|
The 10meg resistor is being used as grid leak bias with the cathode grounded. It's a perfect recipe for high impedance/ hi gain buzz. Unless there's a lack of volume(not likely if it's buzzing) you can try an unbypassed cathode bias resistor with something more like 1meg between grid and ground. The unbypassed cathode will allow some negative feedback and tame things down a little. You'll likely end up with volume control turned up higher. Probably leave the 2 unused diodes ground.
|