Reviews of Attainable Hi-Fi & Home-Theater Equipment

Reviews of Attainable Hi-Fi & Home-Theater Equipment

Resonessence Labs ConceroLate in 2012, Resonessence Labs, based in Kelowna, British Columbia, added to its product line the Concero USB DAC, to join their well-received flagship DAC, the Invicta. Resonessence was founded by Mark Mallinson, formerly of ESS Technology, best known for the Sabre DAC chip; he staffed the company with people with experience in DAC and ADC technologies -- including Sabre chips. Mallinson says that he wanted to “put together a team that includes world-class audio engineers and design audio products without compromise.” It would be impressive if he has achieved the latter -- or has even come close -- in the Concero, which, at $599 CAD, retails for only a fraction of the Invicta’s price ($3995).

The Concero is a compact USB DAC that costs $650 when you include the infrared remote control and USB power adapter. Both accessories have Apple’s aesthetics written all over them, which is hardly surprising -- Apple makes them. The Concero itself came wrapped in a drawstring bag of black nylon that bore the Resonessence logo. I’ve seen other products come similarly attired, but it makes more sense here -- I can well imagine wanting to take the Concero with me on a trip, but not wanting to mar its fine finish. The Concero is small -- about the size of a current-generation Roku or Apple TV -- but substantial for its size. (While the mere weight of connecting cables can tip my little Roku backward, the Concero doesn’t have this problem.) A DAC’s chassis isn’t often touched, but this one exudes quality: the cool feel of the well-machined, black-anodized aluminum, the well-defined edges and smoothly tapered corners, the small rubber feet on which it sits. The Concero is made in Canada and hand-assembled in Resonessence Labs’ own facility, and the attention to detail shows. In front is a cutout of the Resonessence logo, through which an indicator light glows. Around back are a USB port, a coaxial S/PDIF port, and a pair of analog RCA outputs. There is no power switch; the Concero is powered via USB connection. Plugging it into a USB port turns it on, at which point the indicator light glows red.

Resonessence Labs ConceroThe Concero can function in three basic modes: as a USB DAC; as an S/PDIF DAC; and as a USB-to-S/PDIF bridge, the signal staying in the digital domain. These modes can be cycled through from the remote control. Based on the ESS 9023 Sabre DAC, the Concero supports signals with resolutions of up to 24-bit/192kHz, and provides 4x upsampling of 44.1 and 48kHz sources to 176.4 and 192kHz, respectively. Other features include asynchronous USB 2.0 audio and jitter-reduction circuitry. When its USB cable is plugged in, the Concero determines whether it is being provided with only power or also with an audio signal (e.g., from a computer). If the USB port is part of an active computer, the Concero defaults to USB DAC mode. It resets to USB DAC and its default filter when the power is cycled, including when the computer goes to sleep. Many computers have always-on USB ports (typically in front, and to be used for charging your phone, etc.), which would be appropriate for use with the Concero. For use solely as an S/PDIF DAC, the Concero can be connected to a power adapter or an outlet with built-in USB ports. I tried using a powered USB hub, but it wouldn’t work unless the hub was itself connected to a computer. I was able to power the Concero from a computer, or with several USB power adapters that had come bundled with devices from Amazon and Samsung. According to the Windows Device Manager, the Concero draws only 100 milliamps, so the high-power USB adapters that tablets such as the iPad require won’t be needed. The Concero comes with a one-year warranty.


I used the included USB cable to connect the Concero to its power adapter or a USB 2.0 port on my computer, depending on the source I was using. I connected, at various times, two coaxial sources: my Pioneer DV-563A DVD/SACD player and a Music Hall MMF CD-25 CD player. Many of my usual sources have only optical outputs, which the Concero doesn’t support. I’ve criticized DACs in the past for omitting optical and/or coaxial inputs, but won’t do so here -- I don’t know where another connector could be squeezed in! Already, the housings of my interconnect terminations are touching.

A more serious problem was that the Concero seemed a bit sensitive to fluctuations in voltage. Repeatedly, when I played music via both coaxial and USB, the sound would stop and the front-panel light would momentarily switch to red (no signal), then switch back. Using the same outlet, I had not encountered this problem before with any other equipment. Several different USB power adapters yielded the same results. I live in an apartment -- I can’t run a dedicated line for my stereo, nor can I trace just which circuits are shared with, for example, the refrigerator. Four of the ten circuits in my circuit-breaker box are labeled merely “Lites & Plugs” -- not very helpful. After some trial and error, I found an outlet that didn’t exhibit this behavior, and, fortunately, didn’t require that I move my audio rack.

Depending on the listening scenario, I connected the Concero’s coaxial digital output or (more often) analog output to my Onkyo TX-SR500 A/V receiver. In the Concero’s default mode, it outputs the signal through both its analog and digital outputs when a USB audio/data connection is present. Sensibly, a power-only USB connection defaults to using the sole coaxial jack as an input. In general, the experience is less than intuitive, as you’d expect from operation using someone else’s remote control. You will need to look at the User Guide to figure out what the buttons do: beginning in default mode, press up to shut off the S/PDIF output, or down to shut off the analog output; hold up and down to change the LED brightness; and pressing Menu cycles through the filter options. Play/pause, left, and right perform the expected functions with supported software. Nonetheless, I’m happy that the design money went into the audio rather than a better, or at least relabeled, remote control.


