PC audio the future?

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I'm game for the phenomenon....

Well Bas, I prefer the term "Computer Audio" 'cos I'm doing it Mac based ;) There is definate promise, although it's not always plain sailing.
From a noise point of view, I think external DAC's are probably the way to go, unless you can afford one of the professional audio cards with balanced I/O. We have had a couple of threads for USB DAC's using TI chips.

This thread has a post describing my system, and some discussion of sound card merits.
 
think external DAC's are probably the way to go
I think so to. Spdif and/or the synchronous retrieval of data (vinyl has this same problem) is one of the biggest things to hold back digital audio is my perception.....PC audio has the capability to overcome this problem.


Word out on the street is that no stand alone transport can compete with a computer based solution on a performance for your euro/dollar basis. Although at this early stage there are too many variables still. There aren't too many USB dacs around. But there are even reports that USB to SPDIF conversion from computer based audio has advantages over the traditional transport.
 
Avoiding USB and ramblings....

Personally I'm not fond of USB as a an interface. It seems to be the first thing that's "put on hold" when the processor gets a bit busy, which of course it unacceptable for audio. Whether it can be given priority as a background process, I don't know, or maybe bigger buffers are the answer. My M-Audio DAC is USB and works really well with some computers, but less well with others.... There are Firewire versions that may be better. I wish I'd gone the whole hog and got one of those.

There are a lot of devices out there that turn TCP/IP into audio. I use one in my lounge for wireless connection. It sounds pretty good to me, and never runs out of data. No doubt there are those who could improve it. I do have a mind to try it with an external DAC, but the connection would be optical. That seems to have a worse reputation than SPDIF.
 
Konnichiwa,

Bas Horneman said:
So who else is interested in PC audio (maybe a better name should be hard disk audio?) ....very few if you count the posts here at diyAudio? I guess that those interested in PC audio are frequenting other boards?

I am for one interested, but the problems are many.

In my view the best choice would be a Digital I/O (S/P-DIF) card that can operate fully duplex. Then a custom driver for Linux (or maybe even Windoze) could be written with a suitable main memory buffer build in (several MB) which syncronises the S/P-DIF output clock to the incoming S/P-DIF clock if it is sufficiently in range of the originals sample rate.

Ideally use optical connections to kill any earth loops.

Then you need a box that contains a re-clocker (for the S/P-DIF Signal) and can produce suitable sample rate clocks. Given that you can include the source sample rate in the S/P-DIF Headers you could arrange a system where a PIC first checks the incomming sample rate, then selects the neccesary clock to send up and sends back the clock to the PC with the sample rate also in the header, so with with first incoming blockheader of the correct sample rate the software knows to switch into "sync" mode.

The alternative (for a CD only system) would be to fix yourself to 44.1KHz sample rate, which means you can force the sync on permanently.

At any extent, you should be able to get a near perfectly jitter free electrical S/P-DIF output from a fairly small box. For the most basic design you just need a 44.1KHz S/P-DIF transmitter, a suitable clock and a simple re-clock circuit and TORX Receiver and Transmitter.

Now the software platform I'd find ideal for a transport type device would be Linux and ideally we have an asyncronous DAE Mode (CD/DVD) Drive which will automatically "rip" the data transparently to HD when the CD is first played (and plays asyncronous with multiple reads), afterwards, whenever a CD already in the library is inserted it simply plays it from HD. A suitable database system including CDDB connection to download the Tracklists etc. should sit on top of course.

How does that sound?

Sayonara
 
diyAudio Member
Joined 2004
Another fan here!

In fact I have no other sources except the PC, I use it for everything, CD's, MP3's, 5.1 etc.

I did use to have a Pioneer 737 DVD player for movies and an Arcam CD93 spinner but ditched these very soon after discovering high-end PC audio.

I now use an RME HDSP 9632 with the 6 channel input and output draughterboards. Bit perfect playback using ASIO is a delight and 5.1 is fantastic through TheaterTek 2 with onboard decoding.

I've never heard anything that sounds as good with digital.
 
KYW,

Basically what you've outlined is exactly the route I've been looking at. I guess as some have mentioned, getting rid of the SPDIF transmitter/receiver and tapping I2S off the soundcard is a probable idea. BUT there's no ignoring the sheer simplicity of the SPDIF over TOSLINK method. I have the SPDIF-based circuit worked out already though I was still unsure how best to generate and choose between the 44100/48000 timebase clocks, and I could never really decide on a particular actual DAC that I wanted to build. I intended to isolate the SPDIF circuits from the DAC/clock with some new magnetic isolators (cheaper than the capacitive ones and longer lasting with MUCH less current draw/current spikes than optos).

