Sneaking admiration is something I'm more than willing to offer the wily Herman van den Dungen. The crafty old dog has finessed the PrimaLuna ProLogue line into a comprehensive seven-model range using just one main circuit and the same 7.75x11.5x15in (HWD) chassis. He's achieved this by offering the ProLogue One integrated amplifier with KT88s in place of the EL34s to create the ProLogue Two. He then spun off a stand-alone pre-amp, the ProLogue Three, while creating no less than four separate power amps: two stereo models and two monoblocks that differ only in the choice of EL34s or KT88s.
• Read a PrimaLuna Prologue One Integrated Amp Review here.
• Read a PrimaLuna Prologue Two Amp Review here.
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Pistol - a division of Absolute Sounds - supplied the line-level version of the Three and the less-expensive of the two stereo power amps, the ProLogue Four (the one with EL34s). They cost, respectively, £1099 and £799, which places them among some stiff competition - not least the Jadis Orchestra integrated amps from the same importer. While I continue to use the Prologue Two integrated as my entry-level yardstick and have total faith in it, I wasn't quite prepared for the leap in performance evinced by the separates.
PrimaLuna's debut integrated amps revived the decades' old confrontation between the EL34 and KT88 valves [see HFN, June 2004 and March 2005]. Readers with experience of classic amps able to use either tube, or 6550s, for that matter, will have already formed their opinions of the two, and settled on general preferences of one over the other. To spare you searching for the back issues, let's recap on the primary differences in their power amp sections due to valve choice, which will also apply to the ProLogues Four and Five. I wrote that, '...it's about the valves' actual sonic character and even the uninterested would immediately note that EL34s are slightly warmer, more lush, while KT88s are more robust and commanding, and certainly more "modern-sounding" in the lower registers. These two amplifiers from PrimaLuna do not alter that relationship, and if you already have leanings toward either tube type, then you need read no further.'
So, although that inspires you to choose between EL34s and KT88s not on the obvious basis of wattage but according to actual sound, you will also know that - with the PrimaLunas - the KT88's behaviour is not intrinsically superior to the lower-powered, lower-priced EL34. You really do have to audition the Four and Five with the speakers you'd use at home. And as the KT88-equipped Five costs £300 more just for the valve change, you could find yourself saving a chunk of money. So choose with care, not just on assumptions.
To complicate matters - or make them simpler, depending on your faith in my observations - the ProLogue Four with EL34s absolutely thrashes the KT88-equipped Prologue Two integrated amp, including in the areas you'd expect to attribute superiority of KT88 over an EL34. So there's more to separating the PrimaLuna integrateds into their constituent parts than meets the eye/ear: it's not just what serves as the output valves, nor the fact that separate power amps and pre-amps don't have to share power supplies. In this case, it's due in no small measure to the ProLogue Three being something more than merely the pre-amp section of either integrated amp: PrimaLuna has upgraded the pre-amp extensively.
Most obviously, PrimaLuna upped the ante by adding a brace of 5AR4s for full valve rectification; the rest of the valve complements for both the pre-amp and the driver section of the power amps remain pairs of 12AU7s and 12AX7s. Additionally, they made the Three a true dual mono design, with twin toroidal transformers, and it boasts choke regulation. Add that to familiar PrimaLuna practice including designer components like Solen capacitors and ALPS Blue Velvet potentiometers, point-to-point wiring, superb connectors (including two sets of outputs for bi-amping or adding a subwoofer) and you have a seriously well-endowed pre-amplifier by any standards.
But then we come to one other element of the integrated-vs-separates argument. While devotees of the former accept that dedicated power supplies for the pre-amp and the power amp are bound to provide greater performance for the separates - dynamics, power, lower noise floor and more - they do point to something inescapably in favour of the integrated amp: in a single-chassis integrated, the pre-amp and power amp are both perfectly matched, and they talk to each other without a set of external cables and two pairs of connectors tampering with the signal path.
Now I'm not interested in weighing the two, for I have always preferred the separates route just for the added headroom and dynamic behaviour provided by two power supplies over a shared one. Moreover, we all now have so much ears-on experience with cables and connections that the external linking is no longer an issue. Hell, we can even compensate for the presence of sockets and plugs with all manner of slick liquid surface treatments. Whatever the potential for diminished performance when set against an integrated, I settled on the Yter interconnects between the Three and the Four, and the units behaved as quietly and precisely as the integrated Two. (I also used Yter's speaker cable, feeding the 4mm plugs into the Four's rather fine multi-way binding posts; it's fitted with sets for 4 and 8 ohms.)
But what we're looking for is £700's worth of performance above that of the Two. And, oh, do you get it. Not only does the combination seem perceptibly louder, with more robust and extended bass, it also seems to produce a soundstage bigger in every dimension. This isn't a subtle evolution: it's massive.
Whether with my current fave big band release, Kenny Ellis' Hanukkah Swings!, or the majestic swelling of Mendelssohn's 'The Hebrides', the PrimaLuna combo was able to track the dynamic swings without altering scale, suffering clipping or inducing any compression. It even managed this with the rather hungry Sonus Faber Guarneris, but the comfort zone for this combination is something slightly easier to drive. (And here's a tip: if you can't stretch to Quad's new Quad IIs or the QC-twenty-four and II-forty, this package loves electrostatics.)
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In addition to the aforementioned sense of scale and, yes, grandeur, the two pieces together produce a silky sound that's emphatically tube-y without lapsing into the saccharine, chocolate box gooiness of SETs, or of old amps in need of an overhaul. The ProLogues are seriously quick, punchy, but absolutely non-aggressive and able to caress even the most delicate sounds with complete finesse. While vocals were simply authentic enough to convince the listener of their 'reality', it was the reproduction of the harmonics of acoustic instruments that were positively breathtaking. I suspect that sales staff will quickly learn to demonstrate this pairing with unamplified guitar and piano.