I HAD A TASCAM 688...
a great little machine back in the day, for a 8 track on cassette format.
there IS some crosstalk, but the mixer section itself had a nice sound.
but as far as modern recordings go,
i'd not bother with this machine.
way more trouble than it is worth.
you have a couple of options with going digital from this machine:
output each rca out per channel and record each mono track into a DAW;
or just take the stereo out via analog, into the stereo input of a interface to daw.
other than that,
you'll just be painting yourself into an artistic corner.
based on my own personal knowledge from working with a 688 for 3 years.
Agree with all of this, skip the 688.
I had a 688 in the late 90's until 2008. Absolutely my least favorite portable recording studio. My first was a 244 l bought in 1983. In fact l bought the exact same rig George Harrison bought at the time. I bought a 388 in early 1988 and l thought the mixers sounded identical. Then l started getting into PC DAW recording in 1996. The idea behind the 688 was to integrate it into all the new midi technology that was coming out, but nobody really understood any of it. I then got a Roland VS-880 in '96 and that just didn't work out for me. Had early versions of Cakewalk and the brand new Windows 95 os. That wasn't working so l got the 688. Trying to make that whole system work was a form of torture, and l didn't like the way the mixer of the 688 sounded. The 244 and 388 sounded much better. The 246 came out not long after l bought the 244 but l saw the extra channels as useless. I already had a Kelsey 16 channel board all the drums went into before going into the 244 or 388.
Next l got the Yamaha MTX-8 and l really liked the sound on that much better than the 688, although it was darker than the 244. But service wise the MTX was much easier, l thought. And you could swap capacitors and guys were doing mods that made them sound much better, but l don't know about those.
I worked in studios that had modified Yamaha consoles that were up there with Neves. In fact they called then JapaNeves. The guys that were modding Yamaha boards said they could upgrade almost any Yamaha mixer at the time. Now the MTX-8 ll is a different creature, while the upgrades sound great, for overall sound you want the first one.
The 244 crapped out first and l saw no reason to fix it and practically gave it away. I had pretty much every cassette machine made, because l had a cassette duplication business from 1986 to 1998.
At the end of the day l still have the MTX-4, the MTX-8, and the 388. The 388 is currently in retirement and will most likely stay there. If l start recording again it's going to be on the MTX-8. But if l get some money one day, which is doubtful, l would buy the new Tascam Model 24 SD recorder and a Tascam SD20 mastering deck.