I’m not a doctor, but I do know and appreciate one of the principles of the Hippocratic oath: “First, do no harm.”
This maxim applies to audio components, too. Peter Walker, founder of Quad Electroacoustics, famously declared that the aim for his power amplifier was to be a straight wire with gain. You achieve this by minimizing noise and distortion, maintaining linearity, preserving phase, and maximizing resolution.
Many preamps and power amplifiers go a long way toward this ideal. Others deliberately take a different path, aiming for a beautiful sound rather than accuracy, or a bass bump that many listeners enjoy. Some tube amps produce significant amounts of second-harmonic distortion, and can sound warmer and more musical as a result. Don’t get me started on loudspeakers, where deviations from neutrality are frequently far larger.
In this review, I am looking at another source of distortion: imperfections in the power delivered to the electronic components. People will pay good money to improve the quality of the mains power in their systems.
Cleaner power
There are several commonly cited justifications for adding a power conditioner to your system. The AC power supplied to your listening room may vary in voltage during the day, even if you have dedicated power lines installed. The waveform itself may be distorted. It may be affected by other electrical appliances in your home, or pick up radio-frequency interference somewhere along the way. The AC supplied to one component may be adversely affected by the other components in your system.
Different companies address these problems in different ways. PS Audio’s Power Plant and Accuphase’s Clean Power Supply products convert the incoming AC to DC, and use that to charge powerful capacitors, whose output is converted back to AC using a high-precision sine-wave generator (basically, a power amplifier). That AC power is then compared to a perfect sine wave, and a small correction signal is generated and applied to the AC to increase its accuracy.
A variation on this method is to use the AC input to charge powerful batteries when you are not using the system, and rely on battery power for AC generation during playback. This is the approach taken by Stromtank. It is a very expensive and highly regarded solution. However, batteries have a finite lifespan, there may be noise generated by a cooling fan, and the amount of instantaneous power delivery could be limited.
Another group of products contain isolation transformers. Equi=Tech and Torus Power use this approach, whereby power is transferred magnetically. This method can block common-mode noise, reduce ground contamination, decrease hum, and suppress some line artifacts, but a transformer must have a very high capacity to avoid becoming saturated and limiting the power supplied to high-current amps.
The most common approach, taken by Shunyata Research, AudioQuest, and IsoTek, is to use filter networks composed of inductors, capacitors, and other electrical components, acting primarily to reduce high-frequency noise coming from the AC line. Some units, like the Clarus Concerto MKII (US$12,000) reviewed here, isolate the outputs (or groups of outputs) from each other to prevent noise generated by one component from affecting another. Some such designs limit current delivery, compressing dynamics and softening bass impact.
There is another way to approach the problem. Instead of processing the input AC directly (in series), some manufacturers, including Nordost with its QRT series, connect in parallel to the AC line, absorbing or canceling noise on the line without limiting power delivery.
Many manufacturers of components with high power consumption advise against any method that limits instantaneous and sustained power delivery. Some components are designed to perform their own treatment of noise and variability on the AC line, and the manufacturer may recommend against additional power conditioning. You should check the manufacturer’s website or representatives to see what they have to say. For example, Naim, Dan D’Agostino, Simaudio, Krell, and Audio Research all recommend you plug their power amps straight into the wall outlet.
The story of Clarus Cable
If, like me, you are unfamiliar with Clarus, some background may be in order. Back in 2014, Aron Garrecht wrote a detailed review of various Clarus Crimson cables for SoundStage! Hi‑Fi. Aron’s verdict: “I found the entire Crimson line to be the closest thing to invisible that I have heard in my system.”
This is what Aron said about the company:
Established in 2011 in Orlando, Florida, Clarus is a subsidiary of Gordon J. Gow Technologies and sister company to Tributaries Cables. Unlike Tributaries cables, which are well respected in the A/V sector, Clarus cables were created to be used in high-end, two-channel audio systems. While at the 2014 Consumer Electronics Show, I met with Joe Perfito, president and CEO of both companies, . . . [who] told me that “all Clarus products are developed from scratch using no off-the-shelf parts” from their Tributaries brethren, and that every cable in the Clarus family incorporates a host of recently patented or patent-pending technologies that have taken as long as eight years to finalize.
