What is a DAC?

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In electronics, a digital-to-analog converter (DAC, D/A, D2A, or D-to-A) is a system that converts a digital signal into an analog signal. An analog-to-digital converter (ADC) performs the reverse function.

There are several DAC architectures; the suitability of a DAC for a particular application is determined by figures of merit including: resolution, maximum sampling frequency and others. Digital-to-analog conversion can degrade a signal, so a DAC should be specified that has insignificant errors in terms of the application.

DACs are commonly used in music players to convert digital data streams into analog audio signals. They are also used in televisions and mobile phones to convert digital video data into analog video signals which connect to the screen drivers to display monochrome or color images. These two applications use DACs at opposite ends of the frequency/resolution trade-off. The audio DAC is a low-frequency, high-resolution type while the video DAC is a high-frequency low- to medium-resolution type.

Due to the complexity and the need for precisely matched components, all but the most specialized DACs are implemented as integrated circuits (ICs). Discrete DACs would typically be extremely high speed low resolution power hungry types, as used in military radar systems. Very high speed test equipment, especially sampling oscilloscopes, may also use discrete DACs.

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We live in a digital age.

Back in the day, music was recorded using the signal straight from the microphone and tracked directly to tape. The waveform of the microphone is an analog wave, therefore making the wave on the tape analog as well. That wave could then be read, amplified and sent to a speaker to produce the sound it created.

Now, most of the time recordings are saved as digital data. The analog wave is sampled at the desired interval and then turned into numbers that are stored on the digital device. (On a CD, the sampling rate is 44,000 samples per second; so, there are 44,000 numbers stored per second of music). That data is then stored onto the disc in order to be decoded later by a CD player.  

A-D-A FlowA-D-A Flow
By Teeks99 - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=14725795

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THE "GOOGLE TRANSLATE" OF YOUR AUDIO SYSTEM

Yet our ears and speakers can’t “hear” stored data, so we need a device that converts this data into an analog format, hence, a Digital-to-Analog Converter (or DAC for short). Sources like AM/FM radio, a turntable, etc. do not need conversion since they are already analog. CDs, digital downloads and streaming on the other hand are all digital formats and need to be converted before they are able to be heard. The DAC is like the “Google Translate” of your audio system. The converter is a “translator” like English to Spanish, or in this case from Digital to Analog. It’s only one piece of the puzzle, but it is an integral one. 

4bit Linear PCM4bit Linear PCM
By Aquegg – Own word, CC BY-SA 3.0, https://commons.wikimedia.org/wiki/File:4-bit-linear-PCM.svg

 

 

The DAC’s job is to convert this digital data and “translate” it back into an analog signal. To do this, it converts the bits of data from the stored files into an analog electrical signal at thousands of set times per second, as mentioned above, called samples. The DAC outputs these samples into a “wave” that intersects at all the sample points. However, problems can arise in the conversion process which as we will see later can set some DACs apart from each other.

IF MOST OF MY DEVICES ALREADY HAVE A DAC, WHY DO I NEED ANOTHER ONE?

Phones and computers today are amazing pieces of technology. They do a thousand things well, but in the case of audio, not that great. In the case of recording, most times engineers do not use the mic input on their computer tower to record their audio, so why would you use your standard audio output in the same way? Standalone devices do a much better job at this because they are designed and manufactured to do one thing, and one thing only.

NOT ALL DACS ARE CREATED EQUAL

We could get into a technical conversation about how Apple phones use better DACs than their Android counterparts because Apple was always music-centric in the development of their devices because the iPhone was the natural technological progression from the iPod. But looking at the larger picture, external or standalone DACs are usually far superior. The quality of the converter chip most companies use for their devices are just not that great. Most external DACs are far superior because they have one job: to convert digital signals to analog (and to do it well). That’s it. That’s all they do. Of course, there are differences from DAC to DAC, but the one thing they al have in common is what they were designed to do: to convert digital signals to analog.

The audio output from a standalone digital to analog converter is going to be drastically better than your built-in source device like a phone. Why? We’ll get more into that in a little bit.

A DAC FOR EVERY NEED

The next important thing to consider is what type of DAC will you need for your setup? There are a variety of options here depending on your personal audio system and preferences.

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AT HOME OR ON THE GO

PORTABLE DACS

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Phone DACPhone DAC

 

The portable DAC is a useful device for those of us that like to listen to music while on the go or traveling. They can be as small as a thumb drive and are small, affordable solutions for audio improvement. There are a couple types in this category: USB and battery powered portable DACs. USB DACs will connect to your computer or tablet with a USB Type-A connection. These DACs are usually convenient to pack in your bag or with your headphones in any scenario and provide a substantial upgrade in the audio output of your device. 

 

DAC solutions for phone or tablet vary depending on your operating system. iPhone/iPod/iPad (iOS) devices are usually connected via Apple’s proprietary lightning connector or the 30-pin connector on older models. Android devices are usually connected via micro USB or USB Type-C that are more popular on newer models now. Smaller, rechargeable battery powered systems are popular for phones – something you can carry along or attach to your device without adding too much bulk and weight and needing to be tethered to an outlet. These usually plug into the same port you use to charge your device. Just plug in your headphones to the DAC and you’re ready to go. These are great plug-and-play solutions for the frequent traveler or individuals who want an upgraded experience without all the bulk and wires of larger component DACs.

