Recommended Components

Editor's Note: Apart from the Bespoke, CAT, and Shindo, all the Class A preamplifiers offer balanced inputs and outputs. And unless noted, the preamplifiers listed do not have phono stages.

A

Audio Research Reference 6SE: $17,000
An updated version of the discontinued Ref 6, with changes in capacitors and wiring, the fully balanced, tubed '6SE impressed JVS, who noted that when he installed the Ref 6SE in his system, his speakers "poured forth some of the most polished, transparent, and arresting sound" he'd heard from his system. Longer-term listening, however, indicated that the Audio Research preamplifier was sensitive to setup issues. Once he had optimized everything else in his system—cables, footers, stands, AC supply—JVS could report that the Ref 6SE's "warmth and vibrancy of color, prominent midrange, and seemingly more dramatic dynamic contrasts made me want to listen more and deeper." In a Follow-Up, JA felt the Ref 6SE's sonic signature, with its slightly softened highs but superb resolution of recorded detail, would work best with systems that are a little laid-back in the upper midrange and that don't have underdamped or poorly defined low frequencies. (Vol.43 No.11, Vol.44 No.8 WWW)

Ayre Acoustics KX-5 Twenty: $9950 ★
The KX-5 Twenty line-level preamplifier enshrines almost all of the proprietary technologies that, in recent years, have put Ayre Acoustics on the map: Its Variable-Gain Transconductance (VGT) circuit adjusts volume not by throwing away varying amounts of gain but by adjusting, at its source, how much gain is created. Its active output buffer is based on Ayre's "diamond circuit" arrangement of bipolar transistors. And its AyreLock approach to voltage regulation creates, in essence, a push-pull power supply capable of turning on a dime in response to the demand dictated by the music signal. All of this is packaged in a non-huge aluminum enclosure described by AD as "tidy and evidently well laid out." Art was considerably less chipper about the KX-5 Twenty's user interface and owner's manual, for which he reserved such words as "unclear," "unneeded," "less than intuitive," and "both need work." He perked up again on hearing the Ayre's "remarkable and utterly nonclinical clarity, and its convincing, commandingly good spatial performance." Measurer-in-chief JA noted in particular the Ayre's "complete absence of power-supply-related" noise and its remarkably low distortion without reverting to loop negative feedback, declaring the KX-5 Twenty "superbly well engineered." In a Follow-Up, comparing the KX-5 Twenty with the similarly solid state PS Audio BHK Signature, JCA noted the Ayre's drier sound and ability to "[carve] out a slightly deeper space," while giving the PS Audio pre the nod for controls and logistics. (Vol.41 Nos.3 & 6 WWW)

Benchmark LA4: $2499 without remote $$$
Benchmark's usual approach to design is to out-spec the competition, and so it is here. Like other Benchmark equipment he has tested, the affordable LA4 challenged the resolution of JA's test instruments, with "superb" channel separation, "extremely low noise, and virtually no power-supply-related spuriae." Restricting his measurement to the audio band, JA found an "astonishing" S/N ratio of 105.5dB for both channels; it remained extremely low across the audioband. He summed up: "Benchmark's LA4 is the widest-bandwidth, widest-dynamic-range, lowest-noise, lowest-distortion preamplifier I have encountered." In his listening room, KR compared the LA4 to a cable—and couldn't hear any difference. He concludes, "the LA4 is probably the most transparent and revealing audio component I've ever used. It does not seem to leave any fingerprints on the sound." See also HR's review of Benchmark's similar HPA4 headphone amplifier (see "Headphones"). JA found that the LA4 had a more upfront presentation than the MBL N11 or Pass Labs XP-32, with less soundstage depth apparent on his own recordings. (Vol.43 Nos.1 & 11, Vol.44 No.3 WWW)

