Music Interface Technologies ACC 268 Articulation Control Console and MA-X SHD Interconnects
What the heck is an Articulation Control Console? To a cynic, it’s nothing more than a fancy name for a speaker cable. To others, the Articulation Control Console represents the culmination of everything MIT founder Bruce Brisson has learned over his 35-plus-year career designing interfaces between a power amplifier and a loudspeaker.
What everyone will agree upon, however, is the breathtaking price of MIT’s ACC 268 Articulation Control Console evaluated here—$80,000 per pair. I’m acutely aware that most of you will find that number obscene. Nonetheless, this groundbreaking product exists, and sales have been brisk. In fact, delivery of my review pair was repeatedly delayed because MIT couldn’t keep up with the demand. The review pair bore serial number 54, suggesting that MIT had 53 customers for the ACC 268 in the first few months since its introduction, without benefit of advertising or reviews. Because there’s a market for such a product, and the ACC 268 ventures into uncharted technical territory, it’s worth evaluating and reviewing. I would never be able to afford such a product, but there are readers who could. Moreover, the ACC 268 speaker interface and MA-X SHD interconnects are new versions of speaker interfaces and line-level interconnects that I’ve used as my reference for more than eight years. Remember, the name of this magazine is, after all, The Absolute Sound.
The ACC 268 is the top model in the three-product ACC line, which includes the ACC 169 and ACC 206. The numbers in the model names refer to the number of “poles of articulation” in the interface.
For the very few who are sufficiently well-coined to afford the ACC 268, along with a system for which it is appropriate, there’s nothing quite like it. Take its sheer physicality for starters. The consoles are 48-pound sculpted aluminum enclosures that house the termination electronics along with four knobs, the function of which we’ll get to in a minute. The spade-lug-terminated cables—one input and one output—attach to the console via massive screw-on industrial-grade connectors. The cables that run from the console to your speakers, and from the console to your amplifier, are thick and heavy. Be prepared to give up some floor space to accommodate the ACC 268.
The ACC 268 is essentially the technology platform of MIT’s Oracle MA-X speaker interface, but with more elaborate execution along with the addition of “Articulation Control” adjustment ability. The ACC 268’s adjustability takes the form of four knobs on the console’s top panel. Three of the knobs are marked “Low,” “Mid,” and “High,” respectively. The fourth on-off knob is marked “2C3D” (Two-Channel, Three-Dimensional). Rather than interpret the idea of “articulation” in cables, I’ve included an interview with Bruce Brisson so that you get the story straight from the horse’s mouth. I’ll address the sonic effects of these adjustments later in the review.
The console is machined from a solid block of aluminum, with the large internal volume dictated by the size and number of components inside, along with the space needed for optimal layout of those components. These components include the termination networks, the control boards that hold the switches, and a vibration-isolating plinth on which the components are mounted. The control boards themselves reportedly contain 100 circuits. Each pair of consoles requires about 200 man-hours of hand labor to build. The cable part of the whole affair is constructed from large-diameter conductors that are hand-twisted in a specific pattern and twist ratio. There are actually three stages of this twisting, with a technician measuring and then adjusting the twist at each stage.
The MA-X SHD interconnects are a revised and upgraded version of the previous generation Oracle interconnects. They also offer adjustable “articulation” via two small knobs. One of these knobs engages low-frequency articulation, while the second, marked “mid,” offers a six-step adjustment—plus and minus three steps from the neutral setting. A slider switch optimizes the interface for the particular input impedance of the components the source component will be driving. If you don’t plan to change equipment, the MA-X SHD can be custom built for your particular components’ input impedances. The custom interconnects omit the adjustable impedance switch but retain the articulation adjustments.
MIT offers this impedance adjustability because component input impedances vary wildly from manufacturer to manufacturer. There is no industry standard except in professional audio where the input impedance of components is always 600 ohms. But the input impedance of consumer equipment can vary from a few hundred ohms to more than 1M ohm (one million ohms), with most falling in the range of 50k ohms to 200k ohms. The three switch positions on the MA-X SHD are marked “Low, 5–50k ohms,” “Mid, 40k–100k ohms,” and “High, >90k ohms.”
Before getting to these new cables it’s worth revisiting why I’ve used MIT’s top speaker interfaces and interconnects as my reference for many years. As I mentioned, the ACC 268 is essentially the Oracle MA-X SHD speaker interface with the addition of the articulation control technology. I’ve found that MIT cables in general, and the Oracle in particular, offer a particular combination of compelling virtues. First among these is their rich and dense rendering of tone color, particularly in the upper bass through the lower treble. I don’t want to use the term “warm” because that implies a coloration, but the MIT products are the antithesis of thin, bright, threadbare, skeletal, edgy, bleached, and analytical. To me, MIT cables reproduce instrumental timbre with a body, saturation of tone color, and weight that is more like the sound of live instruments. In addition, MIT cables have tremendous clarity, resolution, and openness but without a hint of brightness or etch. The tonal balance is a bit of a paradox, at once voluptuous and neutral, resolving and smooth. In addition, the Oracle products reveal a richly textured and layered soundstage, with tremendous dimensionality and air. Images appear along a depth continuum, separated by a tangible sense of air.
