Except that the HD Radio """standard""" is full of patents, so even if you knew how to make a digital receiver, you couldn't sell it without paying license fees.
And they call it HD to make you think "high definition" when in reality it's barely up to the quality of a 128K MP3. The HD stands for "Hybrid Digital". There is really no need for it to exist other than ZOMG DIGITAL.
Also, nobody cares about stereo on AM anymore, so there's no need for it there, either. AM (in the US) has become talk radio and low-income music for people who don't give a fuck about audio quality. (The AM band is full of Mexican-style music down here in Texas, with the occasional country or rap station in between.) It is also extremely susceptible to RFI, making the sound quality even worse. I even know of two talk radio stations that have LP FM simulcasts so you can get better audio within the metro area limits.
Some of those albums became available on DTS CD. DTS is an interesting format, because it is a 5.1 format that was designed to work inside of red-book CD audio. They even have to drop the high 2 bits from each channel to keep the dynamic range of binary data from killing speakers when played on a regular CD player without the proper decoder. Still, it's the only CD format that supports quadraphonic audio.
But it had little exposure until DVD made digital audio decoders a thing, and even then you had to hook up everything just right to play DTS from CDs.
The Mac Mini is not a viable computer
You mean the new, downgraded Mac Mini with 8GB soldered RAM? I've found three of the 2010-2012 vintage over the past year or two, and they're great, especially as remote servers. One of them is even a late-2012 Quad 2.3 i7 / USB 3.0 model. That was the only time you could get both upgradeable RAM and USB 3.0.
I've been using a Late-2011-17" that I immediately downgraded to 10.6.8 when I got it, and that isn't easy, because it requires at least 10.6.7 and the last retail version was 10.6.3. A few months ago I finally took the plunge to 10.9, and one of my main motivations was that Minecraft (which I haven't been playing anyhow) would fuck up the GPU because of how it used OpenGL in v1.6. I've recently revived an older MacBook Pro to run 10.6.8, so now I can again use some obscure stuff from the PPC era.
I think the thing that bugs me the most is the new document model where you have to use "Duplicate" instead of the good old comfy "Save As". Which is of course not retroactive to older apps, just the updated basic apps from the OS. But I love that it now keeps all my dozens of windows open when I have to restart.
A mathematician is a device for turning coffee into theorems. -- P. Erdos