Tube Power Amp Reviews

I soon discovered how much the bias changed, depending on the time of day. Between 5 and 10:15pm, tubes biased for 190mV would drop to as low as 183mV. Conversely, tubes rebiased to 190mV at dinnertime would later rise to 196 or 197mV. Because each tube seemed to respond differently to voltage fluctuations, vigilance was essential to determine the correspondence of bias to sound. Ultimately, I contacted our locally owned utility company, which is considering installing a more powerful transformer that will provide more stable voltage during times of peak demand.

I wanted to discover a setting at which the tube-like warmth and sweetness I'd heard during Nick Doshi's visit and at audio shows could be toned down a bit. With the bias centered at around 180mV, I was blown away by the air around Jamie Barton's mezzo-soprano in the Sibelius song "Var det en dröm?" (Was It a Dream?), from All Who Wander (24-bit/96kHz WAV, Delos DE 3494). The way Brian Zeger's piano hung in space on a three-dimensional soundstage was very special. Captivated, I continued. With Mahler's Rückert-Lieder, the Doshis communicated Barton's willingness to venture into the depths of emotional emptiness. I sat mesmerized by her instrument and artistry, hanging on every note.

Turning to Murray Perahia's recent recording of Beethoven's Piano Sonata 29, "Hammerklavier" (24/96 WAV, Deutsche Grammophon 479 8353), I found my enthusiasm tempered by the sound's lack of tonal richness. I raised the bias a bit and a greater variety of colors began to emerge. Now I was inspired to write: "I can hear how much Perahia is aware what this music is saying on emotional and spiritual levels. These amps are so supremely musical."

While experimenting with bias settings, I played a variety of tracks. Among these were: a superbly remastered MQA rendition of the cover of Jim Webb's "The Moon Is a Harsh Mistress" on Radka Toneff and Steve Dobrogosz's Fairytales (24/48 MQA FLAC unfolded to 192kHz, Odin CD9561); Peter McGrath's live recording of the Kalichstein-Laredo-Robinson Trio performing Dvorák's Piano Trio 4, "Dumky" (24/88.2 MQA FLAC); and Gabriella Smith's Loop the Fractal Hold of Rain, as performed by Duo Noire (guitarists Thomas Flippin and Christopher Mallett), from their Night Triptych (24/96 WAV, New Focus FCR210). For material with deep bass, maximum slam, big dynamic swings, and instruments playing in all octaves, I chose Revueltas's Sensemayá, with Werner Herbers conducting the Ebony Band (DSD64, Channel Classics CCS SA 21104), and the maximally contrasting final three sections of Stravinsky's The Rite of Spring, with Ludovic Morlot conducting the Seattle Symphony (24/96 WAV, Seattle Symphony Media SSM1005/HDtracks).

The results were incontrovertible. Through my system, a tube bias of 180mV delivered less-than-ideal weight and color saturation, lightweight bass, and sound that was somewhat gray and drab, if quite detailed and often mesmerizing. As I approached 200mV, colors grew oversaturated, and the sound so unremittingly warm that the music lacked timbral variety—like an overripe Honeycrisp apple whose formerly ideal mix of sweetness and tang had degenerated into monotonous mush. There was no need to go higher or lower: Only when the tube bias centered around 190mV did otherwise somewhat gray areas fill in with different shades of living color, the bass strengthen, and body fully flesh out.

Music at 190mV
Two experiments remained before I could just sit back and enjoy the music. First, I compared sounds as I switched between the Monoblock V3.0s' single-ended (direct) and balanced (buffered) inputs. The buffered inputs delivered multiple levels of "almost as": the sound was almost as colorful, as three-dimensional, as transparent, as bass strong, etc., as through the SE input. If I'd heard the Doshi Monoblock V3.0s fed only through balanced interconnects, I'd probably have thought they were very fine amps. Only through SE interconnects did I grok the full extent of their musicality.

Next, using RCA interconnects, I tried floating the ground. At first I didn't feel this was necessary, because a) I'd never had the ability to float the ground in other amps other than with cheapo cheater plugs, which compromise the terminations of aftermarket power cords; and b) I heard no egregious noise through the Alexia 2s.

On advice from John Atkinson, I put an ear just a few inches from an Alexia 2. From the tweeter I heard a bit of soft zzz, and from the woofers a soft, buzzy hum—both noises were at very low level, sounded virtually identical through both speakers, and were inaudible from 1' away. With the ground floated, all noise was minimized.

When I asked JA what difference this might make from my listening position 12' away, he said it might well have "a subliminal effect." Subliminal my tuchus. Methinks John was giving me room to discover for myself just how much more transparent and color-rich the sound was with the ground floated. All subsequent listening was through Nordost Odin 2 single-ended interconnects between the dCS Vivaldi DAC and Monoblock V3.0s, with the ground floated.

