Direct does exactly what the name implies. It transfers the signal without any processing done on it. Theoretically, this should be the cleanest sounding, but in practice it doesn't make a difference if all your DSPs are disabled. That being said, I run my Pioneer in Direct Stereo whenever I listen to music. I cannot stand the thought that something is interfering with or coloring my audio more than is necessary. Certainly my room and speakers color the audio, but practically, it is impossible to eliminate both of those completely in any audio system. I do not feel a need to bring in anything else that further degrades the signal, even if the difference will be negligible.
