According to

http://www.yamahaproaudio.com/global...y/eeengine.jsp

They are effectively using transistors as active filters for switching regulators, pretty much like class D.

High frequency and current are not nice to solder. Some TV manufacturers used eyelets at the connections to the horizontal (lie) output transistor for this reason. The transformer as well.

I've seen that topology before, may have been Yamaha, or some other brand. I don't know if they have it patented or not, or if it is patentable or worth patenting. Crown apparently patented their grounded bridge, how enforceable it is is another story. I think it would be pretty hard to prosecute.

I see this one is actually DC coupled, but there may have been no other way to make it work. Not sure.