Just looked at the specs for the BeQuiet L7-530 SMPS that Peter recommends (and I use) in the XXHE PC.  There are two +12V rails: one for P24 ATX socket and PCIe ports; the second for P8 cpu socket, molex and sata peripherals (video cards, HDD, SSD, USB cards et cetera).  As far as I can tell the +3.3V and +5V rails are shared between the motherboard and peripherals.

I wonder how much there is to be gained by separating power supply to these components to minimise interplay?

Another interesting thing is the ripple rating of the BeQuiet.  Both +12V rails have a ripple/noise (max.) of 120mV while the +5V/+5V Standby/+3.3V rails are rated at 50mV maximum.  Compare this to the supposed specs. of my lab linear psu of 1mV rms, so I should be able to hear a difference if the ripple is an issue.

It's time to organise an oscilloscope.

P24 ATX SOCKET CURRENT DRAW MEASUREMENTS

So last night I got out my trusty multimeter and hacked into the P24 Extension cable that goes between the motherboard and the P24 plug of the BeQuiet SMPS.  My aim was to figure out the current draw of the various rails and ancillary pins.


12V Rail

There are two 12V pins on the P24 socket each of which will successfully power up the mobo without the other being connected.  I cut both wires, twisted the mobo end of the cut together, removed one supply wire from the supply side so that only one 12V wire was coming from the SMPS and made the measurements below...

o/s State	Startup	Music	Shut-Down
Maximised (no cpu fan)	0.83A	0.48A	0.56A
Maximised (cpu fan plugged in)	0.93A	0.59A	0.85A
Minimised (no cpu fan)	0.81A	0.57A	0.81A
Minimised (cpu fan plugged in)	0.92A	0.57A	0.81A

The 12V rail powers the cpu fan in the XXHE PC so I though it prudent to measure with the fan connected as well as disconnected.  The amperage varied when I pressed a key or moved the mouse, so perhaps the PS2 ports are run from this rail also.  As you can see the fan does not make much of a difference to the power draw on this rail, neither does minimising the o/s.



5V Rail

There are 5 5V pins on the P24 socket and each pin alone will power up the mobo if all the other 5V pins are not powered.  I cut all the 5v wires, twisted the mobo end of the cuts together into one joint, remove all but one cut 5V wire from the SMPS side of the cuts and made the measurements below...

o/s State	Startup	Idle	Music	Shutdown
Maximised	4.0A	2.2A	2.2A to start, 2.0A stable	2.3A
Minimised	4.1A	2.2A	start 2.2A, stable 2.0A	2.2A

Like the 12V rail, the 5V rail does not seem to be impacted by the sate of the o/s.  I am not confident that 4.0A peak during startup has been recorded accurately because it is displayed on the multimeter as a rapidly changing amperage which may mean that the peak has been missed.



3.3V Rail

There are three 3V pins in the P24 socket each of which will successfully run the mobo in the absence of power to all of the remaining pins.  I cut the 3.3v wires, twisted the mobo side of the cuts wires together into a single joint, removed  all but one of the cut wires from the SMPS and made the measurements below...

o/s State	Startup	Idle	Music	Shutdown
Maximised	1.43A	1.42A	start 1.43A, stable 1.35A	1.42A
Minimised	1.43A	1.38A	start 1.4A, stable 1.34A	1.4A

Like the 12V and 5V rails, the 3.3V rail does not seem to be impacted by the state of the operating system.



Power On Pin

I was unable to measure the voltage variations of this pin.  It seems as though the act of measuring this voltage with either of my multimeters is enough to drop the voltage out of spec and the mobo will not power on.  I could, however, measure the amperage draw which was a consistent 150uV which must be present whenever the computer is turned on.  If the pin was pulled when the computer was powered on it instantly performed an ungraceful shutdown.  When the computer is turned off, this pin does not draw any current.  The literature indicates that this pin must be supplied +5V whenever the computer is on.



+5V Standby Pin

This pin will supply power to the motherboard even when AC is connected and the computer is turned off.  Measurements were as follows...

o/s State	Computer Off, AC On	Startup	Idle	Music	Shutdown
Maximised	0.353A	1.0A	0.9A	0.9A	1.0A
Minimised	0.353A	1.0A	0.9A	0.9A	1.0A

Draw from this pin was identical regardless of o/s state.  The ATX Standard specifies 1A minimum for this pin, with a recommendation for 2A to be provided to meet future requirements.



