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Mangoaudio

Dedicated lpsu for CPU?

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Not a good idea, if you are asking for the required voltage and current then I would respectfully say this is a mod too far...

I would leave well alone, you are starting to mess with the actual PCB and could cause far more issues than any issues you think a LPSU will solve... The power to a CPU is more than just the power supplies, there are often multiple voltages, these voltages have to stay in tolerance even with the high dI/dt caused by the CPU switching.

There will often be a separate data sheet for the power requirements for the CPU (or a section in the main data sheet) read and understand all the implications...

 

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Thats intresting! D

On 9/3/2019 at 10:52 PM, marce said:

When we do motherboards or other complex digital designs (processor/FPGA DDR memory) the point of load supplies are placed as close to the devices as possible.

 

 

o you design custom motherboards or like commercial stuff, if I may ask?

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On 9/3/2019 at 10:52 PM, marce said:

When we do motherboards or other complex digital designs (processor/FPGA DDR memory) the point of load supplies are placed as close to the devices as possible. Two main reasons, closer the better, any impedance to the current flow (i.e. long wires, here 37.5mm is long, it's 1/4 wavelength of 1GHz signal travelling down a trace with FR4, lower ratios of antenna down to 1/20th may be problematic even though the pick up is way down.) will cause the voltage to droop when the device switches (32/64 data lines and related address lines switching constantly) with instantaneous current requirements getting into 100's of amps. The second reason is this switching noise is reflected in the local supply, adding and external supply with wires could be very problematic, the wires could act as antennas and radiate noise, then there would be the size of the supply, with heat-sinking (again a possible noise radiator), mechanical fixing, extra heat in the box etc.

Also on the motherboard are a whole range of other frequencies being used, Ethernet, USB, busses, all will radiate to some extent, the closer any wires are the more they will pick up... can't make them longer!!!

 

 

Thats interesting! Do you design custom motherboards or like commercial stuff, if I may ask?

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Yes, nearly every day for 30+ years. These days I tend to work on more complex mixed signal boards including microwave. We do some motherboards but they tend to be more for instrumentation, 12-16 layers. We also do pro audio board layout. Personally I prefer mixed signal and analogue layout its more interesting and taxing, especially high speed analogue.

 

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Yes, nearly every day for 30+ years. These days I tend to work on more complex mixed signal boards including microwave. We do some motherboards but they tend to be more for instrumentation, 12-16 layers. We also do pro audio board layout. Personally I prefer mixed signal and analogue layout its more interesting and taxing, especially high speed analogue.

 

We have had a 16 layer MB come in today for a modification, related to your idea. A supply line for one of the ancillary devices was routed as a signal and not a power plane due to a mistake on the schematic. Under switching the track resistance and impedance caused the voltage to sag and current just didn't get there, so the device crashed.

 

There is a big difference between the large SMPS's that come with a basic PC and the small point of load SMPS's you get on all digital and mixed signal boards. These small supplies are high frequency and utilise small inductors and other discrete devices. The supply footprint is small and if the design guidelines are followed the high dI/dt (the high current switching loops, the source of noise) are well controlled and restricted to a single layer, including the 0V (GND), with single point connections limiting any possible noise loops.

This app note gives some basics, the pictures of the ac switching loops (part of all power supplies) are easier to follow.

https://www.analog.com/media/en/technical-documentation/application-notes/an136f.pdf

 

This is a link to some pictures, look at the difference between the small surface mount SMPS's and the larger PC type, just the size of the basic PC ones and the lack of layers! The big SMPS's I have done including up to 16kW output have always been in a screened metal box with a screened umbilical for the main supply if external to the other electronics. The true art in power supply design though must go to the guys that do electron microscope supplies, true art, 35,000V's as well! Done some analogue stuff with them but the HV stuff I have to bow to their experience and skill, i'll stick to the easy stuff, even microwave is preferable and SMPS's heaven...

 

When I first started out as a test engineer, I worked for NCL (early 1980's), PSU's were linear and a pain, to get the current you would have 20-30 2n3055 (I think) all paralleled up in emitter follower mode, heat!!! current sharing! failures! down time. Without SMPS's we would not have this forum.

