I’ve posted my system before and I usually keep it up to date (tho it doesn’t change much these days, … Oops I haven’t updated the description with the P20):
Here’s an older review and overview of the Switchman:
https://hometheaterhifi.com/volume_8_4/emm-labs-switchman-2-preamp-10-2001.html
I like the Switchman, tho it probably isn’t the best preamp in the world, there are precious few that match it’s design and features for multichannel audio. It has 4 input selects, each of which consists of 6 channels. Each of those 24 inputs are individually trimmable. One of the four inputs is unbalanced, two are balanced and the last has both. It’s controllable via a serial port (it’s normal control is wired via that port.) It supports solo like a mixing board.
I have a wired mod to send 1/2 of the center channel to the left front speaker and 1/2 to the right front speaker. I still get a rock solid phantom center and I don’t have to deal with the standard center channel on a video system compromises.