The ACC 268 and revised MA-X SHD start with the sonic performance that I’ve just described, but now bring something new to the party: the ability to tailor the sound to your particular system. Starting first with the impedance adjustment on the MA-X SHD interconnects, I found that setting the switch in the correct position produced the most natural timbre and tonal balance. With the impedance switch intentionally set in the wrong position (for my particular components) the sound was still superb. In fact, I heard nothing amiss. But when set to the correct impedance, the music had a more organic and natural quality, with greater fidelity of timbre. Instrumental tone color was more realistic, and the harmonic balance was more natural and less synthetic. The sound was overall more relaxed and involving. Going back to the incorrect setting (again, for my particular components), I heard a tincture of hi-fi artificiality rather than a natural ease.
The effects of engaging the articulation knobs on the ACC 268 are difficult to describe because the sonic changes they render are unlike any other differences I’ve heard between components, never mind speaker cables. Turning one of the articulation switches to the “On” position didn’t change the tonal balance, soundstaging, resolution, transparency, or any of the other typical characteristics we commonly associate with an alteration of the sound. Rather, the articulation control seemed to increase the textural density through the particular frequency band affected by the control (one control each for bass, midrange, and treble). That is, increasing the articulation rendered tone color with a greater timbral richness and solidity. Concomitantly, the sound had a greater dynamic verve and alacrity that made whatever speaker I was listening through sound faster and more “horn-like.” I’m not suggesting that the ACC 268 added a horn-like coloration, but rather that the ACC 268 had many of a horn speaker’s best attributes. Most notable of these was a high “jump factor,” with an almost startling quality on transient attacks. The combination of greater apparent transient speed, denser instrumental textures, and sensational dynamic verve combined to produce a sound that, in my view, sounds closer to the experience of hearing live music. I’ll draw an analogy with a justifiably famous album, King James Version, the direct-to-disc release from Sheffield Lab. Early on the opening track (“Corner Pocket”) Harry James makes his entrance to take a solo. The sound of his trumpet appears out of nowhere with such startling vividness and presence that even after decades of listening to this album, the trumpet’s sound still knocks me out of my seat. (Try playing “Corner Pocket” for someone who hasn’t heard this album before and watch his reaction.) That’s the type of difference rendered by engaging the articulation control on the ACC 268, but to a subtler degree. Of course, the ACC 268 won’t make every trumpet (or other instrument) sound as startlingly real as James’ instrument on King James Version, but the overall nature of the difference is qualitatively similar. The same differences are apparent in the bass and treble when engaging those articulation controls, although the midrange control seems to have the greatest effect on the overall sound.
Given the advantages of engaging the articulation control that I’ve described, why doesn’t MIT just incorporate that circuit in the cable and do away with the knobs? Indeed, I ended up with all the knobs on the “On” position when the Constellation Hercules power amplifiers and the Absolare Passion integrated amplifier were in my system. But with the Berning 211/845 amplifier driving either the Magico Q7 Mk II or Rockport Lyra (review next issue), I preferred the sound with the “Mid” and “Treble” articulation controls in the “Off” positions. The Berning has a more forward rendering than either the Constellation or Absolare, with a greater and more palpable sense of presence than any other amplifier I’ve heard. With the midrange articulation control in the “Off” position, the sound was a bit more relaxed and engaging, which better suited this particular amplifier and these particular loudspeakers. The beauty of the ACC 268 is that you get the spectacular performance platform of the previous Oracle speaker interface along with the ability to dial-in the sound for your system and taste.
MIT’s ACC 268 Articulation Control Consoles are unique in their conception, design, and, most importantly, performance. I confess to not fully understanding the concept of “articulation” in cables, or how the ACC 268 works, but I can report that no other cable I’ve heard offers the MIT’s foundational virtues or its flexibility in tuning a system’s sound. Yes, the MIT ACC 268 is crazy-expensive, but for those of you well-off enough to afford it, I don’t think that you’ll find a more musically rewarding speaker interface.
