Resonessence Labs

Concero DAC

List Price: $599


Malcolm Gomes


Here's yet another review that fits into our much loved and anticipated "Stereo for Cheap Bastards" feature category. For the uninitiated, S4CB are products that retail for $1,000 or less. At only $599, the Concero is an easy fit.

Having had the privilege of being the first in the world to review Resonessence Lab’s (RL) initial DAC offering - the Invicta and the great enjoyment it provided, it was with great anticipation that I waited to receive their more value priced follow-up DAC model, the Concero. I found two things intriguing. The first is the fact that the Concero delivers on many of the suggestions that I had put on my wish list of what I would like to see in the next DAC from RL. The second is that RL managed to accommodate most of my suggestions and they still managed to bring in the product at a retail price that is less than half the amount that I had opined, would be pretty good value for money; that in itself deserves kudos.

The first thing that struck me when I received the Concero is the size. This DAC literally fits in the palm of my hand. Despite pulling off this incredible shrinking feat, it was very obvious that RL did not cut any corners on the build quality. The Concero may be tiny but it inherits the same bulletproof build quality and elegant façade of its predecessor the Invicta.

Like the Invicta, the Concero is a 192/24, USB 2.0 asynchronouos DAC. The front is adorned with the same LED backlit RL insignia and nothing else. The back has a USB input, a single ended left and right analog output and a digital co-axial that does double duty as a S/PDIF input and as a digital output. When used as a USB DAC, the unit draws its power from its USB connected device, which, more often than not, would be a PC or a Mac. The unit also comes with an Apple USB power adapter, which connects to the USB input on the back of the unit when you use the Concero purely as a S/PDIF DAC. In this mode, S/PDIF data received by the unit is output as an analog signal. The Concero can also be used as a pure USB to S/PDIF converter acting as a high quality bridge between USB output sources like a PC or a Mac and a DAC that is not USB compatible.

Surprising at this price point, the Concero actually comes with a remote control, albeit an Apple one. This is an inspired move as it saved RL the not inconsiderable cost of designing and manufacturing its own remote control while giving its customers a sleek, slim, aesthetically pleasing and well built infra red remote control.


The Concero offers three settings; the first one processes the incoming signal without any up-sampling while leaving the unit’s jitter reduction circuitry active. The second setting is an IIR filter and the third setting is an Apodizing filter. Both these up-sample input signals of 44.1 kS/s and 48 kS/s to 176.4 kS/s and 192 kS/s respectively while also subjecting the signal to active jitter reduction. You can cycle through these three settings by pressing the menu button on the remote control. When switched on the unit defaults to the first setting where the LED behind the RL logo on the façade is blue and when you switch to the second and third setting the LED changes to magenta with a blink to indicate the shift from the second to the third setting.

When used as a USB DAC with a computer as a source, the left and right buttons on the remote let you scroll through the application play list while the play and pause button allows you to do just that.  When you power the unit on the default setting switches on both the analog and S/PDIF outputs. Pressing the up button once causes the LED to blink indicating a switch to analog output (S/DIF output off). Pressing the down button from the default setting changes its S/PDIF output (analog output off/S/PDIF output on). You can also adjust the brightness of the LED display pressing and holding down either the up (for brighter) or the down (for dimmer) buttons.

When you connect an active USB host to the Concero, it is designed to detect the same and then automatically enters into the USB DAC / USB to S’PDIF Bridge mode where it will output both a stereo analog signal and a digital S/PDIF signal simultaneously. The rationale given by RL for this configuration is that it allows customers to use the analog outputs to feed a headphone amplifier and the digital output to a DAC that is not equipped with a USB input. If you do not connect any active USB device to the Concero but it detects that it is plugged into a power only USB, then it will automatically enter into the S/PDIF DAC mode.

When used with a Mac, the Concero has all the software it needs to get going. However when used with a PC, the free downloadable Thesycon Driver needs to be installed before you can use the Concero.

Let’s get some of the technical specifications out of the way. The Concero does not use PLL, rather it employs a low jitter oscillators for reference clocks that offers 28 bit audio DAC processing and can handle up to 24 bit, 192 kS’s data. It outputs a relatively modest 1.2V rms analog signal that will be a good match for most preamplifiers. The output impedance is 300 Ohms and the THD+N into a 100k load is less than 0.005%. DNR is better than 104dB and the unit has three dedicated regulators for the audio section, two in the DAC chip and 1 on-board.

The USB to S/PDIF bridge circuits have a low jitter galvanic isolated S/PDIF output while the S/PDIF DAC section allows selection of a “bit-perfect” mode of operation where jitter is minimized while leaving the digital data intact.


