DAC's: Everything you need to know (and probably more)
The Logistics of a DAC and the Common Myths
DACs are a very important piece of equipment nowadays due to the high amount of digital media we consume. A digital to analogue converter (DAC), also occasionally known as a digital audio converter, is used to take a digital sound and make it listenable, essentially.
- What we hear, sound, as a form of energy is really just quickly changing air pressure.
- This pressure can be created by audio systems, either loudspeakers or headphones by physically pushing and pulling the air around us.
- The signal that the speaker or headphones receive from their source right before it's turned into sound energy is always analogue.
So, we can hear analogue sound in the form of air pressure. Speakers and headphones can create the same air pressure we know as sound. Cool. So we can place a CD into the player and the sound in the disc is heard through the speakers with the help of an amplifier. It's not quite that simple. The sound written on a CD is just really a bunch of ordered 1's and 0's, which certainly don't directly translate to sound. They need to be decoded, or converted to an analogue signal.
There are plenty of common misconceptions about what DACs can be used for and what they should be used for.
Lets first list a few things that are 'digital'. Here are a couple of examples we can use.
- CD tracks
- The songs on your phone or iPod
- Bluetooth signal
Here's the reason why these misconceptions exist.
Most CD players, iPods and phones already have a DAC inbuilt. This means the signal coming out of your CD player is likely already an ANALOGUE signal. Phones are a similar case. If you connect your phone to an audio system through the headphone connection, or the 'aux' as it's sometimes known, you've already got your analogue signal. The reason these are putting out an analogue signal, is the digital media has already been run through the unit's inbuilt DAC. This is not always a fantastic quality DAC. A great CD player will probably have an awesome DAC inbuilt, however phones, iPods and entry level CD players will just have a DAC to get the job done. If you stream your music wirelessly through Bluetooth to an adapter, it's likely the adapter has a basic DAC inbuilt aswell.
Here's where external DACs become handy.
Phones, iPods and SOME CD players also have a digital output. The USB or charging port on your phone or iPod can carry a digital audio signal. If your CD player has a digital output, such as an optical or coaxial digital connection, this too can carry a digital audio signal. Same thing goes for wireless receivers and adapters, they may have a digital output. Going from THESE connections to an external DAC will now mean that the files in the phone or on the CD are being converted to an analogue signal by an external unit.
Here's where the quality can vary in sound reproduction.
Mick also did a great write up on DACs and the reality of their use. You can read that here. His rule of thumb came down to RUBBISH IN, RUBBISH OUT. This means, no matter how good the DAC you're planning on using is, if you have average or bad quality digital files and recordings, they'll still sound average or bad. However, a better DAC allows you to make the most of better quality digital files and recordings.
Using digital outputs on your source allows you to bypass the potentially average inbuilt DAC and get something better to do the work.
So with all this in mind, how can we select the right DAC?
Some DAC's have differing digital input connections, so you need to make sure if you're looking at a DAC for an upgrade it'll have the right connections to match your sources, whether thats a CD player or a laptop or phone.
USB audio connections along-side optical and coaxial digital audio connections are common to find on a variety of DACs.
Here's an example:
Some DAC's even have inbuilt headphone amplifiers, and some run off battery charge. These can be ideal to improve your portable source's signal and can be used with headphones and sometimes an amplifier and pair of loudspeakers too. Here's an example:
In some cases, dependent on both file quality and equipment design and connections, a DAC upgrade may have little to no improvement, potentially even no use at all.
However, with the correct gear, a great DAC can make a great improvement.