The Sonogy Black Knight MKII Power Amplifier
The Sonogy Black Knight MKII Power Amplifier
18 November 2002
Class of operation: very high bias A-A/B
Gain Stage: pure class A
Voltage output: 37.0, 74.0 mono
Current: 40 A peak (<100 mSec); 10 A continuous
Power: 175 Wpc, 8 ohms stereo; 500 mono
Input impedance: 100 K-? unbalanced; 200 K-? balanced
Sensitivity: 1.6V (175W/37V); 60 mV (1 watt)
Gain: 26 dB
Shipping weight: 52 pounds
Dimensions: 6.25" H × 18" D × 21" W
Price: $2,250 (plus any applicable taxes & shipping)
53 Briarwood Road
Florham Park, NJ 07932
Website: none currently
In the final scene of The Wizard of Oz Dorothy declares that the big lesson she's learned is that whatever you are looking for - your heart's desire - will be found "right in your own back yard." In other words, trust serendipity. Most of my audio life has been filled with serendipitous discoveries found in my back yard (wherever it happened to be at any given time), largely through audiophile networking. The latest of these is a power amplifier with a marvelously romantic name, The Black Knight.
The price-no-object cost of so much of today's luxury high end equipment, plus the headlong rush to home theater/surround sound by so many dealers, has served to set up a decidedly tilted playing field for the average audiophile. As a result, we're seeing more audio entrepreneurs who have decided, of necessity, to forego the scramble for capital to invest in extended dealer network sales and marketing efforts (or $$$ advertising). They simply produce great products at low-overhead prices and, if the product is truly worthy and competitive, enjoy a modest success selling direct to a loyal cadre of word-of-mouth happy listeners. None of them are going to get filthy rich, so why do they do it? Because they love what they are doing. And I love what they are doing.
Such a one is Sonogy, Ltd., of Florham Park, NJ, makers of The Black Knight Power Amplifier, now in its current life as the Black Knight MKII. Right up front I'll tell you that the ability to buy direct from them will get you a substantial discount under an already very affordable price, plus a no-questions-asked 30-day return policy. That puts the powerful 175 Wpc Black Knight on your component shelf for a mere $2,250 (plus applicable taxes & shipping), effectively giving the direct buyer a 40% discount off the MSRP of $3,750. Sonogy insists that break-in occurs in 1-2 weeks (presumably of "normal" use), so that makes the buy-direct and 30-day trial option feasible. I cannot personally attest to the break-in time since I auditioned a demo unit that was already "seasoned," but in terms of my recent experiences with a variety of solid-state components, I believe it. For whatever reason(s), they just don't take eons to warm up anymore. One of the contributing factors in the case of the Black Knight MKII is an initial 24-hour "warm up" that must be undertaken before actual use. Sonogy says that this gets the Black Knight MKII to 90% of its optimum, and another week or two of average listening time should do the rest.
The Black Knight Power Amplifier is not a new product. It has been in production since 1996. The current version, dubbed MKII, has been improved with a new circuit board and improved parts. According to Sonogy, "the most important performance enhancements relate to the input stage power supply: Special low-noise hyperfast rectifier diodes are utilized, as well as a toroidal power transformer about twice the size of the original. A separate filter bank/regulator supply for each channel rounds out the final area of change." Otherwise, for all practical purposes it looks no different on the surface, nor is there a model number change or designation to identify it.
The Black Knight MKII is almost worth the money just for it's "gee whiz" looks - beautifully finished, solid, serious, macho. I've seen far more expensive amps that don't look any better, and don't have the versatility and flexibility of this amp.
