separks wrote:corndog71 wrote:What purpose do the 100R resistors serve? Could I run one heater secondary to 2 EL84s and one of the driver tubes and then hook the other heater secondary to the other pair of EL84s and driver tube and then connect both of them to the EL84 cathodes like in the stock circuit?
It serves to provide a voltage divider for phase cancellation (think hum pot). Indeed, you can separate the filaments.
Re-reading the thread, is your amp working and it just has a noisy power transformer? Search the forums - it seems this topic comes up a lot. I'd be tempted to cook in an oven to "reseal" the varnish. I'm sure it's been done before, but mind any odors!
Shannon
Ok, cool. I think I'll try separating the heater secondaries. And yes, the amp has been working all this time but with a noisy PA774. In fact it's my best sounding amp!
I'm almost positive it's due to a noisy power line in my apartment. I've even tried replacing the PT and got the same buzzing. Plus, other devices hum when powered on. (Ceiling fans)
My brother is hooking me up with an oscilloscope sometime soon and then I'll be able to see what's going on with the AC. I hope to come up with some kind of filter to kill the buzzing.