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In Reply to: RE: * NEW * Alternative approach to CPU (P4) power supply posted by Bertel on November 15, 2009 at 08:56:02
Good points.
I'm looking to change our "base" design to 2 ATXs instead of 1 ATX and a few GDs. This way we reduce wiring needed and don't need any "Y" splitters. Also, we don't suffer from PS limitations (compared to GD where you must be under 2A). However, if you already use a dedicated PS for P4, this change will not be useful and should be ignored.
What triggered this design was reports on how sound improved when powering P4 separately. Are we getting improvement from better PS to CPU or is it that we have largely removed its "PS modulation" & ground effects that negatively impacts the critical audio chain (via P24)? My sense is the latter. This question grew larger with hfavandepas' 12V linear+pico implementation. Given that the pico also suffers from ATX like ripple noise, a normal ATX should do. Pico 150XT which passes linear 12V input untouched will likely be better.
My understanding of how P4 is used in the GB mobo suggests its limited to CPU and fans. There may be other components and if they were critical, sound quality would be worse. It's not.
It may seem strange that a "dirty" P4 works so well given that the CPU is tightly coupled to the audio chain. The reason is largely to do with soundcards interacting indirectly with the CPU. For audio streaming, it only sees RAM via the southbridge chipset. Another key factor is how well the CPU / Northbridge interface is significantly de-stressed. This seems to make the twin ATX package work very well.
Follow Ups:
cics,for the recommended "base" setup this is certainly good to start with, especially given your explanation on how little influence the CPU has during audio streaming (I wasn't aware of this and that the focus here is mainly on the southbridge chipset - would be great if we could improve its working environment, e.g. by adding caps to its voltage pins etc., but that's a bit tricky I suppose...).
Over the course of this year I have improved my system also hardware-wise step by step to a point where I use only batteries plus caps during playback, separate ones for P4 as well as P24 (no picoPSU or similar switching PSUs but battery power separately for every voltage rail) as well as for Juli@ and Buffalo DAC. Optimizing on P4 and P24 always brought little but pleasant improvements step by step - but I have to state very clearly that IMHO almost dramatic improvements can be achieved when further focusing on Juli@ (as we know already from the mods Alfred/sonics and Greg/Gstew made).
Powering Juli@ externally is a HUGE step as we know already for some time. There are two Juli@ versions, one only needs additional 5V for sample rates 176 and 192, the other at all SRs for clock timing. As Greg/Gstew has already pointed out cutting the PCI traces for all voltage input ensures that only the clean external voltages are present on Juli@, separating it even further from detrimental external influence.
In the past couple of days I had to learn how crucial even smallest variations are when you power Juli@ externally - it's a bit like open heart surgery, there's no more regulators and smoothing caps and different circuits having their influences, but you directly without any filters inject current in Juli@'s circuits, and parameters like voltage levels (3.25V instead of the nominal 3.33V as well as 4.85V instead of 5.00V seem to work best), output impedance of the current source, purity of power supplied etc. IMHO have a MASSIVE influence on sonics and sound quality - in my setup even small changes to these parameters had a much more noticeable and revealing influence on overall sonics than any other improvements mentioned above. I'm still in the process of testing and identifying and pinning down, as Greg/Gstew had mentioned before shunt regulators probably will be an excellent choice for powering Juli@ directly, that's next, will report as soon as I get there and have reliable and tested results :-)
Sorry for rambling, just wanted to put the relevance and effect of the various mods into the overall picture, at least as I see it ;-)
Best,
Robert
Edits: 11/15/09
Hi Bertel,
Since you PRACTICE (!) a lot of power supply improvements to the cMP2 setup, you might be able to shed some light on to the following question.
I would like to know the degree in (potential) sound quality improvement between: supply chain 2 and supply chain 3:
- Supply chain 1: original chain.
source: 5 volt ‘high quality power’ -> P24 5Volt input connector on MoBo -> MoBo to PCI -> circuit board of soundcard -> ‘sink’ components on soundcard (who need the supplied 5V)
- Supply chain 2: MoBo is bypassed.
source: 5 volt ‘high quality power’ -> circuit board of soundcard -> ‘sink’ components on soundcard (who need the supplied 5V).
- Supply chain 3: MoBo + (parts of) circuit board of soundcard are bypassed.
source: 5 volt ‘high quality power’ -> ‘sink’ components on soundcard (who need the supplied 5V)
I realise that it’s very hard to communicate about sound quality improvements in words, but I still would like too get an impression by description, because it’s better than no communication at all. May be it’s helpful to rank sound quality improvements as I (subjectively) experience them in my setup. I would scale/index them very ROUGHLY like this:
- linear PSU on P4: +90
- Low resistance wire (6AWG or similar) from linear PSU to both P4 and picoPSU/P24: +90 (*)
- Linear PSU on 12 volt rail on P24 through (specific) picoPSU model: +30
- smoothing caps on a switching ATX PSU: +20
- combined optimizations: XP, Kernel and BIOS: +15 <-> + 20
- various releases of cPlay - 2 <-> +4
Is it possible to say where in the above ranking roughly would be:
- by passing the MoBo (chain 2) with ‘high quality power’ from a linear PSU?
I don’t like soldering to my Lynx AES16 or Lynx L22 sound card. But I think I can manage to bypass the MoBo (with help of a PCI riser-card or something. don’t know yet)
(*)
Untill now no other inmates tried out or gave feedback on changing 18AWG wire between a linear PSU and the P4 / P24 for a wire type with much less resistance (6AWG or similar).
