The title is:"There's No Such Thing As Digital..."

07-24-13: Zd542
I'm not sure I get that. I hear comments all the time stating computer audio sounds better than a CD player. Why? I don't understand how ripping a CD and playing the audio file on a computer would sound better than just using a CD player.

Playing a CD is not the best way to source a digital data stream intended for music. Any timing errors expressed as inconsistent spaces between the CD's pits enters the digital/analog converter and distorts the shape of the resulting analog waveform compared to the one originally recorded and digitized. Mass market CDs have jitter just from the stamping of the pits into the substrate. Then the disk is played back, usually on a not-very-rigid CD transport, often made of lots of flexible plastic. As the data stream is transmitted to the D/A converter, more jitter can creep in from reading and re-reading data, from varying impedances, etc. Ripping a CD to a computer hard drive eliminates these timing errors. New timing errors can occur from the hard disk read, especially if the music file is fragmented among several blocks scattered around the disk, but if the data is buffered in RAM all timing errors are basically reset to zero.

Compared to most CD players, a home computer can be a very powerful playback system, with a CPU whose cycles are measured in Gigaseconds, several Gigabytes of RAM that can be co-opted to buffer the data stream and stabilize it, thus removing jitter that might have accrued along the way. Finally the computer-sourced music files are sent to the DAC via an asynchronous USB link. USB, unlike S/PDIF, is a bi-directional link. It doesn't need the clock signal that comes down the datastream pike; it can generate its own freshly when it enters the D/A converter, making for a jitter-free conversion. This is a significantly different way to convert a digital music stream from the typical CD player.

In fact, for a very long time I've wondered why high end audio companies kept
resorting to expensive Herculean methods to lower jitter--diecast metal transports, thick faceplates, expensive vibration-reducing footers and damping materials, etc., when all they really needed to do was put a few megabytes of RAM in there to buffer the data stream and re-clock it. That's what the Genesis Digital TIme Lens (DTL) of the mid-'90s did--for $1195.

Founder Arnie Nudell used to cut demo CD-Rs to show off his speakers by playing the CD's data stream through his DTL before burning the CD. The resulting CD sounded better than the original and made his speakers sound better at the shows.

There is a wide variety of music playback computer software out there, and most of it is way cheaper than a CD player. I use Audirvana Plus on my MacBook Pro. With it I can configure Audirvana to freeze email and automatic backups so the CPU is never interrupted from playing music. I can reserve up to 8 GB of RAM to buffer the music files before decoding. This is especially helpful if you keep your music files on a USB hard drive. I also configure it to upconvert Redbook CD files to 88.2Khz and 48Khz files to 96Khz. If I ever get a 192Khz capable DAC I'll upconvert Redbook files to 176.4 Khz and 48 and 96Khz to 192Khz.

All these things can make the original digital file sound better on conversion, and most of these things are not available on CD players under several thousand dollars.

Kiwi, I suppose if I want to clutter my post with un-ending qualifiers, I should have said "drastically reduces jitter" instead of "eliminates." Still, if you take the time to check the spectrum analyses of several Stereophile test reports, you'll see that the asynchronous USB DACs have very low jitter that is barely visible in the graphs.

Second, I didn't know that reasonably priced CD players were speed-reading and buffering the data first. Can you name some? Since the audio press is making a big deal about the just-released $6,000 Parasound CDP featuring this read-and-buffer feature, it didn't seem that it had gone mainstream yet.

Third, your summary of what computers are for is narrow and dismissive. I landed in Silicon Valley in 1980 and worked in high tech computers from then until the end of 2006. Word processing applications were a relative latecomer. Also, when the industry switched to graphics-based interface and displays, the desktop-publishing apps were some of the most CPU-intensive applications available, right up there with finite element analysis and solids modeling.

Along with that, my MacBook Pro has a 2 Ghz processor and 8 GB RAM, far more processing power than a typical--or even expensive--CD player or DAC. It has an aluminum housing (well-shielded), and no fan. AS I MENTIONED BEFORE, the Audirvana software (and several other packages) can be configured to turn off all CPU interruptions. It's called "hog mode." Look it up.

Once a music data file is buffered in RAM, the clock is reset. It doesn't matter how much jitter was in the stream before, for the moment, bits is just bits. At that point when it enters a new stream to the DAC, it's coming with a fresh and reset clock and is not subject to additional jitter coming from reading a wobbling plastic disc.

Finally, it was Ed Meitner of Museatex who discovered and published about jitter over 20 years ago. At that time listening tests revealed that jitter became audible around 200 ps. This presented a challenge to the industry as the most popular receiving chip at the time was only accurate to 20 ns.

And anyway, at some point arguing the numbers becomes a moot point. With standard CDPs not only did I find myself not enjoying the music, I even noticed that the family got more irritable when the music was playing. With my current computer setup, I can actually enjoy digitally-sourced music. I still play a lot of records and go to live concerts for reference, but the computer-based (especially high-res) digital playback is closing the gap.

The last few posts reveal the perspective as to which is better--how much sound quality do you get for your money? In my case I've never spent a lot for a CD player, maybe $500 tops. I did have an Audio Alchemy transport feeding a $700 SoundStream DAC (designed with help from Krell), but when I later got a CEC CD player, it sounded better. I've heard excellent CD players demoed at high end stores, and I play SACDs and DVD-As on an Oppo.

But I had the laptop for other uses already, and stacks of CDs ready to rip. All I needed was Audirvana Plus for $49 (now up to $79), properly configured, to easily exceed the musical satisfaction of my various digital disk players. And Audirvana just keeps getting better. When I updated to 1.5.2 (now it's at 1.5.4), I noticed a significant and pleasant improvement in the sound quality and how engaging the music is. Not bad for $49.