We talk about it a lot: the d/a converter. Also known as a “dac”. But what exactly is a dac? And do we always need one?
First, let’s explain what a dac – or d/a converter – is. The suffix “converter” already tells you it is a converter. The letters ‘d’ and ‘a’ stand for digital and analog. So a d/a converter converts digital signals to analog signals.
This conversion is necessary simply because we cannot listen to digital signals. Unless you like high-pitched squeaks, crackles and distorted sounds.
Bits to voltages
So the digital signal must be converted to a comprehensible, listenable, musical signal for us. To do this, the dac – very simply explained – converts the bits that are on the medium (CD, DVD, Blu-ray, flash drive, hard drive, or perhaps a stream of bits over an Ethernet or coaxial cable) to voltages. And this creates an analog audio signal.
Now there are various ways – technologies or architectures – to convert things. There are single bit dacs (DSD: Direct Stream Digital), delta sigma dacs (internally working on a few bits), which now are the standard. And then there are multibit dacs (16 or, say, 18 or 24 real bits), although these are becoming very rare because it is incredibly complex and expensive to make them. And then there are NOS and ladder dacs, for example.
We will discuss the most common types of dacs in more detail later. After all, that is interesting stuff!
Need one?
Nowadays you almost always need a d/a converter – dac – because practically everything is distributed digitally. There are virtually no more purely analog sources. Even when making vinyl, dacs are used because – we know from a very reliable source – the majority of music is simply delivered digitally. With a few exceptions, of course.
Already built in!
Now it’s nice to know that although the bulk of media sources work with digital source materials, you won’t be “bothered” by that. This is because the necessary dac chips are already built in. So in a TV, set-top box, CD player, receiver, etc, they are already incorporated.
It is also nice to know that the standard solutions usually work fine. And also sound fine. Can we do better? Of course we can! But a better converter also costs more money. That’s the reason they are not used in the TV boxes we get for free with a subscription. Nor will you find them in a regular TV or, say, a car radio or chromecast-like box, to name a few.
Next level
If you would like to take your musical enjoyment to the next level, it is good to know that there are numerous options for – optional – external d/a converters. There are many brands with fine converters in their product lineup. (About which more in the next article).
Seperate dacs come in all price ranges and also in all shapes and sizes, from compact and affordable to very exotic and for the happy few. We’ll get into that later.
Sound?
Now there are several manufacturers of dac-chips (and separate, external dacs). Examples of chip manufacturers are: ESS (Sabre), Texas Instruments (formerly Burr Brown), Cirrus Logic, AKM and Analog Devices.
Now, do these chips all have their own character? We can be brief about that: yes. Chips certainly have a signature. However, the circuit around the chip is also very decisive for the sound and performance of a converter. So do not only focus on the chips, but also on the circuit around it. Especially the power supply.
Later we will discuss an important aspect that plays a role in the quality of reproduction: jitter and phase noise.
Next time!
In the next part in this series on d/a converters: when is an external dac useful?