I have a cheap bluetooth audio module (with no documentation) that outputs a signal greater than line-level. It was probably designed to be connected directly to small speakers, since the ground on the output signal is floating.
I'm trying to connect it (as line-level) to the input of a more powerful amplifier. I assume that a potentiometer is a reasonable way to adjust the signal level, but should I put it before or after the isolation?
In other words, should I do it like this:
Or like this:
Or some other way entirely? Assuming that I'm on the right track, what value of potentiometer should I be using?