To put what I'm about to tell you in some perspective, my reference system electronics consist of Balanced Audio Technology's VK-75SE power amp, the VK-50SE preamp and the VK-P10SE phono stage. For solid-state variation I move to the H-CAT P12 preamp (another serendipitous backyard discovery). Interconnects are all the Gold Eclipse from WireWorld Gold Eclipse, and speaker wire is their Silver Eclipse. Now, in terms of dynamics the 75SE is just about the most hair-raising amp I have ever heard at any price and I like it because it achieves the same sense of crisp power-to-spare and sheer thrust of good solid-state amps, but without the grain and edgy highs (or, conversely, roll-offs at either extreme). My hot buttons are 1) timbral accuracy (I want to hear resin on those violin strings; indeed, I want to hear it flake off and hit the floor!), 2) crisp, deep, bass extension and unstrained treble, and 3) instantaneous transient response on all of the above. In these respects, the Black Knight MKII was impressively quiet (i.e., transparent) and tube-like in its ability to render a near lifelike representation of instruments and voices. The bass power and articulation is excellent - bass freaks will love this amp! But in the end, this music lover simply appreciated the MK II's ability to straightforwardly render music in an involving listening experience.
When I switched to the H-CAT P12 preamp (the best solid state preamp God ever dreamed of), the combination with the Black Knight MKII was magical. I have come to the personal opinion that amps/preamps that use any kind of feedback circuitry to stabilize the signal simply won't work, and while I can't comment on the technical or engineering reasons why I find them unnatural sounding, I do know that signal integrity and stability (such as in the BAT, H-CAT and the MKII) largely accounts for the realism we perceive. After all, a sound (any sound) in life comes at you at a precise speed. Any more, any less, even a fraction of a digression results in what I call "electronic" sound. Trying to fix a deviation at the output side is kind of like closing the barn door after the horse ran away - it is simply too late. Better to focus on finding ways to keep the signal stable from input to output. Indeed, the precise resolution of the P12 with its signal "cloning" technology revealed the Black Knight MKII's ability to respond with exceptional accuracy, smoothness and musicality. Neither the P12 or the VK-50SE (also free of any such compensating circuitry) are inclined to be forgiving in terms of what they feed the amp, and the Black Knight MKII had no problem responding in kind.
The workmanship inside matches the elegance of the exterior. Again, I'm no EE, but the layout and arrangement of transformers and boards, etc., seemed simple, neat and nicely arranged.
Sonogy's philosophy is that you can build the best mousetrap - or amplifier - in the world if price is no object. Of course, this limits your potential market (all the more reason to charge an arm and a leg). Instead, they go the "less is more" route, taking pride in uncluttered, simplified circuits and eschewing negative feedback junk. Instead, they focus on such critical elements as power supplies. In the Black Knight MKII, totally separate power supplies are dedicated to the gain stage (which operates in pure Class A mode) and to the output stage (which runs in Class A/AB mode). They design the product using carefully chosen high-quality parts finding solutions in better design rather than additional gizmos.
A case in point is the separate power supply design that also has an additional benefit beyond the unstrained, quiet attributes it brings to the gain stage. It draws about the same power as a night-light and is designed to remain "on" permanently (well, unless the amp is unplugged, of course). This means that the Black Knight MKII is always "warmed up" and raring to go. I always left my solid-state components on all the time, and this feature of the Black Knight MKII gave me a warm, energy-conscious, environmentally-kind feeling. As for the output stage, here I really have to quote from Sonogy's own literature because I cannot say it any better: "[The output stage power supply] includes . . . a huge, costly inductor (or "choke"). Almost no one else includes chokes, one notable exception being Cello . . . " I agree. In fact, the only place I've ever even heard about chokes is on the DIY triode/tube mailing list I belong to - and they are a very finicky group.
For the power-hungry, there are watts to spare at 175 per channel, and it sounded like even more probably because it came across so utterly without strain. However, if you are really over the top you can buy two and get 500 watts per side. Last, the Black Knight uses JFETs and bipolars. Sonogy has rejected MOSFET (at least until better versions come along) because they claim they are very capacitive "and thus, potentially non linear."
