LM4562 Destroyed on Power Up, Audible Hum from C2 Coupling Capacitor Surge

The discussion addresses a circuit issue where applying B+ voltage to the plate causes an initial audible hum, indicating a surge through the coupling capacitor C2, and sometimes results in destruction of the LM4562 op amp. The hum may disappear during normal operation, but the op amp can be damaged due to excessive voltage at the non-inverting input during power-up before discharge through resistor R6. Suggested solutions include adding diodes to clamp input voltage spikes, placing a resistor or series inductor in series with the power supply to create an RC or LC low-pass filter with the input capacitor, and increasing the input capacitor value. Additional recommendations involve using ESD protection diodes between the coupling capacitor output and the op amp supply rails, and adding a series resistor at the op amp input to limit current through internal ESD diodes. Anti-parallel diode pairs and fast zener diodes were also proposed to protect the op amp from voltage surges. The importance of proper power switching and input protection to prevent damage to the LM4562 was emphasized.
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