The Concero has three filter options, two of which it shares with the Invicta; they’re selected by pressing the remote control’s Menu button. Resonessence describes them as follows:

Brick wall-type Finite Impulse Response (FIR) Filter (termed “No Filter” in the User Guide): This mode has bit-perfect playback with jitter rejection active. Whatever data is received is sent unmodified.

Minimum Phase, Infinite Impulse Response (IIR) Filter: This filter is designed from an analog filter prototype and exhibits no pre-ringing at all. To achieve this, it has to compromise the steepness of the filter; it corresponds to a fourth-order analog filter. This is a dispersive non-linear phase filter, but the dispersion has been optimized to the absolute minimum consistent with no pre-ringing.

Linear Phase Apodizing Filter: Perfectly symmetrical impulse response, hence linear phase and non-dispersive, this filter achieves a high -96dB rejection at fs/2 and exhibits the minimum of pre-ringing possible while achieving this excellent rejection. 

For short, I will refer to these filters as “default,” “IIR,” and “Apodizing,” respectively. All three offer jitter rejection; both the IIR and Apodizing filters provide 4x upsampling for signals recorded at 44.1 or 48kHz. For the IIR and Apodizing filters, both designed by Resonessence, the company has posted on their website a graphical representation of the filters’ characteristics. Notice how much smoother the IIR graph is than the Apodizing. I was impressed with how open Resonessence was with technical information on their website -- they almost seem to be inviting competitors to outdo them.

When the Concero powers on, it is in its default filter mode; the LED glows blue when a signal is received. One tap of Menu cycles to IIR, another tap to Apodizing, and a third returns to default. The LED glows magenta when either IIR or Apodizing is active. The only way to know which filter is in use is to cycle through them. At the end of a CD, when the signal stops, the light switches to red; starting a new CD resumes with the same filter used with the previous disc. Higher-resolution signals will automatically switch the Concero to its default filter mode, as no upsampling is available.


The first thing I noticed with the Concero was that I had to set the volume higher than with many other DACs and CD players. While my Music Hall MMF CD-25 CD player (using its built-in DAC, a Burr-Brown PCM1732) produces a rated 2V RMS, the Concero outputs only 1.2V RMS. But when I raised the volume to an appropriate level for the Concero, it was emphatically the better of the two. In “Strange Meadow Lark,” from the Dave Brubeck Quartet’s Time Out (CD, Columbia CK 40585), Brubeck’s piano sounded less bright and more delicate. Transient microdynamics were also more pronounced with the Concero. “Take Five” was rendered with a deeper soundstage and more distinct imaging of individual instruments, and Joe Morello’s drumstrokes had more body and resonance. After I’d listened to this album through the Concero, it sounded awfully bright and indistinct through the Music Hall, and less involving. The Concero would be a definite upgrade from this entry-level audiophile CD player of a number of years ago, which itself bests the DACs in my AVR and DVD player.

Resonessence Labs Concero

Over the holidays, I had a chance to visit a fellow reviewer who has a higher-resolution system than mine: Graaf integrated amplifier, Esoteric speakers, Woo Audio headphone amp, Stax headphones. As the Concero is so small, I brought it along. I found the Apodizing filter sounded best; IIR was a bit dry for my taste. To be sure, the differences between the two upsampling filters were subtle -- I strained to hear them through my own system. Both of the upsampling filters are more precise, and bring out Natalie Zhu’s crisp piano on her and Hilary Hahn’s recording of violin sonatas by Mozart (CD, Deutsche Grammophon B0004771-02). The default filter afforded a deep but amorphous soundstage, and more but less-precise bass. I much preferred to upsample for CD playback.

When I listened to Dvorák’s Slavonic Dance No.5, performed by Orquesta Filarmónica de Gran Canaria conducted by Adrian Leaper (CD, Arte Nova 74321 34054 2), the Concero’s Apodizing filter offered a forward and layered soundstage with good space around individual players -- lively, crisp, and clean, but not warm. The Resonessence was unforgiving of Sade’s Diamond Life (1990 CD, Portrait RK 39581), rendering this poor recording with brightness and brittleness: It was knife-edge sharp. The quality of the source material mattered greatly.


I installed the Concero with driver v1.50 on a Windows 7 box and played some of my FLAC files, in both standard and high resolutions, with my preferred player, foobar2000, and the Concero in WASAPI mode. The Apple remote control was able to play, pause, and skip forward and back in foobar2000 and other applications I tried. Helpfully, the Concero handles all of this so that an additional consumer IR input device is not necessary. With well-recorded, hi-rez recordings such as violist Maxim Rysanov and pianist Ashley Wass’s Pavane (24/96 FLAC, BIS/eClassical), the interchanges between the players were crisp, clean, and precise. Richard Dubugnon’s Lied, Op.44b, was rendered with exquisite delicacy, and the Concero communicated the viola’s mournful timbre with great tonal accuracy in Fauré’s Pavane, Op.50. If you ever thought the viola and the violin sound about the same when playing the same pitches, listening to this recording through the Concero will quickly dismiss that notion.