Sonogy uses Full Spectrum™ audio cables throughout, chosen for their ability to provide a coherent impedance to the signal. Jacks are machined, and the two pairs of speaker binding posts on each channel are milled brass, though I was irritated with the plastic covers. My fingers are not strong enough to tighten speaker leads properly (especially large, stiff cable like the WireWorld Silver Eclipse that has a mind of its own) and I have to use pliers - a no-no on these plastic covers. I think all brass binding posts should be an optional offering, even if at a higher price. This amp deserves it.
Functionality? The Black Knight MKII gives you the option of balanced and unbalanced inputs, plus a single XLR for using the amp as a fully balanced monoblock.
Last, the speakers used for this audition are another "backyard" find from a fledgling company that must, for the time being, remain under wraps. They are full-range with forward firing conventional drivers in a cabinet designed so well that they are extraordinarily quiet. I never noticed "quiet" in a speaker before. (Any speaker.) And even up close, no perceptible hum, sizzle or other electronic artifact was discernible, so I have to rate the Black Knight MKII 4-star for clean, quiet operation.
The sound? Perhaps most important was its ability to get out of the way of the music, so free of electronic artifice does it seem to be. Last, the performers appear to be life size - not exaggerated in any way - and the perspective is neither in your face nor too far back. All these things added up to just forgetting about the system and enjoying the recordings. Hey, I'm a "Big Music" addict, whether on vinyl (preferably) or CD. An amp has to be able to handle a large ensemble making complex noise and wide dynamic swings without sounding congested, murky or edgy. The Black Knight MKII was a pleasure to listen to. I found it open and nicely detailed, and especially by comparison with the BAT (at nearly four times the Sonogy direct price, incidentally), I found that the MKII's sonic attributes were of the same character, with tube-like freshness and definition. From its sense of power to spare, it even compared favorably on most counts with my memory of the BAT VK-500 dual monoblock amp.
One of my favorite tests is a cut from the Japanese pressing (vinyl!) of the infamous Rickie Lee Jones album, Girl At Her Volcano, "Under The Boardwalk." This is an acid test for transient response and just plain SLAM in the staccato passage that echos the lyric ". . . under the BOARD WALK! BOARD WALK!!! Oh yeah. The Black Knight MKII's extraordinary bass extension delivered this with even more heart-pounding oomph than the 75SE, though in the upper-midrange/lower treble, such as the sound of Rickie's voice in the opening "Ooooohooooo-Ooooo" had a bit less throat sound than it could have and sounded a hair brighter. But again, this was comparing this amp with an $8,000 masterpiece of tube circuitry (in itself a bargain in its league), so keep that perspective in mind.
Turning to digital, one of my favorites is the fabulous Philadelphia Orchestra all analogue tube CD Nature's Realm [Water Lily Acoustics, WLA-WS-66-CD]. This is a wonderfully non-reverberant recording that has been decried as being too dry, but I value it for the instrumental sounds unadorned by either the over-resonance of the recording venue (i.e. the hall), or of artificial reverb added by the sound engineer. In Lizt's "Les Preludes," the deceptively quiet soft pizzicato opening notes on the string basses sounded round, woody and solid. Cellos too were appropriately gutty sounding. Back to vinyl, on Classic Records' wonderful remastering of Schumann's "Carnaval," Meyerbeer's score for the ballet "Les Patineurs" should sound orchestrally rich and warm (it did) and my acid test for extended treble is the piccolo solo in the first scene. With the Black Knight MKII I gave it a dust-mote rating of 8 out of a possible 10. I was sufficiently transported to the illusion of being in the theater (hence the dust motes in the follow-spots analogy) and a specific impression of the layout of the orchestra, front to back and side to side.
