Hmmm. Seems expensive, but definitely will keep in mind. (Though this piece isn't too bad.) Seems like putting that in the post-preamp effects loop would do exactly the trick.
Post gain is part of the preamp circuitry on this model, not part of the power amp. Turning it down all the way doesn't mute the speaker, and reduces the line-out signal. (Also, the compressor is part of the power amp circuitry, so there's no way to record the compressor direct. God fucking dammit.)
It's solid state, yes, so you can turn the volume down, but again -- that reduces the DI signal, and signal-to-noise ratio becomes an issue. Also, what I really need is to go completely muted, so that I can plug my headphones in and the only sound coming out is the strings twanging against the bass body when the rest of the family's gone to bed.
However, I did try something different, and it seems (so far) to be working. Rather than using the ancient Y-cable, I plugged a patch cable in there, and plugged the other part of the patch cable into the output of an old (and possibly busted) pedal I have. Just to give the input something to be connected to, right? Nothing dangling around, picking up whatever. AND, since the pedal is kinda shitty, I don't feel bad if doing this breaks the pedal. And, so far, it seems to have solved the issues. No random humming or static, in fact it's gone from picking up the signal from the Preamp Out cable to being completely noiseless.
Well, either that, or that last POP! broke the power amplifier.