by logos47 » Sun Apr 29, 2012 12:14 pm
Thank you gentlemen! Geek's schematic is exactly what was done. However, we previously installed a hum balance, so grounding to it's center tap occurs here as well. Interestingly, the obnoxious hum has spontaneously faded away. We can only surmise that the capacitors needed time to settle down.
But I will definitelly pursue the Zobel network addition. With HF sensitive speakers, this may clean up the remaining artifacts quite nicely. Thanks, Shannon!
BTW, these MKIIIs now have 5H Hammond choke input trannies mounted beneath the bottom chassis plate. They are nicely hidden by custom wood cases. I was looking for a way to reduce the voltage to extend tube life and to lower demand on the power transformer. I still have plenty of power to drive the big old 87 db speakers, but the HF Zu drivers absolutely love the improved smoothness.
Thanks again, all!