At Its Finest
Finally, it was time to enjoy all the Monoblock V3.0s could offer. Their signature—a warm, glowing, nonfatiguing, well-controlled, finely detailed sound that was a mite bass-shy yet immensely satisfying for its large, remarkably air-filled, 3D soundstage and glamour—brought me huge amounts of pleasure. My preference may be for a more neutral sound with more substantial images and weightier bass, but the Monoblocks fully lived up to Nick Doshi's desire to voice his products for the music lover "who tends to listen to music for long periods of time."

Then I discovered more: the absolute magic the Monoblocks could deliver. This epiphany came on a weekday afternoon when four of my hubby's hair clients visited, including an inveterate music lover who breaks into tears every time he hears the voice of prima donna assoluta Maria Callas. Despite multiple declarations that they had only 15 minutes to spare, the four spent 40 minutes in the music room as I played three long selections by Callas, then sweetened the mix with others by sopranos Carolyn Sampson, Elisabeth Schumann, and Maggie Teyte.

A superbly recorded high-resolution track of the Sleepwalking scene from Verdi's Macbeth, with Nicola Rescigno conducting the Philharmonia Orchestra in 1958, on Callas Portrays Verdi Heroines (24/96 WAV, Warner Classics 634015/HDtracks), made my mouth drop open. I'd never heard so much air around the solo flute in the long orchestral introduction, or so much depth and beauty from the orchestra. But when Callas entered, awe transformed into virtual disbelief. I'd played this track through multiple amps at home (where components change almost monthly), and at audio shows and dealer demonstrations, but I'd never heard such a clear depiction of the different colors of Callas's voice as it ascended from deep chest tones through a somewhat covered midrange to brilliant highs. The dramatic power of every note, the emotional and spiritual impact of every artistic intention fulfilled—and the hot glow of Callas's high range, which could sear when she turned up the heat—were astounding. Some amplifiers better capture the dark dread in her voice, but few can convey the alchemical magic of her singing as well as did the Doshi Monoblock V3.0s.

Not content with one experience of emotional devastation, I cued up two live recordings of Callas: "Tu che invoco," from Gasparo Spontini's La Vestale, with Alfredo Simonetto conducting the Italian Radio Symphony Orchestra Milan in 1956 (16/44.1 WAV from CD, EMI 67917/ArkivMusic); and "D'amore al dolce impero," from a live recording of Rossini's Armida conducted by Tullio Serafin at the 1952 Florence May Festival, remastered in 2017 (24/44.1, Warner Classics 563901/HDtracks). Despite their air-check sound, neither had ever remotely sounded as satisfying as through the Doshis. My God, I could even discern, in the scene from La Vestale, that Callas's final high C was actually sung, not screamed in desperation. Nor had I ever heard Teyte's high notes glow as beautifully as they did that afternoon. When a voice recorded in 1941 glows, it's time to rejoice.

In Comparison
With no other tubed amplifiers in house, I compared the sound of the Doshi Monoblock V3.0s ($35,995/pair) to that of Dan D'Agostino Master Audio Systems' solid-state Progression monoblocks ($38,000/pair). Given that the Progressions put out far more power (500Wpc into 8 ohms), and were designed by the former mastermind of Krell, it came as no surprise that the Doshis' rendering of subsonic bass interjections in "There's a Limit to Your Love," from James Blake's James Blake (16/44.1 WAV, A&M 949999), weren't as literally room-shaking, or the multilayered bass lines in Michael Tilson Thomas and the San Francisco Symphony's recording of Berg's Three Pieces for Orchestra (24/192 WAV, SFS Media SFS0070) as clearly defined or dynamic.

Through the Progressions, the core sound of percussionist Kjell Tore Innervik's bass drums on his Utopias (352.8 MQA, 2L 2L-141) were better controlled and sounded more realistic. Hey, I could even tell that the strange sound near the start of Morton Feldman's The King of Denmark wasn't of Innervik blowing on something—as requested by Feldman, he was instead running some fleshy body part around the rim of an instrument. The ability to convey timbral differences was especially apparent in Lou Harrison's percussion-rich Violin Concerto (24/48 WAV, Naxos 8.559825)—the distinctive sound of Tim Fain's violin was sweeter and less earthy through the Doshis, the colors of the percussion instruments of Angel Gil-Ord¢ñez's PostClassical Ensemble more varied through the D'Agostinos.

But I had an unexpected reaction: Listening to the Progressions, I missed the special glamour of the Monoblock V3.0s' sound. As a music critic who needs a neutral reference, I know which pair of monoblocks best suits my needs. But if I were someone who wanted to throw all caution to the winds, and eat generous helpings of filet mignon and chocolate cake every night instead of tofu stir-fry and sugar-free dessert . . .

Conclusion
The remarkably air-filled, three-dimensional, gratifyingly warm sound of Doshi Audio's Monoblock V3.0 amplifiers demands a place on the short list of amplifier seekers who listen to music for hours on end. There's a special frisson to the glowing sound of these supremely musical amps that elevates it above the usual stereotypes of tube sound. I can't imagine that any audiophile who enjoys the sound of tubed electronics will feel complete without giving them a long audition and—if the heart calls—a new home.