Can one hear a switching power supply?

[twu]

I am DIYing a headphone amp with a LDO regulator which has lower PSRR than regular regulators, can it effectively filter out the broadband noise generated by the switching P/S?

 

[palstanturhin]

What noise?
Can you hear ultra sonic?
If you can hear the SMPS, you must have something seriously wrong with your circuit.

 

[jcdrisc]

I dont see why a headphone amp would make a switching ps economical to use.
Yes you CAN hear a SPS. I have an LED globe which makes so much EMI (either conducted or radiated) it make AM radio reception practically impossible.
Its a little discussed topic but makes the argument for retaining incandescent globes acceptable IMHO.

 

[canvas]

I am DIYing a headphone amp with a LDO regulator which has lower PSRR than regular regulators, can it effectively filter out the broadband noise generated by the switching P/S?

I think LDO will help, but not much. I posted similar question before, I remember the answer is to use LC or beads after the LDO.

 

[marce]

If it is done right NO.

Yes you CAN hear a SPS. I have an LED globe which makes so much EMI (either conducted or radiated) it make AM radio reception practically impossible.
Its a little discussed topic but makes the argument for retaining incandescent globes acceptable IMHO.

I presume this is a little chhepp thing, that by the sounds of it has not been through any EMC testing, so you cannot use it as a global example of SMPS and SMPS designs.
I have done a board with two SMPS's inthe actual headphone earshell, with some analogue circuitry, it is silent.

 

[JMFahey]

Can one hear a switching power supply?

Of course you can.
As an example, I can hear TV flybacks and most flash units.
By the way, the two earliest and most used SMPS over the whole Earth surface.

 

[SY]

Of course you can.
As an example, I can hear TV flybacks...

Back in the '60s and '70s, those drove me crazy. I hated the noise. I can't hear them any more, so my assumption is that they've improved the technology.

 

[Jay]

it is silent.

I believe it takes experienced listeners to "hear" SMPS problems. In my experience, many times I can "see" the problem only after direct comparison with conventional power supply.

Lately I wonder, why my laptop sound is so terrible (I mean really bad). May be if the power supply is conventional it wouldn't be that bad.

 

[Kindhornman]

Sy,
I often wonder while I am sitting at this computer is it tinnitus or do I really hear a high frequency background noise from the computer fan? I guess I can just shut it off and see!

 

[marce]

As an example, I can hear TV flybacks and most flash units.
By the way, the two earliest and most used SMPS over the whole Earth surface.

Not the best examples, as you've said the earliest. TV's not that many CRTs these days, and you wouldn't use the PSU out of a flash for audio.
Done correctly SMPS's are quiet in the real world and are in numerous products, but I forget they are the devils design
Oh my new flashguns are silent, no whine when they are re-charging! Must be broken

 

[marce]

Jay, putting a scope in a few places would give you an ibdication of the noise present etc, it could be a bad sound card or somthing else, what people keep forgetting with computers and high speed switching digital circuits is the switching noise, and having a linear PSU is not going to change that.

 

[Soldermizer]

For the hard core, there is always the battery...

 

[pdul]

A lot of noise in a battery, though a different kind

 

[Kindhornman]

Add in a charging system to a battery operated device and you are full circle back to where you began. A battery is a poor solution for most things besides maybe a portable headphone amp running on very low power requirements.

 

[marce]

And a battery powering a lap top will have SMPS's after it.

 

[kouiky]

This might not be quite the answer you were looking for, but yes I can hear a switching power supply from some distance. What I hear are the subharmonics in the 15-20kHz range coming from the physical power supply itself. Internet routers, iPod usb chargers, certain TV sets and DVD players are the worst offenders, with routers being so bad I have to close them in another room. I had a Power over ethernet system in 2011 and it was painful.

 

[marce]

Tinitus
Its a bit of a generalisation, do all SMPS's produce sub harmonics in that region, and if you can hear it you can record it, that would be interesting to see...

 

[kouiky]

I don't have tinitus, my hearing threshold is 0dB from 4-8kHz which was regarded as very sensitive. The switch mode psu in my router is loud enough to record at a distance and has to be in a room away from me. Thats a good idea, I should record these things.

 

[marce]

That is sensetive, one of my sons hearing is quite bad, and in that region, his is 20-60dB down in that region, so over the years I've learnt a lot about speach (he had speach therapy for over 10 years). Do voices sound over sibliant.
What worries me is that noisy SPMS's are generaly badly designed and EMC transmitters, and routers are one of the most competetive markets, so I know it is one area where cost cutting is rife.
Communications over power wont help, it is basicly EMC pollution and being on the mains can get into all sorts of equipement.
The reason why i mentioned tinitus, is that I suffer from it and when it kicks in certain frequecies seem that extreme they hurt, luckily I seem to have it under control most of the time.
What make is your router.
New multiphase spread spectrum SMPS's are much better than the older style single transformer or inductor versions, but again it comes down to cost, though as you can use smaller SMD magnetics the cost difference is not as bad as it might be. But they are only now filtering down in to consumer and commercial designs, but they are critical in their layout and effectivly you have x number of controllers plus discrete components, then the spread spectrum controller and the muliphase clock generator, good fun to do.

 

[Kindhornman]

Koiky,
I never thought of the router giving off noise but every time I sit at the computer I do hear a lot of high frequency noise and it does bother me when I tune into it, very distracting really.