Bound for Sound

The Polyfusion 960 - July 1996

Two channel transistor amplifier: $4,700. Polyfusion Electronics, Inc., 30 Ward Road, Lancaster, NY 14086 ph 716/681-3040. 220 wpc 8 ohms, 400 wpc 4 ohms. 12 MOSFET output devices per channel. Single 1.6 kVA transformer. RCA and balanced inputs. Signal polarity non-inverted. AC wall polarity non-inverted. Push/pull design with class "AB" output section. Input impedance 20 k-ohms. ****

This was one of the first amplifiers auditioned in the latter half of the survey; despite that, the nature of its build quality and the character of its sound have remained quite fresh in my memory (listening notes help of course). Short of the Balanced Audio Technology VK-500, this was also the most brute force powerful amp auditioned in the survey (though a little less explosive than the Sunfire, a torque vs. horsepower kind of thing), literally reminding me of a powerful locomotive in the way that it tossed difficult speaker loads aside in favor of the music. It had no less than 400,000 uf of power supply capacitance! The average muscle amp will consider itself a Terminator type if it can boast 100,000 uf. The Polyfusion is all business. The single minded goal behind the design was obviously the accurate reproduction of music in the home under any electrical condition imaginable.

I probably hated to see this amp leave as much as any auditioned. Its power was prodigious, and in a weird way I became enamored with the two large luminescent green bar towers on either side of the front panel indicating power output. The bouncing pillars of green jumped with the music and had a hypnotic effect that after a while was in some ways soothing. Okay, they were gaudy, but they were fast and accurate too. And besides that with the flick of a switch they were disabled. All of which would have been a waste of time were it not for the superb way in which this amp was built.

There is something calming about knowing that the equipment one is using is built to the highest degree. In an audio world where the "kludge mod" was once the norm, the internals the Polyfusion look like they came straight out of the space shuttle Atlantis. No amp in this survey, regardless of price, is built better than the Polyfusion 960. Everything about its construction oozes know how and confidence. Quality parts are everywhere, while no construction shortcuts are obvious anywhere. In a perfect world all equipment would be built to a similar level, and everyone would ride a Harley; anyway...

Set-up. After extensive comparisons, the power cord of choice was the TG Audio Goldstein. Speaker cables were the Apex ICTL (very expensive), and the Metaxas (even more expensive), though in retrospect I wouldn't hesitate to use the newly discovered, and wonderful sounding, JPS (a mere pittance in comparison) cables in single or biwire modes. The quality of the chassis made the use of Bartha chassis weights or esoteric feet a non-issue. The only concession to audiophile-neurosis on my part was the use of the ever trusty Bright Star Big Rock to set the monster on. The Bright Star is solid, it's stable, and it keeps our 1960's shag rug from smoothering the underside airflow.

Regarding set-up there is one thing that must be considered, not only with this amp, but with every amp auditioned. That is the input impedance. The input impedance on this amp is low, and a preamp capable of pushing some current is a necessity, tube preamps are not a good idea. Therefore, if you mate the Polyfusion amp with a conrad-johnson, or similar tube type preamp and the sound is mud, don't come crying to me. I strongly suggest a high current transistor type here such as the Muse, Polyfusion, Metaxas, Symfonia, OCM 58, or the like. The failure to do so will result in sound that is less than satisfying in every regard. And that's not just the case with the Polyfusion 960. It's that way with every amplifier written about everywhere. I haven't been making the point forcefully enough apparently, but every amp has a type of preamp best suited to drive it—it's the natural law of the universe!!! And after eight years of testing and writing, I have come to the conclusion that, short of proper amp to speaker matching, this is the most critical electrical interface in any system, and the area where many systems fall apart the worst.

It's like this. Low impedance loudspeakers require a current capable amplifier to drive them properly. High impedance loudspeakers require a voltage capable amp to drive them. Dan Banquer wrote a Think Piece on this very subject, and the whole relationship between amp and speaker has resulted in BFS labeling certain amps as "current" or "voltage" depending on the kind of loads that they best drive. It's the same thing with preamps and amps. It takes a current capable preamp to effectively drive an amp with an input impedance of less than 75,000 ohms. That's why people driving the Pass amps (10,000 ohm input impedance—very low) with a tube preamp are sitting around wondering why things don't sound so good. On the other hand, when one has an amp with an input impedance of over 75,000 ohms, preferably 100,000 ohms, then a tube preamp makes all the sense in the world.

Tubes like to drive voltage, not current (theopposite for solid state), and the higher the input impedance of your amp the happier a tube preamp will be with it, along with a select group of transistor preamps that are designed to drive higher impedances. The general rule is use transistors below 75,000 ohms, and tubes above. It's a general rule of course, and things such as the output impedance of the preamp can be a factor, but the rule of "75" will basically keep one out of mismatch sheol. Just ask the owner of Spectral gear, he knows.

Enough about the input side of the amp. On the output side, where the speakers are, this amp with its 12 output devices and huge power supply certainly qualifies as a "current" type, meaning that it is at home with low impedance loudspeakers in the 2-8 ohm range. Unlike the current capable Krell KSA-1OOS reviewed several years ago, however, the 960 wasn't forced to its knees when trying to drive a higher impedance loudspeaker of 10 ohms plus. Yes, when the loudspeaker impedance went up to the 10 ohm range, highs started to roll and dynamic contrasts started to meld, but ugly it did not get. This is a wonderful amp for a four or six ohm load... wonderful.

Degree of Absolute Transparency. Its overall perspective is mid-hall and very neutral. It doesn't throw stuff at you, but things aren't going to be in the neighbor's driveway either. We've got some strong middle ground going here.

