This review page is supported in part by the sponsor whose ad is displayed above
The basics
First things first. Electrically and over my seafoam-green 101dB Zu Definition Pros, the Monads proved deadly. Silent. They are perfectly copasetic with ultra-efficient speakers to ace the obnoxious ear-against-drivers test. Even though input sensitivity at 1.7V is low, power is prodigious. An active preamp in a high-sensitivity speaker context will thus come on faster than usual. (Not that the Monads will be used that way by most prospective buyers). Mechanically, my 240V loaners plugged straight into the wall were so quiet that only in the dead of night could I hear the faintest suggestion of activity. It was not common transformer hum. Rather, it was the very distanced whine of the heatsink fan. It took a day for me to even identify what it was. So it proves to be completely academic. For all intents and purposes, the Monads make for a mighty power reservoir that's utterly ripple-free. Noise-wise, it's as still as the proverbial lake before the first morning breeze.


(Not) free masonry
Getting inside the chassis for a look-see is impossible without knowing the secret handshake. Three long bolts, one adjacent to each pointy footer's threaded hole, connect the inset bottom plate to the top. Alas, at least two additional bolts operate from the opposite direction - and their heads do not emerge on the top. Perhaps the cylinder caps can be removed to access the counter bolts. Whatever the proper procedure, I refrained from forcing the issue to prevent unintentional damage. Considering that this chassis appears to be crafted from one solid block of aluminum -- i.e. the cylinders had to be machined out and, like the rest, hollowed from the inside before getting surface-polished all around -- much of the Monads' cost seems tied to the enclosure. Since this is an item at best ordered in very short runs, the machine shop bill to produce a pair of flawless housings is likely rather astronomical. How far retail pricing could be lowered if Butler Audio opted for a more conventional solution as in their TDB Home Series boxes remains a bit of fascinating conjecture.


First impressions
Despite a fair share of preconditioning -- B.K. personally listens to each set of hand-built Monads for a goodly period before consigning his rare creations to their wooden crates -- the amps do want to be warmed up some again. Especially after their initial installation in your digs. At first, you'll hear faint traces of echo as though the space between the notes was oscillating to render the sound slightly phasey. This minute shake or blur settles down a few burn-in hours later to make room for first impressions. "Unlike any 300B amp I've ever heard. More solid-state than tube in fact." Such could be your overriding initial characterizations. That'd be especially true if you came off a micro-power 45 SET like me. Such unwavering solidity and macrodynamic swings aren't what our kind usually plays with. Duly awed, you'll also take note that despite sounding like very powerful transistors because of the very obvious bottom-to-top grip, nothing inherently transistory suggests itself. In particular, there's no harmonic hollowness, no shallow soundstaging. The opposite in fact holds true. Musical proceedings are massive, fleshy, dense and deep - fully incarnated down to their soles. Earth, not sky-bound. You quickly call it warmth with monster kick, rock-solid control and zero edge.
As you adapt to this extremely grounded presentation, you'll eye those solitary 300Bs wondering. Is this presentation as micro-dynamically adept and sophisticated as it could be? Put differently, do these amps resolve as deeply down into the finest of curlicue strands of musical fabrics as does a 2wpc Yamamoto for example (which, needless to say, is utterly underpowered for most speakers)? Not.


Clearly, the Monads are not as lithe as a superior single-ended 45. Their ankles are thicker and they don't accelerate as hard. Yet they jump higher and make deeper tracks in the end. The ultra-substantial heft across the board is so potent that deliberately penetrating it in search of the tiniest data crumbs is not a natural or instinctive reaction.
Impatient readers will naturally want to preempt all foreplay. Do these monos make the magic? Are they really as pure and special as low-power SETs? Not really. Forget the idealized, hallucinatory, fluffy-as-whipped-cream, aerated kind certain otherworldly or extreme SETs espouse. The Monads get down. They're Zorba, not Buddha. That becomes apparent not just with raunchy music. It points that finger at general expectations that have been conditioned by conventional single-ended tube amps. Linearity, drive and control clearly say high current, good damping factor and steep headroom. "Aha. Paralleled transistors." You recognize it immediately. So predominant are those qualities in fact that they seem to leave little room for anything else. At first.
It's only when you query what transistor amps you really know that sound like these monos that easy filing away into genres fails. I don't really know other tube amps to do this particular Monad thing. This compels me to call them high-power transistor amps with tube-reminiscent harmonic density. That's a good hint. Yet it fails to define the thing itself. After what BK shared with us earlier, we must consider that the unconventional element of his mix resides in the linearity of the enhanced valve harmonics. This is not how tubes loaded down by real-world speakers usually behave. Hence none of us will ever have encountered this particular flavor before. We certainly know all the ingredients from here and there. Just how they come fully together in the Monad puzzle is a slightly unfamiliar version of the overall picture.
For example, 845 amps, on the right speakers, can similarly approach the massive attack quality. As a breed, most I've heard simply tended to lack articulation. They
played it loose and fuzzy rather than taut and distinct. In a different way, the same could be said for many single-ended 300B amps. Also, those won't even begin to approach macrodynamics and bass like the Monads. On the other hand, high-current high-power transistor amps are usually drier and flatter. Plus, they can gravitate towards rendering bass transients in an unrealistically brutal and overdamped fashion. Cyborg bass from a hi-tech rave. The Monads can do brute. But it's then brute for tube amps, not brutal per se. Plus, most sand amps fall short in the treble compared to tubes. The Monads clearly do not.


