A standalone or integrated electronic unit for selectively modifying audio or video data for use with an output device. The electronic unit has one or more audio or video inputs and one or more audio or video outputs for outputting the modified audio or video source material. The unit may include sensors, selectors, and/or logic for selecting from among a plurality of modification profiles and applies the selected profile to the audio or video source material before conveying it to the output device. The modification profile may be used to adapt an audio or video source for a specific type of audio or video playback or output device. For audio, the modification profile may be used to modify audio quality by altering the transfer function, and for video, the modification profile may be used to modify video quality by altering the visual characteristics of the video source signal.