Yes, AUX does affect sound quality on a soundbar. AUX stands for Auxiliary audio, and it refers to the input jack on the soundbar that allows you to connect external devices using an auxiliary audio cable. The quality of the audio signal that is transmitted through the AUX connection can vary depending on factors such as the quality of the cables used and the electronic components within the soundbar itself. It is important to use high-quality cables and ensure that the soundbar is compatible with the external device for optimal sound quality.