My receiver has a button called Tone Defeat. What does it do?
If the receiver has a Tone Defeat button, then it also has tone controls, which allow for frequency-response adjustments for the bass and highs. The problem with tone controls is that the circuitry can add distortion to the sound, even if the buttons are left in the neutral position. It’s a small thing, but it’s been apparent to me on the receivers I’ve used. The Tone Defeat button bypasses tone-control circuitry, meaning that you can no longer adjust the bass and highs, but you’ll have purer sound. Therefore, my suggestion is to use the Tone Defeat button if you’re not going to adjust the tone controls, but live with the subtle degradation in sound that the controls bring if you do.