POSITIVE FEEDBACK ONLINE - ISSUE 16
dynamic sounds associates
the Phono-ONE preamplifier
as reviewed by Greg Weaver
All photographs and image processing by Greg Weaver
Defining Divining Vinyl
While living in southern Maryland during the early to mid nineteen nineties, it was my privilege to belong to a small but wildly diverse listening group. It was this troupe's habit to travel, as a pack, to each participating member's listening space, convene therein, revel in their music, and render opinions as to the resultant sound. It was always a blast! Exposure to new music and to a host of differing setups, different product types, applied to differing bias in different rooms. What's not to like?
My first visit to Beacon Place, Dr. Douglas Hurlburt's home in Potomac, MD, some 15 miles NW of D.C., was a remarkable experience. He had just finished a major revision to his KEF CS5s. This was the big change for the other members of the bAS, or backwoods Audio Society as the group has taken to calling themselves (not to be confused with the BAS, Boston Audio Society—or the British Antarctic Survey for that matter!), which was no small thing, by the way. See Speaker Builder Magazine, Issue #6, 1997 for a complete description of the rebuild and his new crossover design. This rebuild resulted in the publication of a paper in the Journal of the Audio Engineering Society (Vol. 48, #3, March 2000, pgs 147-167) that revised and expanded the theory on passive radiator loudspeakers originally published by Richard Small in 1974.
As remarkable as that was, for me, the magic of this visit lie somewhere else entirely. You see, he drove his newly rebuilt KEFs with a set of remarkable mono amplifiers, each the size of a small end table, which he had designed and built himself. These extraordinary devices were permanently mounted out of sight in a large crawlspace in his basement listening area in proximity to the speakers.
Dr. D had managed to garner further favor in my book during that first visit because, you see, he didn't even own a CD player as yet. His only front end was a sleek, sexy looking, highly modified Oracle Delphi, powered by his own outboard power supply, sporting a Graham arm and a Monster Cable Sigma Genesis cartridge. Did I mention that he and Bob Graham worked together at MIT Lincoln labs? No? Let me fill you in a little more.
Dr. D did his undergraduate work in mathematics and physics at the Johns Hopkins University, graduating in 1962. He obtained a M.Sc. in Solid State Physics in 1964 and his Ph.D. in Electrical Engineering in 1972, both from McGill University. His professional career began at RCA Ltd. with development work in microwave integrated circuits and surface acoustic wave devices. In 1976, he moved to the MIT-Lincoln Laboratory where he continued to work on SAW device technologies until 1978. At that time, he became involved in the analysis, design, and development of ultra-wideband spread spectrum communications systems and airborne radar systems. From 1988 to 1990, he served as a Program Manager at the Defense Advanced Research Projects Agency (DARPA) where he managed programs in hypersonic weapons technology and space based radar. Since leaving DARPA, he has provided consulting services, program management support, and technical and analytical studies for the Department of Defense and other agencies and was recently appointed "Chief Scientist" for his division of the Schafer Corporation in Arlington, VA. Not too shabby a résumé, eh?
As early as high school he had begun building kits from HeathKit, Dynaco, and other vendors. Most of those kits were subject to further improvements and "tweaks" of his own design. He has specific design principles that he rigorously applies to all of the system components that he conceives and builds. Foremost is his belief in "sound engineering principles" and the use of only the finest quality components to implement those designs. From an overall design topology approach, he prefers DC coupled designs because he believes that even the finest coupling capacitors can contribute some degradation to signal quality. He also favors designs with minimal "global feedback," preferring to rely on inter-stage feedback, except where there is a compelling reason for the use of global feedback. This approach reduces to the point of elimination the potential for transient intermodulation (TIM) distortion, which is known to cause of "glare" and other undesired artifacts in an audio signal.
The point to all this background is that over the last several years I have watched (and more importantly, listened) as a new state-of-the-technology device has grown from discussion at listening sessions through paper visualizations and schematics to my component shelf. It is my pleasure to be able to announce that the DSA Phono-ONE, Dr. D's first commercial product, is now available at the Dynamic Sounds Associates website, direct to the public only. Would you like to know more?
