How much cross talk you are going to pick-up in a 1 or 2 metre headphone cable. Is it audible? Does it matter?
If you wired it wrongly then at higher audio frequencies you might get enough crosstalk to be noticeable. Anyway, as always, numbers are our friend.
Let us first estimate the inductance of a 2m cable. A closely spaced pair will typically have an RF characteristic impedance in the range 50-100 ohms. That means an inductance of around 0.3uH/m, so 0.6uH in all. At 20kHz this will have an impedance of 0.075R. Comparing this with a ruling impedance of, say, 30 ohms it is at the level of -52dB. The two sets of wires will not be 100% coupled, but nevertheless we can predict crosstalk around the -60dB level. OK, probably not an issue. However, correctly wiring the star quad cable will drop this further.
Let us first estimate the inductance of a 2m cable. A closely spaced pair will typically have an RF characteristic impedance in the range 50-100 ohms. That means an inductance of around 0.3uH/m, so 0.6uH in all. At 20kHz this will have an impedance of 0.075R. Comparing this with a ruling impedance of, say, 30 ohms it is at the level of -52dB. The two sets of wires will not be 100% coupled, but nevertheless we can predict crosstalk around the -60dB level. OK, probably not an issue. However, correctly wiring the star quad cable will drop this further.
O.K., but its only the load that is ~32 ohms, right? I would think most any headphone output's impedance would be quite a bit lower, reducing received EMI at least.
The only interference problem I've ever had with headphones was an occasional output that needed an RF choke -- on a busy street, a passing emergency vehicle radio would sneak in once in a while.
IMHO you may be over-thinking this, but best of luck anyway,
Rick
The only interference problem I've ever had with headphones was an occasional output that needed an RF choke -- on a busy street, a passing emergency vehicle radio would sneak in once in a while.
IMHO you may be over-thinking this, but best of luck anyway,
Rick
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