Interesting and fun facts (related to the above.) Or, "Jason puts on his professor's hat."
About a billion years ago, right after the earth cooled, or when I was still young, you used to be able to buy these things called "crystal radio sets." These were nothing much more than a loop of wire, a diode, and a variable capacitor. When Mike was young, substitute a real crystal and a cat's whisker to create an elementary solid state diode.
Plug the output of a crystal radio into an earphone, and you could tune in strong AM stations. Without any power. No batteries, no AC, nothing.
Read that again.
Now that your minds are blown (and you're thinking I'm actually 122 years old and have the secret to eternal semi-youth), you might as "why is that, and what the hell does it have to do with scratchy pots/weird noises/etc?"
Well, the reason a crystal radio can work without power is that it uses the power of the radio transmissions themselves, rectified with a simple diode. A diode can occur anytime there is conduction one way, and not another. This can happen spontaneously anywhere there is oxidation--corroded connectors, bad cables, etc. If you're using a headphone extension cable, the diode-like connection between oxidized metal can act as a rectifier. Coupled with a long length of wire, boom, you can pick up and rectify all sorts of noise. The same thing can happen in a pot, even in a good conductive-plastic one like we use in Magni. That's why we ask you to rotate it a few times to see if it will clear itself out. It may, and it may not.
Now, you may not listen to AM radio, or even care about radio at all, but ask yourself: how close am I to the closest AM transmitter? FM transmitter? Wireless phone? Cellphone? WiFi router? Bluetooth device? Garage door opener? Roku remote? Because all of those emit RF into the air, and all of them can be rectified with a simple diode.
Hell, there's so much RF running around, they've demonstrated how it can be used to self-power small gadgets. Think about that a bit, too. We live in an RF-rich environment these days, much more so than ever before.
Now, do you wonder why there are so many weird whines/whistles/pops/noises in modern electronics?