The Streaming Revolution, Headphones and Hardware Part One: The DAC

This is a bit of a follow up to my experience at PAX East, and something I’ve been reflecting on for a while as someone who is a content creator. Streaming is changing the entire landscape of content creation – not just for those in the audiophile or personal-audio sector, which is what we usually concentrate on here – and by extension, listening and playback.

In the massive ($150 billion) gaming and entertainment space, streamers are the influencers, press and celebrities of the industry, commanding large sums of money from Twitch and Mixer partnerships, as well as being the essential first stop for any company looking to promote gaming systems, or peripherals... such as headphones or audio electronics for example. A very different landscape than in the two-channel audio or headphone space.

The specific needs of streamers, however, are different than the needs of the average audiophile or gamer, so let’s take a look at what some of those are and why.

First, the DAC; the heart of any digital playback system, has to meet a couple of important criteria. It must be appropriately low-latency, it must have a reliable USB connection and it must be relatively compact. The first of these, latency, is probably the largest factor and all but eliminates many audiophile R2R or ‘multibit’ DACs for the purposes of handling the high FPS (frames-per-second) of games. Latency is essentially how many samples of buffer time a DAC needs to apply it’s processing and convert the digital signal into an analog one. For Delta-Sigma DACs, which are the most common variety, filters are interpolating, which means that they can be applied quickly and with no more than a few samples of latency. By contrast more ‘audiophile’ variety DACs which apply complex filters or use non-interpolating filters may have up to several hundred or even a thousand or more samples of latency, which at the typical 44.1khz sample rate, can translate to multiple milliseconds of latency.

The second factor in latency is also a factor of USB. USB connections inherently have buffers and thus latency, and this is where most latency issues stem from. The time it takes for the computer’s playback system to talk to the USB driver, then transmit the USB signal to be received by the DAC’s USB control chip, clocked and sent to the actual D-to-A conversion stage is non-trivial, and execution is important. In this regard, devices from RME tend to be amongst the most exceptional, with some of the best ones boasting sub-10ms sample latency times. In actual game time this translates to latency times that are well below 12ms – commonly understood as a benchmark of sorts after which audio and video start to lose sync. And while it kicks-in differently at different sample rates, it is a target pretty much all Delta-Sigma style DACs hit with no issues.

For those playing first-person shooter games or other highly-detailed and carefully sound-synced games, the difference between 5ms and 15ms may be a factor in performance. For streamers and E-sports players, this can make all the difference between hearing an important ambient cue or missing it.

USB is also critical when it comes to reliability and noise. Reliability should be an obvious one, and most makers have at this point figured out how to craft a pretty stable interface, but some are still better than others, again, I give a shoutout to RME for having some of the most rock-solid drivers in the industry. Noise is not so simple, and crafting a well-isolated USB input is critical for two reasons. One is that many DACs that are USB-powered may be more susceptible to noise or hum – and yes, ground loops can actually be transmitted via USB, crazy as that sounds. I’ve seen, or rather heard, it happen. Second is that many GPU’s from Nvidia or AMD that are very powerful can put a ton of strain on power supplies, and power supplies are often where gamers tend to shave money off their budget first. Unfortunately, a power supply that isn’t up to the task of running a power-hungry desktop GPU, can actually have enough strain on it that it causes noise to be transmitted to the motherboard and then passed on via USB connections to peripherals.

Many gamers refer to this as ‘coil whine,’ though that’s not precisely what’s happening. Without getting too technical, the issue is related to how a power supply reacts when the demands for DC are too high, and and how relatively isolated the GPU and motherboard are from the USB control chip. This is not a factor even many high-end gaming manufacturers pay attention to, and USB quality in DACs can be a very real factor when tracking down weird noises in USB devices and peripherals.

Finally compactness, another factor that should be relatively self-explanatory. Space is at a premium on many streaming desks, and for gamers in general. Devices that are reasonably-sized and provide great sound quality are important for more than just space-saving measures. Gear that looks relatively nice on the desk is important both for aesthetically-minded gamers as well as for streamers who are looking to maximize available webcam space, or potentially take these units on the go with them.

DACs for gaming playback and streaming are much more than simply serviceable things that need to sound passable, there are a number of very real usability factors that go into what device to select, and we haven’t even discussed microphone inputs, ADCs, headphone outputs or other analog functionality. Hopefully this has been somewhat informative in explaining the differences between what streamers and audiophiles would look for in a DAC, because the reality is that the personal-audio space is likely to see the most crossover to high-end headphones from streamers and gamers than any other sector. Stay tuned for the next installment on streaming hardware where we’ll address some of the other components of an effective streaming setup.

COMMENTS
Martin.'s picture

Is there a reason you don't specify any products to get started, or any recommendations, or something you yourself use? Noticed the same thing in mics.

Btw, great of you to tackle this subject. I feel it's a frowned upon market, as Rafe funnily pointed out in your article about PAX East.

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