My charger provided with Cosmo (EU) emits high pitch whine if not under load. (How high? It's below threshold to be picked up by my cheap Logitech mic, but I'd say somewhere in 12-14 kHz range - near upper limit of human hearing)
Has anyone else noticed this? Essentially: Am I the only one with a charger that has whining capacitors?
I know it's not exactly dangerous or anything, and I guess it's a way to remind me to unplug it. However, if this is not a "standard" feature then I'd rather get a replacement. If everyone else has the same issue then I guess I just live with it and maybe get another charger.
TL;DR: It's there in mine too, though perhaps not as loud as in yours.
I'm still using the Gemini charger (reasonably just an older batch of the same thing). I have to hold it directly to my middle-aged ear to hear the whine, but it's there, as it, in my experience, tends to be in most of the small switched power supplies I've put an ear to (no, I don't habitually listen to them, but my spouse spontaneously hears them very well, so I've double checked a couple).
Anyway, with the help of a studio mic and Audacity, I found (in my particular charger) a fundamental at around 2.117kHz and its harmonics (4.235, 6.355, 8.475, 10.59, 12.71, 14.83, 16.94, 19.07, 23.30kHz) up to the Nyquist–Shannon limit of my 48kHz sample rate. I don't have a response curve for the mic beyond 20k, and I suppose I'm already well beyond what you asked for.
My tip would be to, if possible, compare your particular Cosmo charger to another unit for either the Gemini or Cosmo (they should be the same thing) to see if you just happens to have a unusually loud one, or if you just have better ears than me. I could provide a recording of mine, but I doubt it would be very useful to you. It's just a hissy beep, as expected.