Probably many inmates consider me being an honoured member of ‘the ministry of silly tweaks’. :-) But I’m far from that. If I hadn’t tried it myself, I would be very much in favour of Ryelands comments on it. Http://db.audioasylum.com/cgi/m.mpl?forum=pcaudio&n=54333&highlight=sums+Ryelands&r=
But because you suggested I decided to give it a try. So thank you for the suggestion, because it made (very much too my surprise !! ) a very big improvement.
fully AOB optimized cMP2 PC -> Lynx AES16 -> XLR AES/EBU -> Lavry Black DA10 -> XLR Mogami Gold -> Klein & Hummel O300
H,
I thought I had replied about your 6g wire tweak, but cant find the post.
Are you sure it is not the braiding that helps in sound more than the wire gauge??
Thank you for responding.
I really don’t have a clou of why it does sound much better. Most likely I corrected – without knowing- some mismatch or sub-optimal situation in my setup. (re-connected wires the right way, re-plugged all the gear in the correct way, ect)
I strongly favour Reylands post on this. http://db.audioasylum.com/cgi/m.mpl?forum=pcaudio&n=54333&highlight=sums+Ryelands&r=
But I still would like to know if I accidentally corrected something in my setup for the better without knowing. That’s why I decided to ask other inmates on the AA-forum if they can repeat this and report their findings back to the forum (too try this, one doesn’t need much soldering skills).
I was hoping that a few inmates would try this in their setup. If they would report that it didn’t made any difference in Sound Quality for the better in their setup, than I know for sure that I must have accidentally corrected something in my setup for the better without knowing.
But until now I haven’t got any feedback from inmates who tried it.
fully AOB optimized cMP2 PC -> Lynx AES16 -> XLR AES/EBU -> Lavry Black DA10 -> XLR Mogami Gold -> Klein & Hummel O300
Hi Mark,
thanks for asking, I'll try to produce something meaningful on this issue - but I'm afraid the answer is not so straightforward... ;-)
Those of us that use the ESI Juli@ soundcard are in a very comfortable position when it comes to judging which solution is best - we unsolder the on-board regulator (5-> 3.3V), cut the respective traces on the PCI connector that carry in the voltages from the MoBo, feed Juli@ with clean 3.3V and 5v lines, and we're there. Juli@ has dedicated input/output points (kind of little "drill holes") that are wonderfully suited to take this external voltage supply.
I currently use a Juli@ too but have used a Lynx AES16 before. I have just taken my now obsolete Lynx in my hands and am looking at it - and especially when comparing it with Juli@, it's so §$%§& complex, and sadly this is a complexity that for the most part we don't need... It is an excellent piece of engineering, but I have a hard time identifying a good injection point for clean external power. Ok, there are SMD devices that look like input rail smoothing caps to me, labelled C50 and C51 (far left front side down at the PCI connector) and C52 (far right side), from what I see those could potentially do the job. You also had to take care of 3.3V and +/-12V. While poking around with my multimeter I saw that the PCI traces for these voltages are connected on the board but couldn't find chips that would share that connection. This of course needs more work and thorough analysis. But overall I would say that I do not see why it shouldn't be possible to power at least the whole card with clean external voltages. I personally would prefer cutting traces and soldering regs directly to the board. One next step would be to further identify regulators further "downstream" that do additional regulation, and eventually inject here. But this is open heart surgery ;-)
So since you say you could imagine using a riser card or something similar, i think that goes without bloodshed ;-) and should be easily doable - give it a try!
Do I understand you correctly that solution 3 would be to inject external power directly to the chips or parts of the soundcard? This is complex and challenging and would take a lot of analysis, including soldering then of course, but indeed would be very elegant, since then you maybe could shut of whole parts of the card that are not needed by cMP2 which would be great! But to call that "advanced" would be a massive understatement... ;-)
So apart from my estimation that solution 2 (at least for a start) is the only feasible and viable, here's my judgement od the effect of such an operation: when I did this to my Juli@, i.e. cut the PCI traces, unsoldered the on-board reg, connected clean 3.3V and 5v lines (battery plus cap/resistor plus reg) to the respective onboard connectors, the effect was not subtle at all but in an order of magnitudes. See, by doing that we (i) isolate the soundcard from all the powerline "pollution" on the MoBo, and (ii) feed it with dedicated clean power, thus massively increasing the stability and purity of its working environment. Ok, a card like the Lynx creates its own mess and pollution through its complexity and all that stuff that's onboard and working, so maybe the effect is a bit less, but you could think of adding caps and replacing regs (see Greg/Gstew mods to Juli@) and further improve.
So again: I would expect a top-of-the-ranking improvement. The more regs and caps you can replace or upgrade, the more you can add to this improvement. And as you already suggest: the first step is simple, get yourself a riser card, identify which voltages are really needed, and replace them with external ones (that's how Alfred/sonics had proceeded when developing the Juli@ PSU mod). in a next step you then could follw the way the current takes and improve upon its lines. Give it a try, IMHO you can't loose! :-)
Good luck!
Robert
For those who wish to learn please listen to Bertel. As Cics is the king of the audiophile software, Bertel is the king of audiophile hardware. He is not saying but he has singlehandedly solved the metallic/static noise issue of a juli@/cmp^2 based system. He has helped me tremendously with tweaking my hardware to optimum results. It is not easy to implement a a total battery powered system and I don't recommend it for the feint of heart. I approached it but was limited by my soldering skills. But for those that want to achieve this, it is possible.
A fine young man not too disimilar from Cics in his knowledge of these pc audiophile matters and willingness to help others.
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