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The Pinnacle of The Electrostatic Sound

Thursday, September 19, 2013

Audiophile Review!
Resonessence Labs Concero HP
USB D/A Converter/Headphone Amp
"Impressive DAC For Your Computer"




Brevis...
Price: $850 retail
Likes: pristine sound, DXD,DSD decode
Dislikes: no onboard level indicator


by John Gatski

  In 2011, I reviewed the Resonessence Invicta DAC, a high-end Canadian manufactured full-featured DAC with superb on-board headphone amp, ESS Sabre32 DAC chip, SD card player and a really classy build. For those who thought $5,000 was far north of their budget, the company now has a series of lower-cost models in the Concero line, designed to be used with computers (USB) and traditional outboard gear with SPDIF RCA output.
  I decided to review the Resonessence Concero HP, the headphone output version DAC, priced at $850, which sports the latest version of the ESS Sabre32 DAC chip that is optimized for lower-power devices such as USB’s 5V DC. And it turns out that the Concero HP is an incredible-sounding headphone DAC that rivals combos costing two to three times as much. Heck, from what I remember from the Invicta review, its little brother’s sonics are in the neighborhood of the $4,995 Invicta.

Features
  The Concero is a compact, 4-inch by 4-inch DAC with a simple feature set: a 1/4-inch headphone jack, variable volume (32-bit digital) control with push-button activated upsampling filter option, a USB/power jack, and SPDIF input (or output). That’s it. Plug in the source, plug in the cans, and start listening.
  The heart of the DAC is the new ESS ES9018-2M Sabre32 DAC that is the company’s high-end DAC chip for portable applications, yet it has great sonic character with detail, open soundstage and great depth, yet with a touch of ESS’s classic analog warmth. In looking at its specs, the ESS9018-2M measures a few dB less than the flagship Sabre32 ESS9018 (used in several high-end DACS and players, such as the Oppo BDP-105 and Benchmark DAC2) in dynamic range and noise, but my listening confirms that classic ESS detail and analog texture.


A minimalist cadre of connections


  The Concero HP DAC is packaged as a standalone DAC/HP amp meant to be primarily used with the USB computer connection. It works with iTunes and other software players. There are also two other models in the Concero line including the Concero HD, priced at $850 standalone or $900 with an USB/AC power adapter and Apple remote that controls basic iTunes play functions, as well as the digital in/out routing and the upsampling filters. The HD has the same DAC chip as the HP, but only has RCA line D/A out. The entry level Concero, which is equipped with a mid-grade ESS DAC chip costs considerably less at $599 or, $650 when ordered with the Apple remote and USB /AC power adapter.
  The Concero HP decodes and plays 16- or 24-bit PCM from 44.1 kHz to 352.8 kHz (DXD). The DAC offers two selectable selectable upsampling filters: IIR and Apodizing. In upsampling filter mode, the 44.1 kHz audio is upsampled to 176.4 kHz and 48 kHz gets bumped to to 192 kHz.
  The Concero HP also plays native DSD 64X and 128X via DoP (DSD over PCM) through a compatible software player — such as Audirvana, PureMusic, Foobar 2000 or JRiver — or encoded DoP files from a SPDIF equipped player. DoP is becoming popular for high-resolution download music.
  According to Resonessence Labs President Mark Mallinson, the Concero HP features low-jitter oscillators for reference clocks (no PLLs), a custom asynchronous USB 2.0, and up to 24-bit/352.8 kHz sampling. Windows computers need a driver, but Macs can play up to 352.8 with appropriate player software — without additional drivers. In its normal play mode, the Concero HP output is ‘bit-perfect’ with jitter reduction to weed out the nasty hash.
It is obvious that I was more than impressed by the Resonessence Concero HP. The DAC/headphone performance puts it up there with more costly DACs, including its nearly $5,000 big brother Resonessence Invicta.

  The Concero also sports two selectable up-sampling filters: a Minimum Phase IIR filter, and an Apodizing filter for the 48 kHz and under sampling frequencies. Subjectively, the Apodizing filter works pretty well on lower-res sources, especially in its smoothing action. (more on that later).
  The unit’s specs are not as spectacular as the flagship Invicta, but are very good. Specs include a 2.2 Ohm output impedance. The THD+N is as follows for various power ratings: 270mW into 32 Ohm @ 91dB THD+N; 206mW into 60 Ohm @ 94dB THD+N; 45mW into 300 Ohm @ 100dB (0.001%) THD+N; and 22.75mW into 600 Ohm @ 100dB (0.001%)THD+N. Total Hum and Noise = 3.4uV A-weighted.

