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OAudio

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Posts posted by OAudio

  1. On 5/7/2021 at 6:46 PM, Nenon said:
    On 5/7/2021 at 4:14 PM, OAudio said:

     

    @Nenon 

     

    Wow, 5uV = ~-135db of rejection ( assuming a ~30v rail ) ! 

     

    I have been playing along in the background for a while using simulations of an unregulated supply based on the component choices in your earlier posts. With components listed and tweaking components parameters to near ideal performance levels its hard to get <3mv pk - pk @ 1 amp constant load.    

     

    5uV is exceptional. Can I ask how you measuring the ripple and and under what test conditions ?

     

    Thanks. 

    Expand  

    Have you tried simulating the dual choke CLCLC configuration? 

     

     

     

    I had not spotted the move to CLCLC. Modelling that configuration closes the gap somewhat :-)   

  2. 14 hours ago, Nenon said:

    The unregulated LPS I am currently using has about 1.4mOhm output impedance (it also has about 5uV ripple).

     

    @Nenon 

     

    Wow, 5uV = ~-135db of rejection ( assuming a ~30v rail ) ! 

     

    I have been playing along in the background for a while using simulations of an unregulated supply based on the component choices in your earlier posts. With components listed and tweaking components parameters to near ideal performance levels its hard to get <3mv pk - pk @ 1 amp constant load.    

     

    5uV is exceptional. Can I ask how you measuring the ripple and and under what test conditions ?

     

    Thanks. 

  3. 8 hours ago, StreamFidelity said:

    And the Taiko Audio 500W DC DC-ATX converter shines with a ripple noise of 0.10mV (millivolt).

    Hi @StreamFidelity,

     

    That is an interesting writeup thanks for posting. Its sound as thought the DC ATX is working very well in your system.

     

    The measurement you quoted is interesting, did you make it directly yourself ? If so I wonder if you can say what the conditions of the measurement were ? eg with a DVM an oscilloscope or analyser,  and what were the load conditions for the measurement ?

     

    Thanks,

     

    OAudio.

     

     

     

  4. 29 minutes ago, Dev said:

    @OAudiothe card looks very similar to the Taiko :-) it looks like you guys sharing the same reference design. The user configurable USB ports are an interesting addition. Why not offer it commercially ? 

     

    Hi Dev,

     

    Haha you have some thing there. The Taiko, Core Audio (very nice looking design) and my card have all settled on the same USB host controller chipset and the "house" colour scheme for high end USB cards of black and gold :-). 

     

    The card pictured was built in January this year after 5 months of very intensive development work, but pulls heavily on earlier ideas I had and projects going back a number of years. There was a lot I wanted to packed into the card so its actually had to be larger than the other designs I think and uses a full size PCIE blade. It has been in a 2u case but it was defiantly a tight squeeze. 

     

    My aim is that the components I am producing will by used in the in the server I am working on. I am targeting a very high level of sound quality performance so having the flexibility to change individual components where I need to specifically to suit this application is important rather than producing components for general use.

     

         

  5. 2 hours ago, matthias said:

     

    Hi Matt,

     

    I am defiantly familiar with these two posts, I spotted them some time ago and to be honest they contributed to why I said this.

      

    9 hours ago, OAudio said:

    Important to remember first that there isn't anything mystical about c621 boards, they are just incrementally slightly larger then previous Xeon architectures. Threads on other web sites make it sound complex but they are just computer PCBs. These boards have finite and quantifiable load requirements.

     

    There are some interesting points made in these two links but there a few tangents and assumptions that appear to be there, in order to make the argument that linear supplies can not supply the current levels needed by a music server without descending into mush :-).

     

    This explanation is lifted below for instance which is just a nonsense argument. The math is correct, but no one would be stupid enough to apply a linear supply technology to supply 100 watts at CPU core voltage of 1volts ! Its irrelevant to any real world power solution for a music server (certainly one based on any commercially available motherboard). Nobody will every [be able to] try this for a simple reason. Motherboards have and will "always" use buck technology to step down their external supply rail voltages to the high current low voltages supplied that enable high frequency power efficient chip designs. They are required to meet industry efficiency standards and the drive in data centres to reduce power consumption puts further competitive pressure on motherboard, chipset and processors designs to do this. However the point and all the numbers quoted are then used to underline a notion that linear supplies simply cannot meet the high current demands and perform to the specifications needed for class leading sound quality. Just not the case.....

