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Purist Audio Design Proteus Provectus Speaker and Interconnect Cable Review

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Purist Audio Design Proteus Provectus Cables

Comparing one cable to another should be tedious and amount to splitting hairs. That’s what the objectivists want us to believe. The number crunchers tend to discount the details. Two cables should look the same on a scope when comparing a 1V square wave. But that’s not music. Music is much more complex and difficult to measure. If the fundamental is 1V, the upper overtones will be in the mV range. When you take into account the complexity of the ear and brain (and how the brain can ignore signals that machines can’t), it leads me to believe that measurements are mostly pointless. Just consider how bad virtually all speakers measure in a real room. Do they all sound like crap? No. So, who’s lying? Our ears or the machines?

I have become quite familiar with a fellow audiophile’s system built completely with Purist Audio Design cables. Some of the qualities of that system are unique in my experience. What I wanted to know when I was reviewing the Proteus Provectus was to what extent PAD cables would affect the sound. And by extension, would other cost-no-object cables create easily audible, even profound, differences? At the end, the system does two things better than any other system I know.

First, the distortion in this system is the lowest I’ve heard. I’m not referring to some overly dark and clinical sound that I associate with transistors and too much feedback. What I am talking about is a lack of grunge around notes, whether they are high, low, soft or loud. This system, as it is currently configured, sounds like you are playing early generation master tapes on a professional open reel machine. If you’ve never heard great open reel tape playback, you probably won’t understand that statement. If you do get a chance to hear a high quality two-track at 15ips, pay attention to the ease of dynamics, the transparency and the openness. I would say that if you had to boil it down to one word, it would be “clean”. The textures of notes came through with great truthfulness, as if nothing was superimposed between the recording and the speakers.

The second aspect of the system that is absolutely state-of-the-art is the ability to play unnervingly loud without sounding ugly or aggressive. I’ve heard the system play so loud that I thought it might damage the house. But, it never sounded harsh or aggressive. The only other place I’ve experienced that kind of power is the concert hall. When a full romantic orchestra plays fortissimo, there are no ugly qualities that I hear with reproduced sound. The reason the system can play at high levels without strain is the combination of the “clean” sound with 3,000 watts of power. Four 750-watt amps drive the two-way line-source DALI Megalines. The speakers are nearly impossible to over-power, and that might be just as important as the amplifiers’ reserve power. There isn’t a passive crossover to get between the amp and speakers. An all-tube, fully balanced, active crossover handles the crossover chores. The rest of the system is balanced, which surely lowers distortion and gives it more headroom (balanced circuits are usually clean, have lots of headroom and more absolute power than single-ended circuits).

How much do the cables affect the sound of this system? The owner believed his choice of cable was as important as his acoustic modifications of the room, or the choice of components. I’m skeptical of all claims until I get a chance to see (or hear) for myself. I felt that any competent cable would do an equally good job, but decided that it was important to find out if the Purist Audio Design cables had unique properties that might radically improve the sound of a system. The Proteus Provectus ran about half way up the range and seemed to be a logical choice when asking for a review sample.

The Details

These cables are built like a tank. The terminations and trimming are as good as I’ve seen. The conductor is a specially produced single-crystal solid core that’s cryogenically treated. Jim Aud, head honcho at PAD, uses a process called Cryomag that apparently treats the cable cryogenically while in a magnetic field (that’s my understanding).

These cables are heavy and rather difficult to bend to shape if you are trying to work in tight confines. When you get them to the desired shape, they stay that way. The outside diameter of the cable is 7/8”. The cross section is large enough to prevent sharp bends in the cable. Really, this is a good thing. Sharp bends will cause micro-fractures in the copper and ruin the sound. I will warn you that if you have a really cramped area behind your amp, running these could take some patience. These cables are strong enough to push around lightweight speakers and amplifiers (though that didn’t happen to me).

Other notable details are that these are capable of 25A of current, which is no false advertisement. As you’ll read further down, they are capable of sourcing as much current as an amp is able and willing to dish out. The effective gauge of the copper is 9 AWG. It’s my understanding that the spades are also machined from copper. The bulk of the cross section of the cable is the liquid damping. The price is $6,900 for 1.5 meters and they come in a very nice pouch to protect the cables during shipping.

What’s In The Secret Sauce?