Bryston BP-17³: $4695 ★ $$$
With its five single-ended inputs, two balanced inputs, and mix of single-ended and balanced outputs, the solid state BP-17³ is the middle model of Bryston's three line-level preamplifiers. It can be customized with a variety of add-ons, including a MM phono stage ($750), a DAC ($750), and a remote-control handset ($375). Used with a Mark Levinson No534 power amp (see "Power Amplifiers"), a fully equipped BP-17³ delighted LG with its ability to preserve bass weight and solidity when called for and its no-less impressive recreation of recording-hall ambience. LG wrote that the Bryston "produced engaging, detailed, tonally captivating, utterly natural sound that approached reference quality," while noting that matching with the correct amplifier is critical. JA's report from his lab on the "superbly well engineered" Bryston was similarly to the point: "It is difficult to see how a preamplifier could perform any better on the test bench!" Tests of phono and DAC modules also fared well. (Vol.41 No.6, Vol.42 Nos.6 & 7 WWW)

Convergent Audio Technology SL1 Renaissance Black Path Edition, line-only: $27,995
with phono stage: $29,995 ★
The Convergent Audio Technology SL1, which has grown a long name to match its long life, continues to be revised and refined by designer Ken Stevens. In its Renaissance update, the heralded CAT SL1 line stage received a new circuit-board layout and improved power supply; it was also treated to an A/V bypass, user-selectable gain, and a switch-selectable, moving coil transformer for its optional phono stage ($2000). Compared to its predecessor, the SL1 Ultimate, the Renaissance offered greater transparency, resolution, and dynamics, said RD. JA noted "superb measured performance and an equally superbly linear circuit topology." The most recent (2015) change was occasioned by CAT's development of their Black Path signal capacitor, and named for it; further audio-circuit optimizations and a reduction in noise intermodulation are also among the refinements claimed for the Black Path Edition. After spending time with the SL1 Renaissance, RD pointed to improved rendering of intertransient silence, crisper and tighter percussion sounds, and better transparency and resolution than from the SL1 Ultimate: "I knew I was hearing no minor improvement." (Vol.32 No.11, Vol.38 No.12 WWW)

Dan D'Agostino Momentum HD: $40,000
The two-piece Momentum HD—its power supply is contained within its stand—is an all-balanced, fully discrete, line-level preamplifier with six inputs and two outputs, all via XLR connectors. As with the original Momentum, the HD's aesthetics keep pace with the designs of other D'Agostino creations: Here, the dial at the center of the front panel is a green-lit volume meter, its bezel the volume "knob." Once installed in JVS's system, the Momentum HD brought to a favorite recording of the Shostakovich Symphony No.11 "deeper and more resonant bass and an all-enveloping three-dimensional soundstage that was as thrilling as it was terrifying." He added, "with the Momentum HD, a new window opened, and every recording became a source of wonder." Writing from his test bench, JA noted that the Momentum HD fell slightly short of its predecessor in a few aspects of measured performance yet distinguished itself as "a well-engineered preamplifier." (Vol.43 No.2 WWW)

darTZeel NHB-18NS Mk.2: $53,000 ★
The "stunningly transparent" darTZeel NHB-18NS of 2007 offered spectacular transient speed, resolution, and decay, while providing an overall coherence that "made recorded music, analog or digital, sound much closer to live," according to MF, who added that, with its warm, vivid combination of red case and dark-gold front and rear panels, the NHB-18NS "looks like it sounds." As of the summer of 2008—by which time he'd bought one for himself—MF felt that the battery-powered NHB-18NS matched the resolution and transparency of MBL's 6010 D preamp, while managing to sound less mechanical. Despite the similar name, the NHB-18NS Mk.2 of 2017 is a complete redesign of the Swiss company's preamp but still offers both line and phono stages—the latter, per MF, being "sonically far superior to the original," and more adjustable than many outboard phono preamps of his experience. MF also hailed the new model's digitally displayed volume-control calibration, and the fact that, unlike that of its predecessor, the new model's batteries "have never run out of juice during a listening session." According to Mikey, the new darTZeel's phono section sounds "neither as transparent nor as dynamic" as the far more expensive outboard Swiss Precision P1 ($31,000 without additional power supply) or Ypsilon VPS-100 Silver Edition ($65,000). That said, with the "tube-like richness and generous flow" it inherited from its forebear, the Mk.2 "will more than satisfy casual vinyl listeners." (Vol.30 No.6, Vol.31 No.10, Vol.33 Nos.5 & 10, Vol.40 No.6 WWW)