Summary
At this stage, a maximum of 5 separate rails could be run into the P24 socket alone: +12V 2A min.; +5V 5A min.; +3.3V 3A min.; +5V 0.5A min. (power on); +5V 2A (Standby).  Likewise, a minimum of 3 separate rails may suffice if all the +5V rail were combined.  The real question is whether the extra two rails would be worth the extra expense.

The next step is to have a look at some ATX psu's to see whether all the pins for each voltage are generated from the same rail, or whether the load is split according to pin.

Hi Nick,

Yes, the 'Power On' may be a difficulty, but see my next post for what I have measured with this rail.

Cheers,

Anthony

Yes, that was what I was thinking.  The fact that any pin on a rail is enough to power everything indicates that they have been split for a reason, heat is probably it.


I will look into this.

Thanks,

Anthony

P24 ATX Socket Pins Required by Motherboard

This afternoon I played around with the P24 socket which is the main socket on the mobo that carries the current to run the board, fans, USB ports, PCIE ports et cetera.  Because all motherboards seem to be selective in which parts of the ATX specification they choose to conform with I decided that I would try to figure out some rough rules for the power rails (+3.3V, +5V, +12V, -12V) and associated ATX pins.  What I did was get a P24 extension lead (like this one) and basically push out one pin at a time, startup (or attempt to startup) the XXHE PC and play some music.  The result is summarised in the graphic attached to this post.

Basically, the Asrock X79 Extreme4-M motherboard does not use the -12V rail, the 'Power Good' pin or the +3.3v sense pin.  Each of the +3.3V/+5V/+12V rails are represented by multiple pins in this socket, but the motherboard needs at least one pin (any pin) representing each rail to be powered.  It does not matter which pin this is just so long as at least one pin from each rail is powered.

What does this mean?  It tells me that even though each pin for a specific voltage is represented in this socket a number of times, they all come into one on the motherboard so there is probably little to be gained by even trying to power each pin from a separate rail.  Therefore I propose to measure three separate rails (+3.3V, +5V, +12V) into this socket by joining the wires of each of these rails into one and then running them from my lab psu.  

The '3.3V Sense' pin (#13) is used to allow the power supply to account for excessive cable drops on the +3.3v rail.  I assume that this means voltage loss due to cable resistance and the associated +/- 5% DC voltage regulation for the rail.  If this is the case I think that this can be overcome by making sure we have 3.3v at the P24 ATX socket on the motherboard and not just at the power supply.  Someone please correct me if I am wrong.

I also hope to be able to find an easy way to convince the motherboard to boot by using the +5v Standby pin and the 'Power On' pin.  The +5v Standby pin needs to be active whenever AC power is present and provides a power source for circuits that must remain operational when the computer is turned off (enables the power button on the computer case to work among other things).  The 'Power On' pin could be the tricky one, but I have a few idea on how to get it functional which I will try out when it comes to that.

Anthony

Peter, I think that it would be best to directly measure the cpu socket with the i7-3930 installed because this is where the cpu draws all of its power (I think all).  You would have some sort of lab psu there...maybe fork out for a 4 pin or 8 pin extension cable or even just buy a 8 pin male plug, some EPS pins and make your own extension cable.  It is a bit fiddly but this is essential information.


Very interesting stuff Peter...looks like there is more to be gained here.  It certainly looks like the size of the 12V rail for the CPU will be determined by the shutdown current draw which is at least 5A on my system and probably more on yours.

Regards,

Anthony

#2 of 2 ways to measure the current draw at the P8 CPU Socket on the Mobo

If you DON'T have a lab supply that displays the voltage and current draw, but you do have a multimeter this is still very easy.

STEP 1 - Unplug your XXHE computer from the wall.  Remove the 8 pin plug from the P8 CPU socket on the motherboard.  Plug in the 8 pin EPS extension cable (such as this) and cut all the POSITIVE wires in half (the yellow ones, not the black ones).  With the yellow wires that are connected to the compute PSU, twist them together and screw them into a terminal strip so that all four wires go into the same socket of the terminal strip.

STEP 2 - On the opposite side of the terminal strip screw in the positive probe of the multimeter.

STEP 3 - Screw the negative probe of the multimeter into a different socket of the terminal strip.

STEP 4 - Twist the remaining four yellow wires (that you cut earlier) into one group and screw them into the terminal strip opposite the negative probe of the multimeter.

STEP 5 - Plug the free end of the extension cable, with the multimeter wired into the middle, into the P8 socket of the motherboard.

STEP 6 - Make sure you don't have any potential shorts anywhere and then plug the computer power supply back into the wall and press the start button.  The computer should start normally.

