Good point, and I mentioned this option is one of the previous replies. USB 2.0/firewire OR ETHERNET outboard sound card would act as SPDIF interface, which means to take, let's say, WAV data stream, encode it to SPDIF format, and transmit it to an external DAC. Eencoding to SPDIF stage may be Achilles' heel there, by very same reason why many people mod their CD players with better clock circuitry. I guess that SPDIF interface, if not audiophile-grade (whatever it means) designed, may still cause all kinds of jitter.
However, just find an outboard card of an appropriate quality, and... it's done.
BTW, let me know if you find one. |
Dmitrydr, I think one way to implement the HD playback system is to use an USB 2.0/firewire outboard sound card. They are very common and inexpensive. From there, output a digital signal through SPDIF or AES/ebu to de-jittery device and then to an outboard DAC for playback.
It will not be very expensive either. An outboard sound card is around $200 and up. A 200gig HD is < $200. A cheap desktop computer is around $500. Now you have a decent HD playback for less than $1000. The only problem I see is the lack of remote, but I am sure there is some kind of wireless mouse/keyboard available.
There you have pretty much eliminate the issue of computer noises. In fact, you can ask the sound card to consistently output a 96/24 signal. The only problem is for SACD and DVD-A playback. I have not seem it done on HD system. Besides, the files are too large to store on HD anyway. |
Onhwy61, it's just my well forgotten electrical engeneering education - I moved to a computer programming right away, but it still sits somewhere on a background... :)
CD player doesn't have fans, megahertz buses, usually has well isolated power supplies, less circuitry, boards, contacts... I absolutely agree with you that sound cards designed with professional requirements in mind may eliminate most of the problems. But I'm doubt that typical consumer-oriented sound card that (as I saw on forums) usually used for this purpose, was designed with sound quality in first place. |
Dmitrydr, what makes you think that a typical CD player is not highly polluted with RF? Believe it or not designers know how noisy the computer environment is and some have actually taken step to effectively deal with it. Also don't assume that everybody is using a $200 soundcard. That's no more logical than assuming digital playback is defined by the performance of a typical $500 CD player. I recommend you check out some of the products from RME or Lynx. |
AFAIK RF noise from computer may easely affect SPDIF signal causing timing error (which, actually, is jitter). So signal does get through, but with transmittion errors. External word clock link would mainly resolve this problem, but it indeed very rare option. And the difference in jitter situation between hard disk playback and CDP is in design and build quality between $200 sound card and 10-20 times as expensive CD player. Meaning that if you find sound card of the comparable quality and use it in hard drive music server that made with the same level of perfection (separate power supplies, isolated digital circuitries, etc. - to eliminate electical jitter) as a good CDP, you probably will get better results then in that good CDP.
Another way would be to eliminate SPDIF interface at all: use firewire or ethernet protocols, which can transmit the timing data encapsulated with the actual audio data on a very high speed, 100% CRC checked and confirmed, i.e. lossless. Thus, transmit music data from your computer in your office to a high quality network music receiver on your rack, which would just reformat the data from firewire to SPDIF in a protected environment without fans, multiple boards, and other noise-generators. |
SPDIF will send clock data with the music data, and that is what the DAC will typically sync to. So if the signal coming in is jittery, the sound output by the dac suffers. (My grasp on the science behind it is strong enough that I think I understand it, but weak enough that I couldn't possibly explain it to anyone...) Some DACs now claim to strip the data from the clock and re-clock it. Some DACs claim to be able to eliminate it altogether, like the Benchmark DAC-1. There are a couple of links at the end of this article of theirs (http://www.benchmarkmedia.com/appnotes-d/jittercu.asp) that you may want to check out. www.jitter.de is a good place to go too, I suppose, but there are tonnes of other sites (and opinions!) out there. |
If you have a professionally oriented sound card it will have word clock I/O. Unfortunately, very few audiophile type DACs have such an input. If your DAC reclocks the input signal, then jitter shouldn't be a problem. The jitter situation with hard disk playback and external DACs is really no different than using a standard CD transport and a separate DAC. |
To address the issue of jitter it would seem that the external DAC would need a way to sync to the soundcard "clock". Is this done through the SPDIF connection? |
Let me preface this by saying that I can do no better than regurgitate what I've read elsewhere. RF noise, unless it's pretty substantial, shouldn't be a problem. If the signal get through, the signal gets through. (Satellite tv would be a good example; it looks perfect until it goes haywire.) I suppose that your cable could act as a conduit for nasties making their way into the dac, which I would think is another issue altogether.
