The structure of the system changes depending on whether the entire system is monaural or stereo. If even one audio route in a system is a single route, the system becomes monaural. When using a stereo system, designer must ensure that there are two L and R routes throughout the system.

When it comes to input, a consideration is how to mix. There are four patterns depending on whether the sound source is monaural or stereo, and whether the input system is monaural or stereo, but it would be appropriate to mix it as shown below.