Esoteric Grandioso C1X: $45,000
When tastefully illumined by the adjustable blue LED lighting of its separate power supply, the dual-mono, fully balanced Grandioso C1X line preamp "looks like a million dollars—which, given its healthy price tag, it should," wrote JVS. But even if Esoteric's attention to detail had not convinced him that the C1X was a class act, its sound would have, and did. "The C1X delivered bass every bit as mouthwatering and thrilling as I've come to expect from my system," he wrote. Overall, the Grandioso C1X "could very well be the keeper, the component that delivers a lifetime of joy and pleasure," he concluded. "It is one of those rare products whose excellence is proclaimed with every note. It is more than an object of beauty; it reaches into the emotional core of musical experience and opens a window onto ultimate truth." JA was similarly impressed when he got this Japanese preamplifier in his test lab, writing "Esoteric's Grandioso C1X offered superb measured behavior. Its extraordinarily low levels of distortion and noise rival the performance of contenders from Benchmark, MBL, and Pass Labs." Asked for his rating, JVS says, "If there's an A+ category, it belongs there." There isn't.(Vol.44 No.7 WWW)

Lamm Industries L2.1 Reference: $28,990 ★
The greatest accomplishments of Vladimir Lamm's electronics are like those of the art restorer who removes grime and soot without diminishing the vibrant colors beneath—so believes AD, who said of Lamm's latest line stage, the two-box L2.1 Reference, "[it] reproduced the sounds of bowed and plucked strings alike with color, texture, and humanness." The Lamm does so with an unorthodox combination of technologies: high-voltage MOSFETs in the all—single-ended gain stages; and tubes throughout its power supply, for rectification, regulation, and the amplification of voltage references. The L2.1 Reference, which differs from its predecessor in its use of new current-source transistors and other recently available components, offers switchable signal-phase inversion and easily adjusted channel balance—the latter thanks to its dual-mono volume potentiometers—and further delighted AD by eschewing remote control. His verdict: "the rare product that swept the question of tubes vs solid state into insignificance." Writing from his test bench, JA noted the Lamm's "extraordinarily low" distortion and observed that, "like the other preamplifiers designed by Vladimir Lamm that have passed through my test lab, the L2.1 Reference is well engineered." In his Follow-Up, JVS noted that the L.2.1's presence in his system extracted the best from the Bricasti M15 stereo amp (see "Power Amplifiers"), writing that "the L2.1 did a bang-up job with percussion, restored the horns' natural bite and heat, and enhanced the three-dimensionality and musical intensity." In a different context and with a different recording, he acknowledged that the Lamm "toned down and softened a smidge" the natural edge on a singer's voice while adding, "That is not necessarily a bad thing." (Vol.40 No.7, Vol.41 No.7 WWW)

Luxman CL-1000: $19,995
AD described the massive, full-function CL-1000 as the "antithesis of a bare-bones, 'purist' preamplifier." It uses six E88CC dual-triode tubes in its transformer-coupled output stage, as well as FETs in the single-input phono stage and solid state devices in the power supply's rectification and regulation circuitry. One thing lacking was a remote control, much to AD's joy! Playing LPs, the Luxman appeared to have a flatter frequency response than Art's reference Shindo Monbrison preamplifier and sounded altogether more serene—"but along with that," he wrote, "was also a sense that the Luxman's audible range was a bit more spread out, from bass to treble." AD's auditioning notes included such comments as "Listening to this record through the CL-1000 was a spellbinding, wholly engrossing experience" and "The music had flow and, where appropriate, drive." The Luxman "is simply a hell of a good product, at a high but not unreasonable price," concluded AD, adding "I loved every minute with it." (Vol.43 No.5 WWW)

