DACs: everything you need to know

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You may not even consider it, but most of us make use of at least one digital-to-analogue converter (more handily 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 - it converts the countless reams of digital information into an analogue signal intelligible to the human ear.

Any device that acts as a source of digital sound – be it a CD or Blu-ray player, digital TV box, games console or portable music player – will need a DAC to convert its audio to an analogue signal before it is output.

Traditional amplifiers don’t handle digital information, speakers certainly don’t play digital information and our ears cannot interpret digital information – they all need an analogue waveform. Without a DAC, your digital music collection is nothing but a sizeable collection of “0s and 1s” (more on that shortly) that makes sense only within the digital domain. In short, DACs play a large part in making digital music worthwhile.

The biggest problem is the DAC circuits used in many devices are just not efficient enough to do justice to the original recording, so a DAC upgrade can be the simplest way to improve your digital music and really get the most from your system. Whatever your set-up.

MORE: Best DACs 2018

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 shellac (and later, vinyl) discs, and later still magnetic cassette tapes - but the fragility and unwanted noise of these formats made way for something new. The CD was born, kickstarting the digital audio revolution in the process.

Digital audio takes a very different approach to that of 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 (comprised 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 taken as often as 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.

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 true that not all DACs are created equal. For starters, they might not support all file data rates.

Poor converters can introduce unwanted noise during playback due to poorly designed circuitry, 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.)

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 any computer it may be 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 conversion process will be performed more faithfully.

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 can make any sonic shortcomings more obvious.

You’ll hear 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 2 review

DSD and PCM

DSD, or Direct Stream Digital, is an alternative to PCM and was originally conceived for Super Audio CD (SACDs) - a format championed by Sony and Philips in the late ‘90s and into the ’00s.

It’s a much more niche format, differing from PCM by offering a bit depth of just one, but much higher sampling rates - DSD64 at 2.8 MHz and DSD128 at 5.6 MHz.

The arguments as to which encoding system is better continue to rumble on. Suffice to say if you’re someone firmly settled in the DSD camp, it’s worth checking the DAC you’re considering supports it – not all do.

MORE: What is DSD audio?

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 set aside.

Compact USB DACs offer portability and convenience at a reasonable price. They vary in size between something no bigger than a standard USB stick (such as the Audioquest DragonFly Black) to pocket-sized units that connect via a separate USB cable (iFi's nano iDSD BL, for instance).

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 concerned about taking your DAC around with you, a desktop USB unit - such as the Audiolab M-DAC - 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 want to use headphones, as not all DACs offer this as an option - the new Chord Qutest (the replacement for the 2Qute), for instance, is a standalone DAC without any headphone features. Many alternatives offer this functionality these days, though.

MORE: Naim DAC-V1 review

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 sockets such as AES/EBU – and, potentially, more features too. They'll support the full range of high-resolution music formats, for example, or offer 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.

These can range from the sensible Audiolab M-DAC Plus (£800) to the uber-retro Benchmark DAC3 HGC (£2350), the extravagant Chord DAVE (£7995) or, if money really is no object, the Nagra HD DAC/MPS.

The best DACs you can buy in 2018

Whether you’re spending £100 or more than £1000 on a DAC, we have no doubt the sonic improvements you will hear are well worth a little time spent selecting the right model.

Here's a selection of our current favourites...

Cyrus soundKey

Tested at £100

Unarguably, the best at the budget end is none other than Cyrus' debut portable DAC, which can turn your mobile listening into an authentically high-fidelity experience for just £100.

Audioquest DragonFly Red

Tested at £170

On the next rung up the ladder is the equally portable and convenient DragonFly Red, which was one of the first on the USB DAC scene several years ago remains a firm favourite today.

Chord Mojo

Tested at £400

A brilliantly talented DAC with bags of sonic appeal, the Award-winning Mojo will instantly elevate the performance of your system, be it laptop-based or a traditional hi-fi system.

Audiolab M-DAC

Tested at £600

Effortlessly talented and enjoyable, the M-DAC is still one of the best DACs around.

Chord Hugo 2

Tested at £1800

If you're really serious about sound quality and have a not-inconsiderable sum of money to spare, the Hugo 2 is the best gift you can give to your hi-fi.

MORE: Read all our DAC reviews