While a thorough description of the circuit and design are available at the DSA web site, I do want to touch on some key highlights. In designing the ONE, Dr. D has applied all of his pet principles.
He uses no global feedback. Rather, feedback is employed within each of the four separate gain stages to ensure that all forms of distortion are held as low as possible. RIAA compensation is achieved using passive high pass networks, including the proper time constants, located between the independent gain stages of the amplifier chain, again to achieve low distortion. This also aids in contributing to very high dynamic range and aids in the eradication of transient intermodulation distortion, a common byproduct of phono stage configurations where the throughput gain and RIAA compensation are realized by using loop feedback.
The amplifier chain consists of four FET gain stages, two of which can be adjusted to provide the required gain from whatever phono cartridge is selected. With the exception of the first stage, all of the gain stages are of differential amplifier topography, while the third and fourth gain stages (as well as the output stage), are fully differential.
The ONE employs dual, fully regulated and isolated power supplies. Employing two matched toroidal transformers specially made for Doug in Salisbury, Maryland, their primaries are driven out of phase. That aphasic property, coupled with internal shielding, provide virtually total cancellation of any residual power line interference. Using a separate high bias current Class A output stage for each polarity of the amplified audio signal, each gain stage employs its own precision constant current source and voltage regulator to maximize stability and signal control. The output impedance for each polarity at the output connectors is 75 ohms, contributing to the ONE's ability to deliver up to +/- 20 mA of AC current into any load without compromising the overall performance.
To accommodate the fact that the ONE contains no coupling capacitors within the audio path, and to prevent damage to components that would occur if the high rail voltages (+/- 60 VDC) were applied suddenly, comparison circuitry monitors the power supply. Only when both rails have achieve the proper final values and the regulator has "clamped" into fully regulated mode is an activation signal generated that permits the output stages to be turned on. This prevents operation of the output stage in the event of a failure within the power supply or amplifier board that could result in applying a large DC bias to the output connectors.
Set up and Use
The Loading Card system Doug has chosen to employ in the Phono-ONE is well thought out and differs from the original methods employed in my beta unit. Now, the Phono-ONE uses a pair of user configurable Load Cards (one for each channel) for selecting capacitive and resistive loading values for what ever cartridge you use; one set of identical cards for MC carts and another separate set for MM.
A 12-position DIP switch on the MC Load Card is used to select resistive loading. Eleven ultra-high precision resistors chosen in a binary manner (0.0001, 0.0002, 0.0004, 0.0008, etc) can present just about any load value from 16 to 1000 Ohms with a precision of ≤ 1%, dependant on the particular value selected. A chart is included in the owner's manual to allow the user to select the proper switch settings for the desired resistive load. And, for the real die-hard, a 4-pin socket is provided should you choose to install your own custom resistive value.
For MM fans, load resistance options are 47K, 100K or user selectable via the lower four positions in an 8-pin socket on the card. A 6-position DIP switch provides matching capacitance loading from 125 to 900 pF in 25 pF increments, while the upper four positions of the same 8-pin socket will allow customized values again.
The ONE offers six gain values, 40, 46, 50, 56, 60 or 66dB, selectable by 2 slide switches (one 3 position and one 2 position) on the pre-configurable Load Cards. In addition, with the additive properties of the balanced output, it is possible to achieve yet another 6dB of gain there. So actually, the total effective gain range available from the Phono-ONE is 40 to 72dB as measured at 1 kHz.
Doug sets the Phono-ONE's RIAA compensation curve to be accurate to +/- 0.2dB, with each unit being hand trimmed before it leaves the shop. In addition, the user has the option of applying a 3.18 µ second time constant via a switch on the front panel. This optional time constant serves to level off the high frequency roll-off of the standard RIAA curve at a frequency of 50kHz. Some find this to be a more accurate representation of the true cutter head response characteristic.
