5E3 Cathode Bias

[DustyBadlands]

How worried should I be with the 6V6GT power tubes running at 40mA and 38.5mA . The plate voltage is 365v. 12w. The bais table says 24mA at 350v is where it should be to run at 70%. Would increasing the value of cathode bais resistor help? (using 250ohm 5w). How will this effect the sound of the amp? This is my first build. Any help would be appreciated. thanks.

[Phil_S]

How worried should I be with the 6V6GT power tubes running at 40mA and 38.5mA . The plate voltage is 365v. 12w. The bais table says 24mA at 350v is where it should be to run at 70%. Would increasing the value of cathode bais resistor help? (using 250ohm 5w). How will this effect the sound of the amp? This is my first build. Any help would be appreciated. thanks.

I'd just guessing here. It would be good if you posted both cathode and plate voltages so we can draw our own conclusions. Something doesn't seem right about your post. 12W/39mA= 307v and 12W/365v= ~44mA.

Do us a favor and post in black unless there is a compelling reason. Cyan is very hard to read.

[Firestorm]

The 5E3 is pretty close to Class A. You do need to know the cathode voltage in order to find your effective plate voltage -- the tube only sees the difference between the two. It'll probably be on the order of 20-25 volts, so your effective plate voltage would only be 340-345VDC. If you're drawing 40mA, the tube is dissipating 13.6-13.8 watts. Pretty close to 100% (if they're GTAs). Class A (maybe) if the signal voltage doesn't push it into Class B. Yes, you could increase the value of Rk (a little) if you want to tame it a little. But almost every classic Class A amplifier actually runs too hot (and won't stay in Class A at higher volumes).

[Structo]

man, I can't even read that first post unless I highlight it with my cursor....

[Andy Le Blanc]

as long as you dont exceed the max dissapation for the tube type your ok...
things tend to stiffen up a bit the colder you bias but it also adds a
margine of safety......chathode bias is better for the tubes life span even at
max dissapation....... you probably wont notice a change in tone going with
say a 300 ohm resister..... and itll drop the dissapation by a couple watts

[DustyBadlands]

Thanks to all for the information. I editted the text color to black, sorry for the inconvenience. NewB mistake.