STEP 7 - Take note of the maximum amperage draw displayed on the multimeter at startup (i.e. from the time you press the power button to the time XXHE is loaded), at idle (i.e. when the computer is sitting there with XXHE open, but is not playing music or doing any other tasks), playing music, pressing Alt-X to come out of unattended mode, and shutting down the computer.  This should be done multiple times with both minimised o/s and not minimised o/s

STEP 8 - Post the results in this thread


Note that in the photos below I have also directed the black wires (ground) through the terminal strip.  This is not necessary, they can be left entire and uncut.

#1 of 2 ways to measure the current draw at the P8 CPU Socket on the Mobo

If you have a lab supply that displays the voltage and current draw, this is very easy.

STEP 1 - Make a loom for the P8 socket.  I purchased a 8 pin EPS extension cable (such as this) and cut one end off it (the end that does NOT plug into the mobo), twisted all the positive wires together and fed them into a banana plug, then twisted all the negative wires together and fed them into a different banana plug.  If you already had the 8 pin EPS plug and pins you could make up a cable yourself in about 5 minutes.  Apparently you can also feed the 8 pin P8 socket with a 4 pin P4 connector: you simply install it in the half of the 8 pin socket that is nearest the edge of the mobo.

STEP 2 - Turn on the lab psu and set the rail you are going to use to 12V and plenty of amps (minimum 5A, preferable 8A+)

STEP 3 - Remove the existing psu plug from the P8 socket on the motherboard and replace it with the new cable.  Plug the new cable into the 12V rail on the lab PSU.

STEP 4 - Turn on the lab psu.  You are now using two psu's for your motherboard.  For the computer to start the P8 cpu socket must be receiving its 12V feed before you press the start button on the computer.

STEP 5 - Press the start button on the computer.  The computer should start normally.

STEP 6 - Take note of the maximum amperage draw displayed on the lab psu at startup (i.e. from the time you press the power button to the time XXHE is loaded), at idle (i.e. when the computer is sitting there with XXHE open, but is not playing music or doing any other tasks), playing music, pressing Alt-X to come out of unattended mode, and shutting down the computer.  This should be done multiple times with both minimised o/s and not minimised o/s

STEP 7 - Post the results in this thread

 

Current draw for the P8 CPU Mobo Socket

Today I had a few minutes and decided to measure the current draw from the P8 CPU Socket on the Asrock X79 Extreme4-M motherboard and the Xeon E5-2648L 8 Core cpu.  This is not the standard cpu for the XXHE PC: it is a lower powered (1.80gHz) server cpu with more cores (8 physical) and more cache (20M).  As per Peters earlier advice I measured the current draw in both minimised o/s and non-minimised o/s modes; the results are below.

o/s Mode	Computer Startup	System Idle	Playing Music	Alt-X	Computer Shutdown
NOT-Minimised	3.78A	1.15A	3.3A	--	4.85A
Minimised	3.78A	0.9A	1.2A	1.64A	2.62A

I find these results very interesting.  The CPU draws much less current at shutdown and when playing music if the o/s is not minimised, and a little more at idle when the o/s is not minimised.  Startup current draw seemed to be the same whether the o/s was minimised or not.

What was super interesting was how the current draw of the cpu was impacted by the minimised o/s.  Before minimisation, the cpu voltage was a constant rollercoaster ride that had ran as low as about 1.2A but cycled rhythmically to 2.5A and even 3.3A occasionally, but there was definitely a cycle happening where the current would ebb and flow.  In minimised o/s mode, the cpu was much, much more stable and operated in an amperage range of 1.05A to 1.2A with no real rhythm apparent.  That is a swing range of 0.15A compared to 2.1A which in the context of things is a very big difference.

Is there anybody out there that can duplicate this testing with the Asrock X79 Xtreme4-M mobo and the i7-3930K cpu?  Not only would the difference between processors be interesting, but the information is valuable should a linear psu prove worthwhile.  I will write another post shortly to summarize how to measure the power draw at this socket.

Anthony

Yes, I had seen that Alain and it is interesting.  The current on rails 1 - 3 seem very excessive and rails 4 and 5 will likely be no use (apparently -12v is seldom used these days).   To me the product looks like something that may not have received a lot of testing.

On another point, my three rail linear lab psu has arrived this morning and I am working on getting a suitable oscilloscope as well.  My plan is to measure and get a good idea of what the current situation is with my mains power and XXHE PC (ripple, noise etc.) and then measure the differences when using linear power.

