December 2021

Primus Inter Pares:
Audionet's Category Smashing HUMBOLDT Integrated Amplifier Review
First amongst equals.
Review By Maurice Jeffries

  If review beginnings also function as narrative endings, let me begin this review with a simple summative declaration: Audionet's stunning HUMBOLDT integrated amplifier re-imagines from the ground up how to design a modern integrated amplifier and recalibrates our expectations of what such a device can deliver musically. Boasting unparalleled build quality, a superb set of user interface features, and transformative sound quality, this super-integrated argues without equivocation that the best single-box amp-preamp solutions need not compromise on sound quality compared to similarly priced separates. In the universe of expensive integrated amplifiers, HUMBOLDT sits amongst its peers as a primus inter pares device of extraordinary ability.

The break-neck upward trajectory of the Audionet product line performance-wise has been astounding.  U.S. listeners and reviewers got their first real taste of the Audionet experience (meaning the brand's seamless sonic amalgamation of the extension, transient speed, and dynamic expressiveness of the best solid-state devices with the air, light, bloom, and tonal expressiveness that until recently remained the sole province of the best tubed designs) with the domestic release of the remarkable PRE G2 linestage and MAX monoblock amplifiers several years ago.

Our own Senior Editor Greg Weaver continues to wax poetic over the performance of the PRE G2 linestage and MAX monoblock combo that serve as his long-term references. I added my voice to the Audionet chorus by singing the praises of the firm's stunning little WATT integrated amplifier for Positive Feedback back in 2018.

Not content to rest on the laurels of the MAX / Pre G2 success story, the Audionet team threw down the solid-state electronics gauntlet with the 2017 release of its Scientist Series reference level product line. More than a handful of reviewers and audiophiles who have had the good fortune to hear these remarkable devices for an extended time rank them amongst the finest products of their type in the world. Like its separate Scientist Series stablemates, the awe-inspiring Humboldt makes a damn compelling case for its inclusion on any best-of-the-best list of reference grade integrated amps.

This is not to say that the HUMBOLDT is without peer in the integrated amplifier universe. For starters, I have no way of supporting such a bold proposition. I've not heard everything out there and never will. Moreover, the Audionet does have legitimate competitors in the hyper-audio universe in select performance categories. The MolaMola Kula ($25,000 with onboard DAC and phono stage) rivals the HUMBOLDT in harmonic sweetness and sheer musicality, although the Kula lacks a dedicated output, excluding that unit's use with separate power amps.

The big amp's baby brother, the superb WATT integrated amplifier, approaches the HUMBOLDT in overall sound quality, but comes off as just a tad less neutral and a smidgeon less authoritative in scale and grip. The CH Precision I1 integrated that I have heard at shows impresses with its stunningly natural resolution of musical detail, its remarkable transparency, and its unparalleled level of user flexibility.

Overall, however, no integrated amplifier in my experience matches the HUMBOLDT's extraordinary build quality, its overall sonic prowess, or its preternatural ability to tease the best from speakers of all types. It is an integrated amplifier suitable for most if not all seasons and situations.

That last bit requires a little explaining on my part. First, and for obvious reasons, the HUMBOLDT requires loads of space. Ideally, a perspective owner should mount the unit on the top shelf of a well-built audio rack capable of supporting the amp's gargantuan 450 x 320 x 505mm dimensions and back-breaking 134.4-pound mass, or on the floor between their main speakers (as I did for this review). Second, particularly if you live in an apartment or condominium (as I do), make sure that your mains lines can deliver the clean power that this beast demands.

On a couple of instances, my subpar power delivery lines sagged below levels deemed acceptable by the amp's sophisticated protection circuitry. Blessedly, Audionet's advanced protection architecture automatically placed the amp into standby mode and alerted me to the specific problem via a warning message that appeared on the illuminated front panel screen in bold red lettering. No blown fuses or smoking internals; just a subtle reminder not to feed this beauty shitty power.

