USB-DACs: The new devices that make downloaded music sound good.

Pop, jazz, and classical.
Dec. 27 2010 10:03 AM

Dulcet Downloads

Tired of crummy MP3 sound? A new device will make your digital music truly sing.

Furutech GT-40 USB DAC
Furutech GT-40 USB DAC

A revolution is happening in the world of hi-fi—one that, contrary to the other audio upheavals of the last 30 years, combines technological innovation and better sound quality.

Fred Kaplan Fred Kaplan
Fred Kaplan, Slate's "War Stories" columnist, also reviews high-end audio equipment for Stereophile and writes a jazz blog on the magazine's Web site. His latest book, 1959: The Year Everything Changed, is in paperback. He can be reached at war_stories@hotmail.com.

In the 1980s, the warm, dynamic sound of vinyl LPs was displaced by the cold, compressed compact disc. Then, in the '90s, just when CDs and CD players were finally starting to sound lifelike, along came MP3 and iTunes, which, for all their miraculous portability, didn't even pretend to sound good.

But now, a decade into the new century, comes a set of devices that matches the convenience of new-media downloads and exceeds the sonic standards of CDs.

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This new technology is stirring great excitement among high-end audiophiles, but it's almost completely unknown outside that realm, even among the tech-savvy. It's a fair bet this situation will change soon.

The devices are called USB-DACs (pronounced "dacks")—digital-to-analog converters with a USB input and standard stereo outputs. Connect your laptop, using one of its USB ports, to the DAC's input. Run a stereo pair of standard cables from the DAC's outputs to your receiver or amp. And your streamed music (from iTunes or some other music-server software) will come wafting out of your home stereo system's speakers. You can do this already using various cables and converters. But here's the new thing: Using these DACs, the music sounds better than you've ever heard computer-downloaded music sounding. And if you download the music files in a certain way (more about this later), it sounds as good as, or better than, compact discs.

More alluring still, several of these USB-DACs are cheap. One, manufactured by a California-based company called High Resolution Technologies, costs just $150 (and it's very good).

Let's back up for a moment. Why does music from computers sound bad? It's not just the tiny, tinny speakers. Lots of people have desktop speakers, and some of them are pretty good. Still, compared with even just an adequate home stereo system, the sound is pretty drab, for two reasons.

First, the audio circuits inside the typical computer—its own tiny DACs, its analog chips, and its amps—are terrible. With an outboard DAC, the conversion from a digital signal (0's and 1's) to analog sound waves (which your ears can hear) is handled by a device that's been manufactured to do only that, and to exacting standards. This alone should make a dramatic difference. But there's another factor as well.

The second reason music from computers sounds terrible is that the most common download formats, such as MP3, compress the signal horribly. A little math (just a little) tells just how horribly.

Digital audio encodes a sound wave as a series of 0's and 1's and samples it many times per second. Each 0 or 1 is called a bit; the longer the series of bits, and the more times each bit is sampled, the richer and more detailed the sound.

For a compact disc, each slice of sound is encoded as 16 bits and sampled 44,100 times per second. So the music flows at 1,411 kilobits per second. By comparison, MP3 produces music at 128 kilobits per second—less than one-tenth the information. (Improved versions of MP3 offer rates of 320 kb/s, but that's still less than one-quarter the refinement of CDs.)

There's a reason for this: The greater the compression, the more songs you can fit on your laptop or iPod. There is a tradeoff in quality and quantity. A three-minute song, wrung through the MP3's standard compression, takes up just 2.82 megabytes on your computer. The same three-minute song, passed through uncompressed CD-quality processing, takes up 30.3 megabytes.

So before going any further, take note: If all you want to do is listen to music on your computer or your iPod, MP3 and iTunes are good enough. If you want, at least sometimes, to hear it on your home stereo, and to have it sound good (deeper bass, higher treble, truer tones, more dynamics), read on.

Even if you want to stick with MP3 and iTunes, the USB-DACs will make the music sound better on your home stereo, for the reasons stated above.

But you can also adjust the settings on your computer so that it downloads iTunes songs (and other music files) at higher bit and sampling rates. Again, if you want to listen to this music only on your computer or iPod, this won't matter much; but if you want to stream it to your home stereo, this step alone will make a big difference. (If you're thinking of downloading music at higher bit and sampling rates, you may need to buy an external storage device to hold the extra data. They're cheap these days: about $100 for something that holds a terabyte of data.)

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