The setup 
  I used the Concero HP in a number of audio setups: an audiophile D/A headphone amp with my Macbook Pro computer and as a DAC/HP amp with my audiophile system and home-recording rig. I used AKG K702 and Shure SRH1840 open headphones, as well as Sony’s sealed MDR-7510.
  For comparison purposes, I had a bunch of other headphone DACS on hand, including Benchmark DAC-2D, Mytek Stereo 192-DSD Stereo DAC, Parasound Z-Dac, TEAC UD501 and the USB-input, portable Centrance DACPort.
  I did not stop at headphone listening, however. With the help of a quarter-inch-to RCA L and R adapter and WireWorld analog cables, I also fed line-level signals to my reference Pass Labs XA30.5 and Rogue Audio Medusa amps, which powered my reference MartinLogan Montis electrostatics. The Concero HP was a basic, but rather effective line level D/A preamp as I found out during my listening. The Mac laptop setup was connected via a WireWorld USB cable, and the RCA SPDIF digital input was linked to an Oppo BDP-105 universal player‘s output, courtesy of the WireWorld’s latest SPDIF cable. All IEC recptacle components were plgged into the AC with Essential Sound Products Essence II power cords and power strip.

No manual needed...
  Function-wise, the Concero HP is as basic as you can get. A headphone jack and stepped-volume potentiometer, that doubles as the upsampling filter control, occupy the front panel. The rear panel contains the SPDIF RCA input and USB 2.0 input, which provides 5VDC power and the computer signal to the DAC. There is no onboard power switch; the unit’s logo turns red when no signal is present and blue when signal is detected and the filters are off. Using the Apple remote (that is optionally, supplied with the other Conceros but not the HP), controls track selection, pause Play and Stop in Itunes, plus also can engage the upsampling filters.


One of the few DACs to decode DSD and 24/352.8 DXD


  The volume pot has a substantial feel to its stepped motion, and it is continuous; there is no minimum or maximum stop point. Thus, it is a good idea to test your level before plugging in the headphone. Even though the DAC remembers the last level setting used, you could get a loud blast if the last cut was classical and you now are about to play a rock track.
  The front-panel logo LED toggles between blue, magenta or red, depending on the function being selected. Red indicates no signal. Blue means a signal has been detected and conversion is bit perfect without upsampling. Magenta means you have engaged the upsampling. When a 48 or 44.1kHz signal is detected, the first push of the volume button engages the IIIR filter; a second push engages the Apodizing upsample filter. On startup, and the filters are off. The application of these functions requires some memory to remember which button push does what because there is no on-screen menu to follow.

The audition
  Originally I was sent the basic Concero, and I was puzzled. A computer DAC without a headphone amp? Hmm. But then Resonessence sent me the new Concero HP. Much better. In fact, I found out, in short order, that the Concero HP is an outstanding DAC/headphone amp.
  In connecting the Concero HP to my Macbook Pro, I was astonished by the PCM and DSD (over DoP) playback quality through the headphones. Stunning is an apt description. It sounded close to the $4,995 Invicta headphone amp, which I heaped praise upon two years ago.
  On the Neil Young — Harvest 24/192 DVD-A, the song "Old Man" was relayed with high-end precision I am used to hearing through top-tier DACs. The plucked banjo, backing vocal separation and Young's high-tenor vocal sounded like they were coming through a high-end audiophile DAC /HP amp, when monitoring through my AKG K702 headphones.
 Via Audirvana playback software, the Mozart Violin Concerto in D was exquisite through the Shure and the AKG headphones. The violin tone was about as pure as I ever heard through a set of headphones. Was it the DXD or the Concero? Probably a little bit of both.

  I played the 24/bit/192 kHz 2L classical Music Blu-ray, Ole Bull violin concerto, routing the Oppo’s HDMI PCM output to a Kanex HDMI de-embedder and into the Concero’s RCA SPDIF input. Again, the Concero HP really nailed it through the AKGs and the Shure SRH-1840. Beautiful violin tone with wide soundstage, yet cream smooth tonality. The Concero HP was not too far off from the Mytek or Benchmark, which also uses the top-end ESS Sabre32 ESS9018 DAC chip. The Mytek uses the Sabre32 ESS9016. The Concero was noticeably smoother and wider in soundstage versus the bang-for-the buck HP circuit of the Z-Dac. But it is, after all, twice as much.
  Versus the other USB portable DAC on hand, the Centrance DACPort, the Concero HP costs $550 more, but its uptick in detail and extra smoothness justifies the price. Plus the DACPort only operates on USB 1.0, which is limited to 24 bit/96 kHz maximum. After using the Concero, my DACPort went into the spare gear drawer.
  Since the Concero HP can decode the ultra-high-sampling rate PCM, termed DXD (24-bit/352.8 kHz sample rate), I purchased some DXD classical downloads from 2L to sample the world of mega-sample rate PCM from my Macbook Pro. I am glad I did. Via Audirvana playback software, the Mozart Violin Concerto in D was exquisite through the Shure and the AKG headphones. The violin tone was about as pure as I ever heard through a set of headphones. Was it the DXD or the Concero? Probably a little bit of both. (I also found that iTunes played DXD through the Concero as well, but I could not definitely determine that the Apple Core Audio system was not down converting the signal.)

