Build a dedicated Audio PC

[kyrill]

Kyrill,
Thanks for the answer/info.

Ground, however is a tricky concept. All it is is a reference. It is not necessarily 0 volts. In fact it hardly ever is 0volts as your mains measurement shows.

The important thing with references is that they are stable. If the reference fluctuates, it will cause anything using this reference to also fluctuate. This is the problem to avoid. So avoiding current flowing on the grounds between two chips or two devices is crucial. Controlling this between chips is tricky but not impossible as it is under the control of the pcb designer. In a lot of cases using a star ground ensures that return currents in a chip don't contaminate the ground of another chip.

Controlling ground between devices is more difficult as it isn't always under the control of the designer. So concepts like star ground don't apply. This is where the problems usually arise. If the ground of one device is at a different potential to the ground at another device then current will flow between devices & a voltage potential will develop.

So when you say that a PC's ground is noisy, I believe this noise has nowhere to go if the PC's ground is floating & the USB devices's ground is also floating. This noise only becomes a voltage when it goes to ground, hopefully at the amplifier, where such low voltage noise will not have much audible effect.

When the floating ground is noisy then as you well explained the reference become noisy as well affecting anything else. like the V+ en V_ data lines, they are part of the "hot" signal path eventually reaching the analogue side of the dac where they have been transformed. What I consider "factor X" ( the color or quality of the water) is pure an "analogue factor" embedded in the digital stream. How else can a USB cable between SSD and PC makes a sound difference when JPlay stores a bitperfect copy of the SSD content before rendering the music signal, in memory? All streams stop in memory. Even the memory stores "factor X", or factor X survives memory.

[jkeny]

When the floating ground is noisy then as you well explained the reference become noisy as well affecting anything else. like the V+ en V_ data lines, they are part of the "hot" signal path eventually reaching the analogue side of the dac where they have been transformed. What I consider "factor X" ( the color or quality of the water) is pure an "analogue factor" embedded in the digital stream. How else can a USB cable between SSD and PC makes a sound difference when JPlay stores a bitperfect copy of the SSD content before rendering the music signal, in memory? All streams stop in memory. Even the memory stores "factor X", or factor X survives memory.

Yes, you raise a good point. Let me try to explain. I said earlier that part of Jplay's improvement in sonics was probably due to this reduction in ground noise fluctuation. But I think another part of it's workings is to prevent fluctuation in the USB signalling itself.

The ground in the USB signal doesn't act as a reference as the signal is a differential (balanced) signal with D+ & D- data lines, not V+ & V- as you said. The ground in this case acts as a means to ensure that the differential signal stays within the input tolerance of the USB receiver chip. This is evidenced by the fact that the USB ground can be cut between PC & USB device & USB signalling often still works fine - it's just not good engineering practise. The interesting thing here is that the sound doesn't improve when this USB ground is cut.

So what is happening with Jplay. There may be a reduction of noise riding on the USB D+ & D-. This may have an effect on the sound. Another thing that I think is happening is that the handshaking/timing signals in the USB protocol have less fluctuation. These signals are the ones that are part of the USB data packet i.e start of frame (SOF), etc. You can find the USB packet structure here http://en.wikipedia.org/wiki/Universal_ ... munication. I believe that variations in the timing of arrival of these packets can cause variations in self-noise in the USB receiver chip & this noise can be transmitted through the PS to other critical parts of the USB device.

This is all very tentative because it is complicated & I'm trying to tease out possible mechanisms, other than ground born noise, that can have an influence on devices that use isolated power. I could change my thinking on all this as new information becomes evident :)

[jkeny]

Anyway, sorry, I didn't mean to drag this thread off topic :)

I have some ADUM chips, I believe, which I can mount on boards & try between an external HDD & laptop.

I also meant to say that I looked into this a long time ago & the Fit-PC was the recommended fanless, low power, boxed PC of choice then. Here's a link to the site now http://www.fit-pc.com/web/ & the UK site http://fit-pc.co.uk/

They have a range of boxed, small form factor options that are all fanless - starting at about €300 shipped & upto a i7 core 16GBn fanless "Intense PC" - don't know the price? Looks like it starts at $399 for base config.

Worth investigating?

An even more interesting site is this one for embedded computing http://compulab.co.il/ This is actually the company, located in Israel, behind the Fit-PC

[kyrill]

To build yourself is more economical..

When i have the S3B in house John, I can loan it to you for a week or two
But I don t know when I can buy one. I can get my hands on a prototype DEQX IV (192khz)
If yes then I must stall the purchase of the S3B
BTW what are the ADUM chips? I mistook them for the OLIMEX

[jkeny]

To build yourself is more economical..

I know it should be but the job of assembling all the components & a suitable case, etc. doesn't appeal to me if the pre-configured version is not a big jump in price. But I don't know, is it?

