Topic: MuzCell aka Yacheika Muzikalnogo Sinteza - an obscure sound card
My current strong obsession is this piece of obscurity - a late USSR (1990-91) designed sound card for a Soviet Apple II+ clone called Agat-9.
It was virtually unknown to the public until five years back, when it resurfaced. Enthusiasts restored the schematics and made a modern replica of it using the authentic parts, but as Agat-9 in itself is a major obscurity, it didn't catch much attention. A very recently a guy called Tronix286 made another replica that keeps the sound synthesis part intact, but adds a regular ISA-8 bus, so now it can be plugged into any ISA-enabled old IBM PC compatible, which is way easier to get access to.
What is so interesting there? It is kind of a blend between basic 1-bit synthesis and analog sound processing. It uses a couple of the good old i8253 as square wave generators (5 channels originally, 6 for ISA version). Then the signal goes into a very basic, but analog nevertheless, amplitude shaper (can do very crude decay), and a set of passive register-controlled LP/HP filters, then it also gets into a phase inverter to get pseudo stereo output. It also equipped with crude but kinda analog bass/tom synth and a hat synth. Bizarre combo to say the least.
The resulting sound is pretty unique. It is kinda between SID and OPLL to my ear.
So I got very interested in this, got one from Tronix286 himself (huge thanks!), and is currently working on a MS-DOS (and Windows/Linux SDL fork) tracker for the beast. There is no emulation at the moment, but of course I will work on it, too. I'm posting about the progress at my Patreon and Twitter accounts, and when a runnable demo will be available, will post about it here, too.
An old sound demo from ~1991
The ISA replica related stuff in English