History of Audio Converters
The world’s first digital recording was captured and released in 1971 using an experimental PCM recording system from the Japanese broadcasting company NHK.
Although commercial digital recordings were possible as early as the 70s, it wasn’t until Sony released the PCM-501ES digital audio processor in 1984 that CD-quality digital recording technology would become widely available.
Studios quickly realized the benefits of working in the digital domain, but they weren’t without their limits. In its infancy, digital recording devices were extremely expensive, and those that weren’t tended to sound harsh and shrill.
As technology continued to advance, the sound quality improved, and digital audio interfaces became commonplace in professional recording studios. In 1999, Ricky Martin’s "Livin’ la Vida Loca" was the first song recorded, edited and mixed entirely in-the-box. Today, most professional studios rely entirely on digital audio systems, with much of the workload being carried by the digital audio converters.
What Is a Digital Audio Converter?
Analog to digital (AD) converters transform analog audio signals, such as the output of a preamp or other piece of outboard gear, into digital audio signals that can be processed by your computer.
Digital to analog (DA) converters work in reverse, converting digital audio signals, such as those played by your DAW or web browser, into analog audio signals that can be recreated by your studio monitors or headphones.
Most modern audio interfaces include limited DACs to enable simple digital recording, but for high-quality recording or particularly large sessions, you’ll need a standalone DAC. Most DACs include both AD and DA converters in the same unit, as well as a few other pieces of technology.
What Does a DAC Do?
DACs are responsible for three main tasks in the conversion process. First, they sample the analog audio signal. No, not like sampling a song in hip hop, it’s more like taking a burst photo on your smartphone.
DACs take tens of thousands of ‘digital snapshots’ each second when sampling an analog audio signal. The more samples the DAC is able to capture, the more accurately it can recreate the audio signal in the digital domain. More on that later...
Once the analog audio has been sampled, the DAC assigns each sample to a different timestamp within the waveform through quantization—similar to lining up transients to the grid in your DAW.
Once the quantization occurs, the signal is converted into a binary code that your computer can process. This code represents the exact voltages of the waveform at any given time. By ‘connecting the dots’ of each sample, your speakers are able to accurately recreate the sound being played back from your DAW.
By adjusting the sample rate and bit depth of your DAC, you can control the quality of your digital audio recordings.
What Is Sample Rate?
Sample rate is a measurement of how many samples your DAC takes per second when sampling audio. Most professional DACs offer the following sample rates:
- 44.1 kHz / sec
- 48 kHz / sec
- 88.2 kHz / sec
- 96 kHz / sec
- 192 kHz / sec
The minimum sample rate for CD-quality audio is 44,100 samples per second. It may seem like an odd number to use, but it wasn’t selected randomly.
According to the Nyquist–Shannon sampling theorem: “the sampling frequency must be greater than twice the maximum frequency one wishes to reproduce.” Since the human hearing range maxes out at roughly 20 kHz, the sampling rate had to be greater than 40 kHz.
Digital audio was developed alongside digital video, and 44.1 kHz was deemed the highest usable rate compatible with both PAL and NTSC video. To this day 44.1 kHz remains the minimum standard resolution for digital audio.
However, by using a higher sample rate, your DAC is able to capture more information and more accurately recreate the audio signal. Using high sample rates comes at a cost. It also creates more stress on your processor, restricts the number of channels you can work with, and creates significantly larger audio files.
What Is Bit Depth?
Bit depth controls the amount of dynamic range in a digital audio recording, or the amount of space between the loudest and quietest sounds. Most professional DACs operate at the following bit depths:
- 32-bit float
A bit is a binary digit, or a single unit of code. A bit only has two values: 1, or 0. On, or off. Max volume, or mute. But with multiple bits, you can create more combinations, resulting in more values. For instance, with two bits you can create four combinations: 00, 01, 10, and 11. And each of those values can each be assigned a different meaning.
In a digital audio system, each value is assigned a specific amplitude of the audio waveform. With a high resolution, you can accurately map the exact amplitude of each peak on a waveform. But with a low resolution, you’re not able to be as accurate, and the quality begins to suffer. For instance, in a 24-bit system you have more than 16 million possible values to choose from, while in a 16-bit system you have just over 65,000.
