Making a Custom Mixer Interface for the 1818VSL

In 2011 PreSonus released the 1818VSL, an 8-channel audio interface, with low-latency mixing software. I wrote: All I really need is a box with some amplifying inputs that send tracks from the mic to the laptop and some outputs that let me send mixes back out again. Then any sort of complex eq, compression, or other effects can happen in software on the laptop. So I got one: it's a Presonus AudioBox VSL1818, with eight usable inputs and eight usable outputs. At the time I did worry about how long I could expect it to be supported: Less future proof. My old board is almost twenty years old and is still fully compatible with modern gear. In twenty years will I be able to attach this box to a computer at all? This was indeed a problem: in order to get the latency down, PreSonus had written a custom kernel driver. This integrated very deeply with the laptop's operating system, so that it could mix and apply effects as quickly as possible. In 2015-09, when Apple released OS X 10.11, they…