Annoying cartridges with one channel offering a slightly different output voltage from the other (which, unfortunately, is not as uncommon as you might suppose) can be balanced easily. The left channel remains at a fixed output while the right channel has a gain trim capability of +/- 2.0dB. That trim is adjusted by using a knob between the left and right channel connections on the back panel. My beta unit also has provisions for adjusting both the output balance and output DC offset.
With output drive voltage capabilities of 20 Volts peak-to-peak (+/- 7 VRMS) and 20 mA of drive current, the Phono-ONE can drive amplifiers with an input impedance as low as 1 KOhm, or long runs of cables with capacitance greater than 20 nF with no problems. Sound interesting yet? You have no idea…
Let's get Physical
The DSA Phono-ONE is 17" x 11 3/8" x 3 ½" and weighs in at roughly 22 pounds. On my beta unit, the end and front panels are fabricated from 3/8 inch think aluminum; the other three faces are milled from ¼-inch aluminum. Though the beta has all six faces anodized black with the DSA Phono-ONE moniker stenciled in white to the left of the front faceplate, the production model will feature a gold front plate with black stenciling. At the geographic center of the front faceplate, a recessed panel (flush on the production unit) houses five switches controlling the High Pass filter, Polarity Inversion (including balance adjustment pots), RIAA compensation, Mono/Stereo, and L-R or R-L (only functional in mono mode), as viewed from right to left. Each function switch has a corresponding LED to indicate its status. To the right is the Run/Mute switch with its respondent pilot lamp: orange in Mute mode to show normal operation, red or green if either or both of the twin supplies are not active, then blue when toggled to the Run position.
To the right side of the back panel are the IEC AC socket, fuses and power switch. The large ground lug for the ground is somewhat right of center, while the left side is populated by the left and right input/output panels. Provided for each channel are single-ended inputs and grounds with both single-ended and balanced outputs.
My unit came with some unremarkable, cookie cutter, self-adhering rubber feet. Not to worry, as this both saves you money and lets you select your own isolation products, should you care to use them. I recommend that you do so. I am currently enjoying the brand new Vibrapod Cones from Sam Kennard. I am pleased to report that they are VERY effective and, like the original Vibrapods, dirt-cheap. I have a closer look coming very soon.
Getting Into the Groove
I think I should explain that this has been one of the most exceptional years for me in my entire 30 plus years in this industry. You see, over the last few months, several products from different categories and manufacturers have entered my system that have forced me to redefine how I apply terms like effortless, completeness, and continuous as they relate to music reproduction. I will be writing about them all, and this is the first of those works.
Starting with the foundation, the bottom end is simply to die for. Bass performance is unsurpassed in my personal experience in terms of its absolute extension, rendering of pitch definition, and its overall coherence. Prior to the DSA Phono-One, the bottom octave (20 – 40Hz) had never been so well delineated, with such individuality and articulation. In my experience, it is one thing for a phono stage to resurrect deep bass, yet another to do so with a speed and coherence that lets you identify individual notes easily and without blurring. The Phono-ONE does BOTH, serving up a delicious sense of rhythm and pace in the process. Prior champions in this department, and this product category for that matter, were the Pass Labs Ono series, most recently overshadowed by the rousing EAR 324 Deluxe. Now comes the ONE.
Resurrected passages from the depths of the Mercury Living Presence Saint-Saëns Symphony No. 3 (Mercury Living Presence SR 90012), as organist Marcel Dupré depresses the lowest key on the pipe organ of the Ford Auditorium in Detroit, MI, are simply weightier, fuller and better defined than I've ever experienced from that record. Many good phono stages, some very well thought of in fact, offer up that difficult information as a fluttering "motor boating" distortion rather than the deep bass pressure it actually is. Keeping in mind that this recording is nowhere near the end all in bass performance, the ONE still handles it better than any I can recall.
Midrange is remarkably transparent and exceedingly natural, so much so that it is almost organic in its overall nature. Though this is an inherent strength of vinyl in general, the degree to which it is accomplished by the Phono-ONE is nothing short of astonishing. Listen to things like the inner detail and finesse of a string being bent, from a Janos Starker cello Sonota to a Stevie Ray Vaughn Fender Stratocaster solo, and you will get a sample of what I am describing. Listen for the valving and breath control on well-recorded sax or trumpet. Nothing else I've had in-house unravels these complex and subtle cues as completely and with as much individuality and involvement as the DSA Phono-ONE.
