I'll appreciate if you can comment on my observations and if you think shielded power cords have any benefits around low level signal cables.
Thanks
I'm not Amir, but this largely boils down to "there are no benefits" for two reasons:
1. To keep it simple, if we continue Amir's circuit analogy, since the "shield" is metallic,
it will experience a small leakage current caused by capacitive coupling to the AC signal in the live wire inside the cable right next to it. In other words,
it will be playing the role of in the capacitor that Amir plays in his video with the unshielded cable. Because the person holding the instrument and the shield are basically at the same electric potential, there will not be a current through the tester caused by the shield, because voltage is necessary to cause current. Of course, nothing is perfect in the real world, and with extremely sensitive equipment, you can still be able to pick up some tiny current because not all of the EF saturates the shield, and a little bit will pass through it and again form a second, tinier capacitor in parallel with the first one. Using thicker conductors for the shield will prevent how much can ultimately pass through. There's probably also an even teeny-tinier third capacitor in series with the first one since the person might be a few microvolts off from ground, although this is basically undetectable.
2. None of this is relevant anyway because the induced current in the cable (which is insignificantly low in the unshielded cable) is easily washed out by the noise floor of actual electronics, which is the case in unshielded cables anyway, simply because of input impedance. The power supply's job is to keep separate the noise and distortion in the incoming power from the audio circuit, which is done well by competently designed electronics anyway.
Shielding can matter when running an unshielded cable carrying low-voltage audio signals, like output from a phono cartridge or from a microphone, but this is remedied by using shielding in
those cables. Remember that there is likely plenty of EF noise in the environment coming from other sources anyway, so a shielded power cable won't do much. Keep in mind that the cabling inside the wall isn't shielded in the first place...
Edit: here is
@John_Siau from Benchmark showing the effects of using star-quad cables for audio signals - this doesn't apply to capacitance so much as it does to inductance, but the latter is a bigger issue in audio anyway, and star-quad cable is an actual remedy to the problem. Like with all things, distance matters as well.
)
