Switching over to a fixed bias

[alexmoose]

Hello Diyaudio,

I am thinking of changing my EL34 SE amp over to a fixed bias, I would accomplish this by simply attatching a voltage divider with a potentiometer controlling the voltage, I wanted to ask if I need to treat this as an UNloaded voltage divider, or as a loaded one? if so what is the load?

Thank you very much,


Moose

 

[ray_moth]

There is practically no load but you might want to try using a pot to start with. When you have the pot set to give the right bias for your needs, you can replace it with fixed resistors.

 

[Tom Bavis]

It's essentially unloaded, unless you drive the output tube until it draws grid current. You'll want a small cathode resistor to monitor cathode current. You can also use a combination of fixed and cathode bias if you don't have enough bias voltage available.