In all my years I have never, ever encountered a product that boasts this degree of sophisticated protection circuitry. Bravo, Audionet.

Function Liberating Form
Readers familiar with Audionet's superb Scientist Series electronics (specifically the Stern preamp and Heisenberg mono amps) will immediately recognize HUMBOLDT 's imposing form factor as a chip off the old family block. The HUMBOLDT most closely resembles the firm’s celebrated Stern preamplifier in physical form. (Please note that Audionet does not offer a separate downloadable manual for the integrated. Users must use the Stern manual instead).

Designed by celebrated German industrial designer Hartmut Esslinger, founder of the Frog Design Group and best known globally for his work with Apple, the HUMBOLDT screams quality and cost-no-object build. The Floating Pane Design, a brilliant architectural sleight-of-hand that eschews the "hewn from a solid aluminum block" structure in favor of six massive ribbed and floating aluminum panes secured to an aluminum frame by resonance-optimized pads, minimizes microphonic distortions, and gives the amp its industrial-flavored good looks.

Beneath its Stern-inspired exterior lies a beast of extraordinary power and sophistication. As one would expect, the HUMBOLDT features a slightly scaled-down version of the preamp section from the Stern and the amplifier architecture of the Heisenberg mono amps. Highlights, of which there are too many to list here, include:

If all of this seems like overkill, the end-product represents overkill executed with a ruthless, single-minded, category-redefining intent. Chief amongst core design goals was the elimination of detail-robbing, image distorting, micro-dynamic sapping microphonic distortions. Not only does the amp feel as if hewn from solid steel on the outside. Its interior layout reveals an equal level of fanaticism when it comes to banishing chassis and component resonances.

Take the massive primary and smaller secondary power transformers, for example. Each encapsulated steel transformer rests securely on mounting assemblies made of stainless steel to keep things nice and quiet. Or the analog circuits, each galvanically separated by "optocouplers" to minimize noise and prevent current flow distortions. Or DC coupling of critical circuits with no sound diminishing capacitors or coils and extremely short signal paths. I could go on, but you get the picture.

Everything inside this amplifier, as well as the brutishly handsome exterior, has been mechanically optimized to eliminate detail-robbing resonances. The net result, as I explain below, is like nothing that I (and I suspect most of you) have ever heard before.

The Sound Of The Room
As I teased above, the HUMBOLDT's musical prowess matches its over-the-top build quality and brawny dimensions. All of which adds up, paradoxically I should note, to a sonic presentation that at first left me scrambling for words to describe what I was hearing. In all fairness, I had a similar experience back in 2018 when I reviewed Audionet's stellar WATT integrated amplifier, the baby brother to the HUMBOLDT. In that review, I praised the little WATT for appearing to have no intrinsic sound of its own.

The problem with hearing (and experiencing) an almost noiseless component is that any impressionistic language used to describe the experience invariably focuses on how the component in question makes everything else sound and perform, not on the sound of the component itself.

As I have said before, with most devices, even expensive well-engineered gear, over time one typically hears the subtle colorations and distortions of various sorts, however subtle, that give that component its unique sonic footprint. A splash of honey-scented warmth here, a gentle bit of frequency contouring there; a touch of mid-bass fullness here, or by way of contrast, a sliver of whitish grain over there. Take your pick!

Invariably such colorations (or coloration combinations) rear their off-putting or pleasing sonic heads, thereby making the coloration(s), and more importantly, the component itself, sonically visible.

If the WATT banished any detail-glossing, time-smearing, color-robbing, dynamics-suppressing distortions to near nothingness, leaving behind only a narrow band of upper midrange-lower treble sweetness in its sonic wake, the HUMBOLDT sweeps away any trace of an overt audible "footprint" altogether. Frequency extension, from top to bottom, seems limitless, the amp's measured figures substantiating what I heard in the listening room.