For over 20 years, Purist Audio Design has used proprietary liquids to damp and shield cables. The first time I saw an ad for PAD was 19 or 20 years ago, and I can still recall being shocked (yes, pun intended) that a manufacturer would use fluids in cable construction. The good news is that I’ve never heard of any worst-case-scenario about Purist Audio Design cables shorting out systems or leaking. I prefer to think of the liquid as a gel. It doesn’t move and respond like water, so I’ll refer to it as a gel. Because the terminations of the cable are several inches from where the gel stops, that pretty much eliminates the possibility of a leak causing a catastrophic short circuit. The materials are very tough and build quality is extraordinary. I know from long-time users that the product is very well built and reliable. Your tube amps are going to cause infinitely more problems than the PAD fluid technology.

The gel can help in two ways. First, damping cables eliminates microphonics which smears the signal. The most critical place for fluid damping would be the tone arm cable. Realize that all interconnects have capacitance, and vibration will induce a signal because of the capacitance. In reality, cables can act like ribbon microphones. In the case of the Proteus Provectus speaker cables, there are independent plus and minus runs, possibly eliminating capacitance (and inductance) from the equation. The key would be careful running of the cables. Experimentation can yield interesting results with parallel runs.

Second, because the gel also acts to shield against RFI/EMI, it prevents such nasty stuff from feeding back into the amplifier. Many ordinary speaker cables make excellent antennas. It’s good that Purist Audio Design has addressed something that some cable companies ignore. Shielding IS good. Noise IS bad. Period. Do I know what Jim uses in the secret mix? No, I don’t and I don’t care to ask him. I do know it works. I’ve heard his cables drive 3,000 watts of tube amps with no noise. There was enough power and sensitivity to expose any problem with EMI or RFI. Also, I’ve never heard any of the trademarks of microphonic cables when listening to PAD Cables. Microphonic cables make a system sound confused, aggressive, forward and threadbare. Jim Aud’s damping fluid is real science.

Like Dirty Harry

It’s like when Crocodile Dundee pulls out his knife, or Harry Callahan pulls out his Smith & Wesson Model 29. These cables are imposing. As I said before, they’re a little difficult to bend, one of my two complaints (the other is that I couldn’t afford them). Also, like Dirty Harry, they seem to take charge of the situation when they arrive.

I’ve had a pair of 2.6r Maggies for a while. I’d been procrastinating on an upgrade to the binding posts (see the review of the Music Posts in a previous review), ditching the tweeter loading scheme and fuse, and replacing a ribbon that occasionally distorted on very loud passages. It took one evening of listening with the Proteus Provectus to finish off the weak ribbon. By letting more bass and greater dynamics through to the speaker, the PAD cables caused the ribbon to pull loose from two of the mounting places that hold the ribbons in place.

In all fairness, the other ribbon had already been replaced and Magnepan flatly tells you that they are going to die eventually. The point is that the series resistance of the cables was so much lower than my other unnamed boutique cable, that it let the amp push a lot more current through. Thus, the weak ribbon was finished off. The amps were heavily modified Heath W6M which can do 140 watts peak. The ultra-low resistance of the Proteus Provectus allowed the amps to push a lot more current than my other cables which had a similar gauge. I would guess that the all-copper construction and the excellent termination techniques mean this 9 AWG wire has less series resistance than an equivalent gauge cable of ordinary materials and termination. Lower series resistance also means better damping factor (better control of the amp over the speakers).

After sourcing another ribbon from Magnepan, I was back in business. By the way, the cost of replacing the tweeter was dirt cheap and everything went very fast. In the time being, I replaced the stock binding posts and bypassed all the tweeter loading and fuse hardware for dramatically better treble, and somewhat better low-bass. I’m only following the lead of J. Gordon Holt who pointed out in the ‘70s that fuses in the signal path are horrible ideas. As the fuse heats up, which happens fairly quickly, it acts as a variable resistor. Let’s not even get started on the materials used to make fuses and fuse holders, which happen to be magnetic in many cases. I understand why Magnepan puts them in there, and it has nothing to do with high fidelity playback. They need to protect those fragile ribbons. Anyway, I’m straying too far afield.

Like The Bridges Of Madison County

The first sonic impression of the cable, a cable that is very thick and heavy, is of delicacy. I could get great bass and low series resistance by running parallel strands of Romex. But Romex doesn’t do treble like the Proteus Provectus. I’ll have to say that anyone that says these cables are dark or laid back is mistaken. They may sound laid back, but what they are hearing is the affects of the damping, the nearly negligible amount of series resistance, the nearly perfect termination from wire to spade and the single crystal copper. Poor build quality can manifest itself in noise that is generated as the signal (current) is passed through the cable (which has too much resistance because of bad construction techniques or bad materials). At points where there is significant resistance, noise is generated. Another thing to consider is that this noise, along with EMI/RFI, is injected back into the amplifier. If the amp in question has overall negative feedback, this noise, which has nothing to do with how much distortion the amp is producing, is injected into the feedback loop. What I’m saying is that these cables might sound slightly dark or laid back, but what you are hearing is much lower noise floor, less grunge and a happier amplifier.

