Why do some PSUs make a high pitched squeal / buzz / whine?

Is it always the transformer which makes the noise or can the capacitors also make the noise?

I've heard it referred to as "Capacitor Squeal" before, but then people say it's actually the transformer coils causing harmonic resonance because they're loose or the because the frequency is off.

Could a failing cap alter frequency & create harmonic resonance in a transformer?

If this is the case why do some PSUs that are brand new make squealing noises?

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Re: Cheap vs expensive HDMI cables

Hi, I think while it is true that it is very hard to tell a difference between a bad HDMI cable and a good one, there are differences.

HDMI is not lossless just because it's digital, which is what many people think. It is susceptible to interference & signal degradation (especially by RF & loose impedance control). HDMI has very tight tolerances which are usually not met by the cheap cables. All of this is exacerbated the longer the cable gets.

Determining a good cable from a bad cable doesn't have much to do with...

Re: New Members - please post your introductions here

Hi everyone. I'm tom from northern california and I'm hoping to learn more about PSU design.