Integrated Amp Reviews

The Explorer 150SB avoided the mediocrity trap by committing a few minor, well-chosen acts of omission along with its many good deeds, the latter including rhythmic agility, soundstage organization, and three-dimensional imaging. The Kora's shortcomings were a minor hollowed-out midband coloration that actually contributed to the sound's focus even as it shortchanged the overall harmonic palette, and cut bloom off at the stem—sort of like the sound you get if you make a shallow spectral V with a graphic equalizer. The Kora's dynamic expression was somewhat muted, but while it couldn't scale the big peaks, it got where it could go so quickly and effortlessly that the deficiency wasn't noticeable. In other words, the musical core of the Kora's performance was solid and assured, the drop-offs occurring away from the main, most important action.

When the big Wilson MAXX2s arrived, I was tempted to drive them with my reference Musical Fidelity kW monoblocks. But the Kora it had to be, and the 150SB's performance did nothing to obscure the MAXX2s' massive attack and taut, authoritative personality. Switching to the kWs took the speakers to another level, but weeks with the Kora and Wilsons convinced me that this pairing would hardly be a waste of speaker. A greater compliment to a $2000 integrated amplifier I couldn't pay.

The 150SB–MAXX2 combo created a compellingly transparent and convincingly spacious rendering of Acoustic Sounds' 45rpm, two-LP edition of Thelonious Monk's Thelonious in Action (AJAZ-1190), a live stereo recording from 1958. This was a sonic picture worth watching with the lights out—imagining being in that club and seeing Monk, Johnny Griffin, Ahmed Abdul-Malik, and Roy Haynes was not at all difficult. It was really the big Wilsons doing the communicating, especially of the picture's scale—but the 150SB wasn't exactly muzzling them.

Because of its lack of top-end aggression, its almost sweet yet fast and clean transients, the 150SB managed to be simultaneously easy on the ears and engaging, with a pleasing balance that helped harsh, bright-sounding recordings without dulling or softening really good ones. Though its overall sound was more polite than aggressive, the 150SB was not shy about presenting center images front and center, though in a natural, unforced way. Recordings such as the vinyl reissue of the Weavers' On Tour (Vanguard/Cisco VSD-2022) produced a dramatic three-dimensional picture, voices and guitars arrayed in a line well in front of the speakers, a palpable studio blackness behind.

The 150SB's musical grip and ability to tightly control the MAXX2s' big double-woofer boxes was impressive. Wilson Audio's Peter McGrath, who paid a visit to do the final setup of the MAXX2s, noted this when listening to the Kora. McGrath did the speakers' final placement and voicing using my reference electronics, and as much as he was taken by the big Musical Fidelity monoblocks' sound, and especially by how they gripped and held the speakers' ample bottom-end extension, he kept encouraging me to go back to the Kora—perhaps, in part, because he knew the little integrated's overall performance comfortably validated Dave Wilson's contention about where the bulk of an audio-system budget should be committed.

Problems
Much as I admired the Kora Explorer 150SB's sonic performance, I was frustrated by the remote's odd ergonomics, and its nonfunctioning On/Off and Mute buttons—not to mention the mislabeled Volume buttons. I also found the instruction manual incomplete—for instance, unless I missed it, I saw nothing about how to change the tubes if need be. There was nothing about how to use the headphone jack.

I was also disturbed by the many warnings printed in red throughout the manual. There were many more of these than I'm used to seeing—as if the circuit were rather fragile and had to be treated with kid gloves. The reader is warned in red that "turning on a tube amplifier without a load connected can cause serious damage to your amplifier" and "Never turn off the amplifier with the rear switch, nor disconnect the mains cable without having first turned off the unit with the Power button as this can damage the power section." In the "Troubleshooting" section you are warned that, the first time you fire up the 150SB, it may automatically shut itself down because the power supply is not "loaded." And again in red: "Please remember that any manipulation of the input and output sockets of the Explorer 150SB must be done with the unit turned off." Also, "Disconnecting sockets whilst the unit is turned on can cause an electric short circuit which can damage the unit and other elements of our system," and "any failure of the unit due to an error of manipulation of this type is not be [sic] covered by the guarantee."

In short, there were an awful lot of warnings associated with how this amplifier must be treated or else. I wondered if the design was particularly fragile, which led me to follow the admonishments with great care. During the review period of more than a month, I switched back and forth between the Kora and my reference amplification many times, and switched cables incessantly without problems. I was wrapping up my notes and preparing to begin writing the review when I realized I'd not tried the headphone jack. I took out a pair of Grado SR-60s, stuck them in the phono socket, and blew up the Explorer 150SB. I hate when that happens.

Conclusions
The combination of the manual's many warnings about using and possibly blowing up the Kora Explorer 150SB, and its final demise occurring simultaneously with my innocently plugging a set of headphones into its headphone jack, leave me wondering about the amplifier's stability. I'd attribute the manual's numerous cautions to a carefully written "fail-safe" style were the instructions, in fact, so written. But if this is not the case, it makes it very difficult for me to recommend this integrated amplifier without knowing more about what actually caused its demise.

That's a shame, because the Explorer 150SB offers an attractive combination of sound and features at a very attractive price. To become a competitive, real-world product, the 150SB needs an instruction manual that doesn't insult the purchaser while answering a bunch of obvious but still-unanswered questions. More importantly, Kora needs to demonstrate the design's stability and show that what happened to my review sample was an unfortunate aberration. Those things accomplished, the Kora Explorer 150SB would be an integrated amplifier I would recommend.