The cables are designed by Jay Victor, who also designed the company’s Duet and Sextet Power Blocks, and the Concerto Power Conditioner, introduced in 2019. The Concerto retailed for US$3600 and garnered strong reviews, including one on this site. Now, Victor has developed an upgraded version, the Concerto MKII. The layout as an eight-outlet power conditioner has not changed, but how it goes about its job is another matter. And at US$12,000, it’s a lot more expensive than the original Concerto.
Description
The MKII is seven pounds heavier than the original Concerto, but the aluminum chassis is identical in size, measuring 3.5″H × 19″W × 12.75″D and weighing 26 pounds. There are other external and internal similarities. On the front panel, each has a power button, a dimmer button, an LED display showing the AC input voltage and which output duplexes are active, and a secondary row of LEDs for ground, polarity, and protection-fault status. These will tell you if the power cable and wall outlet to which the unit is connected are in phase and properly grounded, or if the protection circuitry has been tripped.
On the rear panel, both models provide eight outlets—an analog duplex (A), two digital duplexes (D1 and D2), and a high-current duplex (HC)—plus a power on/off switch, a ground post, an alarm on/off switch, and a power input socket.
Both models offer under- and over-voltage protection with automatic shutdown and auto recovery once safe voltage returns. An optional alarm is triggered if the line voltage falls outside of the range 90V to 135V. A metal-oxide varistor provides 960 joules of surge suppression. A temperature sensor will trigger a relay and disconnect power if a critical temperature is reached.
But as you’d expect given the difference in price between the Concerto and the Concerto MKII, the new model has plenty of upgrades:
- The AC input socket is a 20A design, rather than the standard 15A IEC socket on the Concerto.
- The AC output sockets are now NEMA 5‑20 designs, which support up to 20A, while the Concerto used the more common NEMA 5‑15 sockets, rated at 15A.
- The new model has a star-ground and isolated-ground architecture to eliminate ground loops and hum.
- Protection in the Concerto MKII is handled by a hydraulic-magnetic circuit breaker designed to tolerate high inrush currents without nuisance tripping. Unlike the thermal breaker used in the Concerto, this design remains stable regardless of operating temperature.
- In place of proprietary single-stage Clarus Core and High-Current Core filters, the Concerto MKII has multistage nanocrystalline Clarus FluxCore inductors.
Clarus describes the operation of the three types of output of the Concerto MKII (analog, digital, and high current) as application-specific. The filter topology of each type of output is optimized for the kind of equipment supported by each duplex output pair:
- The analog output bank combines FluxCore filtering with ferrite-bead filters and oil-based capacitors to reduce ground reference noise.
- The two digital duplex output banks are individually filtered. They apply differential-mode filtering, followed by common-mode FluxCore filtering to reduce high-frequency interference generated by digital circuitry.
- The high-current duplex output bank, designed for power amps, receivers, or powered speakers and subwoofers, uses common-mode FluxCore filtering, oil-filled capacitors, and a 30A FluxCore HC inductor combined with ferrite-bead filters to reduce conducted noise while maintaining unrestricted current delivery.
A power cable is not included with the Concerto MKII. Clarus recommends using a high-quality cable suitable for high-current applications, and sent me a Clarus Crimson HC cable (8′, US$5490) for evaluation purposes. You can’t use a regular 15A power cable to connect the Concerto MKII to the mains, because it won’t fit.
Listening
For my listening tests, I used a Roon Nucleus One server (US$599.99) to stream from Qobuz, controlling playback via the Roon app on my iPhone. The other digital source was an EMM Labs XDS1 Reference CD/SACD player (discontinued, US$25,000 when available). My DAC-preamp was an EMM Labs DV2i (US$35,000). The power amp was a Soulution 511 stereo power amp (US$59,975) driving YG Acoustics Hailey 2.2 speakers (discontinued, US$55,800/pair when available). All cabling was Nordost Valhalla 2, apart from the Clarus power cable from the wall outlet to the power conditioner, and an EMM Labs OptiLink cable connecting the XDS1 to the DV2i.
I built a new Roon playlist for this review, containing all sorts of music, from jazz to rock’n’roll, klezmer, and classical, with stops in between. My findings were consistent throughout. First, there was a totally silent background, even with the volume at max. A good start. Second, I never detected any reduction in dynamic range with the introduction of the Clarus. Nor could I sense even the slightest softening of transients. The image was never restricted or flattened, and I experienced no polarity, ground fault, or protection issues.
