Author Topic: Building an Audio PC  (Read 13352 times)

Offline Carlman

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Building an Audio PC
« on: May 12, 2010, 07:32:27 AM »
So, I've enlisted the help of my friend, Nick to build a new audio PC... Goals are simple: be the best transporter for flac or wav files.  I don't care much about hi-rez but it should be able to play those too.

I'll let Nick chime in on his hardware choices... right now I'm looking at sound cards.
I found a USB to SPIDF converter ...here...

I thought it'd be best to get the digital path started outside the PC, rather than doing a traditional PCI card.  I wish there was a PCI to PCI extension cord so I could physically move it out and still use a PCI card. 

Anyway, what's the hot solutions for sound cards these days?  Just trying to get a bit perfect and super clean digital signal out of that noisy PC...

-C
I really enjoy listening to music.

Offline mdconnelly

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Re: Building an Audio PC
« Reply #1 on: May 12, 2010, 08:44:44 AM »
Facinating topic, Carl!

I'm scratching my head a bit - when you say wanting to start the digital path outside the PC, what do you mean?  I assume you want the DAC outside the computer (and not on the sound card)  such that the PC is serving up a digital source via either USB or SPDIF or some other method but those are all digital paths.

There's much I want to learn about this so thanks for starting it here!  Are you still going down the Linux path?

Offline _Scotty_

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Re: Building an Audio PC
« Reply #2 on: May 12, 2010, 11:12:07 AM »
Carl,you might want to look at getting a USB to S/PDIF Converter using the PCM2704 codec.
I started out with the USB to S/PDIF Converter that you linked to and it is inferior in everyway to the PCM 2704 codec. The DIGITALPCLINK using the Phillips UDA1321 has a smaller sound-stage,reduced dynamics and an overall grungy sound compared to the PCM 2704. Here is a link to a USB to S/PDIF converter using the PCM 2704. http://cgi.ebay.com/MUSE-HIFI-USB-S-PDIF-Converter-USB-DAC-PCM2704-/120563258242
Good luck with your project.
Scotty


Offline Carlman

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Re: Building an Audio PC
« Reply #3 on: May 12, 2010, 11:22:27 AM »
Mike, I'm not trying to get the DAC out of the case, I'm trying to get the digital source (spdif processing) outside the case.  The DAC is already its outside...

One option I found was that digitalpclink that I linked to that could accomplish this... Scotty found something else that worked better... but using a USB/spdif is just one option.  I'm looking for all ways to get the bit creation process physically removed from the PC as much as possible.  And that's just my theory...

There are a lot of soundcards that claim to be 'bitperfect' yet only the Lynx sounds notably better to me, as a digital transport.... and the others vary a little also.  It 'shouldn't' be the case but it is..  So far the USB DAC has sounded very good to me.. very smooth and whole.. but I'd like to have a reference level spdif out too so I can compare. 
I really enjoy listening to music.

Offline _Scotty_

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Re: Building an Audio PC
« Reply #4 on: May 12, 2010, 11:37:45 AM »
I am looking very hard at the ART Legato USB-SPDIF Asynchronous Converter.
http://www.analogresearch-technology.net/
This may be very close to as good as it gets,the drawback is an inability to playback HiRez files.
The Hi-Face converter also looks promising but I am waiting for a Linux driver.
Scotty
« Last Edit: May 12, 2010, 12:13:38 PM by _Scotty_ »

Offline tmazz

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Re: Building an Audio PC
« Reply #5 on: May 12, 2010, 12:28:23 PM »
I'm looking for all ways to get the bit creation process physically removed from the PC as much as possible.

Carl,

Just curious, is there a specific technical reason why you want to get the bit creation process outside of the PC case? If the reason is simply because I've heard it that way and it seems to sound  better, that's OK. (There are plenty of things that we as audiophiles do that conventional wisdom says should make no difference, but does anyway.  :shock: )

Of course the overall goal is better sound, but I was wondering if there was a specific situation or interaction that you were looking to facilitate or avoid by placing the bit creation hardware a spearate physical space from the rest of the PC?  :-k
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Offline Carlman

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Re: Building an Audio PC
« Reply #6 on: May 12, 2010, 01:31:45 PM »
With the PCI cards I've tried there is a background noise to them that you don't notice until it's not there.. Which has been my experience comparing a PC transport to a high-end cd-spinning transport. 
My PC was better than most cd and dvd players when I used the PC as a transport.  However, that wasn't the case with the Oracle and some other (Raysonic? BAT?) can't remember.. anyway, 3-4,k players seem to do transport as well or better than my somewhat nice PC with $250 pro audio card.

