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What is a Digital Analog Converter?

Introduction | Parts of DAC | Basic Ideal Operation | Practical Operation | Applications | Audio | Video | DAC Types
DAC performance | DAC Figures of Merit | See Also | References | Technical Papers | DAC Links


In electronics, a digital-to-analog converter (DAC or D-to-A) is a device for converting a digital (usually binary) code to an analog signal (current, voltage or electric charge).

An analog-to-digital converter (ADC) performs the reverse operation.

CD's store bits - that is 1's and 0's. Your CD player will read the CD and then convert the digital information to analog information that you will then feed to an amplifier or pre-amplifier. This is a critical process that needs to be done very well in order for enjoyable, fatigue free sound.

Most CD players will only make a half-hearted effort at the Digital-to-Analog conversion process, relying on OEM converter chipset's and less than adequate amplification stages. These will usually share the same power supply as that of the CD mechanism, which itself is very demanding on power because of the constant feedback mechanisms involved in the read-back process.

Many audiophiles will go for a two-box alternative. The first box being a CD transport (or CD player being used as a transport) which, in turn, feeds into a DAC. The DAC then converts the digital signal into an analog one; producing the line-level output that can be fed into a pre-amplifier or integrated amplifier.

Most dedicated CD players will have a digital output on them as well as the analog output. If you connect the digital output of your CD player to a DAC then you will bypass the CD player's "internal DAC" (digital-to-analog portion of your CD player) and the external DAC will then be responsible for the conversion process.

This is an extremely effective way of upgrading a CD-based hi-fi system and can make an extreme impact on the quality of playback. Later, you can then consider whether or not to upgrade your CD player to a dedicated CD transport. It is even possible to use a computer as a transport by use of a USB interface between the computer and DAC (such an option exists for our DAC Kit 2.1 in the form of an internal add-on board) and appropriate software.

Our DAC kits are based on the experience gained from Audio Note's many years of producing DAC's. They produce some of the most highly rated of all DAC's on the market today and have some unique and novel methods of handling the many aspects of the digital-to-analog process - many of which we can pass on to you through our DAC kits.

Instead of blindly accepting all of the then-current theory and dictate from the early pioneers of the technology as most manufacturers did (and still do) one company, Audio Note ( This is a great DIY site for audiophile components), decided to do their own research into how the DAC process should be achieved (they were already experts in handling the eventual Analog portion). They found that simplicity and careful design at each stage of the process was the best way to go. Their resulting approach was, at the time, very controversial and upset many deeply held beliefs in the design world. Today, however, more and more manufacturers are beginning to use some of Audio Note's methods in their own designs and Audio Note are still at the forefront of DAC design.

Parts of a DAC

Below is a simplified breakdown of a DAC (Audionote)


Basic ideal operation


Ideally sampled signal. Signal of a typical interpolating DAC output

A DAC converts an abstract finite-precision number (usually a fixed-point binary number) into a concrete physical quantity (e.g., a voltage or a pressure). In particular, DACs are often used to convert finite-precision time series data to a continually-varying physical signal.

A typical DAC converts the abstract numbers into a concrete sequence of impulses that are then processed by a reconstruction filter using some form of interpolation to fill in data between the impulses. Other DAC methods (e.g., methods based on Delta-sigma modulation) produce a pulse-density modulated signal that can then be filtered in a similar way to produce a smoothly-varying signal.

By the Nyquist–Shannon sampling theorem, sampled data can be reconstructed perfectly provided that its bandwidth meets certain requirements (e.g., a baseband signal with bandwidth less than the Nyquist frequency). However, even with an ideal reconstruction filter, digital sampling introduces quantization error that makes perfect reconstruction practically impossible. Increasing the digital resolution (i.e., increasing the number of bits used in each sample) or introducing sampling dither can reduce this error.

Practical operation

Instead of impulses, usually the sequence of numbers update the analogue voltage at uniform sampling intervals.

These numbers are written to the DAC, typically with a clock signal that causes each number to be latched in sequence, at which time the DAC output voltage changes rapidly from the previous value to the value represented by the currently latched number. The effect of this is that the output voltage is held in time at the current value until the next input number is latched resulting in a piecewise constant or 'staircase' shaped output. This is equivalent to a zero-order hold operation and has an effect on the frequency response of the reconstructed signal.


Piecewise constant signal typical of a zero-order (non-interpolating) DAC output.

The fact that practical DACs output a sequence of piecewise constant values or rectangular pulses would cause multiple harmonics above the nyquist frequency. These are typically removed with a low pass filter acting as a reconstruction filter.

However, this filter means that there is an inherent effect of the zero-order hold on the effective frequency response of the DAC resulting in a mild roll-off of gain at the higher frequencies (often a 3.9224 dB loss at the Nyquist frequency) and depending on the filter, phase distortion. Not all DACs have a zero order response however. This high-frequency roll-off is the output characteristic of the DAC, and is not an inherent property of the sampled data.




