Sumo Polaris II power amplifier Page 2
On instruments that only occupied a portion of the midrange, image placement from front to back was distorted, with harmonicas being reproduced as farther away than normal and guitars pushed too far forward. In addition, there was a glare to the upper frequencies that made certain instruments like Clark Terry's trumpet (on his Chesky CD) too brash. In comparison with the similarly priced Adcom 555 II, the Sumo's midrange was more forward overall, but with marginally more grain. The forward midrange of the Polaris might be welcome in a system that tends toward a reticent presentation; in my system, it was not.
The high end of the Polaris was extended, but lacked the ultimate delicacy of the Muse. Cymbals lacked the air I'd grown accustomed to with the Muse, as well as some good tube amps I've had in my system. The Polaris had some trouble unraveling strong cymbal crashes without an accompanying thickening in the upper midrange, a problem absent in the Adcom and the Muse. As with the midrange, the Sumo's highs were slightly grainier than that of the Adcom, lending the presentation a bit of hardness, especially during loud passages, that made the amp sound a bit smaller than its power rating would suggest. The high-end grain was even more distracting when the Sumo drove the Thiel CS1.2s; their metal-dome tweeters mercilessly revealed any and all roughness, making them a poor match for the Sumo. If I were to assemble a system around the Polaris, I'd choose much softer-sounding speakers than the Thiels.
Soundstaging was, laterally, quite good for the money; it essentially equaled the Adcom in this respect, offering a wide and distinct panorama between and beyond the speakers. As I mentioned before, the midrange variations made accurate depth reproduction difficult, sounding shallower than the Adcom. Cowboy Junkies' The Trinity Session (RCA CD 8568-2-R), in particular, came across as sounding much smaller than with the Adcom or the Muse, the reverb tails all bunching together without spreading out to imply the depth of the church.
Sumo's Mike Custer explained to me that while their more expensive Andromeda was designed to be as neutral as possible, the Polaris was given a more "tubey" sonic signature to endear it to fans of this particular sound. As this revelation came after my listening sessions, it makes better sense to me why the amp sounded the way it did, although "tubey" isn't really what comes to mind. I must say, though, I have a hard time with this kind of "boutique audio" thinking; designing gear to purposefully deviate from neutrality is My-fi, not Hi-fi.
In the $800 price range, you really can't expect sonic nirvana, and you certainly don't get it with the Sumo. What you do get is a decent, forward-sounding amp that might be just the thing for the rock fan graduating from the '70s Japanese receiver he hauled around through college. However, any amp in this group has to face comparison with the standard-bearing Adcom GFA-555 II. I felt, overall, that the Adcom was tonally and dynamically a more neutral amp. While more laid-back than the Polaris, it imposed less of its own sonic thumbprint on the music, which is a good thing at any price and fairly remarkable at the $800 level. What it ultimately comes down to is personal taste and choice of ancillary equipment; those who've been trying cable after cable in hopes of adding some "bite" to the midrange might do well to audition the Sumo in their system. In more neutral or even forward setups, I'd wager the Adcom would be the better choice.
As with every single purchase an audiophile makes, an extensive in-home audition is essential, but I can't stress this enough in the case of the Sumo Polaris II. While I found it to sound as I've described, I think the colorations of this amp might lend themselves better to different-balanced systems. Even at the highest price ranges, there's always a certain amount of "compensation" among the separate components that make up the total system; as you go down the price ladder and the colorations start getting more severe, careful matching is all the more important in getting satisfying sound. There are undoubtedly systems in which the Adcom would sound wimpy and the Sumo alive and kicking; in my system this was not the case. Prospective buyers in this price range would do well to include the Sumo Polaris II in their auditions. Neither neutral nor harsh, it offers a very distinct tonal quality that may appeal to many systems and listeners.