The “Stealth” SE amplifier project design is moving right along. This is over at my friends lab yesterday. We were proving out the output stage design and DC current feedback regulated filament supply for the GM70 tube. This is a very special design of supply it keeps constant current across the filament and is ultra high impedance allowing for no ac signal attenuation as well as aiding in even filament heating and balance so emission is optimal. (a dual symmetrical balanced dc filament , yes really!) We are running our new DC high voltage full regulated supply at 840 volts. The tube is being driven by our signal generator with a X10 reference voltage amplifier and a 1 Khz tone over 21 watts of pure SE class A power and best of all our hum and noise in the output is under 100 micro-volts! Next on the design menu is using our unique DC coupled front end drive topology (Z-direct) with dual symmetrical drive. (No capacitors in the coupling signal path!!!) Bandwidth measurements preliminary over 100 Khz !!!  This will be one of the best amps on the planet and its all mine 😉

Dr. of “Fun with fire-bottles”