While RL touts the fact that the Concero has the same processing engine as the Invicta, it needs to be noted that while the latter uses the ESS Sabre flagship chip, i.e. the ES9018, the Concerto uses the ES9023. The Concerto processing engine is embedded inside a Xilinx Spartan-6 FPGA that runs on a code that is exclusive to RL. This configuration allows the Concero to offer the aforementioned up-sampling filters.  The modus operandi of the two filters also differ from the Invicta in that they are operated by the FPGA engine whereas in the Invicta it is done inside the ESS Sabre DAC chips.

There are already Concero reviews published, which go in depth into its technical configuration and the parts used in it. Rather than regurgitate all that information that sounds like geeky technobabble to most readers, I would rather get right to the meat of the matter, i.e. the sonic performance of this little wonder.

I used four sources; namely the Sooloos 5, the Bryston BCD, the Bryston BDP, an iMac loaded with the latest Amarra, Pure Music and Decibel. Across the three sources, I have around 72,000 tracks so I was able to give the Concero a thorough workout with virtually all genres of music except rap and hip-hop. As recommended by RL, I burned in the Concerto for 100 hours before the review.

The first thing that struck me was the way the Concero transcended the performance hurdles that many sub $1,000 DACs that I have reviewed in the past found insurmountable. One of those hurdles is the struggled to create air around the instruments and voices resulting in a relatively congested sound stage. Not the Concero. It was able to render the sonic image with a fair amount of air. Not to the extent that you could expect from the mega priced DACs but significantly more than the other DACs in its price range.

There are sub $1,000 DACs that are able to retrieve and reproduce more information from the digital signal than the Concero, but to its credit, this little wonder was able to better process the information that it did retrieve. I did detect the absence of some very subtle and nuanced micro details when comparing the Concero to many other DACs in its price range, but the sheer musicality with which the Concero performed made me prefer it to its similarly priced rivals, which retrieve more details but are unable to reproduce them with the same musicality of the Concero. It is this musicality that makes the Concero less fatiguing than its similarly priced counterparts especially during extended listening sessions.   

The height, width and depth of the sound stage created by the Concero were par for the course in its price range. The treble rendition is relatively smooth and airy without being sickly sweet. The midrange has the textures and layering that compare well with DACs even at double the price. The bass compares well to other similarly priced DACs but is not as tuneful and deep as some of the better DACs in the $1,000 price category.

The Concero goes to the top of its price class when rendering vocals, which comes through with good body and palpability. On very well recorded tracks, the Concero makes it easy to establish an emotional connection with the singer.

Dynamic contrast and transient attacks and decays have always been the Achilles heel of entry level DACs but the Concero acquitted itself quite admirably in comparison to its direct competition. The Concero also benefitted quite significantly when used with true high-end interconnects. However, given that the interconnects that helped the Concero perform better were 2 to 3 times the price of the DAC itself makes me wonder if any Concero owner would invest in interconnects of this caliber.

The albums that I used to review the Concero included Nils Lofgren Live, Cat Steven’s Tea for the Tillerman, Chesky’s Sampler Volume 1, Boz Scaggs’ Dig, Clair Marlo’s Let it go and Cantate Domino by Oscar’s Motet Choir. Some of these are redbook 16/44 versions but most are 24/96 or 24/192 versions. I also tried a few lower resolution tracks but found that the Concero was not very partial to tracks with resolutions of less than 320 kbps, rendering many of them with ragged edges and sparseness that was not very pleasant to listen to.

The Concero seemes to relish guitar-dominated tracks like “Keith Don’t Go” by Nils Lofgren. It rendered Nils’ guitar prowess with a lot of authority and you could hear the robust way that Nils strums and picks at his guitar as he belts out this audiophile favorite. It was equally pleasurable listening to Clair Marlo’s “It’s Just the Motion” with so much of the emotion that this diva puts into her performances, coming through in spades.

The Cantate Domino track on Oscar’s album is not easy to get right and the Concero did struggle a wee bit with the task of making the choir sound like a collection of individual voices, but it was still one of the best rendition of this tough track that I have hear on any budget priced DAC. Wild World by Cat Stevens is an evergreen favorite and for an entry level DAC, the Concero did the 24/192 version of this incredibly well recorded track a good deal of justice, reproducing Cat Steven’s voice with all its inflections and especially when he allows his voice to break to emphasis the emotion behind the words.  