Which naturally brings us to staging. The dimensional soundstage was the most elusive, but sought after, sonic quality in audio in the 1970's and 80's. Since that time with the further understanding of phase and dynamic relationships, amplifiers in particular, have become extraordinarily capable of "throwing" a first class soundstage between the speakers. We've come to expect miracles in this regard from the most mundane of amplifiers, and, for the most part, have received them. Still, some amps are able to obtain a subtle advantage in this regard. The Polyfusion, having now had the opportunity to listen to some of the best in the world now, ranks "good" to "very good" in terms of the sonic stage delivered. The 960 falls somewhat short of the holographic 3-D qualities found in the Wolcott Presence mono amps, and I think that it lacks a little of the abundant image density of the BAT VK-500. But the 960 still delivered the inner detailing and quality textures necessary to give it a nice organic feel when the software required. I'm not an engineer, but on more than one occasion I wondered what would happen if the bias were gently nudged upward on all those MOS-FETS (12) powering each channel. Not to go crazy class A for two hundred watts, but just enough to burn a little of the mist off the presentation Its been my experience that "Ya gotta crank a MOS-FET to make it sing!" Which is not to overly disparage the sonics and imaging of the 960, for they are extremely fine. But when things are this good, one starts to think in terms of absolutes and ultimates, and the 960 looks like the kind of amp that might possibly overtake even the migh ty Wolcott if massaged a little in the right direction. It's that good.

Just listen to bass and lower mids on this amp. Timpani were particularly impressive, as this amp was able to do something very, very special. Assuming that one has the right preamp, power cords, etc., and assuming that the ampLifier has had a significant break-in period (MOS-FETS seem the worst in this regard), the bass from this amp is of the type that will turn a head even in a crowded room. For most of us, bass is that low frequency rumble that shakes things. And while it manages to differ in frequency (some things seem lower than others) there oftentimes is little or no pitch definition after the frequency goes so low. Drums go boom, and things shake. This amp can do what no tube amp is capable of (though the Wolcott is close), and very few transistorized amps dare to dream of. It will take a deep bass fundamental and reproduce it without the flatulating overtones, and "burrrrrrthud" that every other amp that I've heard does to some extent with a low impedance speaker. At first the bass tends to sound a little lean; very powerful and taut, but without the "loose energy" that many confuse for bass (video surround sound fans listen up, now!). This is for the most part what audiophile and video fan have come to correlate with powerful bass. It's a loose energy that moves and creates sonic overstimulation without the honesty of really going deep. Being loose is easy and relatively cheap; going deep without overshoot, while maintaining all semblance of control isn't easy, and its not cheap. (Which doesn't explain why amplifiers costing much more than the 960 do flatulate so loudly when asked to delve the depths.) But this amp has—like the Bear amp heard last November—the ability to tingle a listener with its taut tones. In other words, the bass doesn't sound big per se, at least big in the normal sense of the word, but it has an incredible feeling of bold authority all the way to the bottom rung. It's the difference between moving something and shaking it. The Polyfusion can physically move a bass fundamental without destroying the identifying timbrel signature of the instrument. Most amps, almost all amps, shake things with the fundamental. Like shaking a martini, the contents are all mixed up. The fundamental obscures the more fragile colors of the timbre. For those persons who thought bass was bass, some time with the 960 may make them realize that true bass is music. This amp can make a Timpani sound clean, metallic and snappy, all the while maintaining all the power and controlled energy one could want. I'd heard much of this in the RE Designs mono amps, but when you put 200 watts behind each channel it tends to be a little more forceful and noticeable.

Conclusion. This amp is on the edge. It's on the edge of true greatness. The midrange has a lot going for it, certainly good enough that were I forced to live with it indefinitely, I could. Actually, it had many of the same qualities that I now associate with the Bryston 4B ST, though I think the Bryston to be slightly more refined—slightly more touchy feely—though not as much in control. The same is probably true about any comparison between the RE and the Polyfusion, the RE having a lighter tonal color overall, with the 960 being slightly warmer and a little fuller. Again, the RE did sound slightly more refined, and a detail person such as myself would give the gentle nod to the RE. But the 960 does have the advantage in power and lower frequency savvy; exactly where this amp is at the pinnacle. When it came to the feeling of brute force in a silk glove, the Polyfusion was able to deliver bold strokes in delicate ways. Amps such as the Plinius and the Sunfire (not to mention those in Parts 1 and 2 of the survey) have attempted to excel in the area of power delivery and precision only to find the balance struck by the 960 to be out of their reach. Yes, overall I still prefer the Wolcott, but there are installations where the-960 would be preferable.

What really excites me about this amp may be what we are yet to hear. After years in the professional instrumentation field, Polyfusion seems to be still getting a feel for what they want out of a power amplifier. Expert in areas far more complicated than amplifier design, they are still getting their feet wet concerning the nuances that make music sound like music. I've had three of their amplifiers to date (two 860's and one 960), and each has been dramatically better than the last. This is one of those companies that seems capable of doing whatever it wants to; it simply has to discern exactly what it wants to do. Under the steady hand of Alan Pierce this mission into accuracy and music will end happily. After all, the 960 is at the edge now.

Bound for Sound is published monthly by The DeWulf Publishing Cartel, 220 N. Main Street, Kewanee, Illinois 61443 USA. TEL 309.856.5515. Subscription price for one year is $24 to US zip codes; $26 Canada and Mexico; and $32 everywhere else in the known universe serviced by a local Post. Reprints through 1989 are available. Not one word from Bound lor Sound may be reproduced on paper, electronically, or in sign language without first paying homage to the Publisher and doing various acts of yard work (painting, mowing or washing the car) about his home and office.