A followup to my "distraction" post an hour or so ago ... I've got a less than ideal but definitely useable setup running now. I've got two channels left over for instruments/microphones, and I can get anything but the turntable routed into the sound card or the tape deck. (Hmm. If I want to convert LP to MP3, that's something I'll need to fix.) I can get anything but the turntable and the sound card into the multi-effects unit. I can listen to the radio when a selector switch on the boom box isn't flaking out (though I can't get WRNR (103.1FM) upstairs for some reason, so I'm listening to a classic rock station at 104.3FM instead). And the only time I have to reach all the way over to where the stereo amplifier is, is when I want to switch to/from the turntable (and I have to get up and walk around the equipment island to change records anyhow). Because everything but the turntable runs through the mixer, I can adjust volume levels such that changing devices doesn't result in huge changes in loudness (though a couple of my early-music CDs are recorded at a lower than normal level -- *sigh*) and I've got a master volume control for the whole thing. (Well, two master volume controls, but I only plan to use the one that's easy to reach.) From my desk, I can send the monitor output to the bass amp to drown out thumping from the subwoofer on my neighbour's stereo, or conveniently cut that out when I only need normal listening volume. I'll probably change all of this again (especially if I get around to digitizing my LPs (do I have enough disk space for that...?) or do a recording project that requires more than three live inputs at once, but this works for now.
I should really get out the screwdriver and the soldering iron and put a new power cord on the 120V amplifier that I haven't been able to test yet, replace or bypass the flaky selector switch on the boom box, and try to figure out what voltage the amplifier with a non-US plug wants. (The back says, "AC 100/120/200/220/240V 50/60HZ 220W". Does that mean that I can get away with just replacing the plug with an American one and it won't care? I'd feel safer if I can make any sense of the power supply section after I open it up. Not that I have better than a 20% chance of making sense of it just by looking at the circuitry, but I can try.) But I think I'll put that off and try to do something I'll get paid for now.
There's probably some loss of signal quality with all the different places signals pass through on their way to where they go, but given the volume I usually listen at (low) and the quality of my speakers (even lower), I'm not worried. If I actually hear it, then I'll worry about it. As it is, I've got three-band EQ on everything but the turntable, and I can run anything through the effects unit if I get bored enough.
And I have two eighth-inch->RCA adaptors, one quarter-inch->eighth-inch adaptor, one eighth-inch->quarter-inch adaptor, and a few quarter-inch patch cables left over. Not enough to hook anything else up, but I made it all work with what I had in the house.
I'm pleased. I'd like a bigger mixer (so that I can run the turntable into the mixer after I get another amplifier working (gotta have a phono- balanced input) and still have channels left for instruments and microphones), and I still want to get the NT machine's sound card working and into the mix, but I have my tunes, I have a geeky stereo system that lets me Tweak Stuff and Route Stuff, and whether I get any of the more important stuff done that I need to do today or not, I feel like I've accomplished something. Something small, but something.