mbl Noble Series N11: $14,600
This beautiful, multiple-input, multiple-output line preamplifier can be used in its Unity Gain mode for maximum sound quality or with a higher-gain setting. JVS found that the N11 in its higher-gain mode "brought out the warm core of every note," adding that it enabled him to hear "the subtle differences of interpretation, dynamics, and color that are the portals to the truth behind the notes." He found that Unity Gain moved the soundstage farther back in his system with his D/A processors. While perspective was clarified, this mode made the sound less open with slightly reduced transparency and bass. Ultimately, he felt that the N11's Unity Gain "toned down the noisy top ends of some recordings, making for easier listening." The N11's measurements revealed extraordinarily low noise and distortion, especially in Unity Gain mode. However, the CD input's unbalanced impedance of 2.3k ohms will tax sources with a tubed output stage. Those can be used with the balanced inputs or the unbalanced Aux inputs, which have impedances of 10k ohms and 47k ohms, respectively. To his surprise, JA found that inserting the N11 between his DAC and power amplifiers resulted in a more palpable presentation, with a deeper soundstage. (Vol.43 Nos.7, 11 & 12; Vol.44 No.3 WWW)

Pass Laboratories XP-22: $9500
The two-box, solid state, line-level Pass XP-22 provides both balanced (XLR) and single-ended (RCA) inputs and outputs, plus a vestigial tape loop. The XP-22's volume control—an Avago-sourced encoder that JCA describes as having "good bearings and a nice feel"—is the same one used in Pass's upmarket XP-30, and balance is adjustable via a chunky metal handset that "duplicates all front-panel controls, and then some." JCA heard "impressive" bass impact, "pinpoint" imaging within a large soundstage (albeit one that shrank a little at lower volumes), and sound that "seemed a tad more open" than with his reference preamp. In measuring the XP-22, JA found "superb" channel separation, "extremely low noise," an "excellent" (85.35dB) audioband S/N ratio, and "extremely low" THD+N: "superb measured performance." (Vol.42 No.6 WWW)

Pass Labs XP-32: $17,500
Replacing the well-regarded XP-30, the three-box XP-32 looks almost identical. To minimize noise, each channel's audio circuitry is housed in a separate chassis with the "dirty" control and power-supply circuitry in a third. Internal improvements include new transformers and DC-coupling of the balanced and single-ended inputs. The output stage runs a higher class-A bias with lower output impedance than the XP-30, and the volume control now operates in 0.5dB steps rather the earlier preamp's 1dB steps. JA was enthralled by the XP-32's transparency, hearing small details in his own recordings that he had not been fully aware of before. "A great preamplifier will allow through so much information, so much of the music, that the shortcomings of lesser speakers and amplifiers can be forgotten. The Pass Labs XP-32 satisfies that definition," he concluded. (Vol.44 No.3 WWW)

PrimaLuna EVO 400: $4999
PrimaLuna's brand-new flagship line-level preamp—it replaces the company's DiaLogue Premium—the EVO 400 uses tubes for rectification as well as for gain and buffering, and includes input and output transformers that allow balanced operation. Noting that its extraordinary weight (52.8lb) comes not from its steel chassis but from its abundance of power-supply transformers and chokes, HR praised the EVO 400's very high parts quality and lavished similar praise on its "scintillating" presentation and ability to portray vivid, well-saturated musical colors while nevertheless being "more concise-sounding" than its predecessor in the PrimaLuna line. "It generated clearer, more muscular presentations with sharper focus and more distinctly punctuated momentums." Reporting from his test bench, JA noted that "the EVO 400 measures well for a tubed design." (Vol.42 No.7 WWW)