The Black Knight MKII throws an impressive soundstage, yet a believable one. It really allows you to suspend disbelief for a marvelous illusion of musical reality. Back to CD again, and a reissue of a reissue of a reissue of Blue Note jazz masterpieces (one of my supermarket finds, an EMI "Special Edition," no catalog number). Here we had a nicely "spitty" trumpet sound, and it was possible to hear - and physically locate - individual voices in the vocal ensemble humming the melody behind the trumpet obligato on Byrd & Pearson's solemn, introspective "Cristo Redentor." (These are all available on current CD's by Blue Note (and others) up the ying-yang. But, more serendipity - I just happened across this great CD for $2.50, obviously a closeout, and grabbed it. It turned out to be great sounding.)
These are my standard tests, however, on and on it went much like this. Opera recordings were especially revealing with their large orchestras, big choruses, and anywhere from one to six soloists singing different vocal lines simultaneously. Here again, there was impressive dynamic range, and the fluid musicality of the operatic line. The singing voice being one of my favorite instruments, one of my treasures is an ARK pressing of a collection of Bob Fulton's best stuff ("Fulton Gold"), and on it is a remarkably simple rendition of a young woman with a nice soprano voice singing "The Lord's Prayer" with piano accompaniment. This recording is capable of throwing a breathtaking holographic image of both the piano's bulk and the young woman standing in front of it. With the best equipment, you'd swear that she is standing right in the room. To sustain this illusion requires pristine transients, clean articulation and musical warmth and luster. The Black Knight MKII was a terrific performer in all respects.
In short, if you are looking for versatility plus exceptional musicality and power, I have to say that the Black Knight MKII sounds and looks like it ought to cost twice it's dealer-direct price.
Thank you for your insightful review. It is high praise to be considered worthy amongst the pedigree and price ($8k!) of your reference tubed BAT amplifier.
A few minor points of clarification:
The 24-hour warm up period is a "must" ONLY in the sense of achieving optimal sonic performance. The amp will of course play music the minute it's turned on.
The binding posts are indeed nylon ("plastic") covered, and chosen primarily for sonic reasons. Being COMPLETELY removable (the "sixth" way) they allow for a mechanically and electrically superior ring terminal. (Of course, no cable company we know of uses one. A classic chicken-and-egg scenario). And a ONE-piece stud design of solid brass gives excellent conductivity with good strength. The advantage of an insulated post is increased safety, reducing the risk of accidental shorts. The disadvantage is that of increased fragility when tightening cables that are "difficult," which seems like most of the stuff commonly used these days. When we picked this post design, cables were not quite as unwieldy as they are today. It's a very good performer for the money, but future production runs will probably have something more sturdy (and expensive). We are investigating whether other companies' solid metal posts can be retrofitted to the stud & screw size of this one. Stay tuned….
In order to use two amps as balanced monoblocks, your preamp MUST have fully balanced outputs, and to not degrade the sound, those outputs must NOT be an "added" stage to the standard (non-balanced) outputs (all the BAT preamps qualify in this regard).
I'm not sure what "dust motes" are, but I'm glad we scored well in this test!
How can you tell? All current production (like your sample) is officially designated "Black Knight MKII", but there is no OBVIOUS external way to see this. However, there are ways to find out:
The MKII is SUBTLY different externally: On the bottom of the unit there's a new (round) transformer near the rear that is easily visible from the outside (you can see the outline through the ventilation holes and see the center mounting screw). And from the TOP of the unit, also toward the rear, is the new circuit board that looks VERY different from the old. I can supply pictures that clearly show this. (You do NOT have to take the cover off to see these differences).
New owners get an owner's manual with the "MKII" title;
We keep track of all serial numbers that have been updated/produced with the Black Knight MKII circuitry, and anyone who has a serial number and wants to know can contact us for an answer;
The MKII weighs about two pounds more, and has a 1/2 amp internal fuse instead of 1/4 amp (these are admittedly hard to detect changes).
Once again, thank you for the kind words. All of us here at Sonogy are glad you enjoyed the amp!
Sales VP, Sonogy LTD
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