You may not have realised it, but most of us will make use of at least one digital to analogue converter, more commonly known as a DAC, every single day.
Built into the likes of computers, tablets and smartphones, the DAC is the fundamental key to unlocking the convenience of digital music, transforming it back into an analogue signal to make it audible to the human ear.
Any device that acts as a source of digital sound – be it CD or Blu-ray player, DAB radio, set-top box, games console or portable music player – will need a DAC to convert its audio back to an analogue signal before it is output.
Traditional amplifiers don’t amplify in digital, speakers don’t play in digital and our ears certainly don’t hear in digital – they all need an analogue waveform. Without a DAC, your digital music collection is nothing but a collection of “0s and 1s” (more on that shortly) that makes sense only within a digital device. In short, DACs play a large part in making digital music possible.
The biggest problem is that the DAC circuits used in many of these devices are just not good enough to do the original recording justice, so turning to a DAC upgrade can be the easiest way to transform your digital music and really get the most from your system – whatever your set up.
MORE: Best DACs 2015
What is a DAC? What does it do?
The sounds we hear on a day-to-day basis – traffic, instruments, that baby screaming on your otherwise peaceful commute – are transmitted in soundwaves, which travel through the air to our ears in a continuously varying analogue signal.
Analogue recordings were stored on the likes of vinyl records, and later cassette tapes, but the unwanted noise and fragility of these formats made way for something new. The CD was born, kickstarting the digital revolution in the process.
Digital audio is a very different beast to analogue. Digital music files are usually found in the form of Pulse Code Modulation (PCM), and are created by measuring the amplitude of the analogue music signal at regular intervals.
The value of the amplitude is represented as a binary number (of 1s and 0s) and the length of this number is often referred to as bit depth. The timing of the measurement intervals is called the sampling rate.
When recording a standard CD, say, a sample is taken 44,100 times per second. Each of these samples is measured to an accuracy of 16 bits, storing the results in a 16-digit binary format.
Record a high-resolution track, on the other hand, and you’ll take a step up to 24 bits, with a sample rate taken 192,000 times per second.
Digital audio data can be stored in a variety of sample rates, bit depths, encoding and compression formats – but no matter how it’s done, it is the DAC’s job to make sense of it all, translating it as accurately as possible from its binary format to return it as close to the original analogue recording as it can.
More after the break
Why do I need a separate DAC?
While it’s true just about every piece of digital kit features a DAC, it’s just as apparent that not all DACs are created equal. Poor converters can introduce unwanted noise during playback due to poorly designed circuitry – and they might not support all file data rates, not to mention add extra distortion due to jitter.
Jitter is best defined as digital timing errors. The precise timing of a digital music stream is vital to high performance, and if that isn’t done properly (usually because of poorly designed digital-clock circuitry) performance suffers.
Such jitter problems can arise every time a digital signal has to travel around a circuit board – and it’s particularly troublesome when the signal is transferred between devices. In recent years we’ve seen the rise of the asynchronous DAC, which takes over timing duties from the computer it is connected to for just this reason.
The digital clocks found in dedicated hi-fi DACs tend to be more accurate than those used in the average PC, so usually the sound will be correspondingly better.
The source material is all
Of course, to get the most from a DAC you need to start out with good source material – don’t expect miracles if all you’re throwing at a converter is 128kbps MP3s. In fact, better decoding of such a compressed signal could make any sonic shortcomings more obvious.
You’ll hear the optimum results with CD-quality content and above, which is best stored in FLAC, WAV or ALAC (Mac) lossless PCM formats, or alternatively DSD if you prefer.
MORE: Chord Hugo review
DSD and PCM
It’s a much more niche format, differing from PCM by offering a bit depth of just one, but much higher sampling rates with DSD64 at 2.8 MHz and DSD128 at 5.6 MHz.
The arguments as to which encoding system is better continue to rage on. Suffice to say if you’re someone firmly settled in the DSD camp, it’s worth checking that the DAC you’re considering supports it – not all do.
MORE: Chord 2Qute review
What type of DAC is right for you?
DACs come in all shapes and sizes, and offer varying levels of input options and functionality, so you’ll need to think about how you want to use it, not to mention the budget you have to spend.
Compact USB DACs offer portability and convenience at a reasonable price. They vary in size between something no bigger than a standard USB stick to a pocket-sized unit that connects via a separate USB cable.
More often than not, they use the power from your computer, so there’s no need for an extra power source. They largely keep connections simple, with just a headphone socket and possibly a line-level output for hooking up to powered speakers or a hi-fi system.
If you need more connectivity and are not bothered about taking your DAC around with you, a desktop USB unit might be more suitable. These are usually bigger and require their own power source, but often offer several additional digital or analogue audio inputs alongside a USB input for connecting to your computer. Keep an eye out for a headphone amp if you’ll be wanting to use headphones, as not all offer one as an option.
Finally, there are the DACs that are designed to work as part of a bigger home audio system. These will usually have even more inputs – particularly more niche ones such as AES/EBU – and potentially more features too, supporting the full range of high-resolution music formats for example, or offering Bluetooth connectivity for streaming wirelessly from your smartphone or tablet.
Some will even come with volume control, so they can be used as a pre-amp too.
3 of the best DACs
Whether you’re spending £100 or more than £1000 on a DAC, we have no doubt the change you will hear is well worth a little time spent picking the right one for you. Here are three of our current favourites...
Tested at £130
If it's a properly portable DAC you're after, then the USB-toting DragonFly has to be on your shopping list.
Tested at £400
A brilliantly talented DAC with bags of sonic appeal
MORE: Arcam irDAC review
Tested at £600
Effortlessly talented and enjoyable, the M-DAC is still one of the best DACs around.
MORE: Audiolab M-DAC review
Need more choice? Check out our round-up of the best DACs you can buy in 2015...
MORE: Read all our DAC reviews