A/C Master Coupler Review

The Synergistic Research AC Master Coupler

And You Thought Power Cords Don't Make A Difference

by Brian Damkroger

The Absolute Sound, Volume 20, Issue 104

"I'll come over this weekend," my friend Jim said. "I've got something that will really mess with your mind." He had a sort of embarrassed smile and even seemed a bit red-faced. "Power cords," he said and headed back to his office. You've got to understand --- Jim and I are engineers, scientists, seekers of truth and purveyors of logic. Metallurgists by training, we work in a research group that focuses primarily on advanced diagnostics, computer simulation, and process controls. Known to be audiophiles by our fellow co- workers, we are constantly either derided for claiming we hear things that can't possibly be real, or, once co-workers listen for themselves, besieged with requests to explain the underlying physical reason for the differences. Turntables, speaker stands, tip toes, cables --- the list goes on and on. Up until now, we've done pretty well. But power cords? They can't possibly make a difference, can they? And they cost how much? I wonder if thoughts like this once went through HP's head when he first contemplated the "built in a Bronx garage" Linn LP-12? "So this is what the lunatic fringe looks like," I thought as I contemplated the power cords --- excuse me: Synergistic Research A/ C Master Couplers. The couplers are black, with the cable sheathed in a black plastic mesh and terminated on one end with a three-prong plug and on the other by a standard IEC jack. Both connectors are extremely heavy duty and the cable/connector intersections are encased in black heat shrink. Judging by feel, the cable configuration inside the sheath is two parallel conductors, each slightly over 1/4" in diameter. The literature provided with the couplers confirms this, representing the cable cross-section as two parallel multi-strand conductors, each individually shielded. The cable is said to eliminate "RF Interference . . . through a balanced cable geometry [that] shunts noise in the A/C line to ground." The literature also notes that the specific dielectric components used were selected on the basis of listening tests, as were the gold-plated standard connectors. Other lengths, and 90 degree connectors (on either end), are also available. The 90 degree connectors may prove useful in many applications because the cable is quite stiff, requiring several inches to make the turn toward a component. The cable appeared to be well-made and the packaging and literature, while not extravagant, were well presented. The literature suggested several possible sequences for determining the best place to locate a limited number of couplers in systems of various configurations. None of their example system configurations matched mine, but it doesn't really matter --- the instructions boil down to "Try them everywhere, but start with the front end." In my system [see sidebar], this meant the couplers fed my VTL Ultimate preamp and Threshold PCX crossover. (Neither my turntable nor my CD player has a removable power cord.) Prior to any listening, both the preamp and crossover were powered up continuously for 96 hours, and had been playing music or the XLO break-in CD for 12 hours. The literature suggests that the couplers could continue to break in for as long as a month (of occasional listening), but experience with other systems suggested that the 96/12 break-in procedure above would be adequate. Broken in, warmed up, and ready to go, I sat down for what was sure to be a night of careful critical listening and agonizing over subtleties. Power cords. They can't possibly make a difference, can they?

