Thanks @seware! I get to listen to everyone’s suggestions and then I look smart 
@mooselake That hum is normal, it’s just the sound of the PWM signal which control the motor. The left motor sounds different from the right motor because they are controlled using different PWM sources due to the fact that the pin which controls the left motor is also used by the timer which is used to trigger the PID loops to recompute. We’ll probably make them both sound the same eventually just for everyone’s sanity, but they should function the same