Computer Audio Brings High Value Hi-Fi

JustBoom DAC/Amp stack fits into one case as an Audio Player Component

JustBoom DAC/Amp stack fits into one case as an Audio Player Component

Computer audio enables music lovers to maximize enjoyment of their passion while also optimizing value in music listening. You can set up a stereo with digital sources that achieves high-end playback for an unprecedented low budget, compared to old-school, analog-only approaches. Computer (or digital) audio can be implemented in so many ways that you can hold the cost to nearly any budget and successfully transform bits into bravos. It can be as modest as simply listening to streaming music on your smartphone or as grandiose as a roomful of advanced electronics. You probably already have a good start based on today's widespread computer and cellular technologies.

Optimizing your audio system's price/performance depends on a curious, yet cautious thoughtfulness when you select and configure components to access high-resolution music. Skepticism about advertising rhetoric also helps. Listen critically and believe your own ears, rather than hype or hearsay, to stretch music budget and listening pleasure both together.

My example system is a cost-aware approach to creating a value-driven, high-performance music system. A virtual walk-through starts where the music data enters the hardware. My workhorse MacBook Pro laptop is often the source and control device, though with digital input, it makes little difference in the final sound quality which computer, tablet, player or smartphone hosts the application that controls the file library and musical bit stream, as long as you assure noise does not creep in to degrade the sound. A Samsung Galaxy S7 (Android) smartphone also sources this same system, with equivalent results.

The library includes locally-stored digital recordings and playlists of abundant, online streaming music from Spotify and TIDAL. Spotify distributes MP3 files in Ogg Vorbis format . . . but wait, hold those sneers for a moment. The suggested TIDAL subscription is their Hi-Fi option, streamed at 16/44.1 resolution (16-bit data depth at a 44.1 KHz sample rate.) This is already true CD quality and that resolution gets better with some tech magic. Much better, you'll discover, if you give this a try.

Spotify may be less precise musically but their player app's suggestion engine helps you discover more music you like. An insatiable music appetite drives me to develop playlists using Spotify, then transfer favorites to TIDAL, because I love to explore many genres at higher resolutions. Both sources get upsampled to 24-bit/96KHz in this test system, which greatly improves the sound of source recordings. The denser the original data, the better the results. This resampling trickery provides audibly better likenesses to live, original music than either MP3s or even CD-quality would imply. Still, it's impossible for me to listen to Andrea Bocelli for long with dry eyes.

An Audioengine D2 Wireless DAC (digital-to-analog converter,) which is a two-part audio component, transports music across the room to the rest of the system. The D2 Sender (D2S)unit accepts USB 2.0 data from the source device. The D2S upsamples the bit stream to 24/96 resolution and transmits the expanded digital music across a 12-foot space to the D2 Receiver (D2R) through a dedicated, Wi-Fi-like radio channel.

The D2 is a very capable DAC, as well as a wireless optical data link, but one purpose of this article is to test and report on a JustBoom DAC/Amp Player that I assembled. In this case, the D2S passes the digital music to this DAC for conversion to an analog signal that can be amplified.

The D2S not only up samples the bit stream, it also enables me to conveniently sit with the computer in the listening sweet spot, centered at a good distance from the speakers, without a wire trailing across the carpet to the system rack. The D2S is located beside my easy chair. Across the room, The D2R sits on the system rack behind the speakers, against the front wall. The D2R hands off the digital audio data from its optical (S/PDIF TOSLINK) output to this system's active DAC, which is not the D2 in this case, though the D2 has also served as the converter previously, and it will return for encores.

Presently, the active DAC is a JustBoom standalone DAC Board that receives the 24/96 digital music stream from the D2R and converts the digital bits into an analog, Line Out music signal through a Burr-Brown/Texas Instruments PCM5102A DAC chip.

Audioengine P4N Passive Speakers -- big sound from a small but handsome package.

Audioengine P4N Passive Speakers -- big sound from a small but handsome package.

     This line-level audio output goes to another JustBoom standalone printed circuit board, their Amplifier, that is stacked on top of the DAC Board. Both boards are housed inside a sleek, custom polymer DAC/Amp Case. These two, latest-tech PC boards interface through a clever inter-board connector to achieve an integrated DAC/Amp audio component.

A handsome set of Audioengine's bamboo composite, P4N Passive Speakers receive the amplified analog data and transduce it into audible music quite respectably. The stiffer bamboo housings have a slight performance edge over the MDF enclosures of the black and white P4 versions.

An S8 Powered Subwoofer, also from Audioengine, completes this setup. It fills in the lower bass below the 58 Hz rolloff at the bottom of the speakers' range. So this system is no wimp. Turned up loud, it can shake the house when music has powerful bass passages.

