June / July 2010

World Premiere Review!
PrimaLuna DiaLogue Six Monoblock Power Amplifier Review
Worth every penny of their asking price.
Review By Tom Lyle
Click here to e-mail reviewer.

  When I'm shipped a piece of equipment such as the PrimaLuna DiaLogue Six monoblock I'm reminded that audiophiles are a lucky bunch to be participating in this "hobby" at this period of time. No matter what you choose (or do not choose) – analog or digital, dynamic or electrostatic, tube or solid-state – all of these contenders have advanced to the point that it is a matter of listener preference more than anything else. As far as tube amplifier design goes, auto-biasing that is used in many of the top manufacturers of these amps (including a more advanced type in the PrimaLuna), baby-sitting the tubes have become a thing of the past. But this feature would be of little use without the fact that at the same time the price-to-sound ratio (or simply, value) is getting so incredulously high that recommending cost-no-object gear, let alone on-the-high-side of mid-priced gear very difficult to justify.

Of course all of these things are great news for audiophiles, myself included, for reasons that should be obvious to all that are interested in everything audiophile, and of course in everything that has to do with enjoying our music to the nth degree. PrimaLuna has made their very fine tube gear available to more listeners simply by the fact that they are relatively affordable by taking advantage of the lower manufacturing costs in the Far East (and passing the savings on to the consumer. PrimaLuna's gear is designed in The Netherlands and then manufactured in China.

Anyone who doubts that the Chinese are capable of building audio equipment to the most exacting standards that audiophile's should rightfully expect hasn't been paying attention of late. And as far as the expertise of the Dutch PrimaLuna company – if you are not aware that they design and sell high-value excellent sounding tube gear, you also haven't been paying attention. The $4699 a pair DiaLogue Six monoblock amps are one model from the more expensive top-of-the-line model Sevens, thus earning the Sixes the right to be considered high-value amplifiers.

Dangerously Close
Even though the many claim that best gear these days gets dangerously close to the elusive ideal of absolute transparency, its fairly obvious that there aren't any amps (or audio components. Or recordings) regardless of cost that don't stray from this paradigm. So the best manufactures have figured out how to squeeze the most from a given technology at a given price point, and thus find ways of making trade-offs that attempt to bring out the best in their gear.. And my experience with PrimaLuna gear has proven that they've succeeded in not only bringing out the best in tube technology and producing up with amps and other components with first-rate sonic qualities at a reasonable price.

I would also be remiss in not adding that these are quite handsome looking pieces of kit, and especially the Sixes – that were quite impressive looking at that sat on their amp stands in front of the rest of my system. Their superbly constructed chassis are made of heavy gauge steel that are painted with a five-step "automotive quality" high-gloss black finish that is hand rubbed and polished,. The thick face plate can be ordered in either silver (as the review samples) or black. The removable tube cage, rather than hiding the tubes from view is constructed of vertical slats close enough together to prevent damage to the tubes (and the scorching of prying fingers), yet spaced far enough apart to get a clear view of the four EL34 output tubes and the two 12AX7 and 12 AU7 input tubes. The glass side panels of the cage further enhance the Six's cosmetics, and also does not obstruct the tubes and their comforting orange glow.

The PrimaLuna DiaLogue Six takes full sonic advantage of its tube birthright without very few disadvantages, and at the same time it can be considered a relative bargain in today's high-end. OK, I take that last thing back, because $4699 is not an insignificant amount of coinage – yet I'm hardly risking my reputation by saying that these amps can hold their own compared to amps costing much, much more than their asking price. And I'm also willing to risk that same reputation on the fact that one will hear a major improvement if upgrading to the PrimaLuna from an amp of a lesser pedigree. Included in the price of admission are a host of features, major among those is PrimaLuna's "Adaptive AutoBias" circuit that monitors and adjusts the tube's bias, thus making life a lot easier for someone like me who would like to spend time listening to music rather than spend time genuflecting to the amps with a power meter balancing on my knee. The advantages of the automatic biasing circuit, as designed by PrimaLuna (as opposed to the very remedial form of cathode bias used in less worthy amps), is that it increases the power efficiency of the amplifier plus lowers the levels of the already low levels of distortion.

