Plinius SA-Reference power amplifier
Which brings us to the subject of this review, the Plinius SA-Reference stereo power amplifier ($14,495). Plinius Audio Ltd. has had a presence in North America for more than a decade, though it still is not as well known as its products merit. The company was founded in 1980 by Peter Thomson, and today's Plinius components trace their lineage from 1987, when Thomson was joined by Gary Morrison, of Craft Audio. The parent company was renamed Audible Technologies Ltd., and the Plinius name was retained for its products. Technical director Morrison handles circuit topologies and managing director Thomson oversees mechanical engineering and production. In 2003, design director Ross Stevens joined the team, with responsibility for the appearance of all Plinius products. Over the last nearly 20 years, Plinius has steadily progressed in terms of exposure and expansion into new product areas.
Just the basics, mate
For a number of years, the SA-250, in its Mk.I through Mk.IV iterations, offered outstanding performance and enormous power at a reasonable price. When I reviewed the Mk.IV for The Abso!ute Sound back in 2000, it was one of the few amps that could provide total control of my then-reference Apogee Duetta Signature loudspeakers, bouncing them around the room like basketballs. While a bit soft in the treble—the reports of ears I respect indicated that the SA-250 Mk.IV was something of an overreaction by Plinius to complaints that the Mk.III had been slightly aggressive on top—the Mk.IV had superior midrange performance for any type of circuit, let alone a potent solid-state amplifier, and the best bass performance I had heard to that day and for many after.
In the wake of the development of the modular, multichannel Plinius Odeon home-theater amplifier, Thomson and Morrison discovered that the SA-250 Mk.IV was no longer top sonic dog in the Plinius kennel, and Morrison went to work on a significant update of it. The SA-Reference represents his latest thinking on solid-state circuit designs and is a thorough reimagining of the company's approach to high-power amplifier design. It also offers a power increase over its predecessors, generating 300Wpc into 8 ohms and 450Wpc into 4 ohms—sufficient, I suspect, unless you're running a pair of original Apogee Full Ranges in a castle. If you are, two References can be bridged as monoblocks to deliver 1kW each.
Like all Plinius amplifiers, the SA-Reference uses carefully matched NPN transistors in its output stage. This is unusual, to say the least. As Sam Tellig noted in his discussion of the Plinius SA-102 ("Sam's Space," March 2003), in most solid-state amps an NPN transistor is matched with a PNP transistor to form a matched, mirror-image pair. Morrison's approach of using matched pairs of NPNs results, in effect, in a "more push than pull" output stage, as ST put it. Morrison and Thomson steadfastly assert that this approach is more linear than conventional solid-state designs, and that it allows solid-state sound to have the kind of bloom and palpability that are the hallmarks of tube designs.
Thoughtful touches abound in the SA-Reference, including a ground lift switch on the rear panel, handles front and back to ease the shifting of its considerable bulk, and the ability to switch between class-A and class-AB operation on the fly via a toggle switch on the front. The last is most useful; the SA-Ref runs quite cool in class-AB but very hot in class-A. Additionally, the amp has an internal timer that switches out of class-A after a programmable length of time when no signal is present. So if, like me, you occasionally fall asleep in front of the system, the SA-Ref will not roast you to a turn by continuing to sizzle along in class-A. I did all of my evaluative listening in class-A. The only difference I heard was that the SA-Ref was somewhat less dimensional and fleshed-out in class-AB.
Setup was simplicity itself: the hulking, 125-lb beast was placed on the floor between the speakers, where it crushed the thin carpeting down to the cement slab beneath it. I hooked it up via its balanced inputs.
Thunder from Down Under
When I first heard the SA-250 Mk.IV back in 2000, I was wowed by bass performance the likes of which I hadn't heard before. Until I heard the SA-Reference, it was the finest overall bass amplifier of my experience.
The SA-Reference was significantly better; its bass performance was outstanding in every aspect. Many large solid-state amps can play deeply and powerfully, but the SA-Ref had a down-to-bedrock solidity and groundedness that made nearly every other power amp sound a bit unmoored. The deep-down drum samples at the end of Future Sound of London's "You're Creeping Me Out," from ISDN (UK LP, Virgin VX2755), showed not only depth and control, but a particularly convincing spatial expansiveness.
Acoustic basses had the radiance the instrument possesses when heard in person. Buster Williams' full-sized instrument and Ron Carter's cello-sized piccolo bass each had dead-on tonal structure and natural projection on "Sunshower" and "Blue Monk," from Carter's Piccolo (LP, Milestone M55004). The unique characteristics of both instruments were effortlessly defined. My usual monster electronic-bass silliness from Kraftwerk and Kruder & Dorfmeister was dispatched with offhand ease. The SA-Reference must surely be counted among the finest bass amplifiers extant.
Through the vital midrange, the SA-Ref was unfailingly evenhanded and sweet-tempered. Throughout my extensive listening notes, one phrase appears again and again: natural warmth. Not all that long ago, it would have been nearly unthinkable to describe a solid-state amplifier, much less one of such prodigious power, with that phrase, which was the exclusive property of tube amplifiers. Through the SA-Ref, however, the mellow brass in the third movement of Kees Bakels and the Bournemouth Symphony's recording of Vaughan Williams' Sinfonia Antartica (CD, Naxos 8.5507330) had spot-on roundness, richness, and projection.
Several tracks from Nick Drake's Bryter Layter (CD, Island IMCD 71/846 005-2) provided outstanding examples of the Plinius' capabilities. "Northern Sky" is a benchmark of intimacy and soulfulness. Drake's delicate acoustic guitar and supple, melancholy voice did cause me to think I was listening to tubes. While tubes may give a whisker or two of additional palpability, a skeptic would have to audition the SA-Reference back to back with a superior tube amp to notice the difference. John Cale's vaporous, enchanting celeste on "Northern Sky" was as soothing and gentle as a soft breeze on a warm summer day in the countryside. The flute in the instrumental "Sunday" had a fetching and uncannily lifelike presence in my room.
The Plinius absolutely loved well-recorded voices. Eva Cassidy, Buddy Holly, k.d. lang, Jacqui McShee—all sounded unabashedly marvelous, and the increased intelligibility of previously murky vocals was another standout trait. While Jacqui McShee's crystalline voice has always been easy to follow on "The Baron of Brackney," from Pentangle's So Early in the Spring (LP, Green Linnet SIF 3048), I've always found Bert Jansch's Scots-inflected slurring considerably more difficult to make out. The Plinius let me understand more of Jansch's words than have other amps I've used, even my reference Lamm M1.2 Reference.