🔍 Key Concepts

• Coupling capacitor role between amplifier stages (blocking DC, passing AC) • Effect of a leaky capacitor on grid bias voltage of the next stage • Relationship between grid bias, plate current, grid current, and distortion in a tube amplifier

💭 Think About

• Think about what the coupling capacitor is supposed to keep out of the next tube’s control grid under normal (non‑leaky) conditions. • If DC from the previous stage starts reaching the control grid of the next stage, how will that change the grid’s bias (more negative or more positive)? What does that do to plate current? • Once the grid is driven more positive than normal, what happens to grid current and the linearity (distortion) and gain of the stage?

✅ Before You Answer

• Be clear on the normal grid bias condition for a resistance‑coupled audio amplifier (typically negative with respect to the cathode). • Consider whether a leaky coupling capacitor would tend to increase or decrease plate current, and why. • Check if a change in grid bias that increases plate current would also cause grid current and distortion to increase, and how that would affect gain.