I corrected the tone control circuit so you can turn down the fizz.
The circuit designer did not know that C3 had its polarity backwards and also did not know that an opamp NEVER has a capacitor to ground on its output which happened if the original tone control was turned to produce no highs cut.
An opamp with a capacitor to ground on its output would have a phase shift causing oscillation at a high frequency at maximum power causing it to overheat. The 270 ohm resistor I added would be the minimum tone control resistance that you would not hear (27kHz is cut -3dB) and the opamp would be fine.
The circuit designer did not know that C3 had its polarity backwards and also did not know that an opamp NEVER has a capacitor to ground on its output which happened if the original tone control was turned to produce no highs cut.
An opamp with a capacitor to ground on its output would have a phase shift causing oscillation at a high frequency at maximum power causing it to overheat. The 270 ohm resistor I added would be the minimum tone control resistance that you would not hear (27kHz is cut -3dB) and the opamp would be fine.