Music from hard drive better than CD?


Hi folks, I'm considering to buy a MacIntosh G5 for using it as a source in a high quality audio system. Will the Mac outperform the best CD-transport/DAC combo's simply by getting rid of jitter? It surely will be a far less costlier investment than a top transport/DAC combo from let's say Wadia or DCS, hehe. What is your opinion?
dazzdax
Hmmmm. Something is not right here.

$50 portable CD players incorporate electronic antiskip mechanisms by reading ahead 5-10 seconds and storing the data in a buffer--and they are far from audiophile grade transports or players. The challenge of high fidelity playback is not limited to problems with spinning a disk, and it is absolutely no surprise the today's PC hard drive configs don't compete with EMM Labs gear.

CD audio encoding is surprisingly complex (e.g., see http://www.ee.washington.edu/conselec/CE/kuhn/cdaudio2/95x7.htm). And one result of this is very high bit-for-bit fidelity. It is true that the CD Audio redbook spec has less error correction that CD-ROM--i.e., it "allows" a certain level of interpolation of data--but in general it seems that this is not the problem (see a classic at http://stereophile.com/reference/590jitter/index.html); good transports or bad, you can be pretty sure that your DAC is getting a bit-perfect feed.

The next area to look at is jitter. This is any variance between the actual data clock and an ideal clock. Transports, hard drive controllers, DMAs--they are all going to have jitter, so replacing a transport with a hard drive will not remove this problem. It may allow it to be mitigated--or may be not: PCs are hostile environments and jitter is measured in *billionths* of a second.

There is no doubt that mitigating jitter can improve audio reproduction, but in Harley's article at the above URL he looks at CD tweaks and found audible differences yet no difference in jitter; i.e., something other than jitter--at least as he was measuing it--was causing an effect on his "perfect sound forever."

I think the problem is in the CD format when it leaves the factory or the website, and you are doomed before you ever bring it into your house. Here's why: The CD spec does not store the time information along with the amplitude. It just stores the amplitude, and the clock is recovered from the signal. If they had spec-ed it in packets like TCP/IP embedding clock and amplitude, then you could recover ALL the data, amplitude and time, bit-perfect, from a CD, a website, even a carrier pigeon--the transport mechanism wouldn't matter. But the clock is implied in the signal, and that means that it has to be re-created at playback. Ever wonder why transports make a difference on playback? It's because the servo is jerking the DC waveform and introducing trash in other parts of the CDP; same with digital cables: because the clock is not "data" per se, the way your DAC gets the data through your cables from the transport can affect the time reconstruction.

I think computers have a lot to offer audio, and, like digital amps, may drop the price floor on very good reproduction. But for *really* good reproduction, it'll be years before anything beats a CDP or TT.

>>it is absolutely no surprise the today's PC hard drive configs don't compete
with EMM Labs gear.<<

Surprise? Who said this was a surprise?

>>good transports or bad, you can be pretty sure that your DAC is getting a
bit-perfect feed.<<

Okay.

>>jitter...replacing a transport with a hard drive will not remove this
problem.<<

You're not just replacing the transport with a hard drive; If you use
something like the Apogee Mini-Dac, you're also introducing a high quality
clock and DAC.

>>something other than jitter--at least as he was measuing it--was causing
an effect on his "perfect sound forever."<<

There are many things that go into making a great sounding DAC.

>>But for *really* good reproduction, it'll be years before anything beats a
CDP or TT.<<

That's vague. Depends on what you call a *really* good CDP. It has already
been established that a computer plus $1,000 DAC will not compete with
$10,000 Emm Labs gear, but neither will any other digital gear.

A computer plus $1,000 DAC absolutely sounds better to my ears than many
CD players.
For those who can build their own, here are some great links:

1. At the botom of this page you will find nice Multimedia cases: http://www.xoxide.com/silverstone1.html

2. Then you can install a quiet/fanless power supply from here: http://www.xoxide.com/fanlesspsu.html
There is a nice doc by Jon Risch at : http://www.geocities.com/jonrisch/jitter.htm.

I think one can partition what I shall call 'convenience' and 'sound reproduction' roughly to the transport (or source medium) and DAC respectively. Here's what I mean: I really liked Onhwy61's post where he was able to move from song to song, quickly and easily. For me, that would be a wonderful part of at least some of my listening experiences. There is an analogy to DVDs here: in terms of sales, the DVD has been the greatest home electronic success in history. And it is no wonder--DVDs offer a clear value proposition over VHS that virtually any video consumer can appreciate. Similarly, computer-based home entertainment systems (and variants thereof) offer great promise, to the degree that they offer not just more "convenience," but that this can operationally change the way we listen to music.

DACs with on-board clocks can re-clock the data stream, making them virtually immune to the transport, be it CD, hard drive, RAM, whatever. So there is no reason why convenience needs to be at the expense of high quality sound reproduction. But DACs are still not completely immune, as Jon hints towards in this article above. Cable reflections, ground bounce, chip load, etc. these will affect DACs even with on-board clocks, and highly resolving systems will invariably uncover a source medium dependency. Source mediums specifically made to minimize jitter, such as high-end transports, will make it easier on the DAC. There is nothing that I know of in the computer industry that gives computer-based storage systems any translational benefit over to *DAC technology* that the traditional digital audio community is not already aware. So when it comes to sound reproduction, the traditional digital audio community is likely to still command the lead. If this is achieved reasonably inexpensively via pro-audio, or esoterically in boutique audio, is really an issue that is applicable re one's own system, resources, and goals.
One thing missing from all above posts thus far is a discussion on error free music free rippig. Not every CD-ROM or DVD-ROM is created equal. It's not as simple as which format to choose but which ripping SW/CD-ROM.

One of the better SW is EAC (Exact Audio Copy). It's capable of creating an exact copy of you CD. Bit for bit. It does this by slow down the drive and read it at least twice. (with the correct configuration of course).

I ripped my library of 400+ CDs using Windows Media Player 9 and came to discover some of them contain excessive errors. (sound skiping and etc) I am in the progress of redoing all of them. Very painful.

Eric