The ONE absolutely excels at capturing the individual brilliance or sheen of a voice. Listen to the magic of Henryk Szeryng's violin on the Lalo Symphonie Espagnole (RCA "Shaded Dog" LSC-2456). Though somewhat artificially spot lit within the stage (an artifact of this particular recording, not the Phono-ONE), the purity and naturalness of its timbre are undeniable.
For a scintillating taste of the ONE's treble proficiency, listen to the subtle flavorings of the struck triangle buried deep within the track "Aja" from the Steely Dan album of the same name (MFSL 1-033). These delicate characteristics, often lost in the clamor of the rest of this complex jazz/pop arrangement, are wrested from the meticulously woven fabric of the composition. They are given an existence all their own: just outside and behind the left speaker with distinct attack, glorious vibrancy, and delicate decay.
With complex and demanding passages like the opening from Prokofiev's Scythian Suite (Mercury Living Presence SR 90006) or delicacies like massed strings such as those in Tchaikovsky's Serenade for Strings (London "ffrr" JL 41010), it is superb at unraveling the dense and often overwhelming layers of material. The ONE easily and accurately places those layers with vise-like precision in realistic size, shape, and timber throughout the soundstage. Not once under any taxation did it offer the slightest hint of congestion or indistinctness, unless they were the attributes of the recording itself. Lesser devices can exaggerate or constrict this characteristic. Not the ONE, it elegantly and accurately decodes the space captured by the microphones.
For further validation of the ONE's aptitude here, try one of my favorite guilty treasures, Roger Waters Amused to Death (Holland - Columbia 01-468761-20). Utilizing Q Sound to a manner that exemplifies the potential of the process, sounds are happening all around you with a two-channel system. Some of the aural delights here include a dripping faucet behind you on the left, barking dogs outside your wall and directly off your right shoulder, horse drawn sleighs and Ferrari's traversing the stage, and a distant train whistle way out behind your front wall, well behind the plane of the speakers. In track 12, "Three Wishes," the disconnected voice of a Genie fills the room – behind you, left, right, behind the front wall. The power of that disembodied Genie's voice rattles doors in their frames—down the hall, and closed! Yet, all the while, these spatial cues are reconstructed with rock solid location and a degree of coherence that I had not known they possessed previously.
Those of you out there who think vinyl has inherently limited dynamics should try the Rickie Lee Jones 10 inch, seven-song EP, Girl at Her Volcano (WB-23805-1B). Though it was a limited release in 1983, I recently picked up yet another mint minus copy on eBay for $2.99! The verve and subtlety in the piano work on "Walk Away Rene" and the power of drums on "Under The Boardwalk" are simply stunning. This record has long been a favorite test for micro- and macrodynamics. The ONE is simply blistering with this recording. Until the arrival of the ONE, the EAR 324 Deluxe was the reigning champion with this record.
Then too, Chris Layton's snare drum snap near the beginning of the title cut from Stevie Ray Vaughn's Couldn't Stand The Weather (Epic EK 64425), is sharply rendered in its attack: crisp and finely defined with an impact you feel as well as hear. The visceral assault on your senses throughout "L'Daddy" from James Newton Howard's James Newton Howard & Friends (Sheffield Lab 23) is magnificent.
Also from Couldn't Stand the Weather, the muted time-keeping foot tapping of drummer Chris Layton has never been better resolved. During the opening of the title track, there are several breaks early in the cut as the band repeatedly stops then restarts. During these pauses, Layton's ever-so-low key foot tapping is so readily apparent and clearly outlined in space that you can almost tell what brand of shoes he is wearing!