When i have the S3B in house John, I can loan it to you for a week or two
But I don t know when I can buy one. I can get my hands on a prototype DEQX IV (192khz)
If yes then I must stall the purchase of the S3B

Very generous, Kyrill & I can lend you a MK3 to compare to your MK2 & your Audiophileo :)

BTW what are the ADUM chips? I mistook them for the OLIMEX

Yes, one of the ADUM chips is what is used in the OLIMEX device, AFAIK

[jkeny]

Scott, a non-member wrote to me & I thought it worthwhile posting what he said:

there is a wealth of information available on the Computer Audiophile site here:
http://www.computeraudiophile.com/

even a recipe for a system build:
http://www.computeraudiophile.com/conte ... r-CAPS-v20

the recommendation for passive cooling is spot-on, however, the TDP of the processor suggested is quite high. even the 'lower power' CPU that is recommended has a TDP of 65W, which is still quite high. intel is currently rolling out a new line of processors called Ivy Bridge to replace the previous generation Sandy Bridge line (the processors that are recommended in your thread are Sandy Bridge). the details of the Ivy Bridge chips can be found in the table here:

http://www.maximumpc.com/article/news/i ... _date_leak

note that the i5-3470T has a TDP of only 35W... this is ideal for a passively cooled silent running setup and is the processor i am waiting for to utilize in my next build.

for motherboards, everyone has their favorites, but i would suggest intel for their absolute stability and reliability. gigabyte would by my next choice, but only if there was a reason an intel board would not work.

where power supplies are concerned, i have found the X series from Seasonic to be the best. some of the most complete reviews i've found are done here:
http://www.jonnyguru.com/modules.php?na ... ecatnum=13

they have a fanless (silent) model:
http://www.jonnyguru.com/modules.php?na ... y&reid=200

as well as a couple others that i've used with excellent results:
http://www.jonnyguru.com/modules.php?na ... y&reid=169

http://www.jonnyguru.com/modules.php?na ... y&reid=192

another great source of information, though not audio focused, is silent pc review:
http://www.silentpcreview.com/

sorry for the long email - i hope this information proves useful. i've built a few audio pc's so recognize the steep learning curve for those getting started. i'm waiting on the new low power Ivy Bridge chips to become available and will be building another and picking up one a JKDAC32 to go with it. looking forward to hearing that setup!

best,
Scott

[nige2000]

hi

i have a pc build that might suit this as for my audio equipment and ears might not be as good
motherboard ga z77 up5 th
cpu i7 3770k
power supply seasonic 460w passive
ssd drive
nofan c95 passive cpu cooler
16 gb ram

i have a nvidia 660 in there two its got two fans but it could be taken out to use internal graphics for ultimate silence

i also dual boot windows 7 and mac os x which could be an interesting comparison also

for a new price wary build (bear in mind silence will add cost)
http://www.komplett.ie/komplett/product ... tails.aspx
http://www.scan.co.uk/products/intel-co ... che-retail
http://www.scan.co.uk/products/intel-co ... che-retail
http://www.scan.co.uk/products/nofan-cr ... cooler-95w
http://www.scan.co.uk/products/460w-sil ... k)-atx-psu
this would be enough too
http://www.scan.co.uk/products/160w-pic ... acom-cases

just some ideas really to get a pc with no moving parts
would recommend getting from reputable brands and suppliers its really not worth the hassle if something goes wrong (and it does sometimes)

cheers nige2000

[Ken Moreland]

Hi Nige, sounds ideal to use as an AudioPC especially for Jplay . You could probably do without the graphics stuff as the AudioPC in Jplay spends most of it's time hibernating and stream your music from another laptop. Also a good idea to upgrade to Windows 8 for best sound. Let us know how you get on and don't hesitate to call on all for any support.
KM

[nige2000]

thanks for the reply ken

i tend to use osx for day to day use and currently use it in conjunction with audivarna plus would win 8 and jplay be that much better i do have a upgrade to win 8 i just haven't moved from 7 yet.
ill try out win 8 with jplay see how i get on.

but all said I've very modest audio equipment arcam rpac, yamaha a-s500 integrated amp, monitor audio bx 5s and all my music is digital and on a hard drive my cds are in boxes.
ive bought a couple of albums of hdtracks which are great too

but it does get worse as i dont even use the rpac with the pc I've tried it but dont see a significant improvement over onboard audio and i get better use out of the rpac with the macbook and the headphones which the difference is night and day.

i was eying up the jkdac32 to fill this gap would it be a waste of good equipment on my current setup

thanks nige

[Ken Moreland]

You can do a free trial of Jplay ( it has irritating stoppages built in ) but it's worth buying. Try this with Windows 8 and you should be getting a much better sound. You've got to compare like with like though, I mean compare Jplay and Audirvana via, headphones or amp/speakers. The Jplay settings you use make all the difference, try to get to DirectLink buffer, Xtreme engine and Hibernate on.

The JKDAC32 is a great piece of kit and a couple may well be coming up for sale shortly at good prices.

KM