Razin & Musatoff Light Angel Amplifier

Razin & Musatoff Light Angel SE Single-ended tube monoblock amplifier that weighs nearly 90 kg, uses the GU -81M output tube and delivers 150 watts in Class A. 
“During development, we avoided using Class A2 and implemented only A1. But at the same time, a very non-trivial circuit was used. 
With the output tube, almost all outputs are connected to the output transformer: the anode and the second grid, and cathode. The result is 150W of true single-ended audio power with a sufficient damping ratio of 10. 
A serious setup was required for such an output stage – 850 Vpp. And that’s with a distortion ratio of 0.14%. That’s kind of a magic number, by the way, but more on that later.”