With the 1977 Crosby, Stills & Nash release CSN (Atlantic SD 19104), the cut "Fair Game" is sprinkled with a myriad of percussion instruments (maracas, shakers, etc.) throughout the foreground. Each one takes on a definite location in the soundstage and then never budges from the space it initially occupies. Moreover, the individuality of each separate motion or shake is clearly articulated as such, adding to the realism in a way I had never quite experienced previously. Moving to the 1982 CSN release Daylight Again (Atlantic SD 19360), the ONE uncovered the most articulate and deepest sense of layering I've ever experienced from this recording. It has an uncanny ability to present a realistic sense of the "liveness" of the room as vocals and instruments decay.
The Pursuit of Excellence
What distinguishes an exceptional phono stage from a very good one? For me, it is the combined degree of accomplishment. Many phono preamps do some things very well, while they are merely satisfactory (or worse!) at others. Most of us are obligated, through budgetary constraints or the limits imposed by the evaluation process, to select one that plays to our own personal biases and accept mediocre performance in all other areas. Their shortcomings might best be described by a list of omissions rather than commissions.
What musical attributes do you most treasure? Voicing? Timbre? Tonal balance? Tonal accuracy? Dynamics? Dynamic range? Weight? Impact? Presence? Attack? Pace? Rhythm? Coherence? Imaging? Layering? Ambience? Resolution? Air? Focus? Articulation? The DSA Phono-ONE executes and integrates them all with a level of accomplishment I had not expected possible before its arrival. With the ONE, you get the whole sonic enchilada.
I freely admit to not having heard the Boulder 2008 ($29,000). And though I have heard EveAnna Manley's highly regarded STEELHEAD ($7,300) at various shows, it has never capture my attention as the Phono-ONE has. To be fair, it may have been other limitations of the systems in which it was placed as I had found those systems to be wanting in general. My point is that it has never spoken to me as the ONE is capable of doing on a regular basis. So much so that I will be AudioGon-ing some non-essential items and accessing my retirement account, ‘cause this little 22 pound slice of musical nirvana will most definitely NOT be leaving my system.
To say I am captivated with the ONE would be an enormous understatement. Though it does nothing in a mediocre manner, to me its greatest strengths are its ability to render individuality, its extension and utter conviction at both frequency extremes, its seemingly effortless dynamic prowess, its stark quietness and its overall natural presentation; a naturalness that is almost organic in its broadband nature. While I cannot call its near $8000 final retail price a bargain, I do not hesitate to call it an exceptional musical value.
Life with the DSA Phono-ONE, even with my knowledge of Dr. D's capabilities and experience with his prior creations, has surpassed my every hope or expectation, usurping top-honors for Best-In-Class from the remarkable EAR 324 Deluxe. The DSA Phono-ONE is simply the most involving, musical, and natural sounding phono preamplifier, possessing an unparalleled ability to reconstitute the message contained by the recording, in my personal experience. I cannot recall having heard its peer, let alone a conqueror.
It's about the music…
Just last night I was privileged to hear a performance of The Academy of St. Martin in the Fields, joined by accomplished pianist Christopher O'Riley, in the new Leighton Concert Hall at the University of Notre Dame's Marie P. DeBartolo Performing Arts Center. My seat was eighth row center! While the entire evening's performance was spectacular, their repertory standard Tchaikovsky's Serenade for Strings was, without doubt, one of the most memorable performances I have ever had the fortune to attend.
As I approach 50, I have heard hundreds of concerts in a myriad of halls across our nation—from New York to San Francisco, from Washington, D.C. to Naples, FL. Yet in all this time, I have never experienced sound as intimately and as completely as in that extraordinary space last night. This new hall is something quite special. The sonic signature of the wooden bodies of the violins, violas, cellos, and double bass was so apparent, so much an obvious component of the overall sound of the instruments voice, that I wondered how it could be possible not to be able to capture that sound during recording. Yet sadly, it is exceedingly rare that such a wholeness of voice is captured.
If only our recordings could be that natural, that complete, and we could all afford equipment that could reproduce it as such! I guess I want too much, eh? In the meantime, we should be thankful that we have products like the extraordinary DSA Phono-ONE. Enjoy.
Dynamic Sounds Associates