Audio programmer Akash Murthy teaches digital audio basics on his YouTube channel. Photo courtesy of Akash Murthy
Spotify puzzled us when it announced its lossless tier with high-res bit depth, but not a high-res sampling rate. We decided to revisit the basics.
Spotify recently announced its move from lossy to lossless, but didn’t quite step into true high-resolution audio. The new Premium tier offers a high-resolution bit-depth (24 bits) but not a high-resolution sampling rate (44.1 kHz). Perhaps a true high-res tier is coming, but for now, Spotify has clearly made the people's choice to go "good enough" for its Premium level, rather than match the more elite offerings from Tidal and Qobuz, which go as high as 192 kHz.
This (kinda) makes sense since a far higher proportion of Spotify subscribers are listening casually or on the go, while Qobuz listeners are more likely to be found sitting in the sweet spot and scratching their chin as they listen "critically" on gear with sensitive signal chains.
Once you hit CD-quality (16 bit, 44.1 kHz), increases in either bit depth or sampling rate range from inaudible to subtle to quietly profound, depending on a range of variables. We can play you beautifully mastered CD-quality albums that sound high-res, and heavily compressed 192/24 heavy metal albums that sound like they’re off the cassettes we bought in the 1980s. At the same time, the space and ease of a well-mastered high-res track on a system that can reveal these differences is like stepping into clear mountain air.
A lot of people online will try to tell you that digital audio is perfectly simple: a line of marching square waves that either works perfectly or drops out entirely. They insist that “bits are bits” and that it’s impossible for a digital audio signal to have degrees of difference in quality. The truth is, of course, that digital audio signals that are destined to be turned into analog signals, are complex and mutable, with many compromises and choices along the way.
Get Your Dithers
With Spotify prompting us to think about bit depth and sampling rate again, this is a great time to introduce someone actually qualified to talk about these things, Akash Murthy.
(Before we get deeper, if nothing else, watch Akash's video on dithering because it illustrates bit depth using the immensely accessible example of a black-and-white image, and also goes into this fascinating technique that adds noise to create a better signal.)
A while ago, when researching impulse response to better understand Dirac, our content manager Gautam Raja, found Akash's YouTube channel that's "dedicated to audio technology, production and programming." There, he found the clearest, best-illustrated explanation of digital filtering he’s ever encountered. He binged the Digital Filter Basics videos, finally fully comprehending feedforward/feedback, finite/infinite impulse response, and linear phase. Then he revisited digital audio fundamentals in the 12-video series, and was struck by Akash's ability to anticipate exactly which concepts confuse the layperson, and to explain them without either getting deep into math or oversimplifying.
Gautam was so grateful that he reached out to Akash, who lives in a village called Drumshanbo in Ireland, writing, "I actually said 'Bless you' aloud when you said you were going to explain exactly how a digital filter can affect phase—a question I've had from the start, and have never found a good answer to."
Meet the Teacher
Akash is a musician, audio programmer, and ultralight backpacker, and though he doesn't have a lot of audio gear since he travels so much (he mentions a Focusrite interface and AKG headphones), he identifies as an audiophile, saying, "I merely go by the literal definition of the word, as a person who admires and appreciates all aspects of audio."
Fair warning, some of his conclusions about what is good enough for audio, say in terms of bandwidth, don't take into account the level of crazy that we go to in high-end world. Still, in the end, we don't fundamentally disagree with the conclusion that 24 bits and 48 kHz are more than enough for a happy life. It's the darkness inside that leads us to pursue ever higher resolutions with ever-diminishing returns, and Akash seems perfectly happy standing on a mountain and looking at the view, so let's not drag him down our dark rabbit hole. For now.
(Gautam, wishing to make a full disclosure at this point, says: “For a long time, I couldn't hear a difference between 96 kHz and 192 kHz test files, but now, after years of optimizing my system from Frontier router to speaker, I can identify a sense of air and ease when a 192 kHz track plays. I'm not going to pretend your jaw will drop... in fact, your jaw might drop at how small the difference is, compared with the level of power conditioners, filters, cables, clocks, and switches I've needed to highlight it. But as you settle in, the ease and flow are beguiling, and you realize this is a long-term thing. It's less fireworks and roller coasters, and more good book and dog-at-your-feet.”)
Akash uses a black-and-white image to illustrate the concept of bit depth and dithering.
We immediately recognize the audiophile in Akash when he talks about how he got into audio programming: "I was fascinated by the glittery world of VSTs, the beautiful ways of transforming audio on a DAW, and all the flashy knobs and buttons that went with it." (Virtual Studio Technology and Digital Audio Workstation.)
Though Akash is more from the parallel but distinct world of pro-audio, his journey applies to the hi-fi enthusiast as well: "I started off my audio production journey with half-baked truths, an unscientific ear-based approach on questionably accurate gear in the hopes of putting something out there as quickly as possible. So do a lot of people out there."
Even so, he says, "The absence of a formal audio engineering education should not stop anyone from pursuing what they love. Experience plays more of a part than anything else in getting better. But the learning can never stop."
Amen to that. Even if you don't seek to understand everything about digital audio signals, we hope Akash's videos give you an idea of the uncertainty that exists even in the digital domain, and that there are many choices and compromises that a digital circuit designer must make.
Gautam strongly believes that clocking and going "north of the streamer" are the next big areas of improvement for high-end audio. Consider the number of manufacturers now offering high-quality clocks at femto resolution, clock inputs, isolated LANs, SFP ports, standalone master and word clocks, network switches and filters... There is so much more going on here than "bits are bits", and this crazy hobby gets even more fun and involving when we fully understand that.