Belcat delay mods

[944cabby]

Bought this second hand cheap 350ms belcat delay to have a mess about with.
I've removed the smd R18 from the board and connected a 47k resistor to increase the delay time (crudely for the moment on the underside of the pcb).
The delay time has increased quite a bit and the sound doesn't seem as muddy as before however there's a loud "zipper" type sound now whenever you strike a note, which i'm guessing is the chip?.
Could anyone suggest if there's a way of removing this sound?

[Mark Hammer]

Yeah.  Reverse the mod.

The filtering is set to remove the aliasing at those frequencies anticipated at max delay.  By going beyond that delay, you've basically exceeded what the filtering can cope with.  If it was a thru-hole device, maybe you could swap a few values and push things further, but looking at that board, the easier thing to do is just go back to the beginning.  Sorry.