Positive Feedback Magazine

STU'S PLACE by Stuart McCreary

The Polyfusion Audio Model 940 Preamplifier and DAC module - Fall 1995

I've seen some slick full page ads in a few notable audio mags (including our own) featuring products by a new comer to highend audio—Polyfusion Audio. Curiosity got the better of me and so in my sampling of some of the latest DACs, I decided I should give this newcomer, Polyfusion a call. I was more than just a little surprised to learn the history and stature of this Lancaster, New York company—no garage hobbyist beginnings or cottage industry here! The principals of Polyfusion Audio, Ron Folkman and Allan Pearce, cut their teeth as engineers with Moog Synthesizers in the early 70's... yeah, I said Moog! Besides dating themselves with this admission, the association with such a landmark company gained these Polyfusion fellows instant credibility with me. Then I learned that the company they formed after leaving Moog has been doing contract work on serious robotics and system control devices for years out of a 20,000 square foot ISO 9000 facility to the tune of several million dollars gross a year. Like I said... not exactly your average highend startup company.

The principals have been audiophiles since their Moog days and decided—"hey, we've got everything we need right here to produce some killer audio gear, so why not?" If the 940 preamp/DAC module combo is any indication, this decision was very good news to the highend.

The 940 is a $3,250 solid state preamp that has the unique feature of being able to install various "modules" to fit your needs, including DAC and phono modules. My unit came with the DAC module built in which raised the retail price to $4,750. The preamp functions feature electronic (transmission gate) input selectors, a remote DC power supply, bridge or biamp output configuration (with internal jumpers), balanced and single ended outputs, and discrete MOS-FET output drivers which are DC coupled with a servo control.

The DAC module is very carefully RF shielded so as not interfere with the other circuitry that shares the same chassis. There are some interesting features under the hood, including such things as a proprietary current to voltage conversion, running class "A," very low phase shift in the pass band right up to 22Khz and all anti-aliasing being performed after the DAC. You really should get under the hood of the 940 to appreciate what an electronics manufacturer of this stature can do. The board layout, assembly and finish work is absolutely first rate—I doubt whether you will find any better work being done in the audio industry today.

Lets deal with the DAC side of things first. I put the unit in my system just the same as I would any other outboard DAC and ran the outputs through the tape out jacks, thus bypassing the major gain stage of the preamp. In this configuration, I could more easily distinguish the character of the Polyfusion DAC module as compared to other DACs I had on hand.

The DAC module presented a soundstage that was very wide and deep—as wide and deep as the best DACs I'd heard to date in my system. The space between images on the stage and the depth delineation were also excellent, but the true distinguishing feature of this DAC has got to be its smoothness and ease of presentation. You will find none of that evil glare or digititis lurking within this DAC. I could listen intently for many hours with no fatigue... nada, zip. This is a characteristic that cannot be taken lightly with DACs. It is surprising, and I must also say, a little discouraging, that there are still a number of DACs out there that will impose a subconscious message to your brain to turn off the music after about an hour and a half. You might not recognize the sound as being irritating (thank God the days where you felt you were strapped into your dentist's chair are over) but nevertheless after the requisite time has passed, you get fidgety or bored and off go the tunes. Not so with the 940. It's a smooth, relaxing ride that you can lose yourself in.

Now, I should say that for some audiophiles, the presentation of the 940 may be lacking that last measure of leading edge transients and macrodynamics that give extra excitement to some DACs. The Theta DACs immediately come to mind here. The 940 DAC does not have the sledgehammer dynamics and almost technicolor presentation of say, the DS Pro Basic III, but then again, some will prefer a DAC that doesn't call as much attention to itself in these areas.

The bass performance of the DAC module was also quite good, not quite as deep and controlled as the very best (I would again recognize the Thetas as overachievers in this regard), but better than most, including my own Mach 1 Reference Decoder. I would again say that the smooth integration of the bass—its musicality, as some are wont to say—was very appealing to me.

Where this product really shines is when you use it as it was intended—as a preamplifier. Some sonic benefits are realized right off by eliminating the typical analog interconnect between DAC and preamp. In my case eliminating that one link provided a significant, though not dramatic, increase in transparency. What impressed me most, however, was how little of its sonic signature this preamp imposes on the signal it is fed. My current reference for preamp neutrality and transparency is the Reference Line Preeminence passive preamp—a preamp that I have found to place the fewest veils between myself and the musical performance. In direct comparison to the Reference Line Preeminence, the active gain stage of the Polyfusion 940 was surprisingly pure. Yes, there was some veiling detectable, but it was ever so slight—far better than I have heard to date from an active preamplifier in my system. I realize that many systems will not work as well as mine with a passive preamp, particularly systems with long cable runs and high-ish output impedance sources and low-ish input impedances for the amplifiers. If I were to find myself in this situation, I would not hesitate to use the 940 and I heartily reccomend that others do likewise.

For line level preamplifiers, I find it difficult to wax poetic about how they sound. If it's doing its job right it should be a high quality switching device and gain stage, or attenuater, as the case may be, and nothing more—no colorations, no sound of its own. In this regard, the Model 940 is a resounding success. As a combination DAC/preamplifier it is also is a success, though perhaps not hitting the ball quite as far out of the park. If you like your soundstage full sized and the buzz words in your audio vocabulary are smooth, relaxed and musical, then the Model 940 will definitely speak your language.

The quality of this product is so high that it makes me curious about the other products in the Polyfusion line. Hmmm... I guess its time for another one of those phone calls.

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