     

    "As an extreme example, let's look at powering a CPU. A CPU typically operates at 0.6-1.2 volts but can easily draw 100 watts or more, let's assume 1 volt for easier calculations. For 100 watts at 1V you are talking about 100 Amps(!) of current. As current drops voltage over resistance (Ohm's law), a CPU is typically supplied with a 12V voltage rail, so we need to regulate 12V down to 1V. If you would use linear regulation, and you'd have a 100 Amp current draw at 1V, you would also have a 100 Amp current draw at 12V (simplified), meaning 12V*100A=1200 watts. Then we need to feed this 12V by a 16-19V supply (again to account for voltage drop caused by current over resistance), let's assume 19V as that's a very common value to ensure broad compatibility, and we are talking 19V*100A=a shocking 1900 watts. The conversion efficiency here would be ~5%, the other 95% will just be converted to heat. A switch mode regulator is the inverse of this, it can regulate 19V down to 1V at a 95% efficiency wasting only 5% as heat. That is a 1900W versus 105W of power consumption."

     

    Buck and linear designs both have their challenges. They need engineered solutions to manage their respective design hot spots but for my these two posts far too quickly quickly adopt the message linear + high current = guaranteed noise and buck can perform better despite their many many challenges. 

     

    Put and H probe anywhere near any DC ATX and it just sings with emissions. Even more relevant put a scope or analyser on its output and look at the characteristic of the switching noise breakthrough. Both these tests should really be done in a meaning full way, by which I mean whilst driving the intended load, a mother board's power rails. These spit back wide band RF and transients into the supply in question. Its really down to how a supply of any technology behaves under this condition (not necessarily in to a constant bench load) that will determine what the sound quality will be.  

     

    I wanted to link another post, but just could not find the particular post in the long thread. In it linear and buck conversion are again being compared in the same vain. Some FFTs are posted for an example buck supply and linear supply. The buck predictably looks like it performs well al least under constant load and this is attributed in part to an unusually high frequency switch loop in the design (I am familiar with the device I think is being used which switches around 2MHz). The FFT of the linear supply that is provided in the post is however dreadful. I would hang my head in shame if a linear with that spectral content were being used in a supply here in the modules I make and these will supply 24 amps per rail and give the electrical characteristics I have mentioned in earlier posts in this thread.

     

    The point is for me is that the posts maybe not be intentionally loaded to paint buck technology as the logic conclusion to the design decisions that have to be made, but I cannot follow the arguments and logic stated and accept that linear supplies are an inferior choice. I have some direct experience but to those that don't it all looks and sounds very complicated and credible. 

     

    OAudio

        

     

  6. 2 hours ago, wittao said:

    Yes, we are using the same.

     

    They are very nice looking boards in your pics. I had noticed the UPD's 😉 thanks for confirming. Looks like you are also using the 701s with ROM which is the way I went as well.

     

    I have some 711s I might have a look at them again. My understanding was that they are for embedded use where BIOS writes the firmware blocks to the chipset at boot time. That "industrial" comment has me wondering if I missed a way to use these ?

     

     

  7. 5 hours ago, matthias said:

     

    There was no disclosure by Emile, he said it is an "industrial" one.

     

    Matt

    Renasus UPD720202 from the package and circuit's pin out.

     

    The -711 variant is the -40 deg C temp range otherwise not sure what would attract the "industrial" commet if not this, there are only two variants.

     

     

  8. On 3/20/2021 at 5:16 PM, al2813 said:

     

    Yes I just found out exactly the same thing. Just need to see how I can check which version is running to make sure the it is not a HW issue. 

    Hi al2813,

     

    I have developed a USB PCIe card using the UPD720202 and am familiar with the firmware options of the chipset. I don't have a JPlay card but I think the card is laid out so that the that port shut off by firmware is the top port furthest away from pcie connector on the card.

     

    You will not be able to determine if the 2nd port has been disabled by firmware.  The one / two port options are set as part of the chipsets "vendor settings" firmware block by toggling a couple of bits of the image.

     

    Unfortunatly the UPD720202 will not dump this port setting back in an understandable form,  you would need to dump the whole firmware image from the card and then looking at the hex value of the port enable/disable bits.

     

    The best thing to do is just load the "2 port" firmware version onto the card and see if the port comes back up again.

     

    Good luck,

     

    OAudio.

