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DACs: Do You Need an External Digital to Analog Converter for your Hifi System?

by May 14, 2014
Emotiva Stealth DC-1 DAC and Headphone Amp

Emotiva Stealth DC-1 DAC and Headphone Amp

"Upgradeitis" is a term bandied about the audio world to describe the desire to buy new gear that you technically don't need. Sure, an extra HDMI input or a slightly better room correction system would be nice, but they are rarely necessary. When a person is frugal enough to deny themselves major replacement purchases for incremental upgrades, they often start looking at other gear that is less known. An external DAC is a popular choice.

A Digital to Analog Converter, or DAC, takes your digital content and transforms it into analog so that your system can amplify it and play it through your speakers. If you think you already have DACs in your system, you would be correct. Anything that can accept a digital signal and output sound must include a DAC. This includes your phone, MP3 player, receiver, AV processor, computer, laptop, CD/DVD/Blu-ray player with analog outputs, wireless speakers, clock radios, and more. 

But Do You Need a DAC?

If all of these devices already have DACs, why would you need an external one? More to the point, could you actually use it and would it make a difference? Here are the two main conditions that would necessitate the addition of an external DAC to your system:

1) Noise floor problems (i.e. background hiss)

2) Sound quality issues related to the digital to analog conversion 

The first is pretty easy to detect. If you can hear a hiss during the quiet sections of your music, or if your playback is disrupted by noise, you need an external DAC. We've had noise problems that originate from everything from fan noise to hard drives spinning to changes on our computer screen. A poorly designed layout on the sound card (or problematic placement in regards to its proximity to other parts of your computer or device) can add all sorts of noise into your playback. If you are hearing noise there is very little you can do to eliminate it. But that doesn't mean there isn't anything. Here are a few suggestions:

1) For phones, put them in "Airplane Mode" or similar to turn off the cell antenna. If you need WiFi, you can turn that back on after you switch to Airplane Mode.

2) For computers, shut down any unnecessary programs. Don't forget to check the Task Manager for any programs you might have missed that are running in the background.

3) If you have more than one output or input, try switching to different ones.

4) Check the quality of your cables and connections - noise can come from damaged wires as well.

5) Try a different song. It could be that the recording you are using has a high noise floor.

6) Check your settings for different processing modes. If you have the option of different playback programs, try downloading a different one in case your program is adding distortion or noise.

Sound quality issues are much harder to diagnose. If you are hearing warbling (where it sounds like the music is being played on a slightly warped vinyl record) you may be having clock issues (we'll get into what exactly these are in a moment). If you've downloaded some high quality files and your computer won't play them back, you may need an external DAC (though you'll want to check your settings to make sure you have everything configured properly).

dacmagic XS

Some DACs are portable like the Cambridge Audio DacMagic XS

What You Need to Take Advantage of an External DAC

Can you just plug any device into any DAC and experience sonic bliss? Of course not. These are the things you need:

1) High quality (CD or better) digital content

2) Player or source with digital outputs

3) External amplification

If all of your digital content is stored in 128kbps MP3s, then your problem isn't your DAC. It is the file size compression you used to store you music. MP3 and other file size compression solutions reduce the size of your music files by removing content that the MP3 algorithm determines you cannot hear. If the original file was already of low quality (or already compressed), the MP3 conversion process can add all sorts of audible distortions to your music. To take advantage of an external DAC, you'll want content that is at least CD quality. Currently, there are a number of lossless file size compression codecs including FLAC, WMA Lossless (Windows), and Apple Lossless (Mac) that will somewhat shrink your music files while keeping all the content intact.

If you really want high quality music, you can use any number of download sites (HDTracks is our favorite) to get music that is better than CD quality. Remember, CD quality is 44.1kHz, 16-bit. The highest quality you can buy currently (outside of very specialized places) is 192kHz, 24-bit. These high quality files are the equivalent of studio masters and should be the very best quality music you can own. Of course, their file sizes are very large so you'll want to be wary of how much space you have left on your hard drive before you start downloading a large number of these.