As icing on the cake, the amp retrieves the subtlest of recorded details with a precision and focus to rival the world's best electron microscopes, unearthing hidden textures and lyrical strands from familiar digital and vinyl sources alike. And it scales dynamically to meet the demands of even the most densely orchestrated classical recording with a speed and composure that at times makes the best of the breed sound alarmingly real and in-the-room present.

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Two loudspeaker pairs fell under HUMBOLDT's black hole-like gravitational grip: the Focal Sopra No. 1 stand-mounts, my long-term compact references, and the newly-arrived Von Schweikert Endeavor Special Edition floor-standers. The HUMBOLDT teased the best from each speaker I used, but it was the amp-Endeavor SE combination that created the real magic. With a quoted bass response that dips to 28 Hz, the Endeavor SE, when powered by the HUMBOLDT, played with a grace, ease, and sheer sense of scale and drama that proved arresting.

As you might imagine, well-recorded classical fare featured prominently in my listening sessions. The amp's preternatural grip, dynamic expressiveness, scaling, and singular ability to sculpt laser-focused three-dimensional images from thin air mated superbly with the VSA speaker's transient speed, airy top-end, and piston-precise low-end, the combo unraveling with ease the densest, most demanding tracks I could find.

With large-scale works, the HUMBOLDT delivers reference-caliber immediacy and focus, but usefully adds massive doses of dynamic expressiveness, gravity-defying control over the speaker drivers, and unlimited extension and tonal weight. On recordings demanding this heightened degree of power and impact, say Bernstein's delightful reading of Mahler's Fourth, (Mahler: Symphony No. 4 in G Major [Sony/Columbia]), one has the real sense of gazing into the recoded venue (the Manhattan Center recording studios) and feeling the air swirling and pulsating like a living thing. The net effect is a bit like peering through a freshly cleaned picture window of enormous proportions.

But the big Audionet does something, particularly in the sub-40Hz range, that I don't recall experiencing with the smaller WATT. Simply stated, the bigger amp's electro-magnetic noise reduction strategies, magnetically and capacitively optimized circuits, and resonance-dampening build so lowered the noise floor that bass notes seemed to emerge from beneath the floor of my compact listening room. This class-leading clarity, reach, and pitch accuracy in the bass enhances sound staging and imaging to near-reference levels.

Pair the HUMBOLDT with an almost full-range speaker like the Endeavor SE, and the combo sculpts a soundstage whose perceived dimensions rise to the ceiling, expand well beyond the outer reaches of the speaker enclosures, and erupt from deep under the listening room floor. At the same time, the hyper-inflated sound-field never sacrifices image focus and a near tube-like depth of field layering of instruments and voices for sheer expansiveness.

The HUMBOLDT lavishes equal attention on well-recorded pop tracks. A digital release in frequent rotation here, singer-songwriter Anna Tivel's Blue World (Map Room Sessions) [Fluff and Gravy Records], boasts eerie, ghost-like images with oodles of gently applied atmospheric reverb and long, languid decays. The Humboldt does with this lovely release what few brawny solid-state amps can: it sings with an almost tube-like charm and delicacy, the polar sonic opposite of the "Hulk will crush you" brawny disposition and "bend the knee" control that it exerts with challenging classical recordings.

Or take Billie Holiday's late career (and sadly, near end-of-life) masterpiece, Billie Holiday with Ray Ellis and His Orchestra [Verve]. Rarely have I heard strings that sing so sweetly, or a recording studio that breathes so naturally with life and air as here. Certainly, Lady Day's voice lacks the range and power on this outing that she displayed on her path-breaking Commodore and Decca mono releases, meaning before the bourbon, the heartbreak, and the road miles all took their terrible life-shortening tolls. But, oh the expressiveness, the pathos, the spot-on phrasing, and of course Billie's unrivaled ability to get to the emotional heart of any song she interprets. All these qualities, meaning musically the most important ones, remain remarkably and movingly intact with the HUMBOLDT.

