For humans biases can be detrimental to the day-to-day decisions we take in life, however, when it comes to the Valve/Tube amplifiers, its is indispensable and rather determinant of their healthy life.
Further to the basic article where we explained the Fundamentals of Biasing an Amp, this article discusses in depth about the techniques, recent developments, challenges and strategies to address issues in biasing an amp.
A Primer on Tube Operation
Inside a tube the plate has a positive charge, which attracts electrons. The grid is the audio input to the tube and controls the flow of electrons as it accelerates or decelerates the electron flow.
There is a high voltage on the plate of the tube and a heated cathode that emits negative electrons & the moving electrons produce a current flow.
Amplification happens when a signal is applied to the grid which is like a mesh and flows through to the plate. Because the signal voltage is relatively low and the plate current is relatively high, small changes produced by the audio signal at the grid become much larger at the plate and amplify. Biasing is the mechanism to control this flow.