SET-style bloom seems to typically involve a deliberate (or unavoidable perhaps) amount of loss of control. In other words, a high degree of often unpredictable nonlinearities. The Monads simply don't sound as though they gave up any control. In fact, base line THD without the deliberately added 2nd is said to be ca. 0.004%. With the usual precedents of prior valved acquaintances, calling their specific behavior bloom just to distinguish it from transistor dryness; from capacitor-induced warmth as demonstrated by the Red Wine Audio Signature 30; or from superior damping factor effects seems neither accurate nor sensible. In fact, higher regulation and damping always makes for less rather than more bloom. What to call the Monad effect, exactly, is quite the challenge. If you want more than what's already been described. It's a very full-bodied, steadily vivacious and gutsy sound without syrup or fluff. And it does, in a hi-f speaker context, come into glory at higher volumes than the Yamamoto. That's not surprising. The gearing of either amplifier engine happens at very different SPLs. Where the Yamamoto redlines, the Monad is barely in first gear.



Misdirection
In the end, the A100 monos sound exactly as predicted had one indeed and fully considered the implications of their technical background first, not built up unrealistic expectations to equate BK's esoteric second-order harmonic with an instant contact high of intoxication. He has not extracted the very essence of micro-power direct-heated triodes and grafted it onto an outrageously muscled Venice Beach body builder. The Monads are expertly designed solid-state amps with an unusually constant dose of valve-type harmonic density and body. They're tube amps only for that. They're not tube amps for really anything else. In fact, they aren't tube amps at all. At least not any we've heard before. Here's why.


Isolating one solitary ingredient (the 2nd-order harmonic distortion component) and transferring it to an alien context (ultra-tight-regulation transistors), one doesn't resurrect the original aroma. Like any natural eco system, that aroma was irrevocably tied to a 1001 tiny interactions and counter balances. Planting mangos in Hawaii will not have you think you're living in India. Nor will the mangos taste the same if soil, bugs and water are different.


What the Monad circuitry does with its isolated valve-amp ingredient is to strip it of those nonlinearities that were very likely partially responsible for the free tube action that forms the basis of classic DHT-type flamboyant behavior and sonics. By the same token that the Monad 300Bs don't bat an eye lash regardless of load or loudness, they also don't play their typical game of seduction. It seems you cannot have one without the other. The Monads sit far closer to the just-the-facts-ma'm fence than one of those magical real SETs. Yet -- and this is highly relevant -- the Monads inject a controlled and apparently steady amount of 2nd-order distortion to completely avoid the sharp flavor which odd-order transistor amps will impose with ever more bite as you prime their pump.


Would designer 300Bs like Western Electrics change the picture? Not really. In this application, the stock Chinese valves are tailor-made for what's required. Would a slightly higher amount of 2nd-order THD than the one BK has so carefully fixed cause a more pronounced "hello triodes" reaction? Highly unlikely. Too many other elements of what makes the classic single-ended zero NFB valve recipe work are missing, i.e. the entire grab bag of squirrely nonlinearities that make speaker matching an utter nightmare but raise goose bumps when all the stars align.


