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Positive Feedback ISSUE 36



DiaLogue One integrated amplifier

as reviewed by Ed Kobesky






PSB Alpha T.

PrimaLuna ProLogue Two integrated amplifier, Rotel RQ-970 phono stage.

Rega Planar 3 turntable with Linn Basik LVV tonearm and Denon DL-110 cartridge, Rega Planet CD player, Sony DVP-NC875V DVD/SACD player, Pioneer DV-563A universal player.

MonsterCable Interlink 400, 250 and 200 interconnects, AudioQuest Alpha Snake interconnects, MonsterCable XP speaker wire, others.

Record Doctor II record cleaning machine with Disc Doctor brushes, Sennheiser HD580 headphones, Rotel RLC-900 line conditioner.


Hard to believe, but nearly three years have passed since I last heard from Kevin Deal, the owner of California's Upscale Audio and the man behind PrimaLuna electronics in the USA. It was worth the wait. Last time, the west coast's preeminent tubemeister was rolling out his new line of high-value, integrated tube amplifiers. He sent me the ProLogue Two, a compact KT88-based unit that's built like a tank and performs with uncommon delicacy. I raved about it then and still feel it's one of the most sonically appealing integrated amplifiers for around $1500.

Since then, the PrimaLuna line has expanded to include separate preamplifiers and amplifiers (stereo and monoblock) in addition to a well-regarded, optional moving magnet phono card and even a CD player with tube-based clocking device. Kevin's no fool. Unlike many people in the audio industry, he's a smart businessman who does a great job at generating publicity. It would have been easy for him to send me subsequent PrimaLuna products knowing full well I'd probably rave about them, too. But he didn't.

So, when my caller ID did finally light up, I knew it would be about something special—and it was. The new DiaLogue series takes ProLogue performance to the next level with even better parts (if that's possible), more features and higher resolution. The DiaLogue One is EL-34 based while the DiaLogue Two uses KT-88 tubes. Kevin sent me the DiaLogue One and it's one hell of a looker, with a swooping steel and glass tube cage and multiple coats of hand-rubbed lacquer that achieves a flawless finish Porsche would be proud of. The stainless steel remote control feels like it will last a lifetime or two.

Like all PrimaLuna products, the DiaLogue One uses PrimaLuna's proprietary Adaptive AutoBias circuit that continually monitors and adjusts the bias. It works flawlessly and unobtrusively to the point where owning a PrimaLuna tube amplifier is little different than owning a solid-state amp. Every once in a while, the owner will need to replace a tube or two, which is about as difficult as changing an incandescent light bulb but probably less frequent. To maximize tube life even further, it also incorporates a "soft start" circuit to gently power up the amp and reduce thermal shock. Most of the interals are linked by point-to-point wiring, so aside from a few ICs (for the auto-bias and optional phono stage), there's little that might be prone to premature failure.

Unlike the ProLogue amps, however, the DiaLogue is switchable from triode to ultralinear mode at the touch a button on the remote control. For those who don't know (or, like me, hardly care), ultralinear operation basically forms a negative feedback loop around the output stage and allows for higher power output. Triode operation allows for a much smaller voltage swing. Consequently, output power is much lower.

If you're as baffled by basic electrical engineering as I am, just know this: in ultralinear mode, the Dialogue One outputs 36-watts and sounds more dynamic and fleshed out, while in triode mode, it musters 18-watts with a notably more transparent midrange at the expense of just about everything else. I'm not a triode guy, and I never will be. I think the totality of the musical presentation is important so I'm not willing to sacrifice general realism for ultra-realistic, über-present vocals. Then again, I also have nothing against crossovers and have little interest in the kind of full-range horns that triode folks tend to enjoy.

Here's another thing you should know: the DiaLogue One's relatively low power rating completely belies its ability to drive even finicky speakers. It barely broke a sweat with the inefficient Spendor S5e floorstander. Though quoted as an 8 ohm speaker with an 87dB efficiency rating, some testers have reported that it's more like 4 ohms and 83 dB. Even in triode mode, the DiaLogue Two powered the Spendors to real-world listening levels without notable strain—though the combination of British loudspeaker and triode mode was hardly a synergistic match. Of course, a true triode guy would never put those two together. Switching to ultralinear mode, the amp really took control of the Spendor drivers with tremendous authority and helped to deliver more definition and deeper bass than I'd experienced with significantly higher-powered solid state amps. 

