Tube Preamp Reviews

With Sony MDR-Z1Rs: Although relatively sensitive (100dB/mW), Sony's MDR-Z1R headphones ($2299) thrived on the RH-5's gain and power: 16dB maximum, and 1.75W into 60 ohms. The Rogue brought out a taut athleticism that made the Sonys seem more fleshed out and three-dimensional than through either the Linear Tube Audio MZ2 ($1235) or Sony's own headphone amp, the TA-ZH1ES ($2199). It made the Sonys dance and play with a powerful, focused character.

With the Pass HPA-1, the Sony MDR-Z1Rs sounded smooth and precise—perhaps to a fault. In contrast, the Rogue brought to my experience of the 'Z1Rs big doses of sparkle and bold life. The Rogue's extra gain seemed to firm up the 'Z1Rs' bass and midrange. Stringed instruments of all types sounded richer, more full-bodied. The upper midrange moved from slightly set back to slightly forward (tubes can do that). The Sony MDR-Z1Rs are surely one of the best closed-back, over-ear headphones ever; the Rogue RH-5 helped me realize that.

With HiFiMan HE-1000 V2s: It didn't seem possible, but the HiFiMan HE-1000 V2s ($2995) were even more transparently revealing with the Rogue headphone amp than with the MZ2. This unmasking improved the already splendid texture, viscosity, and flow of the HiFiMans' sound. The RH-5 made them sound less like headphone hi-fi and more like something real. LPs, such as Sun Ra and his Arkestra's Super-Sonic Jazz (Saturn SR-LP-0216), evinced an enjoyably vivid, almost grainless sound. Small-scale dynamic contrasts were enhanced, making instruments sound more 3D. The HiFiMan HE-1000 V2s are surely some of the world's best headphones, and the RH-5 made me admire them more.

With JPS Labs Abyss AB-1266 Phis: All summer, I've been lost in two worlds: the hypernatural realm of the Abyss AB-1266 Phi headphones ($4495), and the authentic dirt-floor humanism of Alan Lomax's field recordings. Prison songs, badman ballads, breakdowns, shouts, and hymns suit me better than jazz and cocktails. Lomax's simple one- and two-microphone recordings are intimate, beautifully focused, and unprocessed.

Folksinger and poet Neil Morris coughs between verses of "Anything," from Southern Journey, Volume 7; a truck can be heard shifting gears out on the highway; his guitar sounds wooden and lifelike and about 6' from the mike; in short, Morris was standing right in front of me. With the Abyss AB-1266 Phis, I could see the entire room and all that Southern light pouring in through the window.

Throughout my listening to Lomax's Southern Journey with the JPS Labs 'phones, the Rogue unmasked a lot more information than any other headphone amp I've used, except Woo Audio's WA5. Nonetheless, the RH-5 unearthed deeper, tighter bass than the Woo. Its midrange revealed the bodies behind the voices, and it found more solid detail in the top two octaves. But it couldn't match the Woo's articulation of voices, truth of timbre, well-drawn spatiality, or the earthy naturalism of its midrange. For me, the Woo WA5 remains the amplifier of choice for the Abyss AB-1266 Phis.

Headphone Listening: Comparisons
In terms of price and circuit design, the hybrid RH-5 ($2495) is squarely between Linear Tube Audio's all-tube MZ2 ($1235, formerly called the microZOTL2.0) and Pass Labs' solid-state HPA-1 ($3500).

The most obvious things I noticed while comparing the Rogue RH-5 with the Pass Labs HPA-1 were:

The HPA-1's refined sophistication exceeded the RH-5's by some margin.

The RH-5's higher gain and lower output impedance gave it an electromechanical advantage over the HPA-1 when driving planar-magnetic headphones. With a few less-sensitive planar-magnetics, such as JPS Labs' old Abyss AB-1266es, Audeze's LCD-4s, and HiFiMan's new Susvara (review in progress), I would sometimes run out of gain at moderate volume levels. That never happened with the RH-5.

The HPA-1 produced broader, deeper, more articulated aural spaces—but they were less physically tangible, less attractively lit than the RH-5's slightly smaller spaces. The HPA-1 never quite achieved a state of vibrancy—the RH-5 was vibrant all the time. These differences could easily be attributed to the Rogue's extra gain and lower output impedance, and the glow of its 12AU7 voltage amplifier stage.

