative supply. Did I miss something? Thank you!
I DIY’ed a Pass labs Aleph30. Build the whole thing in my garage from schematics. Dead silent, warm & tube like with the low noise floor and speed of solid-state. 100% class A.
Go do it! Nothing like having your friends oh and awe over system you built yourself. Endless ability for modification and tuning.
The chassis is home build and the fan is not used, but was factored in if ever needed for future designs.
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Class D amps were ‘after my time’, and I have never built one, but I share your confusion. Simple block diagrams explaining the technology sometimes show only a single power rail, but real circuits I have examined always use dual rails. I suppose a single rail device is possible, but it would need to be AC coupled to the speaker. Can you give us a reference to the circuit you were proposing to use?
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a “class a” class d amp - with a big capacitor to couple the output - there’s marketing guff to be had from that design 
A DIY Aleph. How sweet is that! The internal layout looks thoroughly professional. Wish I could lay ears on that puppy. :o)
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It sounds marvelous. I lost count of how many friends have listened to this amp and later bought a Pass amp. It’s literally everything people like about tubes and solid-state without either’s downside.
I have enough critical parts to make another, and always wanted to experiment with bi-amping. There is a significant investment in time matching components and then care in construction to keep a low noise floor.
The first time I played a Japanese pressing of Sargent Pepper CD, the previously unrealized content lurking in the previous amp’s noise floor was a surprise. On the last track A day in a Life, during the long piano decay in I think key of F, you hear someone squeaking a stool about a 1/3 of the way and then one of the Beatles says “Sssh”. Never heard the stool or the call to be quiet until I first used this amp.
DIY is a lot of fun and listening is also more fun rolling your own equipment.
There are plenty of knowledgeable people on the DIY Audio sight that can guide you through this build.