Plus, the circuit of the auto-bias used in the PrimaLuna is not in the signal path of the music. In addition, it is totally passive. The transparency and transient response also improves over the entire frequency range, including the bass as compared to amps with even more power than the amp under review. An even more impressive benefit of the PrimaLuna's automatic biasing is that the number of tube failures decrease, and almost more importantly, tube matching is a thing of the past so it also makes it possible to experiment with different types of tubes where the circuit will automatically adjust for just about any power tube on the market that will fit in the EL34-type sockets such as the 6550, KT88, KT90, 6L6GC, KT66, 7581, EL37, et cetera.

Besides it's behind the scenes auto-biasing feature, the PrimaLuna Dialogue Six power amplifier can be switched between the more powerful ultralinear mode to triode mode from a remote control. Although I found that this remote function was made more useful when also using a remote control preamp because of the loss of volume that invariably occurred because of the amp runs at about half power in triode, still, it is a pretty nice feature, and the folks at PrimaLuna should be rewarded for this (of course an audition and subsequent purchase is probably all the reward they're presumably looking for). More on the triode/ultralinear feature in a bit. Still, as nice as these features are, its internal features are where it's at, and the Sixes hardly skimp on those.

The Six employs something PrimaLuna calls a "dual-feedback" topology, which they use cross-coupled current feedback, and at the same time apply a small amount of negative feedback to achieve an exact gain setting. This, claims PrimaLuna, provides low distortion and a low input impedance, but it also ends up canceling any negative effects that might crop up by using feedback in the first place but with all the benefits – which of course includes increased bandwidth. The Six is designed with a relatively uncommon type of output transformer, a dual-output model that PrimaLuna recently created that not only has a wide bandwidth, but losses very little current, and is meant to handle a much wider variety of speakers.

A 2 Ohm output tap is added to the amp's 4 and 8 posts for additional flexibility, the 2 Ohm presumably for speakers of the electrostatic variety or others that might present a demanding load. Along with a tube plate fuse, the amps have a soft-start circuit which prevents the power from surging through the tubes, thus shorting their lives. The amps also are also constructed using premium parts, including chassis-mounted ceramic tube sockets (rather than cost-saving but flimsy plastic), Nichicon and Realcap capacitors, WBT-style speaker binding posts, and gold-plated input jacks. The wiring is, of course, point-to-point, and the like I stated before (and is worth mentioning again), the impressive looking chassis is made from a five-step automotive quality hand rubbed finished steel. The power transformer is a low hum "dead quiet" toroidal.

Wonderful
As you've read in many of my other reviews, I usually state at least once that a component might be only good as the system in which it is a part. By that I'm not trying to invoke the "weakest link in the chain" apophthegm (however truthful that might be). But lest one think that this review is simply a love letter to the DiaLogue Six monoblock, one should remember that not every piece of wonderful sounding gear is in my system going to sound wonderful in your system. And not only that, even if it will sound good, it has to fit your lifestyle. This is certainly true of the PrimaLuna Sixes because these amps are not the type of components that can't be hidden in a living room's chiffonier along with the television.

These 15.2" x 8.3" x 16" monoblocks weigh in at 64 pounds each, need room to breathe, and take up a fair amount of floor space. And although I think they look ravishing with their gloss black cabinets with their glowing glass bottles lit up in the darkened listening room, one's life partner might not be as enamored with them as I am. But let's put all this aside for a moment and consider their strengths (not to mention my accepting wife) by noting that the sound quality of these amps are top notch in every department imaginable. At 70 Watts per channel in ultralinear mode these amps have enough power for most small to mid-sized speakers (and even some larger models). Each amp has binding posts for connecting speakers with an impedance of 8, 4, and 2 ohms to drive any real world speaker to sufficient volumes with rapturous results.

