The Turbo-CD dock replaces your original AC adapter for powering the console and repurposes it as the drive’s AC adapter for use as a stand-alone portable CD player. I doubt anyone these days is using it as a portable CD player. Heck, it strains the definition of “portable” simply by not having a battery power option.
So, what are you using your old TG-16 adapter for? It’s actually surprisingly versatile... like the Sega Genesis/Megadrive MK-1602.
Yeah, it’s rated 10.5v but most ~9v systems will tolerate it just fine and the voltage regulator will just put out a little extra heat. Simple AC adapters were generally linear/unregulated back then so the voltage was variable depending on load (higher when unloaded) and the systems were designed to take it. Japan was notorious for not including AC adapters with consumer electronics that require them so they were usually designed to tolerate each other’s PSUs. Super Famicom expected you to use the Famicom PSU but you could also use Sega Master System, PC Engine, Megadrive Model 1, Sega CD (both models), etc. EU/AU got a taste of this when Nintendo left the charger out of the DSi XL and the rest of us encountered this with the NN3DSXL worldwide.
Even early Turbo-CD drives and CD-ROM² drives can be identical inside, though one is marked as “9v” and the other as “10.5v” simply because of the different PSUs used between North America and Japan. Clearly, it can take both.
Most old Japanese consoles were center negative polarity where most electronics today with the same 5.5x2.1mm barrel connector are center positive. That makes the TG-16 adapter useful for Master System/Mark III, Genesis/Megadrive, Famicom, NES-001/101 (OEM is AC-AC so reverse isn’t true), some Neo Geo AES, Super Famicom, Atari Jaguar, and more.
I’m using mine with a Neo Geo AES that SNK originally sold with NEO-POW3 10v or 11v adapter. 10.5v lands right in the middle but if you need one for your AES make sure yours is not one of the ones that requires regulated 5v. Those will also fit your TG-16 plug or 10/11v SNK NEO-POW3 but they will fry! Stupid SNK. Supposedly you can’t trust the label on the bottom so you have to either open it up or try a 5v center negative supply first. Dim, blocky patterns with 5v usually indicate a that you have a system that needs more voltage. Easiest source of a regulated 5v is to adapt a 1A USB charger.
Just figured I’d throw this out there in case your original is hanging around as dead weight while you have another console that could use it.