I've owned one for several years a while back.
Audiolab still makes them, I believe they now have more than one model and some changes have been made over the years.
When the MDAC came out, it was ground breaking and sold like hot cakes.
On the plus side, it is a detailed sounding DAC with a very wide and open soundstage. The sound can be tweaked with the filters and the headamp is also decent. It also has a digital volume control and can be used as a pre-amp. I ran mine as a dac & pre-amp with a set of Audiolab 8200MB monoblocks.
On the negative side, the build quality was not great (i'm now talking about the 2015 or thereabouts model) with several people pulling the RCA connectors out of the case when removing cables as an example. The implementation of the Sabre DAC was also a bit brutal with the sound being a bit "digital". Great if you have a very warm system and you want to inject some detail but not great if you already battle with thin/forward sound it will just aggravate the issue.
Back then the designer, John Westlake, was very active on PinkFishMedia. He provided firmware updates, did trouble shooting on the forum, offered advice on how to do DIY upgrades and so on and so forth.
Some info below:
https://pinkfishmedia.net/forum/threads/the-john-westlake-lakewest-mdac-fdac-vfet-and-detox.233225/
I think he left AudioLab somewhere in 2018 or 2019 to start his own audio company but I lost track. I don't think it was a success though. Maybe someone else on here followed the saga and can provide more details.