Change Valves

[nunoazev]

Hello all

I would like to try on my AFD100 three set's of valves: EL34, 6L6, KT66.
Does anyone know if i can do by just swaping them and then Auto-Bias?
Please comment

[Wildone]

Yes, no problem.

[nunoazev]

Someone told me about the (mA) or impedance ? Don't i have to set this? or leave it as it is?

[Wildone]

Your impedance should not change because you put in new tubes, the impedance has to do matching the ohms of your cabinet. I would read your manual and see what it has to say about the mA setting when putting in new tubes. I don't have the amp but I bet it is a setting for how hot the bias will be.

I would put in the new tubes and follow the bias procedure in the manual.

[Mats A]

You´ll have to set the bias adjust screw on the right mA though. Then do the automatic bias setting holding down the effects loop on/off switch while turning on the power on the amp until it starts flashing. According to Santiago at noon (35mA) for EL34´s wich i´ve tried. Mine came adjusted to 38mA for the 6550´s. But if you´re not sure don´t do it yourself. Ask a tech or someone who knows. The impedance has nothing to do with this. Just set it so that it matches the cab you are using.