Schalltechnik_04 Vong Filterung adjustable HPF/LPF pedal.    Bought off here, haven't really got round to using, so surplus to requirements!   Built by @LukeFRC:        Quite a handy thing - switchable HPF and LPF (with frequency sweep), and volume/boost control and DI with ground lift.    Technical info here:   https://schalltechnik04.de/en/instructions/vong-filterung   Selling for what I paid, which is £75 posted.