If one dared to judge the sound of tube amps solely on the PrimaLuna DiaLogue Six monoblocks one might wonder why the term "tube-y" was coined. Although it's pretty easy to look up on the Interweb and find that some audiophiles define the term as "an excess of warmth, exaggerated mid-bass, loss of upper-treble and deep bass, but with a lush midrange and expansive soundstage", the PrimaLuna Sixes, even though they sport eight tubes, other than the expansive soundstage part, do not fit this description. Have the designers of the DiaLogue Sixes found a way to eliminate every negative sonic stereotype and accentuate all the positives? Yes, quite possibly. Although it would be inaccurate to portray the PrimaLunas as being totally transparent, chiefly because I haven't heard any audio product that uses the EL-34 tube that doesn't inject at least a small amount of '34 warmth to the sound of the music, and this includes the PrimaLunas.

I'm well aware that the venerable EL-34s have legions of fans (including me), but when describing the sound of these tubes when being used in the PrimaLuna DiaLogue Six as having an abundance of "warmth", I would only use this term to describe the beauty of music, as in the opposite of "sterile". These amps come awfully close to the paradigm of replicating recordings of real instruments recorded in a real space, as sonic illustrations of real instruments recorded in a real space. During the audition period it was awfully difficult to detect any variations from this archetype that wasn't caused by other components in the chain or the recordings themselves.

Still, even though the source equipment I was using in my second system to test these amps isn't even close to state-of-the-art, I'm aware enough of the traits of the ArcamDiVA CD192 CD player and Oppo universal player to be able to judge what they were or were not adding to the sound. I swapped between the solid-state Burson Audio PRE-160 and the tubed Balanced Audio Technology (BAT) VK-3iX preamplifiers, both of with I consider to be both transparent and otherwise top-notch sounding, albeit for different reasons. Both allowed me to cue in on the sound (or lack thereof) of the PrimaLunas. And both of the pairs of speakers I used during the review period, at first the stand-mounted Dynaudio 110, and only a short time later the more extravagant Salk Veracity HT1-TL floorstanders.

The Salks were especially adept at revealing every change I made in the system during the time that the PrimaLunas were in the system. I'm also sorry to report that changes in cabling also made a difference in the sound of the system, of the four other brands I had on hand my stock of Cardas interconnects and speaker cables seemed to work best with the PrimaLunas. Yet the cabling was just the icing on the cake because these amps ended up sounding extremely musical, that is, very non-electronic sounding, especially when paired with the outstanding Salk speakers with their ribbon tweeter and transmission line cabinet. The near physical reality of the sounds that entered the listening room were very pronounced. Again, I'm not going to profess that the sound of these amps made the system sound identical to "the real thing". But the important cues were clearly evident, and at times led me, even if for just an instant, to suspend disbelief.

Added to this was the sense of the music just "appearing" between and beyond the speakers, and not only because of the Six's wide, deep, stratified, yet believably scaled soundstage. Plus, to my surprise was the (relatively) amazing trait of having transients so outstanding that it was difficult to believe that this sound was coming from an amp that was not only powered with tubes, but EL-34s in particular.

As one might have gathered, the second system is the smaller of my two systems. It is located in a common room which is on the large size, about 18 feet by 12 feet, with a ceiling that is slightly more than eight feet tall. It sounds more live than my treated dedicated room, but it has one wall that has a bay window with three thick Roman-type shades that when lowered provided enough "acoustic room treatment" to keep the sound waves from bouncing around. It has a stone fireplace and mantle on rear wall (stereophonically speaking) of the room, and I assume this might be one of the reasons why there are no standing waves that I can notice, as a result the bass is tight and tuneful with most components and speakers that have been part of the system of late. In the room there are few furnishings other than the table, chairs, an upright piano, and a cabinet with dishes, vases, and such that probably has a French name that would better describe it.

Anyway, the PrimaLuna amps sound excellent in this "real world" room, and moving them upstairs to the dedicated, acoustically treated listening room wired with its own dual 20 Ampere power lines (and way better front end) proved they could handle the much more demanding Sound Lab electrostatic speakers, although with some volume limitations. To describe their use with the larger system would probably fill up an entire second review, most of all because in this system the I fitted the DiaLogue Sixes with a set of KT88s, which boosted the amp's upper treble and helped compensate for the loss in those frequencies when driving the relatively massive Sound Labs.

