I'm putting together a guitar pedal for splitting the signal to two different amps. One of the features I want to put in is a 'ground-lift'; isolating the signal to avoid ground loops between the two different loads.
The traditional way to do that is with the following simple method: a suitable transformer…
simulate this circuit – Schematic created using CircuitLab
However, I don't know how much I trust the transformer to not colour the signal, and I don't mind doing a bit of over-engineering to avoid using one.
I'm more trusting of op-amps and AC-coupling using series capacitors, so I figured the following might be a good workaround:
The load-side of the AC-coupling capacitor is biased by an supply isolated from the source and fed into a buffer.
Is there any reason this wouldn't work the way I think it would?
Best Answer
You cannot expect that circuit to work because the guitar signal ground connection has to connect into the op-amp circuit ground node and without that connection you are just going to get noise. The impact of this is that you are not therefore isolating the two receiver circuits as you previously wished would happen.
Try using fully differential amplifiers such as Instrumentattion Amplifiers but, don't expect miracles - IA's can isolate quite well but only within the voltage range of their respective power rails. In other words, if receive circuit A is offset from receive circuit B by a few volts to a few tens of volts you will hit problems.
True galvanic isolation (up to several hundred volts) is acheivable by using magnetics and therefore transformers.