The starting point is a linestage. I'll assume we need gain, and that we'll be switching at least 2 sources. It will be driving cables, so attention will be paid to its output Z.

The gain assumption leaves some work with developing a load line and interpreting the results. Power supply and component choices can take a lot of space, so in the beginning, I'll simplify for sake of coverage. Just make it clear I am simplifying.

More later...:)
cheers,
Douglas