In fact, the DiaLogue One is a "best of both worlds" kind of product. It provides nearly all of the dynamic slam and frequency extension you'd expect from a solid state amp at this price, together with the liquidity of tubes. Come to think of it, that's exactly what I said about the ProLogue Two three years ago. There is definite design continuity here. Listening to both units back-to-back (using the same EL34 power tubes), the DiaLogue did what the ProLouge does—only better. So, at the risk of appearing unoriginal, I thought it best to go back to my review of the older product for a discussion of listening impressions. (Quotes from the ProLogue Two review are in italics.)

"The first thing I noticed was a unique sense of air and aliveness." Check. Listening to both units head-to-head with a pair of Triangle Celius-202 floorstanders, the DiaLogue One delivered precisely that, only more so. Everything seemed more real, more transparent. If the ProLogue Two is engaging, then the DiaLogue One is positively captivating. Some people might confuse its liquidity for tube-induced gloss, but listen closely with a revealing speaker like the Triangles. You'll find it's not the case.

"When the music started, the ProLogue Two surprised—no, shocked—me by painting a smooth sonic picture that was also controlled and coherent. Many tube amps I've heard are slow in the midrange, dull on top, and loosey-goosey on the bottom. Not the ProLogue Two. It can't compete with solid-state amps in terms of tightness and fastness, but it never sacrifices detail to provide a warm, soothing presentation." Check. The difference here is that the Dialogue One can compete with solid state amps in its ability to deliver deep, controlled bass and stop-on-a-dime transients. It's tight as a drum, and not "for a tube amp" but without qualification.

"I'd have no qualms about pairing it with sources and speakers that cost many times its absurdly low price." The DiaLogue Two may not be quite the screaming bargain its little brother is, but it is a tremendous value and I do not question for one second its potential to be the centerpiece of a system in the $20,000 range. Plain and simple, it's just that good. You'd be forgiven for thinking that no expense was spared in its design and manufacture. You can visit Upscale Audio's website for more information on the many ways in which it is (over)built. Or you can do what I did and simply lift it up. At nearly 65 pounds, it's a bruiser, even for a fit 33-year-old.

The DiaLogue One is built in China but, as brand owner Herman van den Dungen stressed in a recent interview, "it is not a Chinese amp." That is to say, it's a western design that meets European Union specs and happens to be built at a factory in China, where production is overseen personally by either Hermann himself or one of his team members. According to importer Kevin Deal, we're not talking about simple spot checks. "You cannot get a consistent, high-quality western product unless you have western people sitting on the factory hours a day," he said. "That's what it takes, so that's what they do."

For the record, I've had the ProLogue Two in use for three years and it has never been anything less than 100% reliable. I pay it no mind and it demands nothing in the way of special attention. I see no reason to expect less from the DiaLogue series. That's why I would strongly recommend the DiaLogue One for those who, by necessity, have combined their two-channel and home theater systems. It features a nifty home theater pass-through that completely bypasses the preamp section. You can keep your receiver and enjoy tube sound—without the hassle of tubes.

I guess I'm obligated to mention that the original ProLogue One is nearly $925 less expensive than the $2295 DiaLogue One. They sound very similar so, if you like what you hear and can live without a remote control and home theater pass-through, then you can get much of the DiaLogue's performance for less. However, this is also one of those cases where you really do get your extra $925 worth—and then some, and then some more. The DiaLogue One is a significantly more lifelike amplifier that, despite a similar power rating, maintains a much more confident grip on speakers. I never thought I'd run across an affordable tube amp that could make the same magic with fast, efficient speakers like Traingle and taut, inefficient speakers like Spendor, yet here it is. How cool.

I closed my review of the ProLogue Two by saying that "music flows through it gracefully. What comes out is lush but not slushy, alive but not prickly, and involving as all get out. The PrimaLuna ProLogue Two garners my strongest recommendation. It's not merely a great tube amp, but a great amp, period." Ditto for the PrimaLuna DiaLogue One. It's a wonderful, luxurious-sounding amplifier that I'm wildly enthusiastic about. I'll spare you the usual audiophile jargon and close by simply saying that the DiaLogue One sounds about as close to live music as you're going to get at this price, especially if you value warm-blooded, breath-of-life realism. Ed Kobesky

DiaLogue One integrated
Retail: $2299

web address:

Upscale Audio
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