PS Audio BHK Signature Preamplifier: $5999 ★
Like its stablemate BHK Signature 300 monoblock amplifier, the BHK Signature preamplifier is named for its designer, Bascom H. King. Also like that monoblock, the BHK Signature preamp is a hybrid product, using both transistors (N-channel MOSFETs, also as in the BHK amp) and tubes (two 12AU7 dual-triodes, also put to work in the preamp's distinctive volume-control system, whereby some sound-level increments are achieved not through changes in resistance but through changes in tube-stage gain). Ten line-level inputs are divided evenly between single-ended (RCA) and balanced (XLR) jacks—there is no phono stage—as are the two outputs. Apart from noting that the above-mentioned volume-control system emitted an occasional, barely perceptible noise that was ultimately masked by the music, JCA was impressed: after comparing the BHK Signature with nothing at all—that is, with the sound of a system in which a DAC drove a pair of PS Audio BHK Signature 300 monoblocks directly—JCA wrote: "With the BHK Signature preamplifier in the system, the music seemed more lively, and the space in which the images were cast was more tangible." Writing from his test bench, JA observed: "this preamplifier measured superbly." In his June 2018 Follow-Up, JCA compared the BHK Signature—now his reference—to the Ayre Acoustics KX-5 Twenty, noting that, by comparison, the PS Audio "softened … transients just a touch, slightly polishing the edges." But he found much to enjoy in both, and declared his BHK Signature "honest and musical." (Vol.40 No.6, Vol.41 No.6 WWW)

Rogue Audio RP-7: $4995
This line-level preamplifier uses four 12AU7 dual-triode tubes and contains 17 (!) separate power supplies, including an individual regulated filament supply for each tube. Its military-spec circuit board is endowed with heavy copper traces and graced with an abundance of Vishay HEXFRED diodes, Vishay resistors, and Mundorf oil-caps. The Rogue's rear panel is itself abundant with connectors: three unbalanced (RCA) line-level inputs, two balanced (XLR) line-level inputs, and two each unbalanced and balanced outputs, following the same connector conventions. The front panel is notable for more than just its single 1/4" headphone jack and its old-school volume knob: It also includes a Balance knob, which HR loved. Used in conjunction with HR's First Watt SIT-3 solid state amplifier, the Rogue preamp delivered "a superbly balanced and invigorating—nay, intoxicating—system that didn't sound like tubes or solid state. But it did reproduce, with extraordinary weight and saturated tones, my latest favorite piano album." Herb's conclusion: "My new reference." In measuring the RP-7, JA found that, "as long as it's driving a power amplifier with a high input impedance, Rogue's RP-7 offers generally respectable measured performance." (Vol.42 No.3 WWW)

Rotel Michi P5: $3999
This versatile, heavy preamplifier—it weighs 50.5lb—features tone controls and a full array of inputs: Bluetooth with both aptX and AAC support; USB and S/PDIF digital: balanced and singled-ended analog line; and MC/MM phono. It also supports MQA. There are analog, digital, headphone, and subwoofer outputs. Playing LPs with his EMT MC cartridge, KM found that "every instrument was portrayed as a clear, distinct, meaty line, with solid … tone and precise, stable placement within the soundstage. On record after record, regardless of genre or format, every musical line was clear, illuminated, and precisely located." His experience with MQA files streamed from Tidal via the P5's USB input was very positive, writing that "this DAC and MQA were sending me musical information I'd never heard before." KM concluded that, paired with the right power amplifier, the P5 created a deep soundstage with excellent spatial qualities. "It performed with great clarity, good tone and dynamics," he wrote, "and always left me satisfied and wanting to hear more." In the lab, the Michi P5 offered superb measured behavior via its line-level analog inputs and its USB digital input. The TosLink and coaxial S/PDIF digital inputs suffered from relatively high jitter, however. (Vol.43 No.11 WWW)

