The ZAPsolute Mk4 is a kit form (or handbuilt ready to play) high end Pure Class A amplifier, configurable in 50, 78 or 118 Watts in 8 Ohms Class A. Capable of driving down to 1 Ohm with 6 times higher power. (Shown on picture).
The End Millennium, a 100 - 300 Watt Class A/B amplifier in kit form, with short circuit protection, DC servo, easy to build, but with sound quality comparable to the best available factory made amplifiers in the world. Built with high grade capacitors, high quality cabling and a huge power supply, with The End Millennium You'll have the amplifier to knock out Your freinds' 10 times higher priced factory built amps.
Like I say, I'd like to try an efficient class A design of the Millenium using the Nelson Pass patent.As to your remarks about the 'GAS the Nine', the Sumo Nine was designed by GAS founder James Bongiorno. And it did have differential inputs. And it also had horrible capacitors. Unbypassed polarized electrolytics in the signal path, ceramics everywhere, and no power supply bypassing. It's a wonder it sounded as good as it did. But I believe the topology was sound. I just picked up one to play with. I'm sure I will be able to make it sound vastly better with a little bit of effort. Have you seen the schematic on one of these? It's two single ended output stages bridged and driven differentially from a common diff pair. A Wiggins Circlotron.