Vacuum tube audio is the very picture of a solved problem. You can look it up in a textbook or copy the schematic of old equipment. Vacuum device engineering i

Vacuum tube audio is the very picture of a solved problem. You can look it up in a textbook or copy the schematic of old equipment. Vacuum device engineering is alive and well. It's just that a top radio power designer or particle accelerator designer won't throw away his career to become a handbook engineer designing antique reproductions at a what amounts to a toy company.