As a mixer the 688 has 10 tracks which will be fine when using it for gigs/rehearsals...but if we wanted to record anything is it possible to record channels 9+10 to any of tracks 1-8 or is that impossible? All I ever did was record a basic band set-up with channels 1-8 once
Any of the 10 main mix inputs and 10 dual inputs can be routed to any of the 8 groups that correspondingly feed the 8 tape tracks.
There is no 1:1 relationship between channel inputs and tracks as seen on cheaper/more basic multitrackers. Channel 1 doesn't necessarily need to feed Track 1. You can easily record tracks 1 through 8 individually (or simultaneously) with your guitar or mic plugged into track 1, if you wanted, for the entire process.
Conversely, you could combine signals on channels 1 through 10 onto any single tape track. Or across multiple tracks (with panning) if you wanted.
The thing to understand is -nothing is hardwired in the 688.... the routing system is essentially like having a separate 8-buss mixer and tape deck connected via a patchbay. The advantage being you don't need an armload of cables and can save routings for later use.... the disadvantage being it is not immediately obvious where things are routed!
Another thing to consider is that there are 3 different ways to monitor individual channels and tracks, each useful/required for different tracking scenarios.
The 688 is a hugely flexible beast that quite frankly makes almost every other cassette multitracker - and indeed many digital units -look like toys. The cost of that flexibility is complexity - it is not really a box you can just dive in and use. It took me a good few months of use and re-reading the manual over and over to get my head around the routing system to the point where I actually felt like I knew what was going on. I'm still learning new ways how to use it.
It is exciting to have a single SIAB that gives the immediacy of tape, but with the flexibility to route signals pretty any way you want.
Hope that helps. Really, what you want to do is give yourself plenty of time and a few mock projects, and really, really work your way through the various workflows. There's no substitute for practice and experience with this one.
Cheers, Ben.