Listening to music with my components plugged directly into the wall, I could detect a very low-level hiss from the tweeter if I put my ear to it. Without the power conditioner in the chain, I noticed an increase in brittleness and harshness, a reduction in resolution, the presence of some “tizzyness” in cymbals, and sometimes an edge on vocals. In general, I found the sound less musical and more tiring.
I’ll single out Eric Bibb’s superlative new album, One Mississippi (24‑bit/96kHz FLAC, Repute Records / Qobuz). The title track reminds me of Tom Waits (à la “Way Down in the Hole”) channeling Keb’ Mo’. It integrates multiple instruments into a coherent image with terrific bass and color. With my components connected to the Concerto MKII, I heard fine leading edges on the stringed instruments with no hint of harshness. But without the Clarus, there was an edge to the violin and on Bibb’s voice.
The biggest difference was on the Rolling Stones classic “Under My Thumb,” from Aftermath (DSD download, ABKCO 18771‑9477‑2). With the Clarus in circuit, I heard great clarity, tons of detail and power, excellent presentation of low-level detail, and superb image integration. The direct connection sounded harder-edged, and I had to concentrate more to follow each of the instruments in the mix.
Comparison
Strictly speaking, I don’t have a power conditioner. Nordost refers to my QRT QBASE QB8 as an AC mains distribution box. In addition, I have a QRT QX4 power purifier, connected between the wall and the QB8, and two Furutech NCF AC optimizers, plugged into empty sockets on the QB8. My QBASE QB8 has been replaced by a Mark III version, which retails for US$2300. The QX4 sells for US$2500, and the Furutech AC optimizers are US$266 each, which makes the total value of my power setup approximately US$5300. As I experienced with the Clarus system, my Nordost-based setup produces a completely black background.
I compared the performance of my system across the 14-track playlist when using my Nordost setup and the Clarus Concerto MKII. The differences were subtle rather than transformative and appeared only on a handful of high-resolution classical recordings.
On J.S. Bach’s The Art of Fugue (DSD128 download, Channel Classics CCS SA 38316), the period-instrument ensemble Brecon Baroque, led by Rachel Podger, presented in a more austere, slightly less musical fashion through the Clarus. I can’t tell you which was the more accurate. Was the Nordost removing some grunge, or smoothing things a little?
Conversely, Bach’s Goldberg Variations, by pianist Murray Perahia (DSD64 download, Sony Classical 89243), sounded more aggressive with the Nordost components than with the Clarus. Through the Clarus, I noted the sound was forward and fully open, with great attack, presence, and perfect articulation. I kept turning up the volume, and it simply got louder without any change in tonality, dynamics, or image size.
I noticed a small increase in instrumental color from the Nordost setup on Jean Sibelius’s Symphony No. 2, played by the London Symphony Orchestra under Colin Davis (24/192 FLAC, LSO Live / Qobuz). The Clarus-based system also sounded great, with superb brass and a growling orchestra. There was a real sense of scale, weight, and warmth.
Conclusion
The Clarus Concerto MKII power conditioner satisfied my primary criterion: It did no harm. The Clarus preserved dynamics, transient attack, scale, and image specificity, while lowering the noise floor and improving refinement compared to a direct wall connection.
More impressively, the Clarus accomplished this while competing closely with my Nordost-based power-distribution system, which works in a different way altogether.
Whether the Concerto MKII justifies its asking price will depend on the quality of your AC power and the nature of the components in your system; in mine, the Clarus proved itself to be a serious high-end power-conditioning solution. As always with power products, an in-home audition is strongly recommended.
. . . Phil Gold
philgold@soundstage.com
Associated Equipment:
- Digital sources: Roon Nucleus One server, EMM Labs XDS1
- DAC-preamp: EMM Labs DV2 V2i
- Power amp: Soulution 511 stereo
- Interconnect, power, and speaker cables: Nordost Valhalla 2
- Speakers: YG Hailey 2.2
Clarus Concerto MKII power conditioner
Price: US$12,000
Warranty: Three years, parts and labor
Clarus Cable
6448 Pinecastle Blvd., Suite 101
Orlando, FL 32809
Phone: 1-888-554-2514
Email: info@claruscable.com
Website: www.claruscable.com
