So I've spent the last two hours tearing my board and my guitar apart trying to figure this out, and I'm stumped.
I have a functioning OBEL + Waldo's TPC1 buffer. It's been working great for the last two years. No issues, and with my effects off my signal level remains the same when I use the OBEL loop defeat switch on the guitar.
I picked up a Kingsley Jester drive pedal a few months ago for non-GD stuff and really love it. For those unfamiliar with this pedal, it runs on 9VAC and uses two 12AX7 tubes. Unlike a lot of other pedals that use "starved" tubes, the Kingsley runs its tubes at full voltage (something like 300VDC plate voltage) to produce a glorious, natural sounding overdrive. It's a very cool pedal and truly sounds fantastic.
I decided to put it in my main pedal board this weekend, and that's when I encountered the following issue: when the pedal is run in the OBEL loop, I hear a volume drop (and slightly thinner sound) when I switch it on. When I run the pedal outside of the loop with the same settings it functions as expected. Note that this is only when it is on; there's no change in or out of the OBEL when it's off. I've eliminated as many variables as possible, and it behaves this way when powered by alternate power sources, with alternate cables, and when it is the only thing in the loop. So, outside of the loop = great, inside of the loop = less signal/slightly thinner sound from the pedal when it is on. Could this be a signal phase issue? Something else? Any thoughts or suggestions for where to look? I'm stumped.