SOLUTIONS FOR DESKTOPS/LAPTOPS

Digital to Analog Converters can also be larger, more hefty units that are suitable for desktop and home system applications. These usually require the unit to be stationary and part of a larger setup. Just connect via a USB Type A cable to an available input on your device and you’ll likely have to set up the output of your computer to the DAC. Most USB DACs also have headphone amplifiers built into the unit so higher-powered headphones that require extra juice should be fine on most desktop devices.

HOME AUDIO SYSTEMS

You’ll be hard pressed to find a DAC that won’t fit in your home audio system. By far the most versatile input/output options, your component DAC can be configured in a number of ways depending on your source output:

  • If connecting from a computer, you can use a USB DAC to connect to your amplifier
  • If you have a music streaming device, you can connect a DAC depending on your select inputs/outputs compatibility on those devices (SPDIF, AES, Toslink, etc).

*Note that many source devices such as music streamers, Digital Audio Players (DAPs) and even speakers can be configured with high-end internal DACs. Ultimately you will know what you need for your particular set up – if not, please contact us and we’ll be more than happy to answer any of your configuration or gear questions!

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DO I NEED A HEADPHONE AMP OR A DAC?

An amplifier provides output power to a set of speakers or headphones. Depending on your application or set up, it might be possible that you need additional power, say if you have headphones that have power-hungry drivers. For example, if you are listening to music on your phone but don’t have enough juice to power your cans, it will result in very poor audio quality (very important to think about especially with portable setups).  Also important to consider that apart from poor audio quality, overall volume output will be low too. The headphone amp assists with the volume control of your device, bringing it to line level and providing the necessary "headroom" to drive your headphones well. Luckily, many portable amps are also combined with DACs. The Chord Mojo is an excellent example of this DAC amp combo.

Manufacturers are starting to include DACs in their amplifiers out of convenience also. Before, you would have a handful of bulky devices to carry around: your phone, then a DAC, followed by an amplifier and then your headphones. Now we have all-in-one solutions. Some models allow you to deactivate the specific function depending on your setup also. Just want to use it as a DAC? No problem. Just deactivate the amp/preamp option. But be sure you do your research as all DAC/amps are not as configurable.

If your music source does not have an internal digital to analog converter, then you will need a standalone DAC. Keep in mind that a Digital Audio Players (DAP) will not be able to output a signal to a DAC like a computer or iPod does since it already outputs an analog signal.

If your music source, DAC or speakers do not include built-in amplifiers (or enough to sufficiently power your output), then you will need a standalone amplifier for your audio system.

Chord Electronics MojoChord Electronics Mojo

These are all integral parts to your set up. One device cannot be substituted for another, unless like spoken about earlier, they are part of a combo device like a DAC/amp. 

The nice thing about DAC/amp combos is that they can work with just about any system. Portable units can also work well in desktop or component scenarios just as well as they can on the road. With adapters, you can even use your smartphone as the source, and in cases like the latest iPhones that do not have analog inputs, units like the Chord Mojo can bypass the phones internal DAC through the lightning port. If you have high-resolution audio files on your phone, then even an audiophile can take the experience with them everywhere.

WHAT MAKES A GOOD DAC?

There are a few things we’ll need to consider before we talk about what sets DACs apart from each other.

SOURCE MATERIAL

We all know there is a difference between CD-quality audio and MP3, but there’s some math behind it too that will be good to know. There are 3 specific aspects to digital music that determine the quality of the recording: bit rate, bit depth, and sample rate.

  • Sample Rate - refers to how many samples of data were taken in a second.
  • Bit Rate - refers to how much data is being stored per second.
  • Bit Depth - refers to how much data is recorded per sample.

The more information / data the recording has then the more faithful reproduction of the original audio recording your DAC can produce. Sometimes the sparser data is (such as in lower resolution files), then mistakes can occur during playback. Some of these issues are known as jitter or phase noise.

WORK SMARTER, NOT HARDER

Jitter ultimately has a negative impact on fidelity. It occurs during playback when there is a loss of a sample or block of samples in a bitstream. It can be caused by a number of factors including sync/word clock error or even buffer issues with the interface. Regardless, it happens with all digital devices and introduces noise, so that is why it’s important to have more data or higher quality recordings for playback to minimize jitter.

Phase noise is another way to characterize the same phenomenon, but interpreting it using the frequency spectrum. Other issues that DACs have to compensate for are narrow dynamic range and limited bit rate. All of these things make it more complicated for DACs to accurately convert the data and accurately recreate the analog signal.

That is why high bit and sample rates are preferred. More data also results in high bit depth and dynamic range. MP3s and online files are oftentimes compressed (bit rate), resulting in minimizing the dynamic range and flattening out the sound stage. The more data = the more accurate high-fidelity audio. Of course, this also results in larger files sizes, but that is a conversation for another day.

QUALITY PARTS

Another interesting thing to note is that it’s not just about the digital to audio converter chip that matters. You’ll be surprised at how much the overall quality of the DAC also depends on the power supply and the output stage. Two different manufacturers could be using the exact same DAC chip, but because of their different choices in design and build, the DACs can have very different qualities about them. So, keep in mind it’s not just about the chip itself, but the overall components and parts going into the DAC that really helps it stand out from the crowd.

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So, we now have a general understanding of what a DAC is, how it works, what it does, etc. Depending on your high-end audio system set up, or how you like to listen to music primarily will depend on what kind of DAC you will need…

RECOMMENDED DACS

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We're here to answer all your questions about DACs. Got a question or comment? Contact us via the blog or catch us on social media and we'll be more than happy to give you personal and tailored advice on all things High Fidelity! From all of us here at Moon Audio - Happy Listening!