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:
simulate this circuit – Schematic created using CircuitLab
Or like this:
Or some other way entirely? Assuming that I'm on the right track, what value of potentiometer should I be using?
Best Answer
Drive the transformer from a low impedance.
The source impedance and the transformer's primary inductance form an R-L high pass filter which determines the LF rolloff of the circuit.
So with the attenuator ahead of the transformer it'll be all about the treble ... no bass.