Solid State Power Amp Reviews

Setup
Plinius may surround the Reference A-150's heatsinks with aesthetically pleasing curved metal, but their bottom edges are a little bit sharp. My friend Scott, who helped with installation, had no problem lifting with his hands on either side of the amp, but I kept mine toward the amp's center, where the edges are smoother. Having moved several behemoths lately, it was a pleasure to handle a powerful, full-sized audiophile-grade amp that weighs only 83lb.

We placed the amps on Grand Prix amplifier stands. In place of the RA-150's supplied two-piece height-adjustable feet, I used the same Wilson Audio Pedestals I use under my D'Agostino Momentum M400 MxV amplifiers, with Abramo's blessings. Connection to my Wilson Alexia Vs was a snap.

Let there be music
Ignoring Plinius's advice, I couldn't resist a first listen immediately after hooking up the first RA-150 I received. Kudos to Plinius for speaking the truth. The amp sounded flat. 24 hours later, it sounded reborn. On advice from Abramo, I left the amps on, in class-AB mode, 24/7, so that they'd always be ready for listening.

Once warm-up was complete, it took only a few minutes to notice that in the RA-150's default class-AB setting, the sound is less than compelling. For background listening, this smooth, unobtrusive sound is nigh ideal. But if you wish to do more than set mood and tone for an evening at home, class-A is the path forward for focused listening that puts a premium on sparkle, life, and fine detail.

I went back and forth twice between two RA-150s configured for XLR bridged mono and a single amp auditioned in XLR stereo. In stereo, bass was a mite wooly on Grant Green's "Idle Moments" (24/192 FLAC, Blue Note/Qobuz), the title track from the 1965 album of the same name. Images were less weighty, and colors weren't as unique, differentiated from each other, or saturated as I'm accustomed to. On Rafael Payare and the Orchestre Symphonique de Montréal's recording of Mahler's Symphony No.5 (24/96 FLAC, Pentatone PTC5187067), complex passages sounded a bit congested. I found myself thinking about the sound more than feeling the music. On less-complex material, such as Rickie Lee Jones's never-less-than-amusing standby, "Sympathy for the Devil," from The Devil You Know (16/44.1 FLAC, Concord Records/Tidal), a single RA-150 did a fine job of revealing distinctions between the microphone capturing her voice and the others covering her accompaniment.

It was hard not to conclude that a single, stereo RA-150 would be happiest with speakers less demanding than the Wilson Alexia V. I was tempted to lug my pair of RA-150s to Scott's house to pair them with his less-demanding floorstanders and very different front end, until I realized that once we got them up his narrow stairs without breaking our necks—if we did—there would be no place to situate them properly. That put some sense back into my head.

As the refrain "There's No Place Like Home" played on repeat in my earworm–clogged brain, I switched to two RA-150s in bridged-mono configuration. Voilà la difference! Every instrument in Grant Green's colorful assemblage sounded smoother, warmer in the midrange, and more alive. Timbres of brushes and guitar sounded right, and bass notes were depicted with correct pitch and focus. Highs were not as smooth as through my reference, but then my reference costs $50,000 more. Rickie Lee Jones seduced me into falling in love with the devil without fear of retribution. Virtually every instrument sounded natural—I was especially taken by the sound of a fist knocking on the body of the guitar. I could have used more transparency, air, depth, sense of soundstage boundaries, silence between notes, and smoothness on top, but you must remember what I'm used to. What I did hear was very good indeed.

Bass on David Sylvian's "The Ink in the Well," from the 2003 remaster of Brilliant Trees (16/44.1 FLAC, Universal Music/Qobuz), sounded excellent. The trumpet tooted true, and colors were convincing. Scott, who chose the recording, wanted more space in the presentation. Thoughts of space impelled me to turn to François-Xavier Roth and Les Siècles' recording of Mahler Symphony No.4 (24/96 WAV download, Harmonia Mundi HMM 905347), where period woodwinds sounded lovely, full, and round, but air and depth distinctions were less than expected. On Yello's "Electrified II" from Toy (24/48 MQA, Polydor/Tidal), bass scored mightily for strength, solidity, and timbre.

One of my happiest times with the RA-150s came during the Adagietto from Payare's Mahler Symphony No.5. The blend of low- and middle-pitched strings transformed vibrating steel and resonating wood into a thing of beauty. Jumping ahead to the symphony's ultra-demanding final three minutes, the balanced bridged-mono pair was able to unravel almost all the complex detail in passages where every instrument vies for supremacy and every sound conveys import. Another happy moment came during Postcards from Italy: Italian Music for Film (24/96 WAV download, Chandos). On themes from Morricone's The Mission, Marco Albonetti's saxophone sounded maximally smooth, warm, and heart-touching. If the idea of a saxophone carrying the melody on multiple movie themes seems a bit far-fetched or even unpleasant, the sound Albonetti draws from his instrument may turn your thoughts around.

I experienced equal delight from Richard Rodgers's "The Surrey with the Fringe on Top," sung better than I've ever heard it by Nathaniel Hackman on the new Oklahoma! (24/96 WAV download, Chandos CHSA 5322). Idiomatically performed by the Sinfonia of London and a stellar cast under John Wilson, this recording demonstrated how much midrange smoothness and unquantifiable charm a bridged mono pair of Plinius Reference A-150 amplifiers can deliver.

But what about ...
Comparisons! Comparisons! I hear those calls loud and clear. Scott and I, too, were eager for comparisons—but to what?

One of my favorite amplifiers came to mind, the Rotel Michi S5 dual-mono stereo amplifier ($7499.99). Pricewise, a pair of Michi M8 monoblocks would be a better match, though, at $13,998/ pair, still significantly less than a pair of RA-150s. Alas, no one at Stereophile had either an S5 or a pair of M8s lying around, so those comparisons were not possible. I don't feel comfortable calling forth aural memory to draw comparisons between the Plinius RA-150 and the Rotel stereo amp, which I reviewed with a different music streamer and streaming network, a different DAC, different reference monoblocks, different speakers, different power treatment, different electrical system and network setup, and different room treatment. But I remember it fondly. If you're shopping in this broad price range, the S5 (and its M8 stablemate) would be an alternative to consider.

What I did recall clearly were the wonderful-sounding Accuphase A-300 monoblocks I'd just reviewed. Though much more expensive at $51,900/pair, they are significantly less powerful than the Plinius, rated to produce 115W into 8 ohms or 250W into 4 ohms. Also on hand were my more powerful, much more expensive reference D'Agostino Momentum M400 MxV monoblocks.

Power is not in itself a measure of quality, let alone joy. The Accuphase monoblocks produce a sound so ingratiating, seductive, and satisfying that it puts them in a different class. Whether you find paying an extra $21,000 seductive is another matter entirely. This competition isn't fair.

In summation
As labor-intensive, time-consuming, strenuous, and challenging as accurate measurement can be, it is easier to draw meaning from numbers than it is to quantify feelings. But put together, the two approaches can help shed light on the mysteries of musical reproduction. I look forward to reading JA's technical assessment.

I had many pleasurable listening experiences with the Plinius RA-150. A better match for my speakers in bridged mono configuration than in stereo, a pair of RA-150s delivered abundant midrange warmth, fine bass, true timbres, and emotionally compelling sound. With less-demanding speakers, a single stereo would likely approach this level of performance. If you're in the market for an amp of its quality and price, the Reference A-150 deserves a serious listen.