I have since changed things around.. I reconfigured and re-purposed the old audio PC to be the audio server.  Now I use a cheap throw-away PC for the sound room that is very quiet but requires a riser board to do PCI... which I don't have.  So, I'm using USB directly to DAC. 

I just thought about it.. and I think using USB as the digital out is like using a PCI card really... The bits are generated in the noisy environment.  I think a PCI expansion board would work, putting the audio card in its own case... but I wouldn't know unless I tried.. and compared it to one that's inside the case.

I've seen these things made.. but they start in the $800 range by a company called Magna.. just to move the PCI outside the case.. which is nuts to me.  I can't believe no one has made a cable that just plugs into the PCI slot on the mobo and then provides an empty PCI slot at the other end of that cable.  That's what I'd really like to find... It just shouldn't cost very much.

-C
I really enjoy listening to music.

Offline bpape

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Re: Building an Audio PC
« Reply #7 on: May 12, 2010, 02:39:13 PM »
Not sure why going out a PCI slot is any different than going out USB. It's the same signal, no conversion, just on a different bus on the motherboard.  Running USB out and then converting from USB to SPDIF should be just fine.

Am I missing something?

Bryan
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Offline Carlman

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Re: Building an Audio PC
« Reply #8 on: May 12, 2010, 03:57:25 PM »
I don't know.. why do they bother using PCI or USB? Why not just have everything on 1 bus?
I'm not a PC designer... I just know that PCI slots have a lot more pins and that's what all the sound cards use.  From what I've heard, USB to spdif converters aren't all that great... which makes sense... since you're changing the nature of the signal from 1 bus to a device output... and the PCI boards do the same thing but generally better.. So, what IS the difference?
I really enjoy listening to music.

Offline bpape

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Re: Building an Audio PC
« Reply #9 on: May 12, 2010, 04:14:11 PM »
I guess that's my point.  Why even do the SPDIF step?  Why not just a straight USB DAC?  Less conversions, less problems.  Not as many choices but they are getting more available - like the Empirical Designs stuff.

AFAIK, whether you use a PCI or a USB output, there's no difference in data.  Just a change in how it connects to the memory, cpu, peripherals, etc.

Bryan
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Offline richidoo

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Re: Building an Audio PC
« Reply #10 on: May 12, 2010, 05:20:59 PM »
Jitter is the variable. Different kinds of jitter, and different degrees. A PCI soundcard like Lynx with its great onboard clock will output a nice SPDIF stream, even inside the case. If your DAC fixes jitter then just use integrated SPDIF off the mobo. The trend in state of the art computer audio now is USB DACs. The hirez limitations of USB are taken care of in the newest DACs. Anyway, the clocking is the most essential part of moving a digital stream between components. Either buy transport and/or DAC with good clocking and jitter fixing scheme, or use an external clock, or master/slave clock connection between transport and DAC.

Shane brought over a M2Tech USB>SPDIF dongle to my last g2g. We played 24/96 files through it into Buffalo32>Sol's transparent amp>Gemme Katana ceramic drivers>all JP SC3. The resolution was extreme but still smooth. Treble was too hot, but that was the speaker's fault. I would use that dongle without hesitation in my music PC. Definitely high end capable. I would not be surprised if the Lynx products are even better, but only a head to head comparison would show any limitation.

The bits are created at the recording, or at least at CD mastering. From that point not much can hurt them, error correction keeps it pure. Jitter is the only variable, and it is controlled with a clock. The nice thing about the Slim Transporter is the word clock input. Lynx has this too, or use it's own wordclock output to clock the DAC.