The answer is Yes. Unequivocally, resoundingly, and oh my, Yes. How big a difference? Remember the difference you heard the first time you replaced your zip coed with real speaker cables? This is bigger. How about the day you cleaned all your contacts and oriented all of your AC plugs? This is bigger, much bigger. To put it in perspective, the difference is akin to replacing an undistinguished MOSFET stereo amp with a pair of absolutely top-flight mono tube amps --- or replacing a midfi direct-drive turntable with a well set up Linn, Sota, or VPI. To say I was unprepared for the difference these power cords made would be a big, big understatement. The most telling assessment was made by my girlfriend, Bonnie, who loves music but certainly doesn't consider herself an audiophile. Unfailingly, she could tell within the first five seconds of a record, any record I put on, which power cords were in the system --- from the kitchen, which is down the hall and around the corner. But, I'm getting ahead of myself. The differences wrought in my system by the additions of these power cords were positive, dramatic, and immediately apparent. However, unlike some immediate, drastic changes, the differences brought about by the cords didn't wear on me with time. In fact, the more I listened to my system with the Master Couplers in place, the more difficult I found it to believe I had tolerated my system without them. Whenever I removed the couplers from my systems, I found myself shaking my head and wondering, "Have I been listening to this?" To say that the Master Couplers moved my system toward the absolute sound is true, but doesn't really capture the magnitude or sense of that movement. Suppose, for example, that you went from having one penny to having two. One way to describe this is to say that you went from 99 cents short of a dollar to 98 cents short, not a big change with respect to the dollar. However, another way to describe the change is to say that you doubled your wealth --- a big change from where you were. The absolute sound is a long way out there, couplers or no couplers. But oh what those things do for a system! The only way to capture the impact of the AC Master Couplers is to concentrate on the doubling of wealth, to describe the differences themselves. These differences, in decreasing order of apparent magnitude, were an increase in the dimensionally of individual instruments in the soundstage; an opening up of the soundstage, or increase in air between individual instruments; replacement of the smog between images in the soundstage with crystal clear air; an increase in the sharpness of the leading edge of transients, both spatially and temporally; and increase in bass extension and precision; and a decrease in high-frequency garbage. Although all of these changes are inter-related, first I'll try to describe each individually and give examples I noted during my listening sessions. The most immediate and noticeable effect of the Master Couplers was an increase in the dimensionally and body of individual images. This was most apparent with vocals, solo instruments, or small groups. Examples of the first include John Mellencamp on Uh-huh [Riva RVL 7504] or Joe Jackson on Night and Day [A&M SP-4906]. With the Master Couplers, the vocals took on palpable dimensionally and body, whereas with the standard cords in place, they were somewhat twodimensional, layered on the front edge of the soundfield. A mental picture of this two-dimensional image might be a plate, or saucer, hanging in space, with somewhat diffuse edges. With the Master Couplers, the voices became three-dimensional, surrounded by a cushion of air. Here the mental picture was one of, say, a basketball, with sharply defined edges. On Neil Young's Unplugged [Reprise 9362-45310-1], the effect is clearly evident on both the lead and background vocals. Additional insight is afforded by John Klemmer's Straight from the Heart [Nautilus NR4]. In this case, the added dimensionally seems to result from an increase in inner detail --- intricacies of the sound of the air moving through the horn give it size and presence. The same is true of the Sheffield Michael Newman disk [Lab 10]. Here, the relative locations of different sounds --- the fingers against the strings, the initial snap of the string, and the resonance of the guitar's body --- give the instrument its dimensionally. With the Master Couplers in place, subtle shifts in the instruments' position are clearly evident as such. With the standard cords in place, the shifts are barely perceptible, and then only as changes in tonal character. With record after record, the added dimensionally and detail were nothing short of dramatic.

The Master Couplers also opened up the soundstage. I don't mean to say that the outer boundaries of the soundstage moved outward --- they did, particularly in terms of depth --- but that's not what I'm getting at here. The difference was more an increased perception of separation between, or distinction of, individual images in the soundstage. With the Master Couplers, the image centers weren't significantly farther apart, but the edges, of the images and spaces between them were now real, distinct, and three-dimensional. In recordings with a natural acoustic --- for example, the spotlighted solos in the Chesky Scheherazade reissue [Chesky RC4] --- this resulted in the instruments having more body, and the space between becoming more obvious as a separate entity, filled with the mixed resonance and decay of not only the solo instrument, but also the surrounding instruments and hall. Another example is Danse Macabre on Witches' Brew [LSC-2225]. Here, the combination of dimensionally, detail, and the soundstage opening made some of the denser passages seem more like individual instruments combined, rather than simply a canned, congealed sound. The heightened awareness of the space added a bit of the charged excitement of a live performance. On multi-miked rock, the empty space between images was just that -- - empty, really empty. Further, the emptiness had a clarity and sharpness that made it apparent that, with the standard cords, the space had actually been filled with a cloudy film. This is the third wonder wrought by the Master Couplers, the removal of not a veil or film over the soundstage, but rather the greasy, cloudy, grungy matrix that the images were suspended in. I know, I know --- your system doesn't suspend images in a grungy matrix. Well, neither did mine, until that Master Couplers showed me what the soundstage could be like without the grungy matrix! Remember the saucer and basketball images? With the standard cords, the mental picture is of saucers suspended in a three- dimensional rectangle made out of, say, paraffin, or plastic that had been clouded by age. With the Master Couplers, imagine instead basketballs suspended in crystal clear air, like a window you have to touch to make sure it's there, or for we westerners, a crisp, clear morning at about 8,500 feet when you'd swear you could see someone in Kansas if they stood on their roof. This clarity is further augmented, or more likely supported, by the fourth difference I attributed to the Master Couplers --- an increase in the sharpness of the leading edge of transients. This increase had two aspects. The first is temporal, meaning that the transients sound faster. The second is spatial, in that transients seem to arise from a more specific, and rigidly fixed, point in space. One of the major shortfalls of recorded music is an incorrect handling of transients. It's easy to identify a live band down the hall, around the corner, and at the other end of a bar. One rim shot is all it takes. Why? I think a big part of it has to do with transient performance. Maybe it's micro-dynamics, maybe absolute rise time, or maybe phase coherence at the leading edge of the transient. One of the things single-ended/horn speakers systems do is capture this sense of transients. This is the sort of improvement the Master Couplers bring about. Rim shots still don't push the buttons that say "real," but they're sure closer. I expected this sort of almost tactile improvement on the Sheffield Drum Record [Lab 14]. However, it caught me by surprise on Melissa Etheridge's Brave and Crazy [Island ILPS 9939]. Another good example is the added snap on the bass guitar in The Sky is Crying by Stevie Ray Vaughn [Epic E47390].