The minimum standard bit depth for CD-quality digital audio is 16-bits, but using a higher bit depth offers greater dynamic range, improved signal-to-noise ratio and more headroom. Higher bit depths allow you to make the loud moments louder and quiet moments quieter without introducing additional noise.
What Is A Word Clock?
When working with multiple digital audio devices, you need to sync their internal clocks to ensure they record everything perfectly in time—down to the last sample. Otherwise, you run the risk of creating digital artifacts in the form of nasty clicks and pops.
In most home studio settings, the audio interface clock operates as the master clock for any additional devices. But in pro studios, which often require more complex signal routing, many engineers choose to use a stand-alone device.
Similar to upgrading from an all-in-one recording interface to standalone preamps and DACs, a dedicated word clock can offer a significant improvement over your sound.
Suggested Word Clocks: Antelope Audio Isochrone OCX HD Master Clock, Antelope Audio 10MX Atomic Clock, Avid Sync HD Master Clock, Drawmer M-Clock Plus, Black Lion Audio Micro Clock MKIII, Steinberg Nuendo Sync Station.
How To Choose A DAC
There is a wide range of options in the world of DACs and finding something that works within your budget is incredibly easy. From audio interfaces that feature on-board AD/DA converters to modular systems like the Burl Audio B80 Mothership that offer scalability, you'll be able to select the right option for your price.
As for sound quality, professional DACs typically strive for a neutral, transparent sound. However, some converters are known for adding a certain sonic signature. Some models deliver crystal-clear highs, while others offer deep lows. And then there’s the Burl B80 Mothership, which is loaded with transformers to add color, vibe, and soul to your tracks.
When it comes to connectivity, the first thing to consider is channel count. Mastering converters like the Antelope Audio Pure2 offer two channels of high-resolution AD/DA conversion. However, for most recording and mixing projects, you’ll need at least eight dedicated inputs and outputs.
Most DACs include both AD and DA converters in a single unit, and can seamlessly stream anywhere from 8 to 64 channels at a time, depending on the resolution. For large productions in need of more than 64 channels, you can chain multiple DACs together.
Some manufacturers create separate units for AD and DA Conversion. Typically, AD converters are optimized for recording, like the Grace Design m108 and Dangerous Music Convert-AD+, both of which feature built-in preamps.
DA converters, on the other hand, are optimized for mixing with ample outputs for interfacing with outboard gear, as well as surround sound support or even a built-in summing mixer like the Crane Song Egret.
DACs typically offer several options for interfacing with your computer. If you’re looking for a quick and easy way to connect with professional Pro Tools rigs, try a DAC with a Digilink or Digilink Mini output.
For those who need more flexibility for interfacing with multiple devices or rooms, many DACs offer Ethernet and AES outputs for advanced networking capabilities. And finally, if you’re just looking for a high-quality DAC to use with your laptop or desktop computer, most models come with USB, Thunderbolt, or FireWire connections.
Next, we'll further breakdown some of the preeminent converters available to help take your studio to the next level.
Different Options For Audio Converters in Your Studio
Just because you work with Pro Tools doesn't mean you're confined to Avid converters. Many third-party manufacturers make systems that will run perfectly within your workflow.
Audio Interfaces With Built-In Converters
Suggested Audio Interfaces: Universal Audio Apollo x4, Apollo Twin X DUO, Apollo Twin X QUAD, Apollo x6, Apollo x8, Apollo x8P, Apollo x16, Arrow, Antelope Audio Zen Tour Synergy Core, Discrete 4 Synergy Core, Discrete 8 Synergy Core, Orion Studio Synergy Core, Galaxy 64, Avid MTRX Studio, Focusrite Red 4Pre, Red 8Pre, Clarett 8Pre, Solid State Logic SSL2+, Apogee Symphony MKII, Symphony Desktop, Merging Technologies Anubis Pro, Prism Sound Lyra 2, Titan.