What's this circuit for added to the ground on my A/B/Y Switching Box?

[Rontone]

So I got this Torres Amps switching box, it was sold as working but the battery inside had leaked so I opened it to refurb it

Across the ground tabs from the input to the "B" channel output jack [which is plastic isolated type] has this assembly of 3x 33ohm resistors, 2x 1N400* type diodes and a 104 Poly cap, all in parallel [diodes in anti-parallel...]

The input and channel A both have switchcraft jacks, so the grounding connects through the box, is this there as a filter or ground loop isolation or both?