Car Audio DAC: From Analog to Digital and Back

From Analog to Digital and Back

listening to digital music via a car DAC
Car DACs in head units are typically better suited to the task at hand than the ones built into devices like phones. Katja Kircher / Maskot / Getty

Whether you're still holding on tight to your CD player, you’ve made the switch to a mechless head unit, or your listening habits fall somewhere in between, your entire car audio experience probably hinges on your car audio DAC (digital to analog converter). The one exception is conventional AM/FM radio, which starts off with an analog signal, but the other audio sources in your car are all stored in digital formats — whether that be on a physical CD or as bits and bytes on a flash drive.

In order to translate that digital information into an analog signal that’s capable of driving your speakers — and thus creating music you can actually listen to — it has to pass through a digital to analog converter.

So what, exactly, is a DAC, and how important really is this ubiquitous little piece of technology? The answer to the second question is easy: a good DAC is absolutely indispensable in a modern car audio system. The answer to the first question, however, requires a little bit more in terms of explanation.

From Analog to Digital and Back Again

Music, and other forms of audio recordings, all start out as analog signals, and at one time they were also recorded in analog formats. Records and compact cassettes are both examples of analog media formats, but modern audio recording has since moved into the digital realm — first with CDs and later with digital files like MP3s.

The purpose of storing and transmitting music, and other audio recordings, in digital formats is primarily an issue of storage space and convenience.

A compact disc can store more audio data than a record or compact cassette in less space, and digital storage media like hard drives and flash drives can store an even greater amount of audio data — in the form of MP3s and other files — than that.

After an analog audio recording has been converted into digital data, it’s of little use to us until it’s converted back.

While in a digital format, the signal is abstracted as binary data that can’t drive a speaker or create an audible sound on its own. In order to do so, it has to be passed through a digital to analog converter.

Digital to Analog Conversion

Virtually every audio device that relies on digital media contains a digital to analog converter. That includes everything from your iPod to your head unit. In home theater contexts, there are even standalone DACs that are designed for use with CD players that either don’t include a DAC or have a digital output. These standalone units are typically higher in quality than most built-in DACs, so they are capable of more faithful reproductions of the original analog signals.

Although there are different types of DACs, they all perform the same basic function: converting abstracted digital data into a physical signal that can then be amplified and used to drive loudspeakers. This is usually accomplished by converting the digital information into a corresponding set of stepped pulses, which is then smoothed out via interpolation. The quality of the resulting signal is highly dependent on the way the DAC goes about accomplishing this, so the same digital information can provide a quantifiably different sound quality depending on the DAC it’s passed through.

Most digital to analog converters are contained on integrated circuits due to size and cost constraints, but there also DACs that use vacuum tubes to produce a warmer, more detailed sound.

Portable Car Audio DACs and Head Units

Most portable DACs are designed for use with laptops, and they essentially offload the heavy lifting of converting digital music to an analog signal from computer software to a physical device. This type of portable DAC can be used in your car as well, if you have an audio source that is capable of outputting via USB and your head unit has an analog input.

The other way that DACs come into play in cars is that some head units include digital inputs, typically in the form of a USB or proprietary jack. The way that this type of connection works is that it allows you to plug in your iPhone, tablet, or any other MP3 player and offload the processing to the head unit, rather than relying on the DAC in your phone or other device.

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