Hi Arjan,

One of the things that has not yet been explicitly stated in this thread, but I suppose I am doing it now, is that one of the design goals is to have the computer managed by a single well designed power source.  As things are looking now this power source will actually be a number of smaller linear power supplies within the one 'box' that can be managed as a single unit.  This may improve grounding issues and it will certainly improve usability and computer life.  With a 'one box' solution we don't have multiple power supplies of possibly dubious construction feeding hash back into the mains (just one...haha) and the computer can be managed as it is used to being managed and hence its lifespan will be extended. 

I would not be surprised if much of the gains made by this psu were because of the reduction of hash feeding back into the mains to impact other components.  I am sure there will be gains by improving the USB card performance and we will have to wait and see on the other rails.

I don't know if a 160w pico will start up the standard XXHE PC that Peter makes, but there is no need for the picoPSU now because we can build our own version of it without the noisy switching supplies onboard, which should give a better result. 

Cheers,

Anthony

Thanks Coen.  I looked these up but their noise was rather high at about 260uV and no PSRR figures.  I am reading the specs differently to you...but that 25 page spec. sheet very helpful.

Anthony

Even better Peter.  I was of the opinion that best practice would probably be a separate psu for each rail.  Sounds like it may save some development time also.

Anthony

Thanks Coen.  The LT1083 will do 7.5A with 5V and 12V.  They cost about AU$20 each over here.  That may be a decent solution for the two high amp/low spec. rails I mentioned in my previous post.  I would love to hear your other suggestions though...I only had a look this afternoon and these were the best I could find.


To be honest I have not looked into heat too much at all.  An aluminium case with plenty of mass and decent heat-sinking can be VERY expensive to get made (unless there are suitable mass-produced amp cases on the market - now that's an idea) but I would love to make the entire XXHE PC passively cooled, but that may not be feasible if we want the components to last.

Thank again Coen.

Anthony

Based on Peters forward thinking regarding the capacitor bank and the ATX psu to start up and shut down the pc, following are my ideas on a clean implementation.

As mentioned earlier, I am sure that I can use a $2 chip to make a small circuit board to control the linear power rails and motherboard to full ATX power specification.  Peter has said that he has some decent linear regulators used in the NOS1 that can go to 3A output (is this maximum output Peter, or continuous output?).  There are two rails that we will have an issue with needing more than 3A of current:  the 12v P8 socket which will need at least 5A, preferably more during startup and shutdown; and the 5V rail into the P24 socket which will need about 5A at shutdown.  The remainder of the rails can be serviced by a 3A or smaller supply.

So, the only time that we should need more current is during startup and shutdown...which I should be able to identify by the voltage on the 'PWR_ON' leg of the aforementioned $2 chip (each state has a seperate voltage range).  So I propose one power switch and one toggle...the toggle to tell us that we want the linear ATX PSU to go into "Extreme Low Power Mode" because the XXHE PC is optimised and ready to roll in low voltage mode...the power switch to simply turn on and off the pc.

When the toggle is NOT set for "Extreme Low Power Mode" my little circuit board will boot on the pc using the normal voltage rails and a special low spec, low cost 12V 5A+ and 5V 5A+ as well as the normal high performance rails for everything else.  I can use cheap monolithic 7.5A or 10A LT regulators and use a dual wound transformer for thes 'high power' rails.

When the computer restarts with the toggle in "Extreme Low Power Mode" the circuit board will still start the XXHE PC as mentioned in the previous paragraph, but once it is booted it will use the capacitor bank and turn off the high amp/low spec rails and turn on the low amp/high performance 5V and 12V rails.  Likewise, when a shutdown is triggered, the mobo will let the $2 chip know what is going on and it will use the capacitor bank to turn off the two low amperage rails and turn on the high amperage rails for shutdown.

I think I can implement this.

Anthony

The main issues that I have with a lab supply like that for a final solution Peter are noise (the bigger output lab linears are all fan cooled as far as I know) and knobs (and how kids love to tweak them).  Plus, I think their implementation will not be as good as something we build especially for it.

I could not read the manual for that supply Peter...wrong language for me.

Awesome idea with the capacitor bank and the ATX supply to simply start the XXHE PC Peter and of course I have an idea or two in addition.

As mentioned earlier, I am sure that I can use a $2 chip and a small circuit board to do the ATX power on and off stuff.  One particular chip in mind can control two 12V lines (as well as a 5V, 3.3V, 5V SB, PS_ON etc.) which is important for this build.  I am sure that a little bit of additional logic can be included on that circuit board to also manage the supply that is to be used when the XXHE PC needs to boot or even on the occasions when the XXHE PC is not running in minimised o/s mode.

Wait for my next post...I will explain more...I have to put the kids to bed right now.

Cheers,

Anthony

Thanks for the support Pedal.  I will plug away at this but I am now at the limits of my recollection of high school electrical theory (it was 25 years ago!! - how did that happen??).  I really need help with a lot of the stuff from here on and I can see myself wasting a LOT of time if I am allowed to trudge off down the wrong paths.

Saying that, I have been reading this afternoon and it seems that there are two primary ways of making each linear rail:

• Monolithic Linear Regulator from someone like Linear Technology (eg. LT1086 or LT1084).  Decent noise and ripple rejection (PSSR), good transient response, simple implementation (I think), lower heat and quite cheap
• Shunt + Opamp diy regulator in the style of something like Jung Didden and it's derivatives.  Better ripple rejection, lower noise, not sure about transient response but larger, hotter and more expensive to build

Peter and Coen - is this an accurate summation of the two approaches to linear regulation?  Are there more approaches that I have not learned the existence of?