     

     

     

     

  9. 3 hours ago, AME said:

    Looks great,

     

    I am however curious which USB chipset will be used. I understood that it will not be using the ASM 3142.

     

     

    Looks very much like it uses the same host controller I also alighted on when screening available chipsets, the μPD720202. 

  10. 22 hours ago, seeteeyou said:

    They are nice looking units but perhaps not very well suited to powering a quality DC ATX. The PSU's spec's show droop rate performance under load and in particular the ripple and noise specs would be a concern. And there can also be combined noise issues with  an SMPS followed by DC ATX buck conversion.

     

    The specs on the supply linked show:

    Droop Rate (-xDx-R suffix) 50 mv/A
    Ripple & Noise 400 mv

    (Both for the 28v version).

     

    They are big figures for feeding a DC ATX in a server that's focused on sound quality.

     

    I spent quite some time a few years ago looking for a SMPS solution to power DC ATXs. There would be much going for such a setup if it could produce really good sound. None that I looked at worked well feeding DC ATX's for sound quality however. The problem came down to having two unlinked switching controllers, one in the SMPS and a second buck controller for each rail of the DC ATX that followed. Both of stages vary switching frequency and or duty cycle as they see fit to track the current load being consumed by the PC. The result for the combinations looked at was mess of noise both on the input to the DC ATX and on it's output. On the DC ATX outputs there was a combination of the harmonics of the switching frequencies of both stages. Never manged to get a nice sound from the combinations tried.

     

    If you can, perhaps stay with regulated linear or passive filtered power. It's a well trodden path but for good reason.

     

    Something with droop under load in the very low mv/A range and combined noise plus ripple of <5mv. Transient response isn't quoted for the linked PSU but if it is published for another supply a <100us recovery time for a transient of 5 amps would be a decent place to start.

     

     

     

     

     

     

  11. 6 minutes ago, kyoya78 said:

     

    I replaced one of the CPU coolers with my own (A7075). The thin fins are excellent for cooling but still have a negative effect on the sound. I was surprised at the improvement in sound quality even after replacing one of the CPU coolers.

    IMG-4349.jpg

     

     

    Hi kyoya78,

     

    What a difference to the radiator on the other CPU. 

    That's a nice looking CPU block !

  12. On 1/27/2021 at 5:12 AM, vhs said:

    Hi there, any news yet ?

    Hi VHS,

     

    Thanks for the interest, yes things have moved forwards. I wanted to see  if the cooling system performed as per the thermal design I did. I couldn't wait any longer so I did do a trail fit a week ago. They are just about bang on the thermal design which was really nice to see  and they look absolutely superb in the chassis.  The coolers were made by an engineer with decades of work for a jet engine manufacturer, and it really shows. Its such a shame to shut them away inside the server chassis.

     

    They are back out of the server again and the fans are back in for now for the access reasons I mentioned above.

     

    Here is another picture of them with CPU mount attached.

     

    OAudio.

     

     

    CPU Cooler 3

     

     

  13. 51 minutes ago, rossb said:

    Is passive cooling really necessary? The fans on my Noctua NH-D15 are currently spinning at about 200rpm and are completely silent.

    Hi Rossb,

     

    There is a lot of dogma about fans which really makes me 🙂sometimes. You would think they are a complete disaster the amount of attention that "fan-less" setups get, however the truth is that if you: 

     

    • run them slow so you are happy / can live with the with the sound noise levels,
    • isolate them from the servers sensitive power (don't connect via the mother board headers),
    • make sure that the fans ground is not referenced to the servers supplies,
    • run fan wiring well away from the servers wiring and the motherboard etc,

    the sound quality will be absolutely fine.

     

    Sounds like a small auxiliary supply for your fans could be a good thing to try as well. 

     

    Your fan setup is similar to the setup I am using to develop with here. The fans are electrically isolated from the server's power supplies for good measure. In a really high resolution system the set up is very good for sound quality, the impact of turning the fans off completely can just be heard but frankly its not much of a difference.

     

    Last thought is that for DIY a passive heat pipe setup needs careful consideration. There are benefits in terms of physical sound levels from the server and "some" sound quality improvement to be had BUT you may lose the ability to easily move the motherboard from the chassis due to the complication of the pipe system. Not a problem ? possibly, but I need access to the motherboard to do "stuff" 🙂 which means its been in and out of the server 30-40 times at least.  

     

    OAudio

     

     

     

     

     

     

         

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