The exceptionally natural sound of Linear Tube Audio's MZ2 allows voices and instruments to inhabit spectacularly transparent spaces. The MZ2's overall sound is dynamic and luminous, but less dynamic than the Pass Labs' or the Rogue's.

Impressively, the Rogue RH-5 combined a large measure of the sophistication and refinement of the HPA-1 with most of the luminous transparency of the MZ2, while adding generous doses of punch and vigor.

Not surprisingly, each of these preamp–headphone amps made recordings sound like what they're made of. Linear's MZ2 displays all the spacious, colorful, transparent beauty of a pure tube design. The Pass HPA-1 delivers the precision and innate charm of MOSFETs coupled to the brilliant descriptiveness of JFETs. The Rogue RH-5 does tube glow, coupled to the increased damping factor of a low-output-impedance MOSFET-follower.

Listening to Vinyl
For months now, AMG's Giro G9 turntable and 9W2 tonearm ($10,000) have been my daily excitement and reference. I use them with an EMT TSD 75 moving-coil cartridge ($1950) and an Auditorium 23 step-up transformer ($975), connected to the moving-magnet input of a Tavish Design Adagio phono stage ($1690). This combo sings with charm and precision.

As the sun rose on a warm July morning, I listened to Moondog's The Viking of Sixth Avenue (LP, Honest Jon's HJRLP18), and imagined what Moondog must have looked like busking on the sidewalk near Carnegie Hall. I was fascinated by how effectively the AMG–Auditorium 23–Tavish chain displayed the pulsing clouds of reverb that inhabit every track on Viking. This front end, used with the RH-5, made the recording feel completely exposed, wide open for scrutiny. Moondog's gongs and woodblocks, the trucks on Broadway, the horns of East River tugboats, never sounded more like themselves.

The Rogue RH-5's optional phono stage ($400) is identical to the one in Rogue's RP-1 preamplifier, which I reviewed in the August 2016 issue. Could it even approach this level of audio insight?

With the Auditorium 23 SUT connected to the RH-5's MM input, Moondog and his drums and cowbells all became more corporeal, but a goodly measure of the reverb had vanished, its artificial ether replaced by a kind of studio-monitor directness. I could feel Moondog's wooden flute only inches from the mike, but the air around it was reduced. Suddenly, every voice and instrument sounded closer to its mike. Voices were very slightly more intelligible. Bass felt denser. But unfortunately, tugboats and traffic sounded less like themselves. The soundstage was smaller, low-level textural and tonal information diminished.

The new remastering and remix of the Beatles' Sgt. Pepper's Lonely Hearts Club Band (LP, Parlophone PCS 7027) had agreeable authority through the RH-5's phono stage—but compared to the much more expensive Tavish Adagio ($1690) and Parasound Halo JC 3+ ($2999) stages, it sounded a little blunt and prosaic. Happily, the Beatles sounded bigger and richer, more detailed and vivid, with the EMT TSD 75 cartridge plugged straight into the RH-5's MC stage set to a load of 250 ohms.

Folks, the Rogue RH-5's MC phono stage is a super value at $400. It conveyed signals from the EMT TSD 75 ($1950), Hana EL ($475), and AMG Teatro ($2749) cartridges with more realistic weight and dynamic assurance than either of my more expensive phono preamps.

Conclusions
When Sphere and I finally compared the results of our separate auditions of Rogue Audio's RH-5, it was obvious that we shared two conclusions:

1) Because many of today's best headphones use low-sensitivity planar-magnetic drivers, which require an amp with low output impedance and high power output—and the RH-5 is just such an amplifier—the questionable drive capabilities of most headphone amplifiers might be limiting these headphones' potential.

2) Because of its full-bodied sound, selectable gain, and extraordinary ability to drive low-sensitivity headphones, the Rogue Audio RH-5 is an important new high-value product.

Best of all, my meandering investigations have answered my opening questions in the affirmative: The Rogue RH-5 was able to resolve subtle differences among components under review. It will make an effective anchor at the center of my reviewing practice—just as I'd hoped it would.