Finally, the last two effects illustrate that changes, while consistent, can be perceived differently in different systems, or by different listeners. I live in, and am slowly (glacially, according to Bonnie) rebuilding an old adobe farmhouse. An additional electrical service and dedicated power lines have yet to be added to my listening room. At present, the whole system is being fed by two circuits that are shared with major appliances and include stretches of "historically correct" fabric covered wire. Similarly, the power supplies in my VTL electronics appear to be of reasonable strength and sophistication, but aren't as massive as some. I would expect my system to be a fertile environment for anything that cleans, filter, conditions, or otherwise help with power. At the other extreme, however, the Master Couplers were inserted into another system, featuring Krell Reference Series electronics in a custom-built listening room with individual, dedicated 20 amp lines and hospital-grade outlets. A system with measurable clean, stable power and Hoover Dam caliber power supplies.

In this system, all of the changes described above were again readily apparent, and of a similar magnitude as in my system. Additionally present, however, was a significant increase in bass extension, definition, and power. As I mentioned, I had heard the increased bass definition in my system, as an increased snap in the initial pluck of the bass guitar strings on the Stevie Ray Vaughn disk, for example. The increased extension was also apparent in my system, but not nearly to the degree as with the Krells. With the Krells, the improved low bass was so startling, it first sounded as id perhaps the actual effect was an increase in bass definition and a learning out of the upper bass, the 90- 10 Hz region. (The sort of hole that can arise from an unfortunate match of a speaker cable and crossover network.) After several records, though, this didn't seem to be the case. This illustrates how, in different systems, the same basic changes in the sound can be perceived as different effects. In both systems, the immediate listener response to the Master Couplers was usually "dramatically increased dimensionally and body, cleaner and clearer." In the Krell system, it was "much better bass, cleaner and clearer."

The listener response, of course, depends on the listener, which brings me to the last effect of the Master Couplers, a reduction in high frequency garbage. I mentioned earlier that Bonnie could tell immediately from the kitchen, which cords were in the system. To her, the difference was a decrease in what she described as "harshness" or "brightness." She listens primarily to CDs, heard, over the years, on a variety of different (inexpensive) players incorporating different filtering techniques. With these players, a decrease in harshness is often accompanied by a decrease in level of inner detail or actual high frequency extension and air. She finds herself returning to simpler players, unwilling to throw out the baby with the bath water, so to speak. In this case, however, she commented that the "hardness is gone, but it isn't like a filter. There is actually more detail and better high frequency definition." In fact, she found some of her favorite CDs unlistenable with the standard cords. Once she pointed it out to me, it was obvious. On Chain Gang by the Pretenders [SIRE 25664-2], or Pulling Teeth by Green Day [Reprise 45529-2], the sound with the Master Couplers was not exactly relaxed, but the ragged edges on the vocals and/or guitars were part of their inherent sound, not layer on top. It wasn't just CDs that were cleaned up and more relaxed, however. The John Klemmer album was an example of where a noticeable hash was cleaned off an LP. To Bonnie, the record sounded "brighter" and "dirtier" with the standard cords. To me, the sax sounded squeezed, which I've learned is a sure sign of high frequency garbage. This just points out how different listeners respond differently to the same changes. To me, the decrease in grunge was most apparent in the increased clarity, dimensionally, and body. To Bonnie, it was a dramatic reduction in high-frequency hash.