Boz Scaggs’ “Thanks to you” has a wicked awesome driving rhythm that can severely test the speed of most systems and the Concero took it in its stride, rendering it in a way that got my foot tapping merrily to the very infectious beat. The Concero reproduced “Viola fora de moda” from the Chesky Sampler with the delicateness and fragility of a butterfly’s wing. This took me by surprise because hitherto, most of the entry level DACs that I had auditioned made this Ana Caram track sound a bit harsh.

The up-sampling options offered by the Concero are well worth the price of admission. When used with my very neutral sounding reference system I preferred the sound of the Concero without its up-sampling filter options but when I tried this DAC with more modestly priced source components (NAD C565BEE CD Player, Cambridge Audio Azur 651A integrated amplifier, Analysis Plus Clear Oval Cables, Oval One Interconnects and Audes Blues Speakers), the two up-sampling options did add life and sparkle to the sound by adding air around the instruments and by improving the transient attack. Between the two filters that perform the up-sampling I prefer the Apodizing filter by a hair as it sounds a tad less bright than the IIR filter.

I could be wrong, but generally speaking, I would assume that many people considering the budget priced Concerto would probably own or be looking to buy their other audio components that would also be budget priced. If I am right, then the two up-sampling options of the Concero could be just what the doctor ordered to compensate for the shortcomings of many budget priced audio components, which in comparison to their more expensive counterparts, generally tend to sound a bit veiled.


The configuration that allows the Concero to be used as a USB to S/PDIF bridge/converter is a very clever idea. This option allows the user a very attractive path when it comes time to upgrade to a better DAC. This option will allow Concero owners to choose from not just USB DACs but also the models that do not have the USB input option. The bonus here is that in addition to performing USB to S/PDIF duties the Concero also gives you the option of two modes of up-sampling. This in itself should stack the deck in favour of the Concero when choosing a budget priced DAC.

I tried using the Concero purely as a USB to S/PDIF converter between my iMac and the S/PDIF inputs on my reference Calyx Femto DAC that also has a USB input. When I compared the performance of Calyx Femto DAC (priced at close to $7,000 - see my review

here) USB input to inserting the Concero as a USB to S/PDIF bridge, I was surprised at how close it is in terms of sonic performance. I could easily tell that connecting directly to the USB input of the Femto DAC was better but not by as much as I had expected. This would indicate that the Concero would be a high quality USB to S/PDIF bridge that would acquit itself quite well even when used with upper end, non-USB DACs that Concero owners may upgrade to in the fullness of time.   


One area where the Concero was significantly superior to most other DACs in this price range is in fit, finish and build quality. I will even go so far as to say that in this regard it matches its highly regarded sibling the Invicta, even though it is a fraction of the price. Although the Concero offers a fair amount of features and connectivity it has a few rivals at the same price that offer more in this regard. For example, if options like a front illuminated information display, optical, BNC and AES/EBU inputs, balanced outputs and headphones output are important to you, you may find the Concero wanting. But plan to spend much more for those features and sound quality.


To summarize, based on all the entry level DACs that I have heard, to my ears, the Concero is one of the class leaders in terms of performance, build quality and value at its price point. If that is not enough reason to short list it if you are looking for a budget priced DAC, it can also morph into a high quality USB to S/PDIF bridge with two modes of up-sampling which will allow you to consider even non-USB compatible DACs when you feel the urge or the need for a DAC upgrade. The included remote control is a good feature as well.


Associated equipment:

CD Player - Bryston BCD-1 (SS)

Digital Player – Bryston BDP-1

Turntable - Technics SL-1200Mk2 (direct drive) with Goldring 1042GX cartridge

Music server - Sooloos 5 complete 3-piece system, iMac (latest) with Amarra 2.3 and Decibel media players 

Preamp – Bryston BP26 with MPS2 Power Supply

Power Amp – Ayre V3

Phono Stage - Bryston BP-1.5

Speakers – Merlin Music VSM – Master with Master BAM and RCs

Speaker Cables - Cardas Clear Beyond

Power Cords - LessLoss Signature

Interconnects - Cardas Clear

Headphones – Sennheiser HD 600

Digital - Transparent Reference (digital co-axial), Cardas (USB), Analysis Plus (Toslink)

Stands and Racks

Black Diamond Racing (The Shelf for Sources and LM series) 

Black Diamond Racing cones 

Shelfs are placed on a bed of pure silicone sand and equipment placed on the shelf via the cones

Review Equipment is not provided with any tweaks or enhancers

DAC – Calyx Femto DAC

Power Conditioner -  Isotek Sigma II



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