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My experience so far with ferrite/cap filters on the P24 and P4

Hi Theo,

Good too hear you found a new mobo and have it up and running again.

I’m not sure if I correctly understand your questions (and thoughts behind the questions) too provide a useful answer. Some things puzzle me.

> If you can count the caps in the atx power supply all you need are the ferrites over the 5 v and ground lines etc and then the cap in the p24 connector on the mobo.<

* I don’t know if you can assume that the caps inside the ATX PSU will act as being a part of the 3 order filter on the P24 line. May be it works this way, may be it doesn’t. I just don’t know.
So just too be sure, I don’t consider the caps inside the ATX too be a part of the 3 order filter. So I use xxtra caps with the right values too create a 3 order filter. Since we are targeting (V)HF, caps with low ESR and excellent VHF characteristics are important.

> all you need are the ferrites over the 5 v and ground lines etc <
Why do you think this? I see 2 problems with this.

* (V)HF AC pollution travels from the ATX onto the MoBo on all DC plus voltage P24 lines.
You may prevent (V)HF AC pollution travelling on the +5 voltage onto the MoBo, but (V)HF polution than will simply travel onto the MoBo through the other positive DC voltage lines (+ 12, -12, +3,3, 5V stand-by, Power-OK) and return through the combined ground too the ATX.
A clean and steady ground is equally important. ‘Zero’ and ‘Ones’ are recognized as a voltage difference compared too ground. So both supply voltage and ground have too be ripple free. Both are of equal importance. Also the clocks on MoBo and Soundcard are very sensitive too (V)HF polution on supply and ground.
It is even important too prevent (V)HF traveling through the SSD ontoo the MoBo.
I also use a 3 order filter on the power lines too the SSD. And also this give a little SQ improvement.
See photo.
Van on filtering, demping, ect

* How do you avoid DC bias in the ferrites (saturation of the ferrites)? The magnetic flux produced by DC plus and DC minus currents through the ferrite have too be equal too avoid saturation of the ferrites through a DC bias.
It’s not clear too me how you know that the magnetic flux produced by the % volt DC + and DC - minus return currents on the black wires will cancel out each other in the ferrite. The ferrites will saturate and loose there effect if no attention is paid too DC bias. Currents on the P24 are high. See my P24 measurements. Almost 1 amp for the combined +5 volt lines. Most ferrites saturate when there is more than 0.4 amps applied on them. I think one can easily go wrong when just grabbing the 5 volt lines and a some black ones.

> Or you can use a p24 extension to push caps in the extension connector, ferrites on the extension line and caps pushed into the connector into the mobo. Which way did you do it? <

Back in may 2011 I just pushed caps into the connectors of the MoBo and/or connectors on the P24 extension cable. I did that too quickly verify if a 2nd or 3thrd order with ferrites + caps would have some effect.
By now I have soldered the caps onto the P24 extension cable connector. I cut away the plastic on the side of the P24 connector on each side, this way it's easily solder the caps onto the small metal parts inside the plastic connector. See photo.
Van on filtering, demping, ect

> Now on my new mobo I have caps into the p24 connector for the 5 and 12 volt lines, ferrites on the wires...very little improvement <

With only a few ferrites clamped on the P24 In my situation there also was very, very little improvement. As I posted before at least 6 or 7 ferrites on ALL P24 wires are needed to make SQ improvement that is worth the trouble. But one only gets a real nice significant (!) sound quality improvement when creating a 3 order filter through adding caps in front and after the ferrites. I used 7 ferrites which clamp around ALL P24 wires (thus no DC bias) See picture.
Van on filtering, demping, ect

I tried this cap-ferrite-cap filter on the Antec Earthwatts ATX and on the 2 Pico’s I use. In all 3 situations I got the same sound quality improvement. Attention: same amount means: the pico 160-xt with P24 filter still sounds better with the filter than the Antec with the filter.

So my experience with using ferrites so far is:
* ALL power lines coming from a switching PSU need filtering
probably all lines coming from a switching PSU are polluted with (V)HF noise. All these lines need filtering to prevent (V)HF travelling ontoo the MoBo and back through the ground too the switchting PSU.

* As the author on the www.audiosystemsgroup.com pointed in his white papers on the use of ferrites : just a few ferrites will have no effect. You need at least 7 too 8 too create enough impedance too get past the threshold effect (see the white papers)

* A very nice sound quality improvement is realised when also caps are used too create a 2nd or 3thrd order filter

But a 3thrd order filter with ferrites is only effective from 1mHz and up. I also want too filter the 300 kHz switching noise (and it’s harmonics.) So I also need something too filter these frequencies.
So right now I’m experimenting with 10mH ferrite chokes + caps on the P4 lines and the 12V power line too the Pico 160-XT. And whow (!) this also makes a very nice SQ improvement. I simply use the ferrite chokes which are inside these little noise filters. See picture. They are very cheap 3,50 euro’s. And I can easily solder P4 connectors and caps too them.
Van on filtering, demping, ect

It sounds really good. Thankx too audiodan I got this idea. More too come on these extra filters. I need more time for experiments and listening.


Edits: 08/10/11
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