The DiaLogue ships with PrimaLuna’s SilverLabel selected EL34 power pentodes, which sounded pretty good right out of the box. The Russian Mullard reissue EL34 sounded a bit smoother, but in either case, the treble range was a bit too brash for my taste. The Electro-Harmonix KT88 bested even the Mullard EL34 with a smoother and better focused sound. And in particular, its big tone presentation courtesy of nicely fleshed out lower mids won me over. This was most evident in the reproduction of the body and timbre of an upright bass.
The DiaLogue was now sounding seriously good, being in command of dynamic gradations and capable of resolving low-level detail. And although not quite spatially in the realm of single-ended triode amplification, it was able to generate a grand soundstage that was not only spacious and deep but so lucidly transparent that it was possible to “see” the inner recesses of the stage. Make no mistake about it: The stock 12AU7 is a good-sounding tube, so I didn’t feel the urge to roll-in vintage types for quite a long time, that is until its weak spot, an assertive upper midrange, finally wore me down. Lacking a matching sextet, I mixed several brands including RCA 5814A and Philips Miniwatt. While perhaps not the ultimate vintage preamp tube set, it nonetheless achieved greater tonal neutrality and nudged the DiaLogue forward in spatial resolution and textural purity, especially in the treble range.
I’ve saved the best for last. Upscale Audio’s Kevin Deal was kind enough to send me a set of burned-in and matched Tung- Sol reissue KT120. This was to be my first serious listen to the KT120 and I was uncertain about what to expect. The buzz about this tube has been generally favorable, but there have been a few detractors, the main complaint apparently being about grainy midrange textures. Well, I have nothing but nice things to say about this power tube. It struck me even after a short listen as the best sonic fit for the DiaLogue Premium, which now satisfied my sonic palette on all levels. A clear case of full sonic ignition! The KT120 sounded exceptionally linear with sweet and clean midrange textures. Bass definition was excellent and soundstage transparency and dimensionality reached a new high. I was surprised by upper-octave delicacy, transient finesse, and clarity of decay—all of which I did not expect from what is ostensibly a muscle tube. And tonal weight was far more convincing than with either the EL34 or KT88 options. The KT120’s combination of midrange warmth and big tone presentation were mighty attractive and there was also plenty of boogie factor on tap. Needless to say, the KT120 stayed the course for the remaining listening sessions.
It was time to move on from the Basszilla to another speaker load, specifically the Bud Fried Tower. And that’s when I ran into a speed bump, at least while listening in UL mode. The Fried Tower’s impedance minima are 4 ohms at 200Hz and 2.7 ohms at 2.7kHz, the latter minimum being crossover related. I had measured the DiaLogue’s source impedance off the 4-ohm taps in UL mode at 1.6 ohms. The interaction between the amp’s source impedance and the speaker’s impedance minima resulted in about a 1dB reduction in speaker output near these minima. The result was a leaner upper bass range and an upper midrange dip that affected soprano and violin timbre. An effective and simple solution was to flip the DiaLogue from UL to triode mode. The measured source impedance off the 4-ohm taps dropped to about 1.2 ohms, improving the damping factor and thereby reducing the amp/speaker interaction. Not only that, but subjectively the presentation changed dramatically. It became totally relaxed with plusher and sweeter textures. Both violin tone and soprano voice were nudged closer to the real thing. It is reasonable to conclude that operation of the DiaLogue in triode mode is a potent option that can work miracles with some loads. Lesson learned: Don’t be afraid to push the triode/UL button on the remote. Power output drops by about half to around 15 to 20Wpc, but you’d be surprised by how far that will take you in an average-sized listening room with 88dB+ sensitive speakers. While with some types of music or speakers triode mode may offer too relaxed a presentation, one that is lacking in musical tension, it will at times allow you to enter the Goldilocks zone where the music sounds just right.
The PrimaLuna DiaLogue Premium makes a winning argument for integrated amplification. Add speakers and a CD player and you’ve got yourself a high-end system that won’t break the bank. It raises the bar when it comes to user-friendliness and operational flexibility. It is a tube-roller’s delight as it dispenses with the bother of having to deal with biasing issues. The DiaLogue Premium is superbly engineered and built. At its best, it makes no apologies to stereo amplifiers costing three times as much. It is my current benchmark in integrated tube amplifiers.
SPECS & PRICING
Tube complement: Four EL34s, six 12AU7
Power output (KT120, EL34, KT88): 43.2, 32, 35.7Wpc
Frequency response (KT120, EL34, KT88): (+/-1dB), 5Hz–69kHz, 5Hz–30kHz, 5Hz–32kHz
THD (1W/1kHz) (KT120, EL34, KT88): 0.2%, 0.14%, 0.25% S/N ratio (200Hz–80kHz): (KT120, EL34, KT88): 81, 79, 81
Input impedance: 100k ohm
Maximum gain: 36.5dB
Power consumption: 255 watts
Weight: 49.5 lbs.
Dimensions: 8" x 14.4" x 15.4"
Durob Audio BV
P.O. Box 109
5250 AC Vlijmen
PrimaLuna USA (U.S. Distributor)
1042 N. Mountain Ave
Unit B PMB 406
Upland, CA 91786
Basszilla Feastrex Edition DIY and Bud Fried Tower speakers; EAR DAC; Sony XA-5400 SACD player with ModWright Truth modification; Kuzma Reference turntable; Kuzma Stogi Reference 313 VTA tonearm; Clearaudio Da Vinci V2 MC phono cartridge; Pass Labs XP-25 phono stage; FMS Nexus-2, Wire World, and Kimber KCAG interconnects; Acoustic Zen Hologram speaker cable; Sound Application power line conditioners