I was thinking about using an external power supply for multiple pieces of analog audio gear. But it occurs to me that even if I use separate grounds for power and signal, because the wires would run alongside one another, changes in current on the power ground (from a power amplifier driving a 600 ohm load for example) would electromagnetically induce currents in the supposedly clean signal ground. Is this correct?

If yes, how can I model this in LTSpice? I assume it would just be two inductors coupled to some degree. Can someone explain roughly how to model EMI in long parallel wires?


One way to analyze wires is to use NEC (Numerical Electrical Code). There are quite a few frontends for NEC which make life easier, as it requires numerical input, and spews out a lot of numbers.

But it allows you to simulate wires of any shape and position, induce voltages and/or currents, and determine the impedance and voltages.

Have a look at this tutorial, or this nice article in QST in 4 parts (Part 1, part 2, part 3, part 4).


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