Anthony

Thanks Peter.  I don't have a scope but I know someone who probably does.  When the LPSU arrives I will take it and my XXHE pc around to him and see how they compare.  

Anthony

Thanks Peter,

The ripple on that supply is 1mV rms, so it is pretty good, but I don't know how well designed the supply is and how much hash it feeds back into the mains.  Yes, the $200 psu is a cheap trial just to see if I can notice differences with it.  The aim is to figure out what, if anything, works and then use what we have measured and heard to possibly design and build a specialised unit for the XXHE PC.

Is it an easy endeavour to figure out how much hash this linear psu feeds back into the mains?  Are you able to give me instructions?  I probably should get that out of the way first.

Pedal, thanks also for the encouragement.  I hope we find a way to further improve the XXHE/NOS1 sound!

Regards,

Anthony

EDIT:  Peter, I had considered going the super high-quality route from the start and using Hynes regs and good quality transformers, but the cost is prohibitive once the rails add up and I really don't know how many rails I will need in the end.  It could be one, or zero, or six.  Who knows?  At $200 a pop for each Hynes reg that is a lot of money to spend on a hunch.
 

Hi All,

Over the coming weeks I intend investigating the effect of providing linear power to various parts of the XXHE PC and any associated changes in sound quality.

I plan for this experimentation to be methodical rather than haphazard but I am forced to approach this from a beginners perspective, rather than the perspective of someone that has electronic experience or even power supply experience.  So I propose is to break up the investigation into a number of parts:

• Define points of interest i.e. SATA, P24, P8, Fans, Peripherals
• Measure amperage requirements of points of interest.  Best to do this while the XXHE PC is in use
• Feed these individual points of interest with clean linear power and attempt to quantify any resulting changes to sound quality
• Determine which points of interest are worth providing linear power
• If feasible, design and build a high quality purpose built linear supply for the XXHE PC

So, first we figure out what to look at in regards of linear power and then we measure amperage draw, supply cheap linear power, make a judgement call, and then design a suitable supply if deemed appropriate.

To do this, I have invested in a relatively cheap, but decent quality 3 rail linear psu.  I have heard this psu in action in another system where the owner claims a very worthwhile 10% improvement in sound quality (whatever that really means), but of course how this translates to an XXHE/NOS1 arrangement is anybody's guess.  For what it is worth, ItemAudio in the UK also recommend this unit as their pick of the lab psu's that they have tried.

In the coming days and weeks I plan to measure the draw of all the points of interest that I can and publish the results in this thread.  It would be ideal if I could convince others to duplicate this approach (or another approach that can be agreed upon).  Hopefully this can become a group effort with corroborated results in different systems and different countries with an aim to really figuring out if a linear psu for the XXHE PC is a viable or worthwhile endeavour.

For the initial measuring tasks, all that is needed is a multimeter, a screwdriver, some extension cables for whatever we are to measure the amperage draw, and some time to spare.  I would guess that different computers will have different power draws at different points of interest, so the more people that spend some time measuring this stuff the better.

Within my own XXHE PC I have identified four points of interest: the P8 EPS 12 V plug; the P24 ATX plug; the Pang USB Card Molex Connector; the SATA power cable for the Samsung 840 EVO SSD.  The most complex and difficult of these is going to be the P24 ATX plug, but if we approach this in a methodical way I am sure that we can achieve the best outcome.  I have prepared a pinout of these four points of interest in my XXHE PC...
 
Another point of interest will be powering the RAM directly, which is a much more difficult task.  People such as I that use a RAMdisk for playback may get good benefit from clean linear power at this location, but I really think we should leave this until last because it involves modifications to the motherboard.

Other potential points of interest for linear power include multiple internal SSD and/or HDD and even external drives.  I do not use these things myself, so someone else is going to have to measure them and determine if they should be powered individually, as a group, or at all.

So please put up your hands and even if you cannot do these measurements yourself, feel free to make suggestions.  When my gear turns up in the coming days I will post some pictures of how to measure these things for yourself, it is quite easy.

Cheers,

Anthony

Nick, that is an awesome post.  Very much appreciated.  The more that I get into this computer audio thing the more I realise that I don't know.  Regarding your capacitor auditions, I had a mental picture of Peter doing the same thing when developing the NOS1.

Cheers,

Anthony

Hi Johan,

I am using an iPad with the current iOS to navigate this site and not having any issues.  More likely that the issue is your end and caused by the iOS update unless others are having a problem as well.

Regards,

Anthony