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In Reply to: RE: Ferrite/cap filter on the P24: next best thing too a full linear cMP setup? (interim report) posted by hfavandepas on July 07, 2011 at 02:09:29
Hi Mark
I've read your thread with great interest.
Effect of a pgreek filter is reasonable but your realization is just a bit complex for me, my PC is plentiful of cables yet so I've some difficult to put in an extension P24 cable with a lot of Ferrite rings plus capacitors.
So I ask you this question:
have you tried a pgreek filter only on the couple of cable that feeds the pico psu? Following the "garbage in/garbage out" philosophy it could be a simpler solution? Can you try this one against your solution and report the results?
I'm very curious about it, maybe could be not the best solution at all but I'm sure that could be a simpler solution, if effective.
Thanks a lot for your interesting work
Daniele
Follow Ups:
Hi Daniele,
What is a ‘pgreek filter’? I never heard of it.
Also google-ing came up with no results.
What is it?
* About the Pico and the switching noise it (probably) produces.
I’ve red that a Pico is also a switching PSU and thus ‘chops’ 12V DC into 5V DC and 3.3V DC.
So being also a switching PSU, the Pico probably also produces unwanted switching noise.
( I’m not completely sure about this. But I guess it must be)
I can understand your view and philosophy on the "garbage in/garbage out" principle.
I agree with: what you clean before the Pico, you don’t have too clean after the Pico.
But since the Pico probably is adding a lot of noisy garbage by itself, filtering AFTER the Pico can’t be left out.
Most likely this is why replacing the Antec Earthwatt ATX -> P24 with a Linear PSU -> Pico -> P24 in my setup, only gave very little and subtle sound quality improvement.
(Again: I’m not sure about this. But I guess this must be the cause)
Constructing and building a high quality linear PSU myself too power the P24 is far beyond my DIY skills. But constructing a L-section filter or an π-section filter through use of ferrites + caps is within reach of my DIY skills. Actually it is rather easy. Anyone can do it. No special skills needed.
And (very!) much to my surprise, the results are nothing less than truly spectacular.
Especially when compared too all previous PSU improvements I’ve already done in my setup.
Studying the picture of the inside of your Zahlman cMP setup I’m very curious what the schematic is of the DC filters I see being used before the Pico and also on the right side of the case.
Mark
fully optimized cMP2 PC -> ESI Juli@ -> Van den Hul Optocoupler MkII-> Lavry Black DA10 -> XLR Mogami Gold -> Klein & Hummel O300
π filter=pgreek filter . It's my trivial translaction, I cannot find the right symbol :-).
About picoPSU is it a switching or not? It could be possible, or better probably, but in my system I've noticed a great difference in SQ changing from Seasonic to Peaktech to my diy linear PSU, being last one the better.
So i think it could be possible that the disturbance of picoPSU could be amplified by a "dirty" 12V current so if you ameliorate the current quality before pico could ameliorate his 5V and 3.3V currents.This was true in my system.
Beyond the regular capacitor in each PSU of my linear PSU proposal, I've saved only the Silmic run (6000 mF) in the P4 line of my previous setting.
My "noble" Belleson superregulator based PSU units (2 for the soundboard, 1 for pico and last one for P4) are assembled on a single board inside an old ATX PSU case.
The others board you can see on the picture are the 12V and 5V PSU feeding SSD, HDD,Fans, USB and CD-ROM.
No filters on picoPSU line at all.
Hi Daniele,
Sorry I mistakenly studied the picture posted by nagual192 as being your setup. On nagual192’s picture I see a big wired choke on the 12V DC power line that powers the Pico (mounted on a yellow board which is resting on the cpu cooler). I guess that choke is there too filter power too the Pico. So I was curious which frequencies nagual192 targets and how he does the math on preventing the choke from ringing.
This time I studied your pictures.
Do you use your Asus Xonar card as a DAC or as a digital interface too an external DAC?
I guess optimizing power for when the Xonar is used as a DAC, will be extremely challenging and difficult. Slightest micro levels of ripple & noise in power and/or in ground (0 Volt) produced by the MoBo will impact in the DA conversion process. Optimizing this situation is much too difficult for my level of knowledge and skills.
Until some years ago I used a Lynx L22 soundcard but I finally settled on an external DAC.
And only recently I decided too follow Cic’s advice too 100% isolate the external DAC from the computer through use of an (good quality) optical connection.
This way my power supply modifications now only impact the digital processing on the mobo and on the digital inferface. I don’t have too worry any longer on how these modifications will also impact the digital too analog conversion process.
In both situations (Xonar used as a DAC or used as a digital interface) it is important too know if a Pico produces noise on the 12, 5 and 3.3 output. If the Pico is producing noise, than the clean, high quality power coming from the exquise Bellesons, is spoiled by the Pico. Too direct filter actions where they are most effective, it’s important too know if the Pico spoils your carefully generated clean power.
On the other hand it is quite simple too try out your suggestion.
Here’s what springs too mind on what I can do.
* For the experiment I will use the pico PW-200-M.
It is said that this pico regulates all 3 DC lines. (12, 5 and 3.3)
* Use of ferrites
I will put ferrites beads on the 12 DC power line (coming from a linear) too the pico pw-200-M
I will try too realize at least 1000 ohms
I think I can do this through putting 3 or 4 ferrites in series with each a decreasing numbers of turns.
