Has anyone suggested you might need a digital to analog converter (DAC)? Well, chances are you’re hearing the passionate expressions of a true audiophile. Yes, they are a powerful tool, but do you really need one? The short answer is: it depends. Chances are pretty good that you don’t absolutely need one. It really is a subjective topic. What is a DAC? What does a DAC do? Well let’s find out together.
What is a DAC?
As the name suggests, a DAC converts a digital signal into an analog signal so that a device can create sound. So we’re done right? It’s that simple? Well, yes and no. When we want to learn what the potential benefits and pitfalls are, we need to dive a little deeper. DACs and their applications really start delving into the world of high-fidelity sound. Though it is true that a lot can be learned about them for beginners and intermediates alike.
In conjunction with a headphone amp and a high-quality pair of headphones, a DAC can be quite beneficial. Essentially, a DAC will help condense soundwaves into a more low-voltage signal. This in turn will amplify the effect of the amplifier. See what I did there? In all seriousness, you’re wondering why you would possibly even need a DAC. Well let’s back up and learn about the history of DACs first.
Many years ago, people recorded sound purely as an analog signal. It was mainly captured on tape, and then it was pressed onto vinyl records. The needle on a turntable would convert the grooves on the record into an electrical analog signal. That signal was then fed through a preamp and voila, there’s Frank Sinatra blasting out of a pair of speakers. The difference nowadays is the digital form in which music is recorded and stored. That’s where a modern day DAC becomes relevant.
DACs and headphone amplifiers really came about as a necessity. In the olden days of iPod mini’s and those 10 pound bricks that we called laptops, the built in DAC assemblies were somewhat basic. The output was inconsistent in those old systems. Quite often this would introduce a static-y noise that was very intrusive.
I don’t know about you guys, but I remember the days I spent hours downloading countless numbers of MP3 tracks. That exhausting search for those golden 320kbps bitrate songs. Those tunes were much lower-quality back in the day. Digital music has made some incredible progressions since those days in the early 2000’s. Those old DAC assemblies just couldn’t keep up with the modern day bitrates. There are still scenarios where an external DAC can come in handy.
Why would I need an external DAC?
You may be asking yourself, “do I need a DAC?” Simply put, the only reason you’d need to get an external DAC nowadays is because your source —most likely a computer— is producing a subtle noise. Another reason is that you’re running an entirely analog system. I highly doubt that’s the case for any of you. Your source might also be incapable of reproducing sound at the correct bitrate. Alternatively, if you are a professional, a DAC could be very useful in the audio recording process. All in all, an external DAC is a way to go the extra mile and truly achieve audiophile status.
How does a DAC work?
Understanding exactly how an audio DAC works is a little more complex than it’s initial definition. Going back to vinyl records, we learned that sound was stored purely in analog in those days. Whenever an analog signal is recorded, it can be visually seen as a waveform. Moreover, all audio is defined as a compression wave during playback. In that waveform exists multiple peaks and dips. We can recognize those variations as the frequency. This is based on how many of these points of variation occur within a second.
A DAC translates all the bits of data from digital files to analog. It does this at a rate of multiple thousands of times per second. These are called samples. The DAC audio outputs a wave that intersects all of the samples to achieve the analog signal conversion. You must be wondering how this device can do all of this perfectly. Well, actually it doesn’t.
Downfalls of an external DAC
One problem that used to occur in systems about ten years ago is jitter. But, it would be very rare to see jitter happen in a unit today. More importantly, we should discuss aliasing. Aliasing happens at super high frequencies. A DAC can potentially create a lower frequency tone due to a lower sample rate. This creates an unpleasant sound that wouldn’t have been there otherwise. Obviously, the way to solve this is to up the sample rate right? Not entirely. This can help, but simply increasing the sample rate might not be enough. I have another article covering everything about frequency response and how it applies to all aspects of music equipment here.
I mentioned bitrate a couple of times before in this article. We need to talk about bit depth and dynamic range to learn some more shortcomings of DACs. Dynamic range is the sum of all disparate volumes of sounds in a source file. A file with bad dynamic range will have a hard time ramping up in volume. This leads to the overall sound coming off as muted. Bit depth dictates the limits on dynamic range. Greater bit depth equals increased overall loudness. See how these two work together? This is all in layman’s terms of course. Now a greater bit depth being louder doesn’t always mean better. Especially not when it comes to it’s relationship with a DAC.
Most files have an average bit rate of 8 to 16-bits. Although, a lot of folks are becoming more keen on 24-bit nowadays due to the added depth to the dynamic range of a file. There is always a give and take here though. A DAC would need to work harder the greater the bit depth is. The harder the DAC works means it affects the dynamic range. As we talked about earlier, a DAC is converting samples to analog at blinding speeds. If a file has issues with its dynamic range or bit depth, the DAC will be worse at its job. It is fair to point out that most of this is hard to perceive by the human ear.
What is a headphone amp?
Let’s switch gears and talk about headphone amps. I mentioned them at the beginning of the article because they have an important relationship to DACs in the modern world. A headphone amp is a low-powered amplifier that raises the low-voltage of a signal to a more adequate level. The headphones convert that signal into sound waves and you have an overall louder sound. A headphone amp has the same qualities as an amp head you’d see sitting on top of a speaker cabinet for an electric guitar.
Why would I need a headphone amp?
The key reason you’d need a headphone amp is if you have a pair of high-end headphones with high impedance. Impedance is simply the resistance of an electrical signal, measured in ohms (Ω). Studio headphones like this are an extremely useful tool. They do come with a heavy price tag more often than not. Impedance varies greatly in each different pair of headphones. That being said, it’s important to keep an eye out for this when researching high-end headphones.
Last year I bought a pair of 80Ω headphones. I plugged them into my computer and I was met with disappointment. I thought I had a lemon on my hands. I read that 80Ω wasn’t quite enough to warrant buying an amp. Low and behold, I needed an amp. This was due to the fact that either the internal DAC chip or sound card in my computer wasn’t powerful enough.
My story is an example of the signal flow. This term has a couple of other names like the signal path, or the sound quality quotient for the ultra-technical. The signal flow refers to the path an audio signal takes from input to output, and all of the components that make contact with that path. In my case, I added an amp to my signal flow. This in turn improved the quality of the path to output (my ears). Before the amp, there was a bottleneck of sorts due to the high impedance of the studio headphones.
Yes, this is why I wanted to talk about both dedicated DAC’s and amps. Nowadays, most headphone amps have really good DACs built in and they work simultaneously. Modern solutions for modern problems. DAC/Amp combos are usually smaller in size, and more cost effective. Going the route of buying an external DAC and amp separately can be about twice as expensive as a combo unit.
DAC/Amp combos have a unique sound signature. Manufacturers will tune a combo device tailored to what they consider sounds best. Some people will like this sound signature, some people will not. This gets into why you might want them separately. If you’re using a combo device purely for headphones, this variable of sound signature won’t be a noticeable issue. All in all, a DAC/Amp combo is a much less complicated approach, while still yielding great results.
That about sums it up. The issue of dedicated DACs vs. amps vs. combos varies from person to person. If anything, use what we’ve learned here as merely a guideline in your research. At the end of the day, what sounds best to you is all that matters.