Specs & Pricing
ACC 268 Articulation Control Console
Controls: Bass, midrange, treble articulation adjustments, “2C3D” on/off control
Dimensions: 15.75″ x 9.25″ x 10″
Weight: 45 lbs. each (plus cables)
Price: $80,000 per pair
M-AX SHD Interconnect
Controls: Impedance (low, mid, high), bass articulation on/off, six-position midrange articulation control
Price: $21,999 1m pair
MUSIC INTERFACE TECHNOLOGIES
4130 Citrus Ave. Suite 9
Rocklin, CA 95677
Loudspeakers: Magico Q7 Mk II, Rockport Lyra, EnigmAcoustics Sopranino super-tweeters (with the Q7 Mk II)
Amplification: Constellation Altair II linestage, Constellation Hercules II and David Berning 211/845 power amplifiers, Absolare Passion integrated amplifier
Analog sources: Basis Inspiration with Superarm 9, Air Tight PC-1 Supreme, Moon 810LP phonostage
Digital sources: Aurender W20 music server, Berkeley Alpha USB USB-to-SPDIF converter, Berkeley Alpha Reference DAC, Brinkmann Nyquist DAC (with MQA)
Support: Critical Mass Systems Maxxum equipment racks (x2), Maxxum amplifier stands (x2)
Digital interconnects: Audience Au24 USB, AudioQuest Wild Digital AES/EBU, AudioQuest BNC, MIT
AC: Four dedicated AC lines; Shunyata Denali conditioners, Shunyata Sigma power cords
Acoustics: ASC 16″ Full-Round TubeTraps, ASC TowerTrap, Stillpoints Aperture Panels (x12)
Accessories: Stillpoints UltraSS and Ultra6 isolation
MIT Founder Bruce Brisson Talks with Robert Harley
Tell me about your background and how you began designing cables.
My wife Kathy and I always enjoyed music. In 1976 we bought a Pioneer rack system, but quickly moved on to a full Marantz system with the Model 7 preamp, 8b power amplifier, and 10b tuner. I began experimenting with bi-amping and then tri-amping, but since I added the amplifiers over time I ended up using different speaker cables for each connection. The cables were from Monster Cable, Mogami, and Fulton.
One day the crossover broke so I took apart the system to fix it and when I put it back together it sounded different. I had not paid attention to which cables were connected to which drivers, so I ended up with different cables on different drivers than in the original configuration. When I turned on the system it didn’t sound the same. I took everything apart and retested it, but was puzzled because everything worked correctly. And then I asked myself if mixing up the cable brands connecting the different drivers could be the cause. I put it back together the way it initially was, and the sound returned. That got me interested in how cables can affect the sound.
A few years later I was working at Fairchild Semiconductor where I met a guy who repaired test instruments for Hewlett-Packard. He enjoyed music and would bring his records over to my house. Being an employee of HP, he was able to borrow any piece of test equipment it made, and would bring the instruments over while we listened. Between the test instruments and the listening, I was starting to understand the phenomenon that made cables sound different. I began to think of a cable design that would be better than anything previously built.
Around 1980 I was in a group of San Francisco audiophiles called the Hands-On Audio Society. Some of the guys listened to my homemade cables and many wanted to buy them. An employee of Monster Cable heard about my cables and said that [Monster Cable founder] Noel Lee wanted to meet me. I showed him an interconnect design and he listened to it, and asked me to make a sonic change, which I did. I modeled the cable mathematically on a Tandy Model III computer running VisiCalc, and then patented the design. I licensed the design to Monster and it became their Interlink Reference. Many consider this the first true audiophile interconnect. I developed about eight other cable products for Monster, and then founded Music Interface Technologies in 1984.
MIT was the first company to use networks in cables. Why do cables need networks?
As with any passive network, cables contain both resistive and reactive components. This creates resonances and anti-resonances in the cable. A series resonance is when the reactive components cancel each other. At the resonant frequency the complex impedance will be quite low. This series resonance doesn’t impede the signal flow in a cable. An anti-resonance, however, is formed when the reactive components add together to form a highly complex impedance. This “parallel resonance” does impede signal flow in the cable.
It’s generally assumed that the electrical bandwidth of an audio system should be ten times greater than the audio bandwidth. That is, the electronic components should operate out to at least 200kHz. So, what are the first issues that cause distortion when a cable doesn’t work well within that band of frequencies? Cables suffer from a parasitic series resonance at frequencies below about 1.5kHz and from parallel resonances at higher frequencies, determined by the values of the inductance and capacitance. The cable doesn’t function as an ideal inductor. All audio products act as low-pass filters. Cables without networked terminations function as a lossy low-pass filter because of this parasitic capacitance as well as shunt capacitance. The vector seen at the input terminals of an audio signal-carrying cable should be an inductive vector at all frequencies and at all power levels.
We can correct for the parasitic and shunt capacitance by adding reactive components in the network that will offset these effects.
