PrimaLuna DiaLogue Two Integrated Amplifier

Equipment report
Integrated amplifiers
PrimaLuna DiaLogue Two
PrimaLuna DiaLogue Two Integrated Amplifier

With its ProLogue series of tube electronics, PrimaLuna burst onto the audio scene a few years ago and established itself as a serious contender in the value-priced sweepstakes. Designed in the Netherlands, built to high production standards in China, and distributed in the U.S. by tubemaven Kevin Deal, PrimaLuna’s first offerings, the ProLogue One and Two integrated amplifiers, were followed by a separate preamplifier, stereo amplifiers, and monoblocks. I lived happily with ProLogue Six amplifiers during an extended review period and was impressed by their natural and engaging sound, and the quality of their point-to-point wiring and parts. PrimaLuna’s adaptive auto-biasing and soft-start features combine to help make owning an audio component with glowing devices musically satisfying and “easy as pie” to operate and maintain.

At the 2006 Winter CES, Kevin proudly pointed to a prototype of an integrated amplifier from PrimaLuna’s new, upscale DiaLogue series that was on silent display. The first thing he said to me was, “Lift it up!” I did, but I should have put more of my legs into it. This baby was almost double the weight of one of the ProLogue integrated units. Given my very positive experience living with the PrimaLuna monoblocks, I was anxious to audition this new integrated amplifier and see how it compared with its ProLogue Series counterpart. My accommodating local dealer, Brian Hartsell at The Analog Room, kindly loaned me a DiaLogue Two and a ProLogue Two integrated amplifier so I could do the comparison.

The KT88-equipped DiaLogue and ProLogue Two units sport many of the same premium parts, have similar power ratings (when the DiaLogue is in ultralinear mode), and include those wonderful auto-biasing and soft-start features. Consequently, it’s not surprising that they also share several sonic qualities, too, when driving speakers with relatively benign loads. Both have an engaging and highly musical midrange, and their sonic differences in the midband are subtle. As was the case with the ProLogue Six monoblocks, both of these PrimaLuna integrateds get the sound of massed strings and voices right, a failing of far too many high-definition components. They add no additional edge or stridency yet still maintain very good clarity and detail on recordings like Beethoven’s Sixth Symphony (Kubelick on EMI), and Liszt’s Dante Symphony [Telarc]. Strings on the DiaLogue had a bit more realistic bite and presence, but not brightness, resulting in a more exciting performance. Sarah Vaughn’s voice on Ballades [Roulette Jazz] was a tad purer with the DiaLogue, and her voice had more intensity.

Outside the midrange, the gap between these two units widened, with the DiaLogue offering superior transparency, midbass weight and articulation, extension at the frequency extremes, and micro- and macro-dynamic swings. For example, the tympani rolls on the Liszt were more explosive with the DiaLogue, and the ensemble on Electric [Chesky] seemed to play with more rhythmic drive, aided by the enhanced solidity and articulation of Victor Bailey’s electric bass and high-frequency shimmer and decay of Lenny White’s cymbals. With the DiaLogue, performances were more thrilling and 3-D, with clearer ambient cues; instruments like the cello on Haydn’s Cello Concertos [Pierre Verany] had better timbre, with more body and fleshed out overtones.

If you own a speaker that’s more difficult to drive, the DiaLogue is the clear choice. Whereas the ProLogue Two struggled mightily to drive the Quad ESL-2805 loudspeakers, distorting dynamic peaks with either the 4- or 8-ohm taps, the DiaLogue drove the new Quads “effortlessly” and was able to extract more bass extension and weight than I could have imagined, without any bloat or muddiness. I also preferred it sonically to the more powerful ProLogue Six monoblocks, which had just departed from my listening room prior to the DiaLogue’s arrival. Besides its superior bass performance, the DiaLogue out-pointed the Sixes in terms of fine-detail retrieval, upper-midrange purity, and high-frequency openness and extension.

The DiaLogue Two’s ability to faithfully reproduce the realism of the piano was shocking. One literally hears the fundamentals and overtones resonating from the piano’s soundboard. I was amazed at its bass punch and foundation on Alain Planès’ recording of the Debussy Préludes [Harmonia Mundi], its explosive dynamics on Vladimir Ashkenazy’s recordings of Beethoven’s last piano sonatas Nos. 28–32 [London], and the subtle details and nuances that emerged from Ignace Paderewski Plays Beethoven, Liszt, Schubert, Debussy [Klavier]. While Paderewski reportedly hypnotized audiences in live performances, I sat there transfixed listening to his admittedly romantic, but oh-so-wonderful interpretations through the spectacular DiaLogue/ESL-2805 combo.

