Crackling. Not the porcine kind but the audible distortion that plagued this reviewer’s first foray into streaming audio quality amelioration on a Mac. Last June I took Spotify and Qobuz on a diversion via PureMusic’s Streamthrough (formerly PlayThrough) but ended up at an impasse: distortion that approximated the sound of a ‘crackling fire’ would almost always ruin the party. A reboot would fix the issue…but only temporarily.
Back then, I could be found rocking a 2010 MacMini and a 2011 MacBook Air. Both ran OS X 10.8 Mountain Lion and even following Pure Music developer Rob Robinson’s advice to roll back the MacMini to Snow Leopard, the ‘crackling’ issue persisted.
It wasn’t just me that would bear witness to snap, crackle and pop. The reader comments brought forward first hand accounts of other users experiencing the same ‘crackling’ issue. And yet 6moons’ Srajan Ebaen reported zero problems with Streamthrough + Qobuz on his iMac. Unable to progress any further with my investigation, I put it to bed. Good night.
The sales pitch from West Coasting Sonic Studio’s for their SQ and SQ+ software solutions echoes that of East Coaster Rob Robinson’s Streamthrough: that the sound quality of Tidal and Qobuz, as well as lossy services like Pandora and Spotify, can be improved by re-routing the native app’s audio output through an in-house-coded processing ‘engine’. If you can play it or stream it, Amarra SQ and SQ+ can allegedly make it sound a whole lot better.
And also like PureMusic, Sonic Studio’s marketing promises are far from empty. Now at version 3.0 (US$99), thousands of users worldwide apply Amarra’s audio processing to their iTunes libraries whilst others use Amarra as a standalone player. All hear an audible benefit in bypassing iTunes’ own audio engine in favour of a third party solution.
Sonic Studio CEO and Amarra software developer Jon Reichbach explains that iTunes implements sample-rate conversion (SRC), a lossy volume control and routes audio via the OS X’s Core Audio mixer whereas Amarra sounds better because it: 1) doesn’t do SRC; 2) applies mathematical calculations that are less CPU-intensive than iTunes; and 3) bypasses the Core Audio mixer altogether.
SQ/+ works in a similar way but instead installs a software-based sound output device called ‘SonicStream’ to the OS X Preferences pane to which any application’s sound output can be directed.
Think of SonicStream as a virtual sound device: it takes an application’s audio on a detour via the SQ/+ engine – which applies EQ, volume control and dither – before forwarding the audio on to the (hardware) DAC proper.
What’s dither? Jon Reichbach himself confesses to an abrupt schooling of its benefits shortly after he kickstarted Amarra development. When a digital audio signal is truncated to a certain number of bits, mathematical rounding occurs. The resulting round errors cause noise. Noise makes music sound harsh, metallic or (ironically) ‘digital’. Dither is the process of adding noise to the signal in order to mask that distortion. Dither is especially critical when attenuating volume in the digital domain.
(Click here for a more in-depth but reasonably human explanation of dither. Readers capable of even greater on this matter clarity are invited to bring it with politeness in the comments below.)
Like Amarra proper, SQ/+ handles the mathematical calculations required for audio processing whilst continually minimizing CPU overhead. “We’ve tried to keep this real-time process loop as small as possible,” says Reichbach.
Whilst attending CES this year I caught a rumour that some Amarra SQ users were suffering audible distortion similar to their PureMusic’s Streamthrough brethren. Those same Las Vegas jungle drums also reported that a system reboot would sometimes fix the problem, other times not. Interesting…
Reichbach confirms as much. He’s refreshingly candid about the crackling distortion. “Some users are having these issues, yes,” he says. Reichbach reckons the CPU is the more likely culprit than either the RAM or hard-drive.
Like a scientist, Reichbach is careful to temper the definitive nature of his assertions, peppering explanations with caveats of ‘maybe’ and ‘probably’. “Everyone’s Mac is different so it’s tough to isolate the root cause with any degree of certainty,” he concedes.
With similar tempered certainty, I’d wager that the crackling distortion is somehow tied to the CPU’s inability to keep up with each app’s processing demands, particularly when tasked with the time critical nature of audio playback. Reichbach agrees: “Those with higher spec-d machines are PROBABLY less likely to experience crackling distortion than those with lower spec-d machines.”
Time to listen to SQ+.
First up on DAC duties went an ALO Audio Continental Dual Mono. Headphones? Astell&Kern’s AKT5p, a variant of the Beyerdynamic t5p. I’d later switch to a Resonessence Labs INVICTA driving Beyerdynamic T1.
The ‘Transfer to’ dropdown on the left of Roon’s playlist window makes it a cinch to switch between SQ+ and DAC-direct without quitting and restarting the app each time. For Spotify and Tidal sound output device switching took place in OS X’s Preferences pane.
First, the good news: no crackling. None. Zero. Zip. Zilch. To be fair, the Macbook Air I use today has changed since last year’s PureMusic experimentation. I’m now running an early 2014 Air: 1.4GHz Intel i5 CPU, 4Gb 1600Mhz DD3 RAM and a 256Gb SSD.
The ‘bad’ news? From Lou Reed to Ben Salter to System 7, Amarra SQ+ pushes the midrange forward, removes a little low end to render overall acoustic mass a lighter, less immediate and – most obvious of all – narrows the headstaging. Eroded too are the acoustic guitar strums that work the lateral extremes of Salter’s “Boat Dreams” and Reed’s “Walk On The Wild Side”…
..at least, that’s what I concluded after the most cursory of listens. It takes time to acclimate to Amarra SQ+’s deltas. What I first pegged as narrower headstaging was in fact the stage front being moved from skull centre to eyeball line, thus improving on the illusion of depth. It’s a change that also contrasts the SQ+ version of events as lacking inner-head immediacy. Without it, everything is shoved as far as possible inside one’s head. Under SQ+ command, it plays out on the periphery. I also noted a dialling down of inner-throat hardness on male vocals, making them more agreeable to longer-term listening.
The differences brought/wrought by Amarra SQ+ are significant and give emphatic lie to claims that all software players sound the same; they do not.
In addition to its baseline changes to sound quality, SQ/+ offers EQ presets for a selection of well-known headphones as well as the option for the user to freestyle his/her own EQ preferences. At US$49.99, SQ+ allows for even more granular control of EQ than the US$29.99 SQ.
SQ+ also earns it US$20 premium via the inclusion of IRC (available from v2.2 to those with the corresponding software license) and an ‘Audio Conditioner’ (AC) designed to strip away noise from lower quality sources. Toggling ‘preview’ lets you listen to precisely what’s being removed, ranging from predominantly high-frequency information at the low setting to quite a bit of midrange at the high. This might be useful for YouTube but with Roon playing Redbook FLAC from a Macbook Air’s internal SSD the AC’s top-end roll-off is neither required nor welcome.
Whether every listener will prefer SQ+’s audible renovation (or not) is a different matter entirely. That’s where Sonic Studio’s 15-day trial comes into its own. You can download and install Amarra SQ or SQ+ on your own Mac and try it for yourself without having to leave home or trouble a dealer for a loaner (as one might with an in-home hardware demo).
For listeners that find SQ+ to their liking and don’t experience any sign of crackling, the US$50 is easy to part with. For those whose hardware isn’t sufficient to run both SQ/+’s and a host player like Roon, Tidal or even a web browser – for whom crackling does present – my next post might be of interest. I’ll be looking at Amarra for Tidal.
Further information: Amarra