I've added my AudioCircle review, see below.
I received, and agreed to, an offer from Burson Audio to test and subsequently write a review of the Burson Cable+ interconnect; the interconnect was mine for the keeping. Burson Audio is a producer of: 1) a number of headphone amps for main systems (including both headamp/preamp, and headamp/preamp/DAC combos) and portable ones (headamp/preamp/DAC); 2) amplifiers, and 3) the new Cable+ active interconnect cable in three flavors – AUX to RCA (A2R), AUX to AUX (A2A), and RCA to RCA (R2R), each priced at $149 including worldwide shipping, 30 days satisfaction refund guarantee, 2 years standard warranty (option to extend to 5 years).
Why the Cable+? Burson explains below (
https://www.bursonaudio.com/products/cable-plus-a2r/).
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Since then, there is an explosion in the number of source components manufacturer by countless brands big and small. Source components include DAP, smartphone, tablet, laptop, computer soundcard, media streamer, smart TV and more. These devices have very different output designs. Furthermore, even CD Player and DAC designs now come in much greater varieties. Battery vs linear vs switching power supply, tube vs solid-state, discrete vs IC. Each of these again have very different output designs.
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This varieties (sic) makes matching two components confusing and frustrating. Most audiophiles rely on reading countless online reviews. In another word, they rely on luck to find the perfect match. When mismatch exist, there is listening fatigue, a lack of defined bass, a digital sounding midrange with missing texture and emotion and a top end that is not crisp and sweet.
Thus, to more easily match component impedances, the Burson Cable+ active interconnect was born. Consumers, according to Burson, should expect the following results:
The Burson Cable+ is the world’s first active interconnection cable and we use engineering, not magical material to ensure system matching. The Cable+ does not colour the sound, but actively ensures that you are hearing 100% of your system. Regardless of their brand, circuitry design and power supply types, a perfectly matched audio system is always guaranteed. This is the freedom audiophiles have been wishing for! Once the Cable+ is in place, sonic details once lost, will be fully reproduced to create a complete experience. Play familiar – very familiar – material, and you will hear the finest details fully resolved, while the fundamentals take on a new level of life and solidity. That “harsh digital sound” replaced by a wider and more three-dimensional soundstage.
I requested and received the RCA to RCA Burson+ IC cable so I could use it in my main system. The tracked item, shipped from Hong Kong, was received undamaged. Enclosed in the well padded shipping was a plastic wrapped plastic case. The case contained the interconnect and a USB cable; you attach one end of the USB cable to a narrow rectangular, oval ended box on the Burson+ IC, and the other end to either a USB battery or USB charger. Burson reports the box contains a V5i audio module buffer stage, and a low noise high voltage power supply. I had a couple 5V 1A USB batteries, so that’s what I used for testing. The cable is asymetrical in that the length from component end input to the first end of the oval box is 100 cm, and from the other oval box end to your preamp, amp, etc. is only 20 cm. Thus, the Cable+ is decidedly directional. If you choose to use the USB cable with a USB plug in charger, you may need to substitute a longer USB cable as your needs dictate.
My musical preferences are diverse, and I'm (finally) happy enough with gear that provides a high level of listenability and engagement with the music, without draining my wallet going for the last 2-3% of audionirvana. My system is housed in a 20’ x 14’ thin-carpeted dedicated listening room that uses two separate 20A dedicated lines, one for analog and the other for the digital end. Various wall hangings and plants provide some sound treatment, though acoustical panels would be nice. My system’s items used in testing the Cable+ IC included:
- pair of Zu Omen Def speakers (Zu reports 100dB SPL @ 1W efficiency connected to the spades of a 5’ pair of Groneberg Quattro speaker cables, cable off the carpet via cork lifters, and a Shultz hook-style EVS Ground Enhancer on each of the negative speaker terminals.
- Jolida JD-100 cdp, with the following: NOS JHS Yellow Label Sylvania 5751WA triple mica black plates, Herbie's Hal-O 9 tube dampers, Chris VenHaus cryoed Flavor 1 PC, Rich Shultz hook-style EVS Ground Enhancer on the ground post, all resting on a granite slab supported by Vibrapods. The Jolida has two sets of RCA outputs, one of which was currently used to output to a Grover Huffman S 1m interconnect (NOTE: this cable is out of production, superceded eventually by Huffman’s Ex+ IC cable, $200 per 1m pair).
- Warpspeed V4x3 optocoupler-based passive volume control with 3-input/2-output(paralleled) stereo RCAs, powered by a 12V 7.2A SLA battery. The Warpspeed sat on Vibrapods. The Warpspeed, which is made by Allen Flores in a variety of input/output modes, was reviewed in its V8 x W1 version by Srajan Ebaen of 6Moons (http://www.6moons.com/audioreviews/warpspeed/1.html). That article mentions that Mr. Flores uses of pairs of tightly matched light-emitting diodes, and light-dependent resistors whose resistance varies as the light intensity of the LED is changed, so that light provides volume changes, not physical contact. The review reports Mr. Flores says his design of the Warpspeed results in “low volume levels are more engaging…, wider range of volume settings, precise power delivery…works with a wide range of source and power amps regarding output/input impedances.” So both the Warpspeed, and the Burson+ active cable in for testing, were supposed to alleviate impedance mismatches. Hmmm. Also interestingly, Srajan in his review favorably compared the performance of the Warpspeed to Burson’s Soloist. My Warpspeed’s output was connected to my amp by a Grover Huffman S 1.5m IC.