Anthony

Thanks for the reply Coen.  Sometimes I think I am talking to myself in this thread!


I don't think we will get anywhere near 7A on any rail of a linear psu for the XXHE psu.  Two 5A rails, two 2A rails, two 1A rails and a 0.1A rail are all that could possibly be used (not all will necessarily be worthwhile, but that is the most that could be jammed in there).  On top of this the XXHE PC in its standard case has three case fans (plus at least one extra fan slot possible I think) and two cpu fans, so the active cooling is already in place.  Pull out the SMPS and the expansion drive bays and there is 30cm x 12cm x 12cm to fit in some regulators inside the Silverstone GD06B case so there is some scope at least.  Transformers could go outside.


I understand your capacitance/voltage/transient points from  a 'sounds good in theory but have never done it for myself' perspective.  The aim of the project is to have a reasonably priced supply that optimises playback quality with the XXHE PC and NOS1...so while, as you say, it is all well and good to have a computer that works as well as it can whilst playing music, it still does need to be able to startup and shutdown properly.  We now know how much current is needed to achieve these things...the challenge now is to 'right size' everything and minimise the noise in the XXHE PC...which is where I need help. 


I reckon it looks good to me too, but I have a good idea of how much that case costs and it is substantial - probably more than half the total cost of the supply.  This is another reason that I think it may be worthwhile investigating making use of the active cooling already in the XXHE PC.


I think that you could well be right that a picoPSU fed a single linear rail may provide a solid benefit Coen, but as of yesterday I think I can make my own fully functioning picoPSU (minus the switching regulators), and may be able to provide three high quality rails into it for around the cost of a picoPSU plus a good high wattage off-the-shelf linear psu.  That has got to be worth a shot.

If I believed everything that I read online I would tell you that in order of sonic gain the best things to provide linear power to are:  USB card; o/s drive and P8 cpu socket. The great majority of people give up with the P24 socket and simply provide linear power to a picoPSU, but the few that have bothered to do this well report a sonic gain.  The problem with the picoPSU is that it is unlikely to power up the XXHE PC in its standard un-optimised form.

And yes, there are plenty of switching supplies on the motherboard but there is nothing I can do about that.  I have read about providing linear power directly to RAM and also of changing the motherboard oscillators with higher quality units, but they are thoughts for another day.


So where I am at right now, is that I know how much power to poke into various parts of the XXHE PC, and I am pretty sure I can knock up a little circuit board to manage both the linear power supply and the motherboard, but I don't know how to design and construct high performance voltage regulators, so I am looking for help.

Cheers,

Anthony

Hi all,

I thought I would post a couple of pictures of different design approaches for the ATX psu.

The first photo below shows a three rail linear psu that puts 7A into the three rails of the P24 ATX plug and contains the appropriate chip for handling the ATX power sequencing in conjunction with the motherboard.  Nice...I think that something along these lines would be an excellent final product and very achieveable.

The other end result is something like this Teradak photo.  Note that the first picture will also require passive cooling (the heatsinks) and multiple transformers.

Which layout would you would prefer, the circuit board or the box of wires?  I think we may be able to get a circuit board of this type into the XXHE PC (to keep the wire very short from the regulators to the motherboard and peripherals) and have an external box containing the transformers.

Cheers,

Anthony

PC POWER SUPPLY SUPERVISION

After several worthless google searches I have come up with the following information for a way to make a linear ATX supply that will start ANY atx power compliant pc...

Google search "PC Power Supply Supervisor" and you will come up with a plethora of chips that do the ATX power stuff for us...for example.

A good result...with a little effort we should now be able to make a linear ATX supply that will start and stop any pc.

Anthony

I also had an unusually long shutdown last night...a solid 20-30 seconds after the light went off.

My Xtweaks are almost identical to yours Peter (my Balanced Load is 45), and my cpu was set to 'Auto' which means it overclocks at will, which it does, so it goes up to about 2.2GHz and was dropping as low as 1.6GHz.  This was the default setting in the BIOS, so that was were the measurements were made.  I have performed no BIOS tweaks in relation to the RAM or CPU.


I think our amperages are different during playback for a number of reasons, the most important of which is that the amperages that I have measured to date have been inside the computer at DC, while yours is 222V AC before the computer.  Your AC wattages will be much more accurate than mine because I have plugged into a UPS that updates the screen at about 1Hz and seems to have a resolution of about 10 watts (i.e. I see 58w or 68w but nothing in between).  Also, as mentioned earlier, although my Xtweaks are almost the same as yours Peter, until now my CPU ratio in the BIOS has been set to 'auto' which means that it under and overclocks at its own discretion, so my clock frequency varies with load.  Of course I will change this at a later date.  Another thing to contemplate are RAM timings...have you changed yours Peter?

Thanks so much for doing this Peter, it certainly does look like we can go down the pico psu + single linear supply route for the mobo if we need to.

Anthony

Hi Peter,

My Q5 is 5 as it says in my signature.

Cheers,

Anthony

Hi guys,

I'm not feeling the SFS=4 love unfortunately.  In my setup changing completely to Peters settings makes the bass a bit woolly and affects clarity in the upper mids. Soundstaging is also negatively affected.

From what I can tell my settings differ from Peters as follows:

• my SFS=20 and max SFS = 20
• my clock resolution is 0.5ms
• my Processor Core Appointment Scheme is #4

Of course the difference could be just about anything in the audio system, but I wonder if my Xeon processor and PPAstudio card are affecting these things?

Cheers,

Anthony