Maybe that is an aux in?Looking on Jule's instagram... Looks VERY interesting! The little section of schematic in the top right corner of the pic shows channel switching, a portion of a Baxandall EQ section and an eq bypass switch... and is that a headphone out I see?! View attachment 1181594
A lot of pots on there. So guessing here...Low, mid, high, maybe sweepable mid, input and output gain, DI level, perhaps Aux or headphone level, perhaps switches for preamp post eq for di, switches for shifting frequency centers..... I can't take the suspense!!!! AAARRRGGGHHH!!!!!