What Is a DAC (Digital-to-Analog Converter)? Understanding Digital Audio Conversion

A DAC (Digital-to-Analog Converter) in audio is used to convert digital sound into analog sound. It is a chip found in any device that plays digital music formats. It is necessary so that headphones or speakers can play MP3, FLAC, WAV, and other file formats.

What is a DAC?

A DAC (Digital-to-Analog Converter) is an integrated circuit (IC) whose function is to convert a digital signal (binary data) into an analog signal (voltage or current). Physically, a DAC is extremely small — smaller than a fingernail, for example.

Below is an image of the circuit boards of the FiiO M21 Digital Audio Player (DAP), which features four CS43198 DAC chips and measures 6.8 cm wide by 12.1 cm tall.

To illustrate this further, see the printed circuit board of the Topping D70S desktop dedicated DAC, which includes two AKM AK4497 DAC chips and measures 24.5 cm in length by 19 cm in width.

What is a DAC used for?

In audio, the DAC converts the digital signal into an analog one. This is necessary because headphones and speakers only operate using analog signals. However, it is not enough just to convert the signal.

For the diaphragm of a headphone or speaker driver to vibrate and produce sound in an “ideal” way, an amplifier must amplify the analog signal output by the DAC.

Where are DACs found?

DACs appear in different forms in devices that handle audio files in formats such as MP3, FLAC, WAV, OGG, among others. These devices may or may not include an amplifier.

If OP-AMPs (operational amplifiers) or tube amplifiers are present, the device is classified as a DAC/amp. In this case, the chassis contains one area for the DAC circuitry and another for the amplifier components.

However, there are cases where no amplifier is present in the same chassis as the DAC. In this situation, the device is classified as a “dedicated DAC,” and the user must connect it to a dedicated amplifier or to a DAC/amp, provided the device offers the necessary connections.

Are there devices that do not include a DAC?

Yes, there are devices that do not have an internal DAC. The most common case is the dedicated amplifier, which does not contain a DAC inside the chassis. There are also devices known as “streamers” that perform only the “transport” function and do not include a Digital-to-Analog Converter chip.

In audio, the term “transport” refers to a device that handles music playback, whether through music-streaming apps such as Spotify or through local audio files stored on a microSD card or SSD, for example. In this case, not only storage is required, but also an embedded operating system.

How can you tell if a device has a DAC?

There are a few ways to infer whether a device contains a DAC internally. For example:

• The device plays music from digital files stored in internal memory or via music streaming and has a built-in speaker. Example: TVs, smartphones, and tablets (with or without a 3.5 mm headphone jack).
• The device does not play audio files but has a USB port or connector along with an analog output such as a 3.5 mm headphone jack or RCA output for connecting an amplifier. Example: USB dongles (“USB headphone adapters”) and desktop DAC/amps.
• The device plays music locally or via streaming and includes some type of analog output, whether headphone, RCA, or XLR. Example: streamers with a built-in DAC/amp and Digital Audio Players (DAPs).
• The product does not play album tracks locally or via streaming, does not have an internal amplifier, but includes digital inputs (USB, coaxial, optical) and analog outputs (RCA and XLR). Example: dedicated DACs.

How do you know if a DAC is good?

A good DAC has:

• A reasonably good-quality DAC chip — which is not hard to find nowadays.
• A dedicated and good-quality power supply for the DAC to avoid introducing noise into the audio (for example, a linear power supply).
• Galvanic isolation to separate the power, analog, and digital sections and prevent interference.
• High-quality microcontrollers (for example, XMOS for the USB port).
• A high-precision clock to minimize jitter [1].
• A variety of digital connection options (for example: AES/EBU, Bluetooth, coaxial, I²S, optical, USB).

[1] Jitter is a variation in the clock timing that can cause distortion in the conversion of digital signals to analog and analog signals to digital.

How to avoid problems when connecting DACs to noisy audio sources?

Some audio sources — such as computers — may generate a lot of noise. To avoid problems of this kind, you can:

• Plug the computer into a grounded power outlet.
• Connect the computer to the DAC using an optical cable.
• Use streamers or Digital Audio Players (DAPs).