Both D2 housings, the JustBoom DAC/Amp component, and the P4 and S8 Speakers are all suspended on Herbie's Audio anti-vibration pucks. The pucks I selected are the types the Herbie's Audio website recommends for these applications. The materials are not rubber, which is far too resonant for vibration suppression. Anti-vibration with these proven, engineered-polymer discs is one of the best price/performance enhancers that small money can buy.

This spare assemblage of hardware is integrated into a modest room audio system with commodity interconnects, nothing costly or exotic. I have been listening to various genres with pure delight.

This system's compactness is obvious in shorthand:

Computer > D2S/D2R > DAC/Amp Player > P4 & S8 Speakers


Cases in red or black make a Player device of your DAC and Amp Board stack.

Cases in red or black make a Player device of your DAC and Amp Board stack.

 What you don't hear matters as much as what you listen for. Fewer artifacts spoil the pleasure when there are no spinning mechanisms to handle media or transduce physically encoded music data. This system needs no physical media at all, which means: no surface noise, clicks, pops or crackles; no hiss, wow, or flutter; and no hum lurks in the background. Playback is crystal-clear. The music stands out like an infinite star field in a clear, night sky against a velvet-black silence you can feel in the pauses.

Here are some selections that exploit and showcase the musical performance. These dynamic recordings demonstrate excellent fidelity due to their pure provenance. Some are streamed from online and some from my local disk storage:

  • Mike Mainieri, Man Behind Bars
  • Norah Jones, Come Away with Me
  • Bill Frisell, Gone, Just Like a Train
  • Mo Foster, Bass Themes and 50's and 60's Rock 'n' Roll
  • Fabrizio Paterlini, The Art of the Piano
  • Chuck Loeb, E-bop
  • Dustin O'Halloran, Piano Solos and Piano Solos Vol. 2
  • Oystein Sevag & Lakki Patey, Visual: an Ambient Experience
  • Céu, Céu
  • Jerry Douglas, Glide
  • Kilowatts, Seven Succulents
  • Adam Hurst, The Secret
  • Leonard Cohen, Live in London
  • Bob Dylan, Fallen Angels
  • Praful, The Silent Side of Satie
  • Harry Manx & Kevin Breit, In Good We Trust

These playlists cross several popular genres: Brazilian Pop; Electronic and Ambient; Jazz, including Female Vocals; Classical Piano and Cello; Rock; Bluegrass; and Male Vocals. I purposely choose an eclectic listening experience to hear an array of instruments played in different venues. Such range provides telling musical impressions. Eclecticism is helpful to characterize how a setup sounds; to reveal both virtues and faults. There is much to appreciate throughout this mix of masterful artists and composers who demonstrate outstanding musicianship and often, advanced virtuosity.

Access to variety makes a quantum jump when you include streaming sources in your music collection. Through TIDAL and Qobuz, we are experiencing a transition to 16-bit resolution in online streaming. This brings listeners increasing returns—–all the beauty of CD-quality music but without the plastic-disc downside.


Audioengine's S8 fills in the low bass below the P4's rolloff at 58Hz.

Audioengine's S8 fills in the low bass below the P4's rolloff at 58Hz.

Listening impressions of this system are favorable across the board. Hearing new things in familiar recordings alerts me to significantly increased musical fidelity. Then I listen closely to details. The stars of this show are JustBoom's DAC/Amp Player and Audioengine's P4 Speakers.

The sound of the JustBoom DAC/Amp Player through the extremely articulate P4N Passive Speakers is rich, full, well-balanced, natural, transparent, and highly realistic. This 11 by 15 by 9 foot room is filled beautifully as the P4s easily handle any listenable volume from the Amp Board, without noticeable distortion. The P4s are efficient enough to sound lifelike with only 25 WPC (Watts per channel, RMS) maximum power. Perfect for a small to medium-sized room. Also, I love the bamboo composite look even if that does add a little cost. The black or white versions could save you some cash.

The P4 speakers are front-ported. At first, I placed them too far out from the front wall. When I moved them back to a two-foot clearance, the soundstage shaped right up into a holographic presentation. Soundstage is natural and detached from the speakers, covering the whole room's width with instruments that appear spatially separated on all three room axes. In some recordings, instruments seem to float out beyond the extents of the speakers' lateral separation, with depth extending beyond a line between the speakers.

The D2 contributes in two ways to a natural sound: first, by up sampling all the selections to 24-bit/96 KHz resolution. The D2S resamples any file type, at any bit-depth and sample rate, before streaming to the D2R. This means that the D2R outputs audio at 24/96 resolution from its optical output, even from Spotify's MP3 source data. This split component elevates the listening experience appreciably. Try it out on your purist friends secretly. Maybe even blindfolded.