Of note, there are some pretty cheap soundcards that already synch to external clocks automatically, (though I don't know what sort of state the linux drivers are in, if they even exist). Also they support bit-accurate sound API's so you can skip the windows mixer and so forth and get an exact output, even with something silly like winamp (though foobar and jriver media center are more likely sources, and they of course support it as well).

Ultimately the drawbacks I saw:

1) If we stick to SPDIF for simplicity of cabling and the ability to place the computer FAR away from the system, and use TOSLINK to break grounds, you need to do SPDIF<->TOSLINK conversion next to the PC, not really a big deal just an extra little box.

2) Choosing between 44.1/48.0 timebases, and then between individual sample rates. Just need to use one of those fancy programmable clocks, or have two master clocks and some divider circuitry. We could easily send sample rate selection data from the computer to the DAC via a third TOSLINK cable transmitting basic RS232, but none of the software (foobar, winamp, jriver, etc...) supports such function by default (of course), so it would have to be added.

3) Just availability of formats/music on the PC. Pretty much limited to CD only as there is no working DVD-Audio or SACD ripping software, and most likely never will be for SACD. Still... I think a setup like this if done properly is definitely the ultimate transport for CD ... so still a worthy project.

If anyone has ideas on clock generation/selection I'd love to hear 'em.
 
Konnichiwa,

Rescue Toaster said:
Of note, there are some pretty cheap soundcards that already synch to external clocks automatically,

Which ones? I'd be gratefull if you have any info.

Rescue Toaster said:
1) If we stick to SPDIF for simplicity of cabling and the ability to place the computer FAR away from the system, and use TOSLINK to break grounds, you need to do SPDIF<->TOSLINK conversion next to the PC, not really a big deal just an extra little box.

Yes, but that box can use a suitable set of cable drivers/receivers and a standard Cat5 network Cable to send/receive clock and signal with two pairs in the Cat 5 left for powering the liittle module.

Rescue Toaster said:
2) Choosing between 44.1/48.0 timebases, and then between individual sample rates.

To me that means two clocks:

24.576MHz and 22.5792MHz.

With a divider we get the correct clock rates for:

32/48/96KHz and 44.1/88.2KHz

The CS8414 can read the sample rate from the S/P-DIF headers in consumer mode up to 96KHz and the CS8404 can send the sample rate up to 48KHz (surprisingly both on page 24 or therabouts of the respective datasheets).

An 8420 may also be used as it has independent receivers & transmitters on board, but I think you need to use software controlled mode and a PIC to get the sample rate from that, on the CS8404/14 you have hardware pins available.

So, you simply take the Toslink signal, buffer it and send it down your long cable (with the correct drivers 100m Cat 5 no sweat). At the end you re-clock the dignal but ON TOP you send it over to a CS8414 to give you clock selection signals. You use a CS8404 to send the clock masked as S/P-DIF back again including the clock settings where available. Together with two clocks, dividers and a little selection logic this could be a very small PCB.

Rescue Toaster said:
3) Just availability of formats/music on the PC. Pretty much limited to CD only as there is no working DVD-Audio or SACD ripping software, and most likely never will be for SACD.

Wrong on both counts, DVD-A can be ripped (just like DVD's) and SACD is coming to the PC as well, if converted to PCM IIRC. Only a question of time IMHO.

Rescue Toaster said:
If anyone has ideas on clock generation/selection I'd love to hear 'em.

See above, I'm a bit oldfashioned and in a pinch prefer to do things in hardware....

Sayonara
 
Acoustic noise

Whatever method is used, it's essential to consider the effect on ambient noise levels.
For most, this means a fanned computer needs to be in a different room.
Laptops are almost silent. Fanless computers are an option. The Mac mini is almost silent. Some of the Via ITX series PC motherboards are fanless, and are completely silent when a fanless power supply is used.

This is the device I use in one location: AirPort Express Base Station with AirTunes
At £88.99 ($129) I think it's a bargain. Will work on Mac or PC with iTunes. Works wirelss or wired.
 

