BIas Formula for Amp

[Lou]

I remember reading a Bias Formula depending on the plate voltages.

Can anyone help me with this?



Thanks


Lou

[Flames1950]

The formula for your target bias current is based on idling the amp at 70% of the maiximum heat that the tube plates can dissipate. Most EL34's, 6L6/5881's are rated for 25 watts of heat dissipation (nothing to do with the amount of power the tube can put out.)

70%(25watts)=E*I where E is your plate voltage, I will be the target maximum bias.
In the case of the 380-390 plate volts you (I think it was you?) posted in the Marshall forum,
70%(25watts)=380*I
17.5=380*I
17.5/380=I so your max bias current would be .046 amps, or 46mA.

[Lou]

Dude Thank you soo much. That makes total sense...I will make adjustments to the amp as it is set at 35...

The fact that it is running lower , does that mean cleaner or diry tone out of output tubes...



Thanks again