But what was so amazing is that even though this was a much greater challenge for these amps the general characteristics of the amps remained the same, that is, in a word, entrancing, especially in their ability to more than compensate for the second system's lack of front-end refinement. Nevertheless, I will state as fact that the PrimaLunaDiaLogue Sixes were a better match with the easier load of the Salk Veracity HT1-TLs than the electrostatic hybrids upstairs. Another reason I'm mentioning the details of the downstairs second system's lack of front-end fortitude is that it is entirely reliant on digital disc playback. Lately, in the big rig I've converted standard resolution CDs to a computer based system which are fed to a Benchmark DAC1PRE. To say that the difference in sound between the old and new methods of playback is huge is an understatement.

But even if I'm digressing a bit from the subject at hand, again, I'm only stating this to emphasize that the PrimaLunas' performance was outstanding regardless. I'm just glad I had the Oppo in the system to play SACDs every once in a while to fully satisfy my digital appetite.

Even so, standard Red Book CDs easily demonstrated why these PrimaLunas are worth every penny of their asking price. On the the purely instrumental work he drew from his opera of the same name, the CD released in 2009 of John Adam's Doctor Atomic Symphony, the first thing to grab my attention (and should be the first thing to rouse anyone that has a pulse) is the opening salvo led by the horns, tympani, and bass drum(s). Yes, it shook the room without the system being sub-woofed, and the Sixes were able to sort out the complex score without ever sounding blurred, or worse, tube-y. Though the Salks are claimed to "only" be rated down to a low frequency response of 35 Hz (+/-3dB), their bass more than effectively gave a sense of what went on during the original recording session.

While the PrimaLunas were in this system I was much more likely to notice the sonic temperament of the speakers or the other associated gear, the PrimaLunas getting out of the way and simply amplifying the signal without adding any characteristics that couldn't be described as, again, musical. This led the focus to be on the music (and the recording, I'm afraid), so during the furious 16th notes that open the second movement of this symphonic essay exposed the multi-mic technique of the recording engineers. Now that this modern method of recording seems to be de rigueur, I've become accustomed to the democratization of the orchestra as portrayed on just about every modern classical CD I've purchased or otherwise acquired for almost as long as I can remember – so a mixing engineer's heavy hand on the mixing console balancing the relative levels of the instruments in addition to the conductor and the musicians doing this for themselves doesn't bother me nearly as much as it once did.

Although it does render the expansive soundstage a bit on the man-made side of things, the Saint Louis Symphony Orchestra as led by David Robertson was still laid out between and beyond the speakers in a coherent manner. When the complex score quiets down about ten minutes into the second movement, the winds and strings take become quite literally center-stage, rarely has the overused term "palpable presence" been more applicable. The instruments hung in space between the two speakers in a nearly three-dimension diorama of sound.

Switching gears I put on some smaller scale music, some selections from the amazing four CD set of John Coltrane's The Complete 1961 Village Vanguard Recordings that comprise every note that was played between November 1st and 5th, 1961 by his legendary band. As much as I respect every recording that engineer Rudy Van Gelder has ever made, that has more to do with the subjects of his art than his recording arts in itself. The hard panning, ultra-close mic'ing, ofttimes limited frequency response, and questionable techniques when recording the piano often plague Mr. van Gelder's recordings, and yet the quality rarely distracting, and to be truthful, some are outstanding recordings regardless. And that goes for this CD set, which finds John Coltrane playing both tenor and soprano sax in top form in the later period of his career when he was signed to Impulse Records.

When playing one of the now legendary versions of the pianoless Chasin' the Trane, one without alto-saxophonist Eric Dolphy, the PrimaLunas enable one to follow Coltrane's lines to the near impossible feat of imagining one is inside his head, so to speak. Every inflection created by his amazing breath control, and every convoluted line coming forth from his ostensibly magical improvisational style is transported through to the speakers exactly as it appears on the extraordinary mastering of these Red Book CDs. Rarely have I hear his instrument's harmonic texture so expertly reproduced.

