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Positive Feedback ISSUE 47
january/february 2010


pi audio group


as reviewed by Victor Chavira


Image by Dave Clark from his system





Marten Design Miles II.

Magnum Dynalab MD-209 receiver.

Oppo BDP-83, Apple Mini-Mac and a LINN Axiss turntable with the Adikt cartridge.

Nordost Quattro-Fil interconnects, Analysis Plus Oval 9 speaker cables, and El Dorado power cords.

Audio Magic Stealth Power Purifier, Vibrapods, Townshend 3D sink Table, and Echo Busters.


Power conditioners are important part of a high fidelity audio system no matter how extravagant or modest. Power conditioners play an important role in reducing the considerable amount of noise inherent in common house circuits as well as protecting components from potentially harmful power spikes. Some audio hobbyists claim that certain power conditioners restrict dynamic impact as their circuits lag behind the peak demands of challenging material. Therefore, careful consideration is important when purchasing the optimum power conditioner to meet the needs of your current and future system.

For the past eight years, the power conditioner in my system is the Audio Magic Stealth Power Purifier. The Stealth is a sealed black box with three hospital grade duplexes. I do not know the inner workings of the Stealth but it is instrumental in creating a quieter and darker background for musical events to occur. The object of this review, Pi Audio Group's Über BUSS is also a sealed black box with one 15 amp Leviton quad receptacle. Pi Audio Group's design is proprietary and contains passive parallel technology that filters radio frequency and electromagnetic interference.

For this initial review, only the Magnum Dynalab 209 receiver with integral USB DAC was plugged into the Über BUSS. Since nearly all of my listening time is spent with the Mac Mini playing iTunes, I found it unnecessary to plug in or listen to other sources. In contrast to my usual procedure of listening to an item for review over the course of several days or weeks and taking notes, I decided to listen to a playlist of several diverse songs in my standard system before installing the Über BUSS and repeating the playlist. The following paragraphs describe my aural observations with the Über BUSS in line.

The first song I played was Hunting Wabbits by Gordon Goodwin's Phat Band. The music is a rousing stylistic mix of Canadian Brass meets Count Basie. Even before the first note played, I noted an overall reduction in low level background noise. Then the music just appeared in the room and did not seem to emanate from the two speakers before me. The room dimensions extended out and notes decayed longer into a pitch black vacuum. Instrumental images were precisely rendered with sharp crisp lines. Cymbals and percussion became vividly clear and rhythmically engaging. Each brass and woodwinds unique timbre was unmistakably present. Bass propelled with more marked timing and drive. Needless to say, I was both very impressed with what I was hearing and a little disturbed because I didn't think the improvements would be that dramatic over my high quality power conditioner.

The next selection I listened to was Enterprising Young Men by Michael Giacchino from the new Star Trek motion picture soundtrack. This is another dynamic piece with large orchestra and heavy low frequency transients. Once again, the Über BUSS helped my system produce precision instrumental images and enhanced the illusion of space as never before. Directional clues were strikingly present. Musial sounds could easily be traced back their position on a massive soundstage. The soundwaves of large drums and massed basses seemed to travel some distance before slamming with the listener's ears and body.

Here I must interject a few words about room treatment as a basis for understanding the effect of the Über BUSS in my system. My 13' by 20' listening-living room is untreated with windows facing the street on one side and open dining area on the other side. Even under the best conditions, noise is a part of my listening experience from the sounds of birds in the trees of my backyard to the occasional car passing by to the quiet hum of the refrigerator or gentle flair of the pilot light in the wall heater. The sound of music with the Über BUSS in line reminds me of the sound I've heard in the best acoustically treated rooms in audio salons or other listener's dedicated listening rooms. A well treated room suppresses exterior noises but is not overly damped or lively and allows the listener to hear deep into the musical experience. That's what the Über BUSS did for my system. The Über BUSS allowed me to listen profoundly and effortlessly to the music. Old familiar recordings were rendered fresh and new as I discovered hidden detail after detail.

The song "Whichita Lineman" is given a slow bluesy tempo by singer Cassandra Wilson from her 2002 CD Belly of the Sun on Blue Note. The instrumentation is sparse with acoustic guitars, double bass, and percussion. Ms. Wilson's throaty voice holographically emerges from dead center flanked her band on a deep dark soundstage. Instrumental images are sharp and focused. Rests between notes are absolutely silent. Then at three minutes into the song after Cassandra refrains "Still on the line", she rests and quietly clears her throat before singing the next verse. My jaw dropped in disbelief! I've heard this tune many times but I never heard that detail before. I repeated the track without the Über BUSS and there it was again only this time I had to focus my concentration on the event or it would pass by without notice. Generally, I am not a listener who is obsessed with with the squeaky leg under the third viola player's chair. However, small non-musical details give a recording character which I appreciate when they occur. In essence, the Über BUSS doesn't highlight details but rather lifts a very thin layer of transparent film revealing increased clarity and depth of perception.

In my opinion, removing the Über BUSS from my system resulted in a one degree decrease in overall focus and sharpness of musical images. One degree may not seem like much but it's that last touch of the fine focus that snaps images to life. Cymbals seemed to suffer the most. With the Über BUSS in line, cymbals had body, brilliance, and an effortless extension that had me thinking that the one inch inverted ceramic dome tweeters in my Marten Miles II speakers were replaced by the tall ribbons of a Magnepan 3.6.

Therefore, I will reluctantly return the Pi Audio Group's Über BUSS until I figure out to how purchase one without sacrificing two months of my son's high school tuition fees. Will I be miserable until then? Of course not. I wouldn't think of listening to music or watch DVDs without my Stealth. However, I now know that my system is capable of an even higher level of refinement with the Über BUSS. Given that my Audio Magic Stealth Power Purifier retailed for $1600 when new eight years ago, the cost of Über BUSS is quite fair given its high level of performance in my system. Victor Chavira

Retail: $995

Pi Audio Group
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