As for jitter, there are numerous technologies in DACs that lay claim to the ability to reduce or even eliminate jitter, and some quite convincingly.
All in all, I'm beginning to think those that those "purists" who dismiss a HD transport out-of-hand are sounding more and more like luddites every day...(as improvements are made to narrow the gap, of course!) |
How do you, guys, handle emi interference? If you connect sound card using SPDIF, AFAIK it'll be affected by RF noise. Another option is TOSLINK, but it's by itself compromises sound quality.
And, jitter: how do you know your card produces low jitter? I read that $200-$400 "professional" sound cards are not really good about jitter. Just compare quality of the clock on $200 card and in $2000 DAC... Chain as strong as its weakest link is... |
Dallas,
I think that as long as you've got a soundcard that's pumping out the right bits, I say go crazy. Every audiophile out there does something to his or her transport that improves the sound quality, whether it's some sort of cd cover, magic spray or putting it under three phone books and a bag of sand. In other (their) words, there is no perfect transport. Is your hard drive a perfect transport? Not likely. But I'm sure there are tonnes of things we'll figure out along the way to make it better. For now, all we can do is go with a technology, be it vinyl, CD, or HD, and do your best to overcome its limitations. I'm of the opinion that hard disks are the way to go.
PMI_Guy, you mentioned HDCD. Windows Media Audio 9 decodes it...
Deke
|
Given some of the inherent limitations listed above what would you folks recommend as an "upper limit" on what would be resonable to spend on a DAC. i.e. it seems silly to buy a Mark Levinson reference DAC to connect to a $200 soundblaster soundcard.
But, I bet many have tried and experienced the difference an audio component DAC can make over letting a receiver (or the soundcard itself) do the analog conversion.
I was just curious what combinations folks have tried and whether there was a noticable difference. |
There's been alot of favorable comments about EAC (Exact). The link Is:
http://www.exactaudiocopy.de/ |
I have a question. To create wav file from a CD, do you guys have any idea on which CDROM/CDRW/DVDROM/DVDRW to use, what is the reading speed, and which software to use to get perfect wav file?
Thanks. |
I think that hard disk playback systems should be the future but we're not there yet and we may never be.
As mentioned, software and ease of use are lacking. It's kind of a DIY area now. Also, audiophiles are generally the at the analog end of the spectrum. DIY computer projects are not something an analog guy relishes and are not something that the audio mags often review.
There are format issues also. Audiophiles are generally not happy with 16 bit CD quality. Both 24 bit digital formats (SACD, DVD-A) have copy protection so they're out. The wild card is HDCD which Microsoft bought. Who knows what they're thinking.
On the plus side, I think that a hard disk has the potential to be an excellent transport. We will be able to store 1,000 CD's on a hard drive within a few years. The potential to create playlists is awesome. I'll be looking at this type of system seriously when the drives get more capacity, especially if it becomes a little more mainstream as far as software, interfaces, etc. |
Mdoughty, drops, pops and clicks can be eliminated by turning off all other programs when you rip the CD to your hard disk. |
MOTU and Metric Halo both make Firewire based interfaces for Apple Macs. Each has a multitude of I/Os which most audiophiles will find superfluous, but they also sport digital ports which will allow you to connect an outboard D/A to the Mac Cube.