Let me put it another way: if her heart-rending rendition of Don't Worry 'Bout Me doesn't bring you to tears of musical joy, you need to find another hobby.

Summary Judgments
Even well-heeled audiophiles should only consider the HUMBOLDT if they don't mind parting with almost $60K of their hard-earned cash. The performance-focused neighborhood where this behemoth resides (and plays) ain't cheap. Sure, you can get competing top-flight sonics for much less from other integrated amps, but not I think, the HUMBOLDT's unparalleled ability to conjure three-dimensional sound-fields from thin air, the addictive doses of light and air that it delivers without breaking a sweat, or its pole-vault like dynamic expressiveness.

Second, while the HUMBOLDT can, when the music demands, sing with considerable delicacy, finesses, and grace, it is not a sweet, warm, fuzzy sounding device. Poor recordings and mediocre companion sources have nowhere to hide. If you crave the warm embrace and lyrically inviting charm of a great tube amp, look elsewhere to something like the MolaMola Kula, a sweet little number with charm to spare.

Third, you need a boatload of floor or shelf space to house this hulking brute's mass. Its cartoonishly big frame just won't fit into most smaller listening rooms, no matter how much do-re-mi you have. OTOH, this is no mere black box with run-of-mill push buttons from controls. The HUMBOLDT, like the Scientist Series separates, leaves a lasting visual and tactile impression. It is a real looker if such things matter to you (they do to me), with visuals that rival its remarkable sonic performance. Just remember to bring a friend to the unpacking and packing ceremonies. This thing is heavy! Kudos to U.S. distributor and GTT Audio & Video head Bill Parish for designing a world-class bottom-loading flight case that makes packing and unpacking this silicon mammoth a much easier task.

Finally, if your aging source components exhibit even a hint of DC artifacts in their output stages (one of my workhorse DACs did just that), HUMBOLDT's sophisticated protection circuitry will reject the incoming signal with a Hulk-like wagging of its index finger and a front panel/screen scowl instructing you to unhook the offending dullard and replace it with something worthy of His Highness. If you own subpar sources, be prepared to fork over even more do-re-mi to enjoy the full HUMBOLDT experience.

Still, as I said of the little WATT back in 2018, I can't imagine sensitive listeners not loving this device's supremely fun, shockingly revealing, heavy-hitting, and even better sounding sibling brings to the party. If you are at all familiar with the sound of the WATT, just imagine that unit's sonics amped up as if on steroids. Apart from the few caveats outlined above, the mighty HUMBOLDT does it all, from the softest of whispers to the loudest of symphonic roars.

An outrageously fine reference-grade integrated amplifier then, one suited for all musical tastes and seasons (almost), and very highly recommended!

Specifications
Type: Integrated stereo amplifier
Amplifier Output Power: 320 Watts @ 8 Ohms, 460 Watts @ 4 Ohms
Frequency Response: 0 to 700.000 Hz (-3 dB), DC 0.3 to 700kHz (-3 dB)
THD+N: <-100 dB @ 1 kHz
SNR: > 120 dB A-weighted
Channel Separation: >140 dB
Input Impedance: Cinch (Line): 50 kOhm
Symmetrical (XLR): 35 kOhm
Dimensions: 450mm x 320mm x 505mm (WxHxD)
Weight: 61 kgs.
Finish / Colors: Aluminum, Silver, or black display light or dark TFT
Price: $58,000

Company Information
Audionet GmbH
Brunsbütteler Damm 140 B
13581 Berlin
Germany

Voice: +49 (0) 30 2332 421 0
E-mail: contact@audionet.de 
Website: Audionet.de

United States of America Distributor
GTT Audio & Video
356 Naughright Road
Long Valley, NJ 07853

Voice: (908) 850-3092
E-mail: av@gttaudio.com
Website: GTTaudio.com