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Hi Guys

Can I throw in my 2 cents worth?

this is what I would like to try to do :

a) Have a dvd drive in a PC acting as one music source (plays CD and DVD-A etc.)

b) Having something like iTunes controlling everything including access to audio files on the hard disk whether they be MP3 , WAv or whatever. Essentially a big juke box..

c) Output via some sort of digital thingo essentially like the digital out on just about any cd /dvd player these days. (Can this be on a sound card and if so which and would the card degrade audio quality??)

d) take the "standard" digital out (S/PDIF ???) out to my dcx2496 electronic over (it willl accept digital signals) which will split the signal 3 ways in the digital domain before using its own DAC's for conversion.

e) Run analog outputs from the dcx2496 into a volume control based on a "triple decker" version of the PASS x2 preamp to control 3 seperate power amps..

f) but backtrack to this (and this is the main reason for not just running a CD player into the DCX) .......................before outputing the digital signal from the PC , treat it along the lines of a digital 1/3rd octave eq -used in conjunction with a PC based RTA OR BETTER STILL some software based version of a DEQX (http://www.deqx.com/) system.......

If this works we may be able to go fully digital from the CD source (or HD) EQ it and pass on to DSP xover and then its DAC's and into an analog amplification chain. .. the signal to the speakers would be eq'd to match this way..

Any comments ??
Please go easy - I don't have a great grasp of electronics and especially digital lingo...


Cheers from down under
 
I'm swiching for an analog active crossover system to an all digital pc based system.

pros: I can do ALL.... Crossover, convolution, EQ, control, etc, etc, etc.....
it's funny, maybe.... too much funny
Can improve the sound, specialy using DRC tecniques (digital room correction)

cons: Time to setup... , technically quite complex and too much posibilities
 
George,

A: When you play discs in this kind of setup they run at high speed. The noise level can be high. It's better to rip the disks to Hard Drive first, although it is possible to play them from Hard Drive while they are being ripped.

B: iTunes is great for this as long as you don't want to play protected WMA files.

C: The SPDIF out of sound cards is sometimes no better than the analogue. Some even do a sample rate conversion to 48KHz even if the source file is 44.1KHz (as ripped from CD). The quality of your sound card is paramount. This is why we are considering external DAC's.

Can't comment on D E or F.
 
Konnichiwa,

george a said:
c) Output via some sort of digital thingo essentially like the digital out on just about any cd /dvd player these days. (Can this be on a sound card and if so which and would the card degrade audio quality??)

You can do that. You can even get quite excellent multi channel PC to AES/EBU Pro-Audio interfaces, however just as with a DVD or CD Player, the output quality varies widely.

george a said:
d) take the "standard" digital out (S/PDIF ???) out to my dcx2496 electronic over (it willl accept digital signals) which will split the signal 3 ways in the digital domain before using its own DAC's for conversion.

e) Run analog outputs from the dcx2496 into a volume control based on a "triple decker" version of the PASS x2 preamp to control 3 seperate power amps..

You can do that without problems, or at least no more such as you would have anyway.

george a said:
f) but backtrack to this (and this is the main reason for not just running a CD player into the DCX) .......................before outputing the digital signal from the PC , treat it along the lines of a digital 1/3rd octave eq -used in conjunction with a PC based RTA OR BETTER STILL some software based version of a DEQX (http://www.deqx.com/) system.......

There are solutions for that too, but they consume a good deal of computing power. If you do that you could just as well throuw the Digital X-Over function into the PC as well (and use multiple DAC's or just a really good 6-Channel Soundcard - there are some projects like thaton the net).

That said, given the cost for Behringers DEQ2496, why not use that one? Also, the DCX has the ability to apply quite a bit of equalisation, you may find it will suffice.

Sayonara
 
The solution I chose for PC audio is the Slim Device's Squeezebox2. I am building a file server running on Redhat 9.0 that will be a storage box running slim server. The file server will be in my utility room just below my listening room. The squeezebox has either wired or wireless ethernet connections and puts out a SP/DIF signal which I will run into my DEQX.

The Squeezebox isn't dirt cheap but it is a really nice interface and allows me to get the file server out of my room. The software is open source and runs on Linux or Windoze (not sure about mac).
 
Squeezebox

Slim server is indeed available for Mac. What is less clear to me is whether Apple Lossless format audio files are supported. I've found ambiguous info.

I did consider the previous Squeezebox for my system, but was put off by the high UK markup - nearly twice the US cost. It was also impossible to order from their US website directly with a UK address.

It does look a nice, well built unit though.
 
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