Why is my 2n3904 amp bass-boosting?
Your circuit is missing an emitter resistor. You need the resistor to set the bias voltage and also reduce the low frequency gain. It's also the reason that your RL is getting so hot. In your setup, the transistor is fully on almost all the time, so it wont dissipate much heat, but it will be letting a lot of current pass, which will ignite your RL.





Input - Left output - Right output

Link to simulation

Notice that theres still some distortion in the output of the left one, although its not nearly as bad