On many recordings, I was impressed by how the bass and treble were better tied together. With the other cables, loud bass passages seemed to modulate the rest of the frequencies. With the Proteus Provectus, the bass frequencies were in correct proportion to the overtones, and stayed that way even at high power. Regardless of amplitude, the mids seemed to ride effortlessly on top of the bass, and the highs effortlessly on top of the mids. It’s important to remember what a complex musical signal is and what it is not.

People like to think of a musical signal as many individual tones being reproduced at one time. That’s wrong. In the concert hall, there are many individual tones coexisting, but once they’re captured by a microphone, they’re all condensed down to a complex electrical signal. In a way, what the microphone and speaker are trying to do is similar to what a zip file does – compress things down to something impossibly small and try to recreate it to the original. Think of the musical signal flowing down a wire as many signals modulating each other, being superimposed and riding on top of one another. There are huge signals, like a massive wave, with much smaller things, like surfers, riding on top. What I think many cables do is knock the surfers off the boards, squash the top of the wave, and add other waves. Wipe out! The same thing can be said of any amplifying circuit. The Proteus Provectus in my system let through much more of the detail, with much less distortion than I had previously noticed. At first it did sound laid back, but it was simply more natural and better balanced tonally.

Every type of music benefited from the improvement and I listened with several amp and speaker combinations. I’d refute the idea that these cables are “too big” for a low-powered amp. I’d say the opposite is true: a smaller amp with a smaller power supply will have to work harder to overcome crappy cables. Some of the most amazing results were with a medium-power transistor amp and the Gemme Audio Tantos that I reviewed. There was much better interplay of rhythm, bass and treble.

The bass of these cables is state-of-the-art. With such low series resistance and the ability to carry insane amounts of current, they’ll do anything within reason. You might find a better cable for bass if you were biwiring and choosing a wire just for bass. However, it’s very likely that a speaker cable that’s better at bass would be weaker in other departments.

In imaging and staging, I found that the Proteus Provectus pushed the sound further behind the speakers, which really benefited classical recordings. It made some of the Decca masterpieces by engineer Kenneth Wilkinson sound flat out humongous. The recording venue seemed to be better laid out and more continuous. You could sense the back of the hall and how it wrapped around from left to right. When coupled with the other Decca hallmarks of great bass and tonal balance, the Purist Audio Design cables proved to be a classical lover’s dream come true.

Where the Proteus Provectus really excelled beyond the competition was with electronica like the soundtrack to the documentary Moog. Also, it was out of this world on my Goldfrapp vinyl. Anything with other-worldly soundscapes or synthesizers seemed to thrive in the system. I would guess that the Proteus Provectus was allowing all those odd little sounds from the synthesizers to come through without rounding off the edges. On Beck’s Sea Change, the recording seemed much bigger and spacious than before.

I wish I could find something world-shattering to say about what these cables do, but it’s more about what they don’t do. They don’t introduce microphonics and noise into the system. Every recording I listened to seemed to have more atmosphere, more texture and better integration of the bass and highs. They are, without fail, the quietest and cleanest cables I’ve heard. Also, these cables allowed the amplifier to play with more authority. Obviously, this all comes at a price.

They are expensive and I quite sadly had to return them. I said earlier that good cables can allow smaller amps with inadequate power supplies to better control the speakers. Am I recommending that you pair these cables with a budget amp? That’s not my job here. I am recommending them without reservation, regardless of price. It would be interesting and instructive to audition a complete Purist Audio Design system of tonearm wire, interconnect and speaker cable. Contrasting the results with another high quality cables should tell me just how effective the Purist Audio technology is in terms of clean sound. I do think that I verified that the Purist Audio cables were making major contributions to the system I heard. In my system, the sound got cleaner, quieter and there was noticeably fewer hi-fi artifacts.

What if you already have a cost-no-object system with cost-no-object cables? Well, you might be set. But you have to ask yourself: if I’ve invested in a state-of-the-art system, do I have the cables that tie it all together? I’m sure there are other cables that do things very well, perhaps some things better than the Purist Audio Design. But, in my experience, Purist Audio Design must be on your short list of cables to audition. These get my highest recommendation.

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