My new, and totally awesome, Reverend Charger 290, made me discover an issue with my QC I never knew it had.
I was messing with the bass contour knob - which is basically a knob which rolls off some bass like a cut - and it seemed to just act like a second volume knob, just without going completely silent.
I felt like this couldn't be right so I checked a video and the behaviour they were getting wasn't not what I was getting.
At first I thought the guy I got it from ripped me off. But then I remembered there was an impedance knob on the QC so I tried that first and I turned it down one notch and the guitar, which had the bass contour down, sprang to life.
Funnily, though, when I put the knob back to default, the guitar was still functioning as intended.
I turned the impedance knob all the way down and I ended up with that same, initial effect, with the impedance knob draining volume.
So it seems that when I start my QC, though not all the time as I found out through tests, it starts with the impedance at the wrong setting, and you have to move it and back again to get it right.
I have no idea how long it's been like this. Maybe always.