Tweet
I've seen hum reduction mod that has 6.3 v heater wires in parallel to the tubes. Some say use two 100 ohm resistors off of the filiments on the 6V6, and tie both together at pin 8. Others say tie both together and run to ground. Which is it? Why?
-
-
Either. Most builds are OK with 100ohms from each leg of the heaters tied to ground.
Running the 100ohms (or a PT centre tap if you have one) to pin 8 of the 6V6 dc biases the 6.3VAC heaters and can reduce hum.
This philosophy can be taken a stage further by running one leg of the heaters to a 220K 2W resistor from the main b+ supply, and from the same side of the heaters running a 22K-27K 1/2W resistor to ground to give 35-40vdc (no more, no less) biasing the 6.3VAC. There is no other ground reference in this circuit (centre tap etc).
Comment