Of course the magic of a properly engineered tube amplifier lie in its proficiency in rendering of the midrange frequencies, and the PrimaLunas do not disappoint in this area. I could have easily spent the entire review discussing the unmatched beauty of the Six's reproduction of all sounds that have significant energy within these frequencies – and since there a few instruments that do not have significant energy in this most important of frequency ranges, this bodes well for the listener. Vocals are especially well served, and whether I was listening to male or female in large groups or small, and regardless of musical genre, the vocals came through the speakers as if I was eavesdropping on the recording session.

This is as good a time as any to discuss the PrimaLuna's ability to switch between ultralinear mode, in which the amp puts out 70 Watts per channel in ultralinear, and in triode mode 40 Watts per channel. The manual states that when one listens to the amp in triode mode one should hear a sound "best described as warmer on top and bottom, a little compressed, with the midband now slightly more pronounced". Since I did not try these amps in triode for a super-long amount of time, I'm not sure that I'm one to fully judge whether triode mode is "better" than ultralinear. But I know what I like. When I used the DiaLogue Six when in triode mode through either the Dynaudio or Salks at normal listening levels it wasn't that appealing – most of what I like about the PrimaLunas were gone, and in its place a more colored, less lively sound.

At low volumes with simple material it was OK, but this was not how I perform serious listening. And even when listening to the Sixes playing in the background music the loss of definition bothered me. The owner's manual spends quite some time discussing the difference between the two modes, and stresses that one should "never let people tell you what sounds right". And so I won't either. But what I will say is that it is quite nice that one has the choice of either ultralinear or triode operation, and that the switch is available on a remote is quite a nice touch.

Assumed
Lastly, I should address the fact that most should be aware that PrimaLuna's current top-of-the-line DiaLogue Seven has been reviewed quite favorably in the audiophile press, and, I've always assumed that it is more popular than the Six. Or maybe not. It wouldn't be fair (or honest) to compare these two amplifiers without the two models connected side-by-side.

But if you ask me to choose between the Six's using EL-34 or KT88s, I wouldn't be going too far out on a limb if I chose the Six with its '34s (not for a moment slighting any amp that uses the KT-88 tube). Admittedly, I've used far more amplifiers using the EL-34 more than the KT88. According to Kevin Deal, PrimaLuna's US distributor, the DiaLogue Sixes are the exact same amplifiers as the DiaLogue Sevens except the Sevens have Solen capacitors, fast-recovery diodes, and obviously, KT88 power tubes. Of course, one is free to use KT88s in the Sixes. The KT88s might have more treble energy than the EL-34s when used in most systems, but in the system using either the Dynaudio or Salk speakers the Sixes sounded much better using EL-34s.

The KT88s sounding a bit "brittle" in comparison. But much like ultralinear vs. triode mode I'd be a fool to say that one tube is "better" than the other, just that I prefer one more than the other. Plus, one can save some money by choosing the Six. I, for one, would never second guess your decision. And neither should you.

Specifications
Type: Vacuum tube stereo amplifier
Output: 70 watts ultralinear, 40 triode
Tube Compliment: Two 12AX7 and two 12AU7 and four EL34
Frequency Response: 10 Hz to 100 kHz (+/- 3dB)
THD: Less than 0.25 percent @ 1 watt, 
SNR: 83dB
Input Sensitivity: 1.1V
Dimensions: 15.2" x 8.3" x 16" (WxHxD)
Weight: 63.8 lbs
Inputs: One unbalanced RCA 
Outputs: 2, 4 and 8 Ohm speaker taps 
Price: $4699

Company Information
Durob Audio BV
PO. Box 109
5250 AC Vlijmen
The Netherlands

E-mail: primaluna@primaluna.nl
Website: www.primaluna.nl

United States Distributor
PrimaLuna USA
1042 N. Mountain Ave
#B PMB 406
Upland, CA. 91786

Phone: (909) 931-0219
Fax: (909) 985-6968
Website: www.primaluna-usa.com