Auto-Bias
Auto-bias automatically sets and maintains the electrical operating point of an amplifier’s output tubes.
Bias is the voltage that establishes this operating point. The resulting standing current flows through the tube even when no music signal is present. A bias meter displays a reading; a meter alone does not adjust anything.
Auto-Bias — Power Amp
In a tube power amplifier, individual tubes differ, and their characteristics change as they age. The bias needed for the intended operating point can therefore change. Auto-bias takes over routine manual adjustment, reducing that maintenance task.
It does not make every replacement tube compatible. Use the tube types approved for your amplifier model, even if others fit the socket. Check its manual for any required tube-type or bias-selector setting: automatic adjustment can still require you to select the correct range.
Sources
- Adaptive AutoBias: technical explanation — PrimaLuna
- EVO power amplifier manual: bias and tube compatibility — PrimaLuna
- Tube compatibility FAQ — PrimaLuna
- M150 manual: manual tube-bias adjustment — Rogue Audio