A conventional [non-networked] cable will also operate in a “bi-stable” state. State analysis shows that a system can work in three states—stable, astable, and bi-stable. A cable carrying a low signal level will function in a bi-stable state because of the parasitic capacitance within and between the individual conductors, which when twisted or coiled together form the inductor of the cable. The low-level signal must overcome this parasitic capacitance before it can pass current (the audio signal). So the cable shifts between a capacitive element and an inductive element many times per second because of the audio signal’s varying amplitude. The cable must carry sufficient current to overcome the parasitic capacitance. That makes the cable bi-stable.
During the time it takes for the cable to shift from being astable to stable, the low-level signal carried by the cable is turned into noise. We call this “analog jitter.” Removing analog jitter is one of the reasons why MIT cables have such a black background and have such good low-level detail. The result is proper timbre, transparency, soundstage size, and point-point location of images. No jitter equals no noise component.
Think of a cable carrying two tones of the same frequency, but one is very high in level and the other very low in level. With MIT cable the low-level signals remain intact and are not converted into noise, and are sent in-phase with the high-level signal. Also, the harmonics of the low-level tone are transported in time within the complex tone’s envelope.
All of this describes the technologies I’ve developed over the years: “2C3D,” “JFA” and “JFA-2” (“Jiiter-Free Analog”), and “SIT” (“Stable Image Technology”). SIT means that the image of the instrument or voice won’t move within the soundstage.
The circuit elements in our networks are “time invariant.” That means the relationship between the input and output signals doesn’t change over time. The system should not respond differently to the same input signal at different times.
We have a whole range of impedance analyzers that we’ve bought over the years. We can increase or decrease the applied voltage and measure the impedance with varying power levels at any frequency. This allows us to fully characterize any capacitive or inductive component we use in any given cable. MIT is the only cable manufacturer that quantifies the performance of the products.
Can you explain the concept of “poles of articulation”?
A pole of articulation can be thought of as a pole that is holding up a tent in the center.
The tent will have a slope or skirt associated with it on both sides of the pole. Electrically, a pole has a magnitude and it stores energy. How much energy the pole stores is determined by the size of the storage elements—linear capacitors and inductors. Capacitors store voltage for a period of time and return that voltage back to the cable or network. Inductors store current for a period of time and return that current back to the cable or network. If the capacitor or inductor is larger it will store more energy. An articulation pole stores energy and then over a predetermined amount of time can deliver energy to the load.
All cables have one articulation pole, the point where it is most efficient at transporting energy, which is usually around 1500Hz. This is why most cables sound OK at about 1.5kHz but sound brighter at high frequencies and muddy at low frequencies. With just a single articulation pole the first few harmonics of middle C and A are not correct with regard to timbre, and won’t image properly. We end up with an articulation response in conventional cables that is shaped almost like a bell. The highest point in the bell-shaped curve is the highest articulation frequency of the cable, again, about 1.5kHz. We add more poles of articulation above and below that frequency by adding additional capacitive and inductive elements to produce a straight-line articulation response. The first technology we invented that helped overcome these issues was our MIT 2C3D Technology. I wrote a paper about this in 1991 called “Transportable Power in Audio Cables and Energy Storage Elements.”
Going back to our Jitter Free Analog technology, the new version of that, JFA-2, is the primary reason the Articulation Control Consoles are so sonically superior to the Oracle products before them. The Articulation Control Consoles also use a very improved 2C3D technology, which also helps imaging and soundstaging within the very important frequency range of 80–800Hz.
Why have you included impedance adjustments on the interconnects?
Because all audio components have different impedances, the network’s articulation response will vary with that impedance. The adjustable impedance allows the user to optimize the articulation response for their particular components.
The MIT white paper titled “The Effects of Audio Cable as Related to Articulation of Speech and Music” includes the articulation responses, in percentage, of cables I had measured into different impedances. I helped design the FFT analyzer along with a Hewlett-Packard engineer. It uses a “single-shot unit step pulse” not a swept sinewave. This is a dynamic measurement. The measurement uses as a reference the “unit step pulse” spectra in both magnitude and frequency against a clock in the computer. This is a one-of-a-kind FFT that cost me about $135,000 to build back in 1998.
Using this analyzer, we show in the white paper the articulation plots of various cables. You can see immediately what happens when the cable is not terminated into the proper load impedance. The articulation response suffers. We developed a technology called “Impedance Specific Networks” that allows the user to switch between three impedance settings and optimize the interface for his components.
By Robert Harley
My older brother Stephen introduced me to music when I was about 12 years old. Stephen was a prodigious musical talent (he went on to get a degree in Composition) who generously shared his records and passion for music with his little brother.More articles from this editor
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