I have a situation where I need to stack one circuit board via spacers on top of another due to space restriction. They will roughly be 25mm apart do you think I should use a shield between the two circuits as well as it is for audio use.
I was thinking of maybe using blank circuit board material with the copper as the shield & grounding it.
Unless the circuit boards have some high impedance signal lines it's highly unlikely that you will get any noticeable crosstalk between the two boards.
Well, it's spacer installed and easily and completely reversible both ways so you aren't losing anything by just comparing what you get with and without it.