Plus, it's very easy to contribute from your own grab bag. Simply strap the Monads to a premium valve preamp like the 101D/6SN7 Supratek Cabernet Dual. Off you are to the direct-heated triode races in high style. It also makes for far more predictable results. After all, an amplifier's first order of business is to drive any reasonable speaker with complete control and negligible distortion. That's called load-invariant. That's what you (should) pay for with a well-designed high-power amp of significant expense. No longer are you expected to fish only in the tiny pond of SET-friendly speakers. The whole sea of speaker choices is yours. If you're sensitive to (and inclined against) predominantly odd-order harmonic distortion, the Butler Audio Monads are your poison pure and simple. They're even-order muscle amps of seemingly limitless reserves.


Just like an expensive perfume that's been adroitly applied, the Monad aroma is omnipresent across the board, bass to treble. Yet it's all of one piece. It is not at all overpowering and thus seamlessly enfolded and far harder to pick out. Though many tube amps try for such evenness, the way it sounds here is still different and certainly far less spectacular.


In reverse psychology fashion, this stands out far less than the archetypical midrange focus of deep-triode amps. Hence it's not cloying. It's a nearly subliminal enhancement that makes for more robust inner solidity. It's not imbalanced or skewed. All tones have the same juicy kernel, the same amount of central fill. This is sufficiently novel in presentation to require a bit of reorientation.



Cypriot audiophile Dan listened to the Monads in his extreme system and bought 'em on the spot. In fact, he ordered a second pair. That's because after running his 6-way ALE 110dB+ horns off the Monads except for the 30' straight bass horns, we switched chairs and did the unthinkable. We 'wasted' the Monads on just the low bass system while the Red Wine Audio Signature 30 covered the remainder. Standing in for his usual Audio Zone AMP-2 chip monos, the shit-eating grin splitting Dan's face clearly confirmed that monadic control applied way down low produced the best bass he's yet heard from this setup. He just had to have that for more than a few short hours. Hence the second pair.


Among many other styles -- his record collection is as extreme as his rig -- Dan likes psychedelic music from the 60s, large-scale Classical and old-timey Rock like the Scorpions. His sizable and dedicated sound room affords playback levels unhampered by the usual constraints. Having owned and listened to some of the finest tube and solid-state amps made (including the Ongaku, the darTZeel, the Wyetech Topaz, Wavelength's finest, Electronluv's best, Korneff customs, all of Shigeki Yamamoto's creations), Dan's journey has by now clearly defined what he wants. "75% facts, 25% poetry" as he calls it. Strapping his customized Supratek Cabernet Dual preamp with inbuilt active crossover slopes to the Monads, that's exactly the mix of mental and emotional math one hears. All that's required to fully get the Monads is to think of them as transistor amps without transistor bite, not tube amps with transistor brawn.


Concluding impressions
Slap real rather than audiophile-approved vinyl or digits on the burner, hit spin, crank the dial for befitting sound pressure levels and presto - realism without wincing. Or as Dan quipped, "this could be the closest thing yet to a straight wire with gain". Which, considering BK's involvement with guitar wranglers to know what live music sounds like, must be exactly what he was after with the Monads. It's a well-worn truism that most playback systems fall apart when you attempt to recreate realistic SPLs with unsanitized music. They become painful in ways the real thing never was. That's what the Monads remedy. That's what puts them in a different class from most all classic tube amps. They don't sanitize and prettify. They don't go abstract or fancy in some idealized pursuits. They simply eradicate the electronic nettle of odd-order distortion bite while welcoming all manner of music that would get you expelled from any trade show exhibit in a heartbeat. That -- not traditional tube magic -- is the essence and specialty of the Monads. If they have any competitors at all, it would have to be from Nelson Pass' XA amp stable. Its mission statement suggest a similar focus, of endowing transistor amps with tube-reminiscent 2nd-order harmonics - albeit without tubes. Not having heard any XA amps yet, how close or not their sonics might be to the Monads is pure speculation at this point.


The ultimate amps?
The Monads certainly live up to their technical descriptions. It simply requires deciphering those correctly to anticipate the corresponding results. High-power handle-most-anything transistor amps that would satisfy listeners standing in the tube aisles are exceedingly rare. This exclusivity does render the spotting of a bona fide example somewhat of an ultimate event. By that definition, the Monads are indeed ultimate amplifiers. Simply strike 'the' to remain realistic. This also leaves the door open for other denizens (of slightly different stripes, of course) which could be roaming this particular stretch of the audiophile jungle and simply haven't been sighted yet...

Manufacturer's website