Resonessence Labs Concero

While the Concero switches to its default filter mode when it detects a signal with a resolution higher than 16/44.1, a 24/44.1 recording can be upsampled with the IIR or Apodizing filters. If you had, as I did, a preference among the three filters, you’ll find it handy that switching back to 16/44.1 track will restore your preference. With Enescu’s Romanian Rhapsody No.1 in A major, Op.11, performed by the Romanian Radio Symphony Orchestra led by Josif Conta (16/44.1 FLAC, Marco-Polo/eClassical), the Concero’s Apodizing filter presented an excellent image of the full orchestra throughout the rollicking, whirling folk-dance passages. But the default "No Filter" option, it turned out, was not perfect; there was something missing, and the soundstage became a muddle. Tinsley Ellis’s “Tell the Truth,” on Gibson Presents: Hot Tones in High Definition (16/44.1 FLAC, Alligator/HDtracks), offered up tight blues riffs, well-rounded reverb, and occasionally a nice “growl” on Ellis’s lead vocal. While the default mode afforded a touch more of the bass strikes, the sound was thinner than through the Apodizing filter. For the blues, it was, if anything, too clean. The Apodizing filter just gave a bluesier feel, particularly of the guitar solo. It was just more engaging.

Lossy MP3s sounded like, well, lossy MP3s. Natasha St-Pier and Pascal Obispo’s duet “Mourir Demain,” from St-Pier’s L’Instant d’Après (MP3, Columbia Europe), is less overproduced than most pop songs. I found that I actually preferred not to upsample this track, as I wanted a bit more rocking bite, but for others I needed the IIR filter to soften the hard edges, which made me wince. I appreciated being able to switch filters with the remote.

One bug I noticed was that DirectSound applications -- I’m assuming this is the relevant characteristic, as foobar2000 in WASAPI mode did not have the issue -- such as MOG Desktop would stop outputting music after less than an hour, and had to be closed and relaunched. Occasionally this didn’t work, and the Concero had to be power-cycled. I hadn’t experienced this with my computer's built-in Realtek DAC, or my normal E-MU USB DAC on the same machine. Most applications, including Web streaming, force one to use DirectSound. Of course, for active listening, an application that supports WASAPI, such as foobar2000, is much preferred.


In the Concero, Resonessence Labs has made several core features of their far more expensive Invicta DAC available to a broader audience. While in recent years the marketplace has been flooded with USB DACs, few of the lower-priced ones have high-quality upsampling filters. Resonessence makes, in my view, a compelling argument for such filters. Most of my digital recordings, whether on optical discs or a file server, are 16-bit/44.1kHz, a resolution to which the upsampling filters can be fruitfully applied. Most often, I was pleased with the sound of the Concero’s Apodizing filter: clean and well defined. I appreciated the ability to easily select filters with the remote control -- the ideal filter for a specific recording will depend on that recording. I do wonder how my 24/96 tracks would sound upsampled to 24/192, which the Concero can’t do. But when I fed it lesser-quality recordings, I felt I got honest representations of their sound -- and quickly moved on to higher-quality content. The Concero is well worth an audition, particularly for those with large collections of CDs and other 16/44.1 recordings -- that is, most of us. The Concero is a fundamentally good value that stands out in a crowded field with a well-chosen set of features and a focus on bringing the most out of good recordings for a surprisingly affordable price.

. . . Sathyan Sundaram

Associated Equipment

  • Speakers -- Wharfedale: Diamond 8.2, Diamond 8 Centre, PowerCube 10 subwoofer; Infinity Primus P162; M-Audio Studiophile DX4
  • Analog sources -- Goldring GR1 turntable, Rega RB100 tonearm with Elektra cartridge; Cambridge Audio 540P phono preamplifier
  • Digital sources -- Music Hall MMF CD-25 CD player; Pioneer DV-563A DVD/SACD player; Roku XDS with MOG Primo; Intel H61 desktop computer (2.6GHz, 8GB RAM, Crucial SSD) running Windows 7 Pro SP1 (64-bit), Windows 8 Pro (64-bit), foobar2000, XBMC, with Realtek ALC887 DAC/optical output (WASAPI driver); E-MU 0404 USB DAC; Synology DS211j SMB/DLNA server
  • A/V Receiver -- Onkyo TX-SR500

Resonessence Labs Concero Digital-to-Analog Converter
Price: $599 CAD ($650 bundled with Apple remote control and AC adapter).
Warranty: One year parts and labor.

Resonessence Labs
863 Coronado Crescent
Kelowna, British Columbia V1W 2K3
Phone: (778) 477-5536