Monday, March 7, 2016

LG's G5 is coming with a DAC module but what is a DAC and who should care about one

LG already has a DAC in the V10 and is bringing another (from Bang & Olufsen!) as an option to the LG G5.

A DAC is a Digital-to-Analog Converter. We're going to focus on how things relate to your smartphone, but a lot of other things you probably have — like a DVD player or a computer — also have a DAC inside and they work the same way. A DAC has one task — convert digital audio information into an analog signal that can be sent out to a speaker or amplifier.

While that's the correct and simple definition of a DAC, it's important to understand the difference between digital audio data and analog signals to see why having a good DAC matters.

An analog signal is an electrical waveform that's analogous (see what I did there?) to the pressure of a sound wave that your ears can hear. Higher pressures are represented by higher voltage, and translate into higher frequencies and louder sounds. A microphone takes sounds that you can hear and turns them into an analog electrical signal. Speakers — or headphones or an amplifier — take that waveform and turn it back into sounds that you can hear. What happens between those two stages is where a DAC comes into play. Every phone has a DAC. Every Bluetooth headset has a DAC. Every device that lets you listen to a digital audio file has a DAC.

A good example of how you can "store" an analog signal is using vinyl. A record's grooves force a needle to move, skip, jump and vibrate to create an analog waveform that's sent to an amp, which is made strong enough for a set of speakers to play. But that's hardly practical when you're looking for something portable. You need to store the audio information digitally if you want things to fit into your pocket.

To do that, you sample an analog signal over time, and store that data as 1s and 0s inside an audio file. CD-quality audio — 16-bit at 44,100 Hertz — creates audio samples up to 65,535 data points in size, 44,100 times per second. 24-bit audio can have up to 16,777,216 data points per sample, and 32-bit audio can have a whopping 4,294,967,296 points of data. The more data you store, and the more frequently you sample, the higher the file size and higher the audio quality. There are other variables like oversampling and floating-point numbers behind the science, but this is a basic breakdown.

"Lossy" file formats — like MP3 — take source audio and use compression algorithms that reduce the amount of data needed to produce a copy that's close to the original. Our CD quality example from above has its file size reduced by about 90 percent when converted to a 128 kbit/s MP3 file. It also will still sound OK to most people, which is the goal. By reducing the size of the file, streaming the audio also requires less network bandwidth and speed. But you still need a DAC to play it back because it's still a digital file.

When you play an audio file that's stored on your phone, the digital data is sent to a DAC to be converted into an analog signal that you can hear. Every phone has a DAC. Every Bluetooth headset has a DAC. Every device that lets you listen to a digital audio file has a DAC.

Not all DACs are created equally

The phone you have in your hands now also has a DAC in it. You plug in a set of headphones, or use the external speaker, and fire up an app that has sounds and you hear them. Even the little bloops and dings our phone make when we touch stuff or get a message require a DAC so that we can hear them. Every phone has a DAC — we just don't usually talk about it. (And in most cases they're not worth talking about.) All an end-user really needs to do is use the right equipment to play lossless audio files. The rest is automatic.

To be perfectly clear — the DAC in your phone may not be a high-end processor that recreates sounds the way the audio producer intended them to be heard and all that audiophile jazz. But it may be perfectly acceptable to you, and that's all that matters. DACs are easy when it comes to engineering, and even the low-quality ones do a fine job turning files into sounds. If you stream all of your music, this includes using Bluetooth to stream digital audio information from your phone to a Bluetooth speaker or headset that has its own DAC, your phone's DAC isn't quite as important. Audio designed to be streamed is stored in what's called a "lossy" format so it can be transferred faster with fewer "mistakes." And for most people, the quality is fine and we just enjoy the tunes.

Other people want higher-quality audio. The term "audiophile" gets thrown around, but you don't have to care about the science and technicalities to enjoy music that's a bit cleaner than average. It's a fun hobby to have, but all an end-user really needs to do is use the right equipment to play lossless audio files. The rest is automatic. If the DAC you're using isn't able to process audio at the same (or better) quality in bitrate and frequency as your source files, you won't have the "better" audio lossless files can provide. You'll still be able to play them, but at a lower quality.

The technology we have now to produce high-resolution digital audio files and play them back means all you need to do is have a 24-bit DAC with a decent headphone amp and a pair of headphones with the right impedance. There are a lot of terms like "quantization" and "SNR" that are used to debate things, but the limits of integrated circuits mean that 21-bit audio is the point of diminished return, and anything higher doesn't really bring "better" sound to the table. You can buy 32-bit 192kHZ remastered audio files, and I'm not saying you shouldn't, but right now you'll probably not notice any difference in sound from a 24-bit recording. You will be ready in case advancements in technology change how we create digital audio, and how it's converted to analog, and if any of it changes the 124 dB SNR limit of today's equipment. Even then, you might not hear any difference. But it will be fun to try.

I'm a person who wants music to sound the best it can when I listen to it. I like to geek out over signal-to-noise ratios and dynamic range and dither, but when it comes right down to it I'm pretty satisfied with my current portable setup — iPhone 6s, portable DAC, and a pair of Audio Technica ATH-M50x over the ear headphones. When I'm buying music I look for 24-bit/48kHZ files, and when I'm making music I store it at 24-bit/384kHZ as a "master" file, with a 24-bit/48k copy to listen to.

The people making our phones are starting to care about audio quality once again. This is great news for everyone, even if you're not an audiophile nerd. A good DAC will make even streamed music sound better, and a decent set of headphones are pretty affordable. I'm still not very keen on the LG G5 and the swappable module setup, but I am looking forward to trying one with the B&O DAC to see if it will replace my portable DAC

Audio quality in 2016 is where camera quality was in 2015. Expect to hear good things.

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