Any Diy PC Power Noise filters ?

[nigelwright7557]

Originally Posted by marce

A few notes on spread spectrum SMPS's,.

I use spread spectrum pulses on a flyback SMPS and the transformer plays some great tunes on power down.
It uses 4 different pulse widths depending power demand.

[marce]

Yes they can sing.
One advantage of multiphase is you can use cheeper and smaller magnetics, often off the shelf Wurth parts or similar.
Here is a link to another thread that has some relevant info in the links regarding keeping the noise down, filtering etc:
Switcher EMC design

[Eudyptes]

Other SoTM products that supposedly filter & solve/reduce a PC noise problem is the SoTM USB PCI/PCI-E cards.

SOtM - Ultimate High Performance Audio

SOtM - Ultimate High Performance Audio

These things are more than twice the price of a decent sound card in the UK and for all I know are just more audiophile bs.

Is there any merit in these products? I'd particularly like to hear marce's and phofman's view.

[zibra]

What do you think about this product?:

APEXI Power Filter Card for Computer Audio Enhancement for PCI and PCI E Slots | eBay

[marce]

Not a lot. Filtering has to be done in the right place, or the noise is out there. And whilst SMPS docontribute some noise to a digital system, but the system switching also conributes a lot on noise. Also the supplies on PCI will more than likely be routed down to a voltage plane, so sittibng the filter in the middle of a plane wont do an awful lot.
The Sota cards, again may have some effect, but again I think they are taking advantage of the fear of noise, and as there marketing says...I have highlighted the relevant word, could.

For this purpose, tX-USBexp has noise filter circuit which could reduce the noises inside of PC affect to USB audio devices, and also use Ultralow noise voltage circuits and ultra-low-jitter oscillator circuit to reduce the noises causing the product itself.

Basicly if the noise reduction isn't built in to a digital design through proper design strategies then these are only like putting a sticking plaster on a gaping wound (IMO)

[JLOP]

Hi Marce

You are of course right, better design is superior to remedies. But how to select properly designed components for Pc based music centers ? No or few data is available on that issue on datasheet ? How to manage it practically ?

BR
Jean-Louis

[marce]

A thread here is discussing motherboards:
Best Motherboard for Audio
I use logitech squeezboxes over wireless so have full galvonic isolation. PC components generaly will not publish noise figures, not a good marketing move, and also somewhat dependent on other parts of the system.

[crosswinter]

I found a great pci power noise filter "AXF-104 Pro"

[qusp]

whats great about it? what exactly will a bunch of normal quality polymer electrolytic caps do about smoothing a HF signal? it will at the same time depending on what its connected to, reduce the effectiveness of the regulation, so may actually make noise worse

[magnoman]

Regarding spread spectrum SMPS for audio:
First does spread spectrum include phase modulation (as opposed to frequency)?
It would appear to me that given a fair comparison (same number of converters near their sweet spot etc) the total radiated energy is the same, thus its just it's characteristic that can be changed from narrow peak to modulated multiple peaks.
Although possibly measuring better wouldn't any kind of frequency modulation potentially introduce components moving throughout the audio range?
Wouldn't it be better to synchronize switching frequencies with the sampling systems, such as the DAC's ? At least then aliasing shows up at dc and one can even adjust phase to minimize this dc effect?

Thanks
-Antonio