Offline tmazz

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Re: Building an Audio PC
« Reply #11 on: May 13, 2010, 06:22:49 AM »
With the PCI cards I've tried there is a background noise to them that you don't notice until it's not there.
Much of the noise associated with PCs is generated by the switching power supplies that they use. Unfortunately this means that the noise is distributed to every component in the PC along with the DC output. :( I would think one of the best ways to deal with this noise is to try and cut it off at the source. Have you given any thought to trying some of Alan Maher’s CBF devices inside the PC?  I would  suggest putting (at least ) one onto the outside of the power supply case with double stick tape and another one on the bundle of DC output leads using tie wraps. These little boxes do an admirable job of pulling the nasty artifacts from refrigerators, air conditioners and the like of your AC lines; I don’t see why they wouldn’t do the same for internally generated power supply noise in a PC.  And heck they are only $25 a piece, so what do you have to lose?
« Last Edit: May 13, 2010, 06:26:12 AM by tmazz »
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Offline tmazz

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Re: Building an Audio PC
« Reply #12 on: May 13, 2010, 07:31:46 AM »
I don't know.. why do they bother using PCI or USB? Why not just have everything on 1 bus?
I'm not a PC designer... I just know that PCI slots have a lot more pins and that's what all the sound cards use.  From what I've heard, USB to spdif converters aren't all that great... which makes sense... since you're changing the nature of the signal from 1 bus to a device output... and the PCI boards do the same thing but generally better.. So, what IS the difference?

PCI and USB are fundamentally two different animals with totally different functions within a PC. PCI, (whose full name is the Peripheral Component Interconnection Local Buss) is a set of specifications defining standards that enable different components within a motherboard to “talk” to each other. These components can either be integrated circuits soldered right onto the motherboard or separate card that the plugged into a connector that has commonly become known as a PCI Slot.

USB (Universal Serial Buss) on the other hand is s specification that was developed to facilitate the connection of external devices to a PC. As opposed to moving data around the inner workings of the PC USB ports were devised as a replacement to the parallel and serial ports that used to be used to connect devices line printers to a PC.

So the two busses serve separate purposes and are not really substitutes for each other. The real question from our standpoint is, what is the best way to interface an external DAC with a PC music server?

In a PCI based solution the digital bit stream is combined with timing information on an expansion card and outputted to the world as a standard s/pdif signal  which can then be interfaced with out DAC via a coaxial or optical cable.

In the case of a USB interface the digital data is transported out of the PC to a DAC where the s/pdif conversion is done before the signal is passed off to the D/A section. (This is my impression based on what I have read. There are certainly other AN members with more experience in that area than I and I welcome any comments or corrections from them. Lizard King – any thoughts?) It is interesting to note here that using a USB interface does not avoid the PCI buss as all of the internal communications within the motherboard to deliver the signal to the USB transmitter goes over the PCI buss.

So back to Carl’s original question, which is better?  As usual, there is no single answer here because each of the designs involves a number of tradeoffs.  The use of a PCI audio card provides a more straight forward data path , but at the same time limits us on the S/P dif side. Most audio cards are designed by computer geeks. Even under the best of circumstances, I would dare say that an audiophiles standard of what constitutes good sound is quite different from the standards of a geek. (Not to mention the difference between what we would be wiling to pay for an audio component vs. what the rest of the human race would consider a reasonable price for a similar functionality.)

In favor of the USB interface, putting the s/pdif processing in the DAC allows that conversation process to be designed and optimized by engineers that not only are used to designing to audiophile standards, but are also likely to have the budget to do what needs to be done. However; the downside of the USB interface is that the digital signal has to go through additional stages of signal processing and protocol conversion leading to the possibility that while the USB DAC might be better equipped to process the digital season, it can be faced with the possibility of getting a lesser quality digital signal to work with right from the start.

So both methods have there own advantages and challenges, each of which is wrapped up with words like “could”, “might” or “in theory”.  IMO the whole thing boils down to implementation.. Unfortunately, at this point the only way to know for sure is to set the stuff up and listen for ourselves. Perhaps as more and more people do this and share their experiences her and on other forums like this we will be able to see some patterns emerging and get a better idea of which technology  is starting to sound better overall.

But for now, trust only your ears.  8)
Remember, it's all about the music........

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Offline tmazz

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Re: Building an Audio PC
« Reply #13 on: May 13, 2010, 07:35:31 AM »
If anyone is interested in further info, here are the Wikipedia links for the PCI and USB Busses:

http://en.wikipedia.org/wiki/PCI_bus

http://en.wikipedia.org/wiki/Usb
Remember, it's all about the music........

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Offline richidoo

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Re: Building an Audio PC
« Reply #14 on: May 13, 2010, 08:56:04 AM »
Good info, thanks Tom!