🔍 Key Concepts

• Indirectly heated cathode construction in vacuum tubes (separate heater and cathode sleeves) • Electrical potential difference and its effect on insulation stress • How AC heater voltage can introduce hum into the signal path

💭 Think About

• How does a large voltage difference between heater and cathode affect the thin insulation between them? • If the heater is powered by AC, what happens when its voltage is far from the cathode’s voltage in terms of induced hum? • Would matching potentials help one, both, or neither of these issues?

✅ Before You Answer

• Review how an indirectly heated cathode is physically built (heater inside a cathode sleeve with insulation between). • Consider the effect of high heater-to-cathode voltage on both insulation breakdown and unwanted coupling of AC into the cathode. • Check which options address electrical stress versus signal hum and whether both can be valid at the same time.