Just picked up a few of these, off Craigslist, they look brand new: Shure SCM 810 8-Channel Automixer
https://www.shure.com/en-US/products/mixers/scm810
It's meant for conferencing... you can plug up to 8 mics into it, and it uses a compander/limiter and gates to auto adjust the levels. The guy was asking $10 each, and had three, so I figured why not? I had a 20 in my wallet, so I went for two, figuring if the output was mono (which apparently it is) I could use one for left and one for right, and use these to record drums with a shitload of mics arrayed around the kit, and even if the placement were kind of random, it should do a pretty good job.
We met up and he ended up giving me the third one free... I guess no one else was interested. These things go for close to $2K, new. They're a lot less used... the main clientele are probably corporations, and those folks don't generally buy used stuff.
The one negative is it doesn't have XLR jacks... it has 1/4" plus these odd rectangular balanced things, with three male prongs in a horizontal line inside the rectangular hole. So I'll either have to figure out what those are and get some and make some adapters, or just wire up some XLRs directly to them. OTOH, I've got some XLR to 1/4" cables... that might be all I need. I don't know if these are T/S or TRS. I would guess they're TRS. I should probably read the manual...