This 6V6 amp was built following the
push-pull (PP) EL84 / 6V6 Dynaco A-410 output transformer schematic.
There are a few minor deviations from the original schematics. Instead
of Dynaco transformers, Hammond 1608A audio output transformers and a
Hammond 272HX power transformer were used. The
EL84 / 6V6 PP Dynaco A-410 output transformer schematic
showed a 1000 ohm feedback resistor which resulted in bad amplifier
oscillation. Feedback resistor Values between about 6 and 10 k-ohm
worked well and I settled on 10k. A 5Y3 rectifier would have been to
small for a stereo amp so a
JJ GZ34
rectifier was used. It became necessary to put a 100 ohm resistor
before the first power supply capacitor to bring down the B+ to about
325 volts as I was getting in excess of 345 volts (there is less
voltage drop through a GZ34 versus a 5Y3).
Click here for project details.
http://diyaudioprojects.com/Schematics/DIY-Push-Pull-PP-6V6-Tube-Amplifier/