I’ve probably reviewed well over a hundred amplifiers, but I can’t say I’ve ever really heard one. I’m always listening to an amplifier driving a speaker, so the sound is really the combination of the two.
I’m pretty sure Nelson Pass has not only listened to more amps and speakers than I have, he’s designed more than a few of my favorite high-end amps.
Pass is the founder and CEO of Pass Laboratories, but I first met him in the late 1970s when he was still with his first company, Threshold.
Even then he was known for his amplifier designs, but he was hard at work developing an experimental speaker with a seemingly impossible design goal: no moving/vibrating parts! He dubbed it the “Ion Cloud” speaker, which ran very high voltages through tungsten filaments (of the sort used in photocopy machines) to ionize the air to produce sound. Right, zero commercial potential, but it worked! The Ion Cloud looked like a screen door and its sound wowed the crowds at the Consumer Electronics Show.
Pass next went to work perfecting amplifiers with “simple circuits,” because as he once so eloquently put it, “complexity tends to be the nemesis of musicality.” As he refines a design, he listens to how individual parts—capacitors, resistors, semiconductors, etc.—change not only what he can measure, but they also put their “signatures” on the sound.
So with these simple circuit designs there’s a strong correlation between what Pass measures and what he hears. And he listens a lot. If anybody can distinguish between the sound of an amp from the speaker it’s driving, it’s Nelson Pass.
The Pass Labs INT-30A is a 30-watt-per-channel, stereo integrated amplifier, but it sounds a lot more powerful than any 30-watt amp I’ve ever used.
The power rating refers to the amp’s output while operating in Class A mode, into 8 ohm loads, and doubles to 60 watts into 4 ohms. Not only that, the INT-30A can easily deliver 100 watts on peaks, but only the first 30 watts will be Class A watts. The amplifier is 19 inches wide, 7 high, 19 deep and it weighs a hefty 60 pounds.
Along with simple circuits Pass believes that Class A circuits are essential if the goal is to produce the best sound. So if it’s such a nifty idea, why aren’t all amplifiers Class A? There’s a bunch of reasons, but first and foremost Class A is significantly less power efficient. Green, it’s not.
For a given amplifier power rating, say 30 watts per channel, the Class A amp draws twice as much power from your AC wall outlet than a 30 watt Class A/B amp would, and most of the additional power draw is turned into heat. So don’t even think of placing the INT-30A in a closed cabinet. Class A amplifiers are also bigger and heavier than other amplifier types of the same power rating. But Pass feels that Class A operation is worth it, because “Class A amps make people happy.” That’s not something I’d expect to hear from an engineer, but Pass isn’t your average engineer.
Sticking with the keep-it-simple theme, the INT-30A’s front panel is a model of simplicity. There’s an easy-to-read fluorescent display, and buttons for power, mute and the four line-level inputs. You won’t have to read the owner’s manual to use the INT-30A.
’Round back you’ll find four singled-ended RCA inputs (inputs 1 and 2 offer the option of using balanced XLR inputs). There’s also RCA and XLR preamp outputs, which might come in handy if you ever needed to bi-amplify speakers with a second amp, like Pass’ 30 watt basic stereo amp, the XA30.5. One obvious connectivity lapse: the INT-30A lacks Tape Outputs. I don’t consider that a major oversight.
I really liked the INT-30A’s snazzy all-metal remote, first because it looks like it belongs with a high-end amp like the INT-30A, and because it’s not one of those ridiculously heavy metal remotes.
My two reference speakers, the Zu Essence and Magnepan 3.6/R are both great, but very different sounding speakers. The Zu is dynamic and lively, but it lacks the resolution of the Magnepans. The Magnepans can’t rock the house like the Zu speakers can, but they’re more see-through transparent. The Magnepans need a lot of power to sing, so the INT-30A wouldn’t be the best choice for Magnepan owners who like to crank their tunes. The 150 watt per channel INT-150 integrated amp would be a better alternative. Even so, the INT-30A made both speakers sound a whole lot better than I thought they were.
The INT-30A seems, well, quieter than most amps I’ve tried. Not that there’s less audible noise per-se, but the spaces between instruments seem “blacker” and deeper so the sound is more three-dimensional. I don’t usually comment on amplifiers imaging capabilities, but the INT-30A was among the best I’ve heard. The amp revealed spatial details, like the layers of depth on the Moody Blues’ To Our Children’s Children’s Children CD. The music floated like a cloud in my living room, and within the trippy haze specific details hovered in crystalline focus. The soundstage simultaneously projected far forward of the speakers and extended beyond the wall behind the speakers.
The amp’s way with rhythm is also remarkable: I’ve never been more aware of the way Tony Williams’ drums lit up Miles Davis’ Filles de Kilimanjaro CD. The pulse fueled Davis and company, so the kinetic energy was truly palpable, they way it is on a really good night in a jazz club. I’ve played this CD on dozens of systems, but never felt that level of sonic and musical intensity before.
To finish up I put the INT-30A in my two-channel home theater with the Zu speakers. I’ve used the Black Hawk Down Blu-ray to test the dynamic stamina of many a home theater system, and even through the worst of the hellish gunfire exchanges, explosions and helicopter crash the INT-30A never cried uncle. Thirty watts indeed!
Nelson Pass is still trying to design amplifiers that sound like nothing at all. That’s probably impossible, but the greatness of the INT-30A lies in what it doesn’t do—it lets the music speak for itself.
CONTACT: 530.367.3690, passlabs.com
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