It's a shame that the playback software doesn't support higher resolution recordings. I've written to Apple, but there's been no reply. |
I was using a hard disk playback system with my Apple G4 cube. Now however I use the dvd drive as the source. The cube is perfect for this application, it is small, it has no fan, and it is a beautiful machine. I got away from encoding my collection into wav files, it just got too time consuming and I couldn't perceive any audible differences between itunes playing the tracks off of the dvd drive or as a file from the hard drive. If your experiences are different please let me know. The cube does not have pci slots for sound cards so you have the option of using any one of a number of usb or firewire products built for the pro audio market. My system consists of the cube as a source, a roland ua 30 which is a usb d/a or a/d interface which provides volume control and a set of stereo rca outputs (digital toslink and coax in and out as well) to a mcintosh mc 2102 amp to living voice avatar obx speakers. Cabling is nordost blue heaven throughout.
These are some of the perceived limitations of a hard disk playback system.
1. Computer enclosuers have lots of emi interference which induces noise, this can be mitigated by using an outboard d/a converter as opposed to a sound card which is in the tower.
2. I have found no pro audio device which addresses the first limitation that has similar d/a conversion of audiophile grade equipment. Additionally most pro audio devices are engineered for hard disk recording as opposed to playback and these devices have alot of inputs for recording which is superflous to playback.
3. Computer software. I have never been pleased with the playback quality of itunes. Lets face it, these programs are designed for mp3's, which no audiophile who has invested countless hours and dollars in their system would consider using. I have experienced many dropouts and pops in my music as a result of this player (itunes). Also there is not as yet software that can handle hi rez sources such as sacd and dvd-a or even a program that can playback hdcd disks.
I would love to hear others ideas on equipment that can address all of these problems. I have been considering whether or not to buy a decoder which will reclock and convert the signal coming from my transport (computer) by using the coax output of the roland but ideally there would already be a high end device that could do this that had a usb or firwire input so I could get rid of the roland. Otherwise I'll be buying a wadia 861. |
We'll all just need massive hard drives in our Mac's (PC's for those who still use them!)
KT |
Onhwy61,
You get no argument from me on anything you said. I didn't elaborate but "most" audiophiles want all kinds of tweaks to be done to their CDP's such as isolation feet, high-zoot interconnects, aftermarket power cords, on and on. I doubt that a computer case would satisfy that need. It wouldn't trouble me a bit to plug this sucker (if it were quieter) into my system and sell my CDP. This type of use will become more common as we go along especially if the big guns get their way and sell digital music through downloads only and cut out the retailer. |
Lugnut, regarding your comment about computer based systems not being good enough for most audiophiles, I think you're misinformed. The key to getting high quality sound is the interface between the computer and the rest of your audio system. If you rely upon the D/A conversion on your computer soundcard, then the sound quality is limited and I agree that most audiophile would not find it more than just satisfactory, but if your soundcard can output a stable, low jitter digital signal, the sound quality can match that of a high quality CD transport. I use an RME Pro96 card which outputs both an AES/EBU (24 bit) and S/Pdif (20 bit) digital signal.
You should also note that virtually every CD release in the past decade was edited on a computer based hard disk system. That includes all the horrid sounding overcompressed pop/rock releases as well as the great sounding minimalist recordings so loved by audiophiles. As such, I don't see how a computer based system is not good enough for most audiophiles. |
The cost of the Linn keeps me from seriously considering such a move. The computer based systems are not good enough for most audiophiles. |
I have my network server running 2k server, and I use windows media to encode and play my files. At one point I had a 400 gb raid setup, and ripped all of my files as .wav. Playback was good, but the limitations were the connections to the stereo. I was going to buy a stereolink or onkyo usb audio device, but have since moved my pc's out of the rooms where I have my stereo's, so now i just listen through desktop speakers when I am on the pc. I am suprised at the noise you got with a G3/4 based system, they usually run alot quieter than windows based systems since they use heatsinks instead of heatsink/fans. I did use my powerbook at times and listened to music off the network and had very good results with that setup, very quiet and did not take up much space. |