- A custom built Niteshade Audio NS-40 tubed amplifier with extra heavy duty 12V filament supply / 240 watts upgrade, a pair of closely matched NOS Motorola labeled GE 6SN7GTA tubes, a quartet of closely matched Sovtek 6L6WXT+ power tubes, tube dampers, micalex tube sockets, supplied by a cryoed Triode Wire Lab 10 Plus power cord. The NS-40 amp sits on Vibrapods.
- All tube pins, IECs, and power cord prongs were treated with Walker SST. Unused RCA outputs were covered with Cardas Audio Signature Series RCA RF/EMI and dust protection caps. Before testing all ICs and RCAs were cleaned with Deoxit, then treated with ProGold. Components are housed on an Ikea Norden occasional table. See image below.
The Jolida cdp has two sets of RCA outputs so I could use each set for a different cable, which made the A/B process a bit easier. The second set of outputs was rarely used. After using the ProGold, I first connected one end of the Cable+ to the relatively unused second set of Jolida outputs, and the other end of the Cable+ to the second input of the Warpspeed. I noted that the Cable+ RCA plug connections to my system’s RCA didn’t seem at all tight – they slipped on and off easily - especially when compared to the tight grip of the Grover Huffman RCA plugs. Also, the Cable+ wire’s diameter measured slightly over 1/8”, while the Huffman cable’s diameter was noticeably thicker at a bit over 3/8”. I connected the USB cable to one of the USB batteries and then to the Cable+. The 1m Huffman IC was connected to the first Jolida output and first Warpspeed input respectively.
When corresponding with Burson’s representative, I asked if Burson felt its IC would benefit from burn-in. The question was supposedly forwarded to Burson’s tech side, but I didn’t receive a reply (update: got a reply on 3/28/17 after the review was written: "yes"). Still, I used the Isotek Full Sytem Enhancer track 2 on repeat for an hour to help get my system optimized and do a bit of burn-in to the Cable+ and the second Jolida output. After some casual listening, I felt the Cable+ might benefit from some extended burn-in. I thought I could try to get at least 100 hours or so of burn-in on the Cable+ as well as the second Jolida output. Mother Nature postponed some of my plans as an ill-timed Nor'easter blizzard, and resulting power / cable outage, interfered with doing the burn-in more quickly than desired. Even with the interruption, I was able to get over 120 hours of burn-in on the Cable+ / second Jolida output. A couple times I A/Bd volume levels re: Cable+ v. Huffman ICs, using Abc Apps Sound Meter, and each time the Cable+ was about 11 dB greater than with the Huffman IC at the same volume knob setting. So during actual testing I used the Sound Meter app to help match volumes for each of the cables. The Warpspeed has no remote, so I would get some exercise. Initially the level matching with the Sound Meter was a PITA but a necessary evil and one that grew much easier as I got familiar with the change in volume knob range.
I let my system go silent for a day and concurrently recharged the USB battery and the Warpspeed’s SLA battery to make sure they were fully charged, then used the Isotek CD’s cut 2 to warm up the system: first on the Huffman IC, then on the Burson Cable+. Off Alison Krauss’ Forget About It album I cued up “Empty Hearts”, then “Stay”. Having been enthralled with the instrument that is Ms. Krauss’ voice during a number of her concerts with Union Station, as well as with Union Station’s playing, I thought the recording might provide some insight on the Cable+. The JHS Yellow Label Sylvania 5751WA triple mica black plates in the Jolida historically brought realism and airy life to most recordings, including wonderfully representing female vocals, so I thought this would be a good start. My findings with these two tracks would be consistent throughout subsequent testing. The Cable+ R2R IC was subtractive in that my system the R2R presented less space, texture, transparency, and resolution. For example, with the R2R Ms. Krauss’s voice was strained, much more one dimensional and at times quite compressed, and sometime sibilant. The Huffman IC’s presentation made Krauss’ voice more realistically embodied and texturally palpable, more positioned in space, her breathing became apparent; in a couple places the Jolida added some hotness to her voice, but it was never sibilant like with the Cable+. The R2R expressed percussion with less strike and decay, less fullness, less detail; the Huffman had noticeably better attack, decay, presence and detail. The soundstage on both cuts was always between the speakers with the R2R sometimes seeming a bit deeper than the Huffman but not consistently; the Huffman soundstage started a touch more forward, usually went as deep, and extended the soundstage well beyond the speakers, the background seemed blacker. Instruments such as Jerry Douglas’ dobro, Sam Bush’s mandolin, and Matt Rollins’ piano were much better located, detailed, and realistic sounding with the Huffman than the Cable+. From listening to other systems I know the Jolida cdp is not the last word in resolution, but it is very listenable and capable unit.