Denon DA-300USB

Denon DA-300USB DAC

If your player only has analog outputs (RCA red and white or simply a headphone jack), you can't add an external DAC. Well, sometimes you can but the external DAC is simply taking the analog signal from your player, re-converting it to digital and then back to analog, before sending it through. If the DAC in your player is the problem, this re-conversion process isn't going to help. 

Those working with phones or portable players with USB outputs should also be wary before adding an external DAC. Some phones do conversion even over the USB connection so you won't hear a difference by adding a DAC. You'll want to make sure that the DAC is connecting digitally to your device (they should say this in the specifications of the DAC).

Lastly, you'll need some sort of amplification. If the DAC has a headphone output (and you will be using only headphones), then the amplification is built right in. But if you are connecting a set of speakers, you'll need either self-powered speakers (like many studio monitors) or an external amplifier to power passive speakers. 

But Seriously, Do I Need an External DAC?

In our opinion, you rarely "need" a DAC. DACs are a fairly mature technology and most mid-level receivers and other sources have perfectly adequate DACs. If you are having sound quality issues, make sure you eliminate every other possible source of distortion (including your speakers/headphones) before you decide that the DAC is to blame. The most common "real" reason to need a DAC (outside of a high noise floor) is because of clocks being out of sync.

In your source (your CD/Blu-ray player, portable device, etc.) there is what’s known as a digital “clock.” This tells your DAC (in the same device or in another, like a receiver) the timing of the content. Now, there is also a clock in your DAC. Your content is encoded with a specific frequency (you might remember from above when we talked about 44.1kHz up to 192kHz). If the clocks in your source and DAC don't exactly line up, your music might sound a bit off - like the warped record we talked about earlier. We call this "jitter." 

DACs sometimes have two modes of operation: Synchronous or asynchronous. The easiest way to think of the difference is that, with synchronous, the DAC uses the clock in the source. Asynchronous, on the other hand, uses the clock in the DAC. Most DAC aficionados say that asynchronous is better at eliminating jitter than synchronous.

A last point about jitter: Jitter doesn't always happen between your source and your speakers. Jitter can enter a system between the microphone and the ADC (Analog to Digital Converter). So if you are experiencing jitter with only one or perhaps a handful of recordings, it may be the recording and not your system. In that case, an external DAC will do you no good. 

One situation where we often find DACs recommended is with headphones. When you are connecting to a computer, often with a stock soundcard, noise and jitter can be real problems. Adding an external DAC can be a good solution but not always the cheapest. If the soundcard is the problem, check into upgrading that before you add a DAC. You may find that you can get not only better audio performance, but more options (like surround sound) for about the same money, or less, as a DAC. If you are using a laptop however, you may find that a USB DAC is your only real option.

For headphones in particular, loudness can be an issue. If you have expensive and hard to power headphones, you might find that the output of your computer or device just isn't loud enough, even at full volume. In that case, what you need is a headphone amplifier. Many USB DACs have headphone amps built in so you can experience the best of both worlds. 


There are lots of reasons people buy external DACs, but the most common is because they are pretty cool. You are unlikely to find many of your friends that have a DAC. Nothing screams, "I know more about audio than you," than having a device that has your friends scratching their heads. While there are a number of reasons to buy a DAC, the best two are to eliminate noise from your source and to combat systemic jitter. If these are your issues, an external DAC is the solution.


About the author:
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As Associate Editor at Audioholics, Tom promises to the best of his ability to give each review the same amount of attention, consideration, and thoughtfulness as possible and keep his writings free from undue bias and preconceptions. Any indication, either internally or from another, that bias has entered into his review will be immediately investigated. Substantiation of mistakes or bias will be immediately corrected regardless of personal stake, feelings, or ego.

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