See http://www.audiosystemsgroup.com/publish.htm why.
* Use of Caps
I will put Oscon caps in front and after the ferrites to create a л filter. 47 uf after and some 300 uF before the ferrites.
* Results.
Give some 2 weeks too come up with first impressions, as I don’t know how much time I will want to spend on critical listening sessions indoor.
Besides a very nice spring, until now we had lousy summer weather in The Netherlands. But when weather changes, I will be out with friends in the park in the evening. Enjoying BBQ and drinks. When living in the northern part of Europe, one has too grab all chances too enjoy the summer when weather is good. ;-)
Mark
Hi Mark
first I agree with you about BBQ in summer time. I live in Sardinia, I'm bored by sun and summer, and just now I were dreaming some cold: here we have 40°C! So good BBQ in the north country!
I use only the analog output of the Essence and after my last upgrade ( sandy bridge CPU+MoBo and Belleson PSU) I think that picoPsu (150 and 160XT, I've on my 2 cMP2) or wears only simple regulators for 5V and 3,3V or is really the best Switching PSU in the world, IMHO!
SQ of my system is now astounding, background silence is incredible, each instrument rises from nothing, with music cue ( and decay too) so natural and dynamic that seems impossible to me they could come from a digital source. Sandy Bridge is a very effective upgrade in the war against electric rumor and picoPSU is a fantastic ally.
All this is too difficult to acheive from a switching PSU, and I must repeat that, in my experience, linear PSU are'nt all the same: my peaktech sounds worse than the Belleson, surely when feeds the PicoPSU. So Is it the pico sensible to the current quaity? My response is yes.
I'm starting to use ferrite rings. So I'll wait to yours next "cold" tests, in the meantime I carry on with mine.
Buon appetito e salute! Enjoy
Daniele
Hi Daniele,
Last 2 weeks the lousy summer weather even got worse in The Netherlands. In some places it rained for 20 hours on a row. According our national weather forecast service (KNMI) this hasn’t happened since 1954. : -(
Despite this weather, I did not spend much time on the project on filtering the power supply (filtering the 12V DC power input) too the Pico PW-200-M.
Although I made some progress. I did choose and order the parts needed for a variety of filter setups. I not only want to do some experiments on filtering the input side (as you requested), but I also want too do filter experiments on the output side of the Pico. As it is cleaning the output of the Pico, that I’m most interested in.
Last week I did some research on the WWW too see if I could discover what switching frequency is used by the Pico. I discovered that both Pico’s in my setup (the PW-200-M and the 160-XT) use the LM2642 Two-Phase Synchronous Step-Down Switching Controller (with a magnifying glass one can see the part number on the controller). This controller is manufactured by National Semiconducter.
See: http://www.national.com/ds/LM/LM2642.pdf
This LM2642 chip consists of two current mode synchronous buck regulator controllers with a switching frequency of 300kHz. This 300Khz switching frequency will probably result in widely scattered band of noise on the Pico outputs. As I don’t have a scope, I don’t know how well this noise is filtered, but putting an π-section filter made of ferrites + caps on the pico output, resulted in a very nice sound quality improvement. So I think the output of the Pico is not filtered much. Probably only so much filtering is done as is needed too comply with EMI regulations. Since an π-section filter from ferrites + caps only ‘bites off’ noise effectively in the upper regions (1 mHz - 300 mHz) of the widely scattered hash of 300 kHz switching noise, I’m also looking for ways too filter the HF noise from 100 kHz too 1 mHz.
Since ferrites are not effective in this region, I will need too use filters made of inductors + caps. So I probably will end up with some sort of 2-stage filter. First stage for filtering the 100 kHz too 1 mHz region with a combination of inductors + caps. The second stage (1 mHz - 300 mHz) with a combination of ferrites + caps.
So Right now I’m searching the web for idea’s on how to filter SMPS noise with a combination of chokes/coils + caps and what value’s too use for L and C.
I also want too experiment with such a filter design on the input and output of the Pico.
See: http://www.hamill.co.uk/pdfs/azrtatad.pdf
Some inmate on the diyaudio forum pointed too this.
* on the P4, a standard 230 V AC power line filter, combined with a π-section filter from ferrites + caps gave a very nice pop sound quality!
Just out of curiosity, I threw a standard EMC- 230 V AC Power Line Filter for 1-Phase Systems (2 x 10mH + 2x 0.015 uF + 1x 2.2 nF) into the 12 V DC power line too the P4. See: Ontstoringsfilter 1 A (Conrad Electronic) .
I already use an π-section filter (2x 100uF + 2 ferrites (with 4 turns) + 2x 47uF) on the P4 12 V DC power line coming from the Velleman Lineair PSU.
I put the standard 230V AC power line filter before the π-section filter.
It made a real nice SQ improvement !
Every time I’m still surprised on what a little noise –cleaning can do for sound quality in a cMP setup. So I can’t wait too start experimenting with various combinations L + C filters. I expect the ordered parts too arrive at the end of this week.
So coming weeks/months I will be busy experimenting with various concepts and various combinations of L + C filters on the input and output of the Pico’s in my setup.
I will start on the input side of the pico.
As soon I have have results I let you know, but this surely will take another few weeks.
Mark
Hi Mark
Great job and very good questions to ask.
I'll wait for your experiences, you are a prodigy of learning!
Daniele
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