I decided to power down my system, and swap the positions of the ICs: the Cable+ was connected to the first Jolida output and to the first Warpspeed input, the Grover Huffman was connected to the second Jolida output and to the second Warpspeed input. I again warmed up the system, an half hour of the Isotek track 2 with the Huffman cable, then an half hour with the R2R. I listened again to the tracks and there was no change in my findings. I kept this configuration for the remainder of testing.
Peter Murphy's driving yet melodic "Cuts You Up" from his Deep album was cued up. Back and forth between the Burson and my stock IC for a while. My notes showed that the Burson+ IC offered a seemingly punchier (louder) bass that was less detailed, and the song’s violin sample, cymbals, guitar, and vocals were sibilant and lost extension, air, detail, and placement when compared to the Huffman IC; percussion seemed flatter, notes less extended with muted attack and decay. The soundstage of the Cable+ again was collapsed side to side and back to front, perhaps in part due to the detail that wasn’t coming through. The Huffman’s counterpoint presentation was preferred: Murphy’s powerful and resonant voice was more present, keyboards were more realistic - detailed and sweeping in parts, percussion expressed attack / decay, the bass not as heavy yet more realistic from opening to end, instruments more palpably located, blacker background, soundstage beyond the speakers with good depth albeit with slight forwardness. I next cued up the first track, "Deep Ocean Vast Sea," with the Burson+ R2R still similarly lagging to the Huffman in the aforementioned areas.
I turned to Tom Petty and the Heartbreakers Mojo album for “Jefferson Jerica Blues”. My notes showed the Burson Cable+ was again reductive, Mr. Petty’s voice sounding compressed and nasal, Benmont Tench’s piano not as present nor realistic; the notes played on the vintage guitars used by on the track by Mr. Petty and the group (’64 Gibson ES-335 Sunburst, ‘59 Les Paul Sunburst, ’65 Fender Jazz Bass) were less toneful and detailed. The nod easily went to the Huffman.
A few more tracks rounded out my notes, although I continued to listen to the IC for some time afterward with little deviation in my impressions.
- Bonnie Raitt’s Slipstream album offered “Split Decision”, but there was no split decision in denoting my preference for the Huffman IC. The Burson+ lacked depth and realism: Ms. Raitt’s electric slide sounding toneless and shrill at times, the bass presented with more weight again but sounded pushed instead of melodic, the soundstage still compressed side to side and front to back with ok positioning that became compressed when the music got busy. By contrast the Huffman made Ms. Raitt sound more natural with vocal timbres more realistic, like she was at the mike; her electric slide was tuneful and never shrill, the soundstage was wider than the speakers, had good depth, and never compressed when the music got busy. Again, the background was blacker than that of the R2R.
- Tool’s Aenima album brought “Die Eire Von Satan”, the hash cookie recipe industrial-feel song with drum and guitar hammering along with the guttural German recipe recitation and crowd noise. One crazy song. That scraping, electronically distorted, creepy, clangy sound with thumped percussion is treated nicely by the Huffman IC, great tone and detail; when the crowd is present, you can pick out voices; there are “you are there” spaciousness and depth cues to the militant rally feel of the song; the strident and aggressively intense vocal reciting the recipe sounds is expressed with air and detail. Not so for the R2R, which collapses and made shallow the soundstage, absents most of the individual crowd voices, and makes the main vocal and industrial feel less malevolent.
- Eric Clapton’s Old Sock album offered my last written notes, for the song “Gotta Get Over”. The Huffman IC gives a more detailed, better soundstaged and instrument located version compared to the Burson R2R. The Huffman IC lets you hear the detail in Chaka Khan’s vocals including her laugh nearer to the end of the song; infectious vocals by Clapton, the song’s great bluesy guitar and organ are palpably and gloriously present, great rhythmic bass line, and my toes were tapping. By contrast the Burson Cable+ lacked the depth and fullness of the song’s voices and instruments: again the attack and decay were less present, Clapton’s honeyed guitar playing was missing the instrument’s tone and air, the bass again weightier but less defined, Clapton’s voice was absent its depth and fullness, Chaka Chan’s voice sounding compressed at times and lacking timbre, some of the song was congested sounding, soundstage could not get outside the speakers and was shallow, and instrument and vocal placemen suffered. My toes still tapped, but the musical subtraction by the Cable+ made for a less pleasing result than the Huffman.
So what to make of the Burson Cable+? In my system, it fell behind the Huffman by a noticeable margin across the board. The type of music didn’t seem to make a difference, as realism, detail, attack and decay, soundstaging, etc. all were in the win column of the Huffman IC. Was there a mismatch between the Burson Cable+ and the optocoupler-based passive volume control, something to which the Burson was supposed to averse? I don’t know. The Burson R2R will, at the same volume setting, play louder than other ICs. I can see where to some that might be important. However, whether that preference overshadows passing through more detail, presenting voices and instruments in space and more naturally, making the background blacker, giving a fuller soundstage outside the speakers and front to rear – you’ll have to be the judge. I remind readers that I did not test the other two configurations of the Burson Cable+. Also, my findings may not be representative with your system’s gear, or aligned to your specific musical preferences.