Up sampling improves noise floor. The curve-smoothing of expanded resolution also helps provide a more accurate representation that's closer to the music's native waveforms than the available input data. Without up sampling, the JustBoom DAC would be converting 16/44.1 data instead of 24/96. To my ears, 24/96 seems beyond the point of diminishing returns. I don't feel a pressing need to escalate resolution infinitely.

Audioengine's D2 is a clever innovation that uniquely resolves an inherent issue with digital streaming to room audio systems, which is: the computer that manages music is usually near the listener, who's located across the room from the speakers. With this test system's setup, the listener receives the benefit of good distance from the speakers with no wire needed to haul the bit stream to the conversion device.  

The JustBoom DAC/Amp is a notable value for a 25 Watt (RMS) digital music player. The parts went together easily, without a hitch, in an hour or so with no soldering. JustBoom offers a high-value product line targeted toward the maker movement. These guys are helping to revolutionize serious home audio. They have a lot to offer a music lover with a hobbyist inclination, some manual dexterity and a few common hand tools.

The bulk of cost for components in this system is rolled up below, assuming you already have a computer, high speed Internet access, a local library of digital music files and/or a Spotify or Hi-Fi-level TIDAL subscription.

The DAC/Amp Player assembled from JustBoom items comprises the following:

  • Standalone DAC Board: $55
  • Standalone Amplifier Board: $90
  • DAC/AMP Case: $16
  • Power Supply: Power Pax 3102D, estimated: $18

     Subtotal: about $179

The whole system is an excellent value even considering cost of the Audioengine D2 that is the key to required spatial arrangement:

  • D2 24-bit Wireless DAC & S/PDIF Converter: $399
  • P4N Passive Bookshelf Speakers: $325
  • S8 Powered Subwoofer: $349

      Subtotal: $1073

Grand Total: around $1252

Audioengine's D2 DAC / Wireless Optical Link plays a strong supporting role.

Audioengine's D2 DAC / Wireless Optical Link plays a strong supporting role.

Thinking through a desktop setup for this JustBoom Player did briefly give me pause. It only accepts either optical or coax input, so one can't connect this directly to a computer via USB. However, noise issues actually disqualify USB for the connection when a long cable run is needed. The USB 2.0 specification does allow cable length up to 15 feet but a USB cable that long (in a previous project) caused noisy results. Optical or coax are best for this bandwidth. Optical is best for noise isolation.

Desktop issues arise for this Player when a computer lacks an S/PDIF or coaxial PCM audio output. For room audio, the D2 resolves this issue neatly but its two-part architecture doesn't fit typical desktop real estate. The wireless design is intended for more distance. Audioengine offers their D1 DAC with USB input for more compact desktop applications. Or the JustBoom standalone DAC works well. I would use headphones for desktop, though, and this DAC conveniently includes a high-quality headphone amp and jack for close listening.

To set this Player up on a desktop with passive "computer speakers" flanking my 2011 MacBook Pro laptop, I could certainly use S/PDIF to connect directly from the laptop's headphone socket, which has a digital optical sender integrated into this 3.5mm analog audio jack. However, my personal preference is never to sit at a desk to write. "Desktop audio" is too near-field for me to to prefer when a whole room is available to develop the full acoustic bloom of recorded music.

Simply keep in mind that to implement this whole example system, you will need some way to connect your digital music player device to the JustBoom DAC/Amp Player component, either via coax/RCA or S/PDIF. If you include the Audioengine D2 Wireless DAC as your data link, that issue is resolved. I already had a D2 on hand because I have been using it as my demo DAC for quite some time.

The summary listening impressions are all positive. Across a wide variety of musical genres, P4 Passive Speakers sound wonderfully natural driven by the JustBoom DAC/Amp Player. I hear accurate instrument and vocal timbres and good balance throughout, with stunning realism, including the ambiences of the venues where recordings are captured. There's plenty of power to fill even this medium-sized, acoustically softer room where I work.

After many hours of listening, I like this system well enough to keep it going. This hardware performs well for the cost. It's a value star. I'm not waiting to revert to my previous system setup, which is Audioengine's internally-amplified A5+ Powered Speakers with their S8 Powered Subwoofer via the D2 Wireless 24-bit DAC. I'm content to keep listening to my collected music and to continue making new discoveries as-configured for this article. That says a lot in favor of the P4s with the JustBoom Player because I like my A5+ Powered Speakers very much.

But by all means, please decide for yourself. I'm always interested to know what you think. Please comment HERE, or drop me an email using the Contact page form in the navigation bar.

Enjoy the Listening,

Joseph Riden