By Michiel Ter Burg
See also http://www.luidsprekers.org/STA/.
The goal was not to build a super Hi-Fi amplifier, but to see if it would be possible to build a reasonable amplifier using standard transformers. This turned out to be feasible.
The sound on different drivers (irrespective of impedance) is as expected from a tube amplifier: detailed by low output volume and smoothly overdriven for large input signals. Although the measured bandwidth was a little disappointing, the overal sound quality is sufficient.
It all fits on a single-sided PCB of 90 by 83 mm with 7 wire bridges, however it is worth the trouble to design a double-sided PCB for the amp.