Clearly, all of these effects are different manifestations of the same change, so how do they all fit together? For whatever reason, the AC Master Couplers allow a system to better preserve the fine detail and phase integrity of a signal, simultaneously reducing spurious noise that results from either external sources or internal interactions. The result is a huge --- I repeat, huge --- leap forward in the realism of the sound coming out of a system. The difference between, say, the sharper ring and decay of an Ovation guitar and the deeper body and resonance of a Martin take on a new level of prominence. With the Master Couplers, you get a much better sense of hearing the body of the guitar, rather than just a sound emanating from an area in space. Similarly, the spatial dimensionally and layering of multiple images within a soundfield are more apparent. With a densely orchestrated work, the effect is an increase in both the body and overall acoustic envelope and the ability to distinguish individual voices or edges of the soundfield. I've already mentioned Danse Macabre. In the case of rock records, where the individual instruments don't interact in an acoustic space, the effect is sort of a "virtual reality" spatial and temporal interplay of the voices. For example, listen to "In a Lonely Room" on the Smithereens' Especially for You [Enigma ST-73208]. The dance between the instruments, particularly the vocals, is enchanting. Another example is the Etheridge Brave and Crazy, and the song of the same name. Part of the fun on rock records is listening to the effects superimposed onto individual images, and how the producer or engineer used these effects, in the construction of the soundfield, as part of the voice itself. For example, listen to the feeding in and out of the echo on Jennifer Warnes' voice on We Take Manhattan [Cypress 661 111-1]. Intended or not, the effect is to move the vocal into and out of the soundfielld, not so much in terms of absolute position but rather in apparent interaction with the surrounding instruments. Another example is "Raise the Morning Star," the opening cut on Bruce Cockburn's Stealing Fire [Gold Mountain GM 80012]. Here, an echo gives the background vocals an otherworldly presence. Record after record, I found myself grinning as I discovered new wonders and pulled out new records to try. Fun!

So we come full circle. Power cords. Can they possibly make a difference? In the case of the AC Master Couplers, the answer is an unequivocal and emphatic Yes! So what do I tell the crew at work when they demand and explanation? This is where it gets sticky. It seems like there are three possible explanations. The first is the "power cord as antenna" theory. That is, the power cords function as an antenna, happily picking up RF and other garbage and feeding it into the 60 Hz --- less so in the case of the Master Couplers. The second theory is the "power cord as filter" idea. In this case, rather than adding garbage to the 60 Hz, the Master Couplers might actually be removing grunge from the line. Third, there is the "power cord as shunt" theory, where the power cord is somehow adsorbing all of the high frequency components caused by the AC/DC rectifications and ringing back through the power transformer. Finally, there is the "power cord as transmission line" theory. In this case, the power cord is designed, or terminated, to add resonance gain to a 60 Hz signal (or exact harmonic), thereby diminishing the relative effect of any other spectral components. Suffice to say, all are theoretically possible but . . . In each case, it's not that simple. I've made numerous measurements and calculations of not just power cords, but speaker cables and interconnects as well. At work, we routinely design, build, and tune cables for data transmission (analog and digital) in hostile environments. All of the above components --- shielding, filtering, shunting, and resonance --- are considered, and it's still a bit of an art. In our cables, however, we have the luxury of not having a ruthless quality control measure --- a listener's ear --- to answer to . If the oscilloscope and spectral analysis say it's right, that's good enough. In audio cables, that's just a starting point, maybe not even that. We've made a bunch of measurements, performed numerous calculations, and constructed several computer models. Editor willing, I'll discuss cable design from this aspect in a future piece. "But for now, the short answer is "I don't know how they work."

To summarize, I can't possibly recommend the Synergistic Research A/C Master Couplers more highly. At over $200 for a power cord, they're insanely expensive for what they are. However, for what they do, they represent the biggest bang for the audio buck I have seen. The only things I can recall as being even close in terms of value were the first time I Fluxbusted a cartridge (after many, many hours), and replacing a set of 30-year-old tubes in a Dyna ST-70 with a new set of Sovteks. Both were small investments, but for striking differences. However, in the case of the Fluxbuster or the tubes, the change was to make an audio system sound like a much better audio system. The Master Couplers do something a little different, and to me, far more significant. They make an audio system sound more real. They take a system from one plane to a slightly different one, one that is genuinely closer to the absolute sound. My system is still a long way away from that sound, but with the insertion of the A/C Master Couplers, it has taken a big step in the right direction.