At the push of a button on the remote, I switched the DiaLogue Two from ultralinear to triode operation instantaneously. Adjusting for level (the output is halved in triode), the sound became a bit warmer with more image depth, at the expense of a slight increase in noise level and some softening of the bass and highs. Massed strings were slightly lusher, with a lighter, “feathery” quality.

However, one’s preference for either triode or ultralinear mode will likely depend on the speakers used, the type and brand of output tubes, and even one’s mood. For example, if I wanted more impact, I switched to ultralinear, but for more aggressive recordings, I moved back to triode. On my original Quads, I preferred the more relaxed triode mode, but on the new Quad ESL-2805s and Hyperions, I found myself typically listening in ultralinear mode, with its more extended, dynamic, balanced, and thrilling presentation.

Since the linestage of the DiaLogue can be completely bypassed, I also used my reference preamplifier with the DiaLogue Two, and the soundstage was literally wall-to-wall on great analog recordings. String tone was gorgeous, and trumpets had the requisite “ping” on Holst’s A Fugal Overture [Lyrita], suggesting that the performance of the amplifier section of the DiaLogue is very fine, indeed. Using only the MFA’s phonostage with the DiaLogue, string tone remained beautiful and the soundstage was still surprisingly expansive, but the image did not extend outside the boundaries of the speakers. Nevertheless, this level of performance through a modestly priced integrated amplifier is quite stunning.

Despite its outstanding performance, the DiaLogue Two has some limitations. While it has more dynamic explosiveness and midbass weight than any 38- watt integrated amplifier I have ever heard, you might need to look elsewhere if you have power-hungry speakers. But don’t be surprised if the DiaLogue’s output is all you need. Some may prefer the immediacy and purity of the best SET amplifiers using 300B or 845 output tubes, but the DiaLogue comes close to that sound, particularly in its triode mode, and offers many other compensating virtues. If you need more lushness, try a set of EL34 output tubes, but the stock Genelex KT88 knockoffs sounded lush enough to me and have a tad more power, bass authority, detail, and high-frequency extension. Lastly, a PhonoLogue moving-magnet phonostage can be added internally to the DiaLogue, but it is limited to moving-magnet or high-output moving-coil cartridges. While its performance rivals separate phonostages around $500, and is definitely a good value, I’m hoping that PrimaLuna will introduce a companion DiaLogue phono card, or external module, that’s even better.

Great wide-bandwidth transformers, a hefty damped chassis, an intuitive remote control with triode switching, and an effective direct-bypass capability combine to raise this PrimaLuna’s performance at least another level (or “Two”) above the fine ProLogue Series. If the DiaLogue Two is representative of forthcoming units in PrimaLuna’s new, higher-performance line, audiophiles and music lovers who are value- and performanceconscious and want tube electronics that anyone can operate and maintain are in for a treat. The DiaLogue Two is a keeper.

Design Elements

Several well-executed design elements combine to significantly improve the performance of the DiaLogue Two over its ProLogue Two counterpart. The most obvious are the unit’s significantly increased chassis weight and improved cosmetics. However, the most important of these are the DiaLogue’s “beefy” wide-bandwidth output transformers. Just because an amplifier’s transformers are more massive doesn’t mean it will actually sound better overall. This is a tricky business, and there are too many cases where a company’s amplifiers with smaller output transformers sound better in the midrange and highs than those with larger ones. Typically, a larger transformer will yield better bass drive and control, but can actually degrade the quality of the midrange and highs. To reap the sonic benefits of these heftier transformers across the entire frequency spectrum, PrimaLuna used a labor-intensive “halfspeed-winding”technique. According to PrimaLuna’s Herman van den Dungen, during the DiaLogue’s design phase the resistance of the transformers was measured after each coil winding. Many versions, with different coil windings, were evaluated sonically until the one with the best combination of low distortion and the right balance was identified. Ranges of different isolation materials and types and thicknesses of iron were also evaluated—to reduce distortion. Tighter-tolerance parts were used in the DiaLogue, as well as PrimaLuna’s proprietary Adaptive AutoBias circuit, reported to reduce tube distortion by 40% to 50%. The result is an integrated amplifier with incredible bass slam for its output rating, a seductive midrange, and extended “fatigue-free” highs.

It appears that a lot of thinking went into the design of the remote control, too. The unit fits easily and firmly into your hand and the volume can be controlled by your thumb. The button to switch from ultralinear to triode mode is at the top of the remote, so it takes a deliberate action to change modes. A red light, easily seen on the top of the DiaLogue, indicates ultralinear mode and a green light indicates triode. Switching is instantaneous, but beware. When listening in triode mode, you can easily increase the gain only to be jolted by an increase in volume when you switch back to ultralinear. As a precaution, I found myself reducing gain a bit in triode prior to moving to ultralinear.