Big sound from a compact-sized DAC

  Using the Audirvana playback software, I also was able to listen to a number of home-brew recordings of acoustic and jazz guitar cuts I had recorded in DSD on a TASCAM DVRA-1000. I transferred those selections to the Macbook, and engaged the DSD over PCM (DoP) function in Audirvana. Like the Mytek, Benchmark and the TEAC DACs, the Concero HP’s DSD playback is detailed, yet silky smooth. The Resonessence DAC is not cheap, but its golden-voiced, sonic delivery is worth every penny.
  I eventually connected the Concero to my audiophile main system with MartinLogan Montis speakers, and Pass amp. That’s right, I used the Concero HP as a line-out preamp/DAC, thanks to that quarter-inch-to RCA line out adapter.
  Guess what? Though a touch less impressive than the headphone sound, the Concero HP’s headphone-to-line sonic signature would put some dedicated preamps to shame. That cherished analog warmth and ample detail came on through the MartinLogans. I was particularly impressed by the 2L Ole Bull Music Blu-ray, and George Benson — Breezin' DVD-A. A big thumbs up on the Concero’s piano solo presentation on GB’s “Lying On the Ground.”
  The Concero HD with its dedicated stereo analog RCA outputs would likely better match a playback system with speakers than the Concero HP. Still, the line-out option via an adapter can do the job.
  I only have two minor criticisms of the Concero HP. You have no headphone output reference when using it as a standalone DAC/headphone amp when connected to an outboard device. There are no minimum or maximum positions with the continuous digital volume control, and no visual indicator on the unit to show where the level is. The Concero does remember the last level used in playback when you come back to it, and the playback program in the computer may have a volume indicator, but if the last thing you played was Classical and you now want to listen to Rock, be careful.
  The other niggle is the filter indicator. When either filter is engaged, the logo LED illumination turns magenta. You have to remember that one push of the volume pot is the IR filter and the second is the Apodizing filter.
  One other thing I noticed: when using the Concero DAC with iTunes, the Mac OSX system volume control and audio settings also seemed to change when I turned the Concero HP’s manual volume control. Normally, the Apple system volume, a digital control, is set to maximum to provide the maximum resolution digital output to the external device. The device volume control or the player’s software volume control is then used to adjust the volume.
The headphone performance is such that the Concero HP should not be confined to computer audiophile buffs; it also is perfect for computer-tasked home recording and even pure professional audio monitoring.

  Although it appears that the Apple system audio volume control is active and a loss of resolution would be possible when turning down the volume, in reality, the level control is all done through the Concero HP. According to Resonessence Labs‘ Mallinson: “Since the Concero HP presents itself as a USB DAC with a hardware volume control, the volume control is passed onto the Concero HP. So to the user, they may think the volume control in OSX is a software one, but that is only the case if the DAC doesn’t support its own hardware volume control.”
  “To prove this fact,” he explained, “simply play DSD and change the volume level. If it had been still touching the PCM data, the DoP formatting would be lost. This is not actually what happens; it simply pushes the volume change commands to the hardware and expects it (Concero HP) to do the scaling, which is does, in the 32-bit domain, inside the onboard Sabre32.”

The verdict
  It is obvious that I was more than impressed by the Resonessence Concero HP. The DAC/headphone performance puts it up there with more costly DACs, including its nearly $5,000 big brother Resonessence Invicta. It is not quite there, but you can tell they are related.Versus the gaggle of sub-$500 DACs popping up all over the place, the Concero HP seems expensive, but in the realm of its performance, DoP and DXD decode ability and the fact that it is made in North America, I do not think it is overpriced.
  The headphone performance is such that the Concero HP should not be confined to computer audiophile buffs; it also is perfect for computer-tasked home recording and even pure professional audio monitoring. Perfect for a headphone check of newly mastered high-res music, or a tracking engineer’s just mixed down stereo mix. It is that good! Add in the DSD and ultra sample rate DXD PCM decode/playback, and the package becomes even harder to ignore if you are DAC shopping.
  As a result of this review and numerous hours of pleasurable hi-res listening, I heartily recommend the Everything Audio Network Stellar Sound Award on the Resonessence Concero HP.

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1 comment:

cansman said...

Hi John,

I really enjoyed reading your review of the Concero HP. You, however, only mentioned in passing about the sound quality of the apodizing filter. Would you kindly care to comment more about the IIR, apodizing and non-upsampling filters / modes? Also, do you have a personal preference?

Thanks so much!

Cheers,
cansman