Shindo Monbrison: $12,900 ★
Some months after the death, in 2014, of founder Ken Shindo, Shindo Laboratory's long-lived, second-least-expensive preamp, the Monbrison, vanished from the line—a consequence, many presumed, of the company's having run out of Monbrison-specific enclosures and other parts. Soon after, their next-most-expensive preamp, the Masseto, also disappeared. Both products have now been replaced by an all-new preamplifier: a Monbrison in name but a Masseto in function. (Unlike the Monbrison and like the Masseto, the new model uses output transformers.) The new Monbrison is also the first of Shindo's full-function preamps (including both line and phono stages) to be designed by Ken Shindo's son, Takashi Shindo, who departed from previous Monbrisons by eliminating one of two sets of phono inputs (and onboard step-up transformers) but retaining their use of ECL 94S triode-pentode tubes for line-level gain and 6X4 diodes for rectification. Shindo's signature steel casework endures, but now the Monbrison's enclosure is a two-level structure, as in the company's most expensive preamps. After a lengthy break-in period in AD's system, the Monbrison "demonstrated nuances of expression I've never heard from the Masseto: The new Monbrison doesn't just convey momentum—rare though that talent is in the larger context of consumer audio—but begins to hint at the emotional and intellectual energies of the players." AD added that the Monbrison is "realistically, generously colorful and expresses sonic textures convincingly and without etch." He praised it for providing "greater listening pleasure than any other preamplifier I've had in my system, save for the considerably more expensive Shindo Vosne-Romanee." (Vol.40 No.9, Vol.43 No.5 WWW)

Sugden Masterclass LA-4: $4650
Sugden's solid state, line-level-only Masterclass LA-4 offers four single-ended (RCA) inputs and one balanced (XLR) input, with outputs of both of those types. (The circuitry is fully balanced overall.) Gain is generous—JA would measure ca 20dB, single-ended or balanced—with signal attenuation courtesy of an old-school volume control. With the Sugden in his system, JCA noted "more ambiance with good recordings" than through his reference PS Audio preamp, but also "a touch less body." Overall, the Masterclass LA-4 "subtly illuminated the music" and "preserved subtle soundstage cues." JA's measurements uncovered lower-than-specified output impedance, thus indicating good compatibility with a variety of power amps, but a "disappointing" wideband S/N ratio. (Vol.42 No.4 WWW)

The Bespoke Audio Company Passive: $16,000 and up
As reviewed: $23,235 ★
Built around a stereo pair of hand-wound, multitapped transformers, the Bespoke Audio preamplifier—which provides attenuation and source selection, but no gain—is a passive line stage that exudes an "unsurpassed" level of quality, according to AD. While declaring that he is not normally a fan of passive preamps, owing in particular to a paucity of musical impact in systems so equipped, AD noted that the Bespoke unit was better in that regard than he expected, and that its use brought enhanced clarity to some recordings; Bespoke Audio has, he believes, offered "the best justification yet" for the passive approach. In the June 2019 Stereophile, MF wrote of borrowing a version of the Bespoke passive pre with all-silver-wire transformers and Furutech Rhodium input and output XLRs ($23,235), praising its "black" backgrounds and declaring it "the most beautiful" high-end product of his experience. (Vol.38 No.10, Vol.42 No.6 WWW)

Zesto Leto Ultra II: $10,900
This well-engineered, tubed line preamplifier offers single-ended, transformer-coupled balanced inputs and outputs. A unique "Presence" control knob applies high-frequency rolloff with five choices of corner frequency. KM liked what he heard, writing that the Leto Ultra II was one of very few preamplifiers he's had in house that in some ways equaled his long-term reference Shindo preamplifier. "Record after record, the Leto Ultra II's neutrality, transparency, and recovery of the last iota of sustain gave fresh insight into familiar recordings," he wrote, concluding that "Superbly clean and transparent, the Leto Ultra II's midrange-to–upper treble focus and lucidity was off the charts, giving fresh insight to familiar LPs. Silky and smooth, its tone was also good." In a Follow-Up, JCA explored the effect of the Presence control and found that the top three settings, which progressively roll off the top octave, were beneficial with recordings that had highs that had been balanced on the hot side. JCA was also impressed by the Leto's overall performance, writing: "This is a preamp that wears its tubed nature lightly, imparting a slight creaminess on the sound while giving up little in the way of transparency. Instrumental timbres remained natural and soundstage depth was preserved." (Vol.44 Nos.2 & 9 WWW)

Editor's Note: There are currently no Class B, C, and D preamplifiers listed.

Deletions
Rogue Audio RH-5, not auditioned in a long time.