Top-loading CD player and external digital-to-analog converter.

Most modern audio signals are stored in digital form (for example MP3s and CDs) and in order to be heard through speakers they must be converted into an analog signal. DACs are therefore found in CD players, digital music players, and PC sound cards.

Specialist stand-alone DACs can also be found in high-end hi-fi systems. These normally take the digital output of a CD player (or dedicated transport) and convert the signal into a line-level output that can then be fed into a pre-amplifier stage.

Similar digital-to-analog converters can be found in digital speakers such as USB speakers, and in sound cards.


Video signals from a digital source, such as a computer, must be converted to analog form if they are to be displayed on an analog monitor. As of 2007, analog inputs are more commonly used than digital, but this may change as flat panel displays with DVI and/or HDMI connections become more widespread. A video DAC is, however, incorporated in any Digital Video Player with analog outputs. The DAC is usually integrated with some memory (RAM), which contains conversion tables for gamma correction, contrast and brightness, to make a device called a RAMDAC.

A device that is distantly related to the DAC is the digitally controlled potentiometer, used to control an analog signal digitally.

DAC types

The most common types of electronic DACs are:

DAC performance

DACs are at the beginning of the analog signal chain, which makes them very important to system performance. The most important characteristics of these devices are:

Other measurements, such as phase distortion and sampling period instability, can also be very important for some applications.

DAC figures of merit

However many monotonic converters may hav a maximum DNL greater than 1 LSB.


DAC Kits for the DIYer
Audio Notes
Hagerman Tech
Welborne Labs
K&K Audio

Consumer DACs
Lavry Labs
Wavelength Audio
Cambridge Audio DacMagic
PS Audio
Music Fidelity V-DAC
Audiophile..some cheap buys

Currently there are many sound cards and audio interfaces available. All of these are DACs in that they take a digital signal and produce an anolog wave that is reproduced through your speakers. Here you can find some great deals for the money. What the computer user needs to be aware of is that many of today's sound/audio cards are designed for gamers and so they may be lacking in true audiophile quality. I have specifically gone out to buy audiophile quality sound cards/interfaces and would suggest the following:

E-MU's 0404 USB 2.0 Audio/MIDI Interface delivers an unparalleled level of audio performance to your Mac or PC with premium 24-bit/192kHz A/D and D/A converters. For $200 you can't go wrong. Mac and Windows.
E-MU 0202 USB 2.0 is great if you are on a budget and can only spend $100.E-MU's 1616M PCI Digital Audio System delivers everything you need to produce audio on a PC with professional results- 24-bit/192kHz converters (the same A/D converters used in Digidesign®'s ProTools® HD 192 I/O interface. Mac and Windows.
E-MU's 1616M PCI Digital Audio System delivers everything you need to produce audio on a PC with professional results- 24-bit/192kHz converters (the same A/D converters used in Digidesign®'s ProTools® HD 192 I/O interface. This replaced the 1820M...the difference being that the 1820M had a word clock. The 1616M will set you back over $400, but it is a great device. Windows only.
Apogee Mini-DAC is the ultimate portable and compact solution for studio playback, reference monitoring, FireWire connectivity to your DAW (optional), and premium home audio systems offering professional quality 192kHz D/A conversion. About $800. Mac only.
The M-Audio Audiophile 2496 sound card is an easy way to upgrade your Windows or Mac computer's integrated audio for professional-level audio production. This card is not for gaming, but is made for the audiophile. For $100 it is one of the best sounding cards around. I used mine for years until I upgraded to the 1820M.

Technical Papers

The Data Conversion Handbook

The Data Conversion Handbook, edited by Walt Kester (Newnes, 2005), is written for design engineers who routinely use data converters and related circuitry. Comprising Data Converter History, Fundamentals of Sampled Data Systems, Data Converter Architectures, Data Converter Process Technology, Testing Data Converters, Interfacing to Data Converters, Data Converter Support Circuits, Data Converter Applications, and Hardware Design Techniques, it may be the ultimate expression of product "augmentation" as it relates to data converters. The last chapter discusses practical issues, including common pitfalls and solutions related to the non-ideal properties of passive components.

The Data Conversion Handbook can be purchased from your favorite bookseller.

Chapter 1: Data Converter History

(pdf, 9456 KB)
Chapter 2: Fundamentals of Sampled Data Systems
(pdf, 1418 KB)
Chapter 3: Data Converter Architectures
(pdf, 4547 KB)
Chapter 4: Data Converter Process Technology
(pdf, 5520 KB)
Chapter 5: Testing Data Converters
(pdf, 3135 KB)
Chapter 6: Interfacing to Data Converters
(pdf, 1075 KB)
Chapter 7: Data Converter Support Circuitry
(pdf, 1899 KB
Chapter 8: Data Converter Applications
(pdf, 5479 KB)
Chapter 9: Hardware Design Techniques
(pdf, 3171 KB)
DAC and ADC Vocabulary


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