Sorry for going on but as we seem to be the only two on the thread its peaceful.😁

 

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Mango - I suggest you isolate the DAC from the storage using WiFi or fiber as a trial - some DACs seem to be sensitive to noise on the USB line; others are not.

 

A high quality (low noise) SMPS or LPS can feed your DAC -- assuming the designer of the DAC did not use 2 or 3 of them to begin with...

 

If you already have an xlnt. DAC then HiRes source material and searching for the best masterings will likely prove more rewarding than tinkering...


"The overwhelming majority [of audiophiles] have very little knowledge, if any, about the most basic principles and operating characteristics of audio equipment. They often base their purchasing decisions on hearsay, and the preaching of media sages. Unfortunately, because of commercial considerations, much information is rooted in increasing revenue, not in assisting the audiophile. It seems as if the only requirements for becoming an "authority" in the world of audio is a keyboard."

-- Bruce Rozenblit of Transcendent Sound

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On 9/5/2019 at 1:05 PM, Ralf11 said:

Mango - I suggest you isolate the DAC from the storage using WiFi or fiber as a trial - some DACs seem to be sensitive to noise on the USB line; others are not.

 

A high quality (low noise) SMPS or LPS can feed your DAC -- assuming the designer of the DAC did not use 2 or 3 of them to begin with...

 

If you already have an xlnt. DAC then HiRes source material and searching for the best masterings will likely prove more rewarding than tinkering...

Unfortunately I dont have usb DAC , Iam using Lynx pcie soundcard and this probably is not ideal for audiophile but Iam stuck with it at the moment. Thanx for suggestion, I will keep it in mind.

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On 9/5/2019 at 12:07 PM, marce said:

Yes, nearly every day for 30+ years. These days I tend to work on more complex mixed signal boards including microwave. We do some motherboards but they tend to be more for instrumentation, 12-16 layers. We also do pro audio board layout. Personally I prefer mixed signal and analogue layout its more interesting and taxing, especially high speed analogue.

 

We have had a 16 layer MB come in today for a modification, related to your idea. A supply line for one of the ancillary devices was routed as a signal and not a power plane due to a mistake on the schematic. Under switching the track resistance and impedance caused the voltage to sag and current just didn't get there, so the device crashed.

 

There is a big difference between the large SMPS's that come with a basic PC and the small point of load SMPS's you get on all digital and mixed signal boards. These small supplies are high frequency and utilise small inductors and other discrete devices. The supply footprint is small and if the design guidelines are followed the high dI/dt (the high current switching loops, the source of noise) are well controlled and restricted to a single layer, including the 0V (GND), with single point connections limiting any possible noise loops.

This app note gives some basics, the pictures of the ac switching loops (part of all power supplies) are easier to follow.

https://www.analog.com/media/en/technical-documentation/application-notes/an136f.pdf

 

This is a link to some pictures, look at the difference between the small surface mount SMPS's and the larger PC type, just the size of the basic PC ones and the lack of layers! The big SMPS's I have done including up to 16kW output have always been in a screened metal box with a screened umbilical for the main supply if external to the other electronics. The true art in power supply design though must go to the guys that do electron microscope supplies, true art, 35,000V's as well! Done some analogue stuff with them but the HV stuff I have to bow to their experience and skill, i'll stick to the easy stuff, even microwave is preferable and SMPS's heaven...

 

When I first started out as a test engineer, I worked for NCL (early 1980's), PSU's were linear and a pain, to get the current you would have 20-30 2n3055 (I think) all paralleled up in emitter follower mode, heat!!! current sharing! failures! down time. Without SMPS's we would not have this forum.

Sorry for going on but as we seem to be the only two on the thread its peaceful.😁

 

Iam curious to know what do you think is a good mobo choise in terms of SQ? What mobo are you using?

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17 hours ago, Mangoaudio said:

Iam curious to know what do you think is a good mobo choise in terms of SQ? What mobo are you using?

Wrong person to ask...😁 Plenty of opinions out there, me  any decent PC.

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