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Inherent in all that clean clarity is a very grand soundstage of superior intelligibility. Image allocation is very specific but not chiseled. For that, the high frequencies are too benign. Bass is well damped and powerful. By virtue of the overall coolness, vocals, though very direct, lack that peculiar intimacy I get from the Emission Labs 300B XLS in my Yamamoto. It's another interesting bit of syntaxation how directness or immediacy need not equal intimacy. Immediacy yes, intimacy no. This was more of a captive voyeur's than immersed participant's perspective.

Obviously, this amplifier is in control. You notice that during crescendos macro and micro, from orchestral forces gathering for the final swell to the emphatic upward rush of a guitar arpeggio that peaks with a fat vibrato on the highest note. You notice it during complexity when diverse strands remain discrete and don't blot out. What you won't get is some of the 'connective tissue' that valve amps which are otherwise neutral enough insert between the notes. Whether that's an overlap of harmonic halos; low-level noise like subliminal tape hiss that seems to raise contrast ratios; or some other octave-doubling interactive side effect - the INT-150 banishes that stuff. Again, great clarity from perhaps superior noise performance and low colorations.


Because my ASI Tango R speakers run brilliantly on 8 watts of premium triode, any relevant test of an integrated muscle amp would of course run speakers thirsty for higher power. The arrival of the 85dB Davone Rithm from Denmark provided just the right opportunity.

To truly square the circle, ModWright's KWA-150 arrived as well. For convenient comparison between the two American amps, I  defaulted to Esoteric's C-03 transistor preamp. It was set to zero gain to essentially become a passive preamp, albeit run off 38V rails. Final conclusions would again report on the INT-150 driven direct from the source but for the amplifier comparison, I wanted a simple cable swap scenario. Now the Pass amp clearly shifted into a far more optimal torque zone of its engine when asked to put out more and handle a grown-up load.

Clearly, now I had the right job for the tool at hand. The equivalently powered KWA-150 maintained context and a side excursion via my DeVore Fidelity Nines established more to gauge how these amps compared. We'll jump straight to the conclusion. The INT-150 is very capable in the bass, getting from a 7-inch SEAS coax driver in a small though very clever enclosure far more LF extension and heft than seems possible. It's perhaps appropriate to call this aspect heroic. This integrated combines reach, pressure and control and is of proverbial muscle amp caliber.

The INT-150 also gets fleshier and fuller as load requirements increase. Compared to the ModWright KWA-150, the Pass integrated puts more emphasis on the speed, impact and attack elements of the performance. This pertains to the entire bandwidth but particularly in the bass creates a wiry mien when called for. While the KWA-150 extends just as low, its overall character is more relaxed and includes a modicum of warmth. This emphasizes the weight aspect over impact.


The treble quality between these powerful amplifiers is different too. The Pass is black coffee, the ModWright adds some sugar and just a whiff of cream. In keeping with the caffeine image, the INT-150's top end is more energetic to key in on quick alertness while the KWA-150 tones down the illumination some for less highlighting of recorded reflections.

In the eternal mix'n'match game, the ModWright + DeVore Nines created a very comparable set of strengths to the Pass Labs + Davone Rithm combination. That's because the 0.75" tweeter of the Americans is the more lit-up and finely nuanced operator over the 1" concentrically loaded Dane; and the enhanced mid-bass heft of the Rithm is better complimented by the thinner blood of the Pass than the inherently leaner and more linear Nines.


Adding it all up
The first integrated amplifier from Nelson Pass majors on dynamics and speed, a very informative treble and exacting soundstaging. Transient reflexes are very keen to create a subjectively cooler climate but some warmth comes into play as the load burdens increase to get the amp out of 1st gear. Apparent resolution is very high to translate into great visibility of and into the virtual stage. Bass is prodigious in the best sense of the word. The INT-150 sounds completely in command which minimizes the legato effect -- the ebb and flow -- one recognizes from low-powered tube amps. That is replaced by factual imperturbability. Presumably highly load-invariant into more challenging speakers, the same does not exactly apply in reverse. If my experiments translate more widely, sonics bleach out into non-reactive loads. This is not a 1st-to-last watt egalitarian then. This machine comes into its own as it begins to 'pull' some real speaker weight rather than 'rev empty'.

The deliberately color-shifted shot above reflects the somewhat distanced cooler 'Scandinavian' personality of the INT-150 into less copasetic low-watt speakers. This warms up with appropriate transducers but the underlying core virtues of incisive articulation, high resolution and great organizational power remain stable. Likely due to its very low distortion and formidable power reserves, the INT-150 is ideal for complex large-scale works that rely on unerring separation and stability; and a machine par excellence for bass freaks. You could remain ignorant of your smaller speaker's true LF virtues until it ends up in the grip of the Pass to then rewrite secret notions about needing bigger and more expensive boxes. This is also a highly dynamic amplifier which tracks voltage fluctuations very tightly to peel out of the surrounding thicket momentary spikes like percussion hits and bass accents in high relief. In fact, high relief is a perfectly suitable all-around abbreviation to summarize the INT-150's very linear sonics...

Quality of packing: Very stout.
Reusability of packing: Multiple times.
Ease of unpacking/repacking: Easy.
Condition of component received: Perfect.
Completeness of delivery: Power cord, owner's manual, remote control.
Quality of owner's manual: Very good.
Ease of assembly: None required.
Website comments: Recently updated. Very good.
Human interactions: Always professional and friendly.
Pricing: By containing a full-bore X amp and high-quality buffered preamp section, not as high as apparent at first glance.
Final comments & suggestions: Not its best on 'wimpy' speakers. As true muscle amp, wants to be put to work to fully come alive.
Pass Labs website