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?
Hard Disk Playback Systems
Why are more audiophiles not using hard disk playback systems? The category includes full blown systems by Linn, Escient or Revox; stand alone machines from Yamaha or Harmon Kardon and computer based systems such as Apple/MacIntosh running iTunes software. I've been using an Apple system for about a year and while there are a few drawbacks, the positives are overwhelming.
First the negatives:
- it can be expensive. The Linn or Revox turnkey systems are over $15k. The Apple system I've assembled (including multiple hard disks) cost nearly $6,000.
- a computer is noisy. I've had to place the computer tower within a closed cabinet, but it still introduces 4dB of added background noise into the listening room. I don't believe any of the dedicated systems have this problem.
- the initial setup is tedious. If you have a medium to large CD collection (say 500+), then individually "ripping" each CD and typing in title and song info is quite tiresome. However, if your hard disk/computer is hooked up to the internet, then that info can be automatically downloaded.
The positives:
- assuming you stored the music at full redbook spec (16/44.1), then the sound quality is comparable to a high quality CD transport.
- you have virtually instant access to all of your music collection. Additionally, using "playlists" you can organize your music whichever way you like. THIS FEATURE CANNOT BE UNDERVALUED.
- burning compilation CDs is very quick and easy. Simply click and drag whatever songs you want to a new playlist and hit "burn".
- it's networkable. The computer based and high end Linn/Revox systems have the flexibility to distribute a digital signal throughout your house. This can even be done wirelessly. - it's transportable. Say you going to your vacation home, what would you rather drag along, 100 of your favortie CDs, or a couple of 120Gb firewire hard disks with ALL of your music. Apple based hard disk systems also offer the possibility of downloading playlists to their iPod unit for even greater portability.
I'm sure I've probably left out some aspect of using hard disk playback systems, but I think I've highlighted the major points. The bottom line is that since switching over to a hard disk system I'm listening to music more often and because of the easier access I'm listening to music that I would normally not have selected. As far as I can tell, hard disk systems are a major advance in the enjoyment of digital based music.
First the negatives:
- it can be expensive. The Linn or Revox turnkey systems are over $15k. The Apple system I've assembled (including multiple hard disks) cost nearly $6,000.
- a computer is noisy. I've had to place the computer tower within a closed cabinet, but it still introduces 4dB of added background noise into the listening room. I don't believe any of the dedicated systems have this problem.
- the initial setup is tedious. If you have a medium to large CD collection (say 500+), then individually "ripping" each CD and typing in title and song info is quite tiresome. However, if your hard disk/computer is hooked up to the internet, then that info can be automatically downloaded.
The positives:
- assuming you stored the music at full redbook spec (16/44.1), then the sound quality is comparable to a high quality CD transport.
- you have virtually instant access to all of your music collection. Additionally, using "playlists" you can organize your music whichever way you like. THIS FEATURE CANNOT BE UNDERVALUED.
- burning compilation CDs is very quick and easy. Simply click and drag whatever songs you want to a new playlist and hit "burn".
- it's networkable. The computer based and high end Linn/Revox systems have the flexibility to distribute a digital signal throughout your house. This can even be done wirelessly. - it's transportable. Say you going to your vacation home, what would you rather drag along, 100 of your favortie CDs, or a couple of 120Gb firewire hard disks with ALL of your music. Apple based hard disk systems also offer the possibility of downloading playlists to their iPod unit for even greater portability.
I'm sure I've probably left out some aspect of using hard disk playback systems, but I think I've highlighted the major points. The bottom line is that since switching over to a hard disk system I'm listening to music more often and because of the easier access I'm listening to music that I would normally not have selected. As far as I can tell, hard disk systems are a major advance in the enjoyment of digital based music.
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- 23 posts total
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. |
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. |
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. |
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. |
- 23 posts total