Coil whine question

[IntelGuy1]

Hi guys,

I have a XFX 650 PRO Series and my PC is connected to a APC UPS (Back-UPS ES 700). II realized that when I'm using the UPS battery my PSU starts making a buzzing sound (coil whine). Is that normal, or my UPS is broken?

Thanks.

 

[InvalidError]

It is most likely normal: if the ES is like the bulk of affordable UPS out there, it outputs a "stepped approximation sine wave" and the buzzing you are hearing is the APFC coil vibrating from magnetostriction as the APFC controller attempts to keep up with the non-sinusoidal waveform.

Although possibly annoying, it should be harmless.

 

[IntelGuy1]

The UPS makes some coild whine too when using the battery (the PSU too).

And this extends to every other component. For example, if I have a microphone connected to the mic jack in the back of the PC, people can hear the interference.

So it's normal?

 

[InvalidError]

If we are talking about when you are plugged into the UPS and running off of the battery (power outage/brownout), then yes. The PSU dealing with the different waveform introduces noise at higher frequencies than normal and filters that are in place to cope with the normal PSU noise may not be as effective at cutting those other frequencies out. That noise gets out and picked up by everything else, especially low-level inputs such as analog microphones.

 

[IntelGuy1]

Many Thanks for your explanations.

Yeah It only happens when I'm using the battery. The only thing that happens when I'm not using the UPS battery, is that when I'm downloading something at high speeds, if I'm using the audio jack in the back of the PC, I can hear some noise in the headphones (but very very low), like the "coil whine" noise. I think it's normal too right, since onboard sound normally isn't the best option? (The audio jack and the LAN port are very close, so maybe the audio jack is picking some sort of interference?). Anyway, I don't use the onboard sound anymore, since my headphones are using a little USB "soundcard".

Also, I can hear some coil noise coming from the graphics card when playing games, but nothing too high if the case is closed I can't hear it.

And yeah, the microphone interference (using the back mic jack) and the coil whine coming from the PSU and UPS only happens when the UPS is using the battery (for example, during a blackout).

So, all of this is completely normal, right?

Many thanks for your explanations

 

[InvalidError]

Some amount of 'coil noise' is nearly inevitable. Also, some multi-layer ceramic capacitors have piezoelectric properties - they make noise when they receive high ripple current. Those could be responsible for some of your directly audible noise.

 

[IntelGuy1]

So, everything I described in my previous post is normal, right?

 

[InvalidError]

Probably. You'd have to ask the manufacturers for confirmation.

Basically, it goes like this: PSU receives odd-looking power from the UPS and this causes the PSU to put out a little more irregular noise on the voltage rails. Local voltage regulators on the GPU, motherboard and other places pick up that noise and that causes their own switching supplies to generate additional noise. What you end up hearing is the combination of all the noise sources and their mixing byproducts.

If you want to get rid of that noise, you may want to try a "pure sine wave" UPS but those tend to be considerably more expensive and less efficient.