Zu Druid 6


TL; DR: VIVID! Sean finally built one for himself.

In amateur astronomy, we have orthoscopic eyepieces. Orthoscopic optics are designed for absence or near absence of dimensional distortions in the optical view, and they use relatively few glass elements for high light transmission, scant aberrations and low-to-no light scatter. Orthoscopic eyepieces are the standard for critical visual astronomy of planets, due to the undistorted detail, minimal glass and resulting contrast rendering fine details observable at high magnifications. Newer optical designs emphasize other characteristics, particularly wide fields of view for a more immersive experience in observing the night sky, but designing for wide fields trades away some orthoscopic properties to gain something more spectacular and useful in a different way, to the point where intentional spatial distortions are introduced or accepted in order to tame worse ones when field of view goes very wide.

Not wanting to go all the way down another hobby’s wormhole here, I’ll leave the matter of orthoscopics at that as a way of shifting your mindset to orthosonics for a similar agenda to design for authentic sound in hifi audio. It’s more difficult than it seems.

Last year marked 50 years elapsed since I spent my first dollar of my own money on gear to replay music. 2018 also marked 50 years elapsed since I spent the first dollar of my own money on guitars. I’ve been buying recordings longer than both. I mention this because one thing has remained absolutely consistent in all this time, and counting: at any given time, and for any given category of products, there are only a small handful that are worth buying. There’s always lots of choice, but choice isn’t the same as worth. I am aware of the full panoply of audio gear but am undistracted by most of it, because….well…..most of it at any price isn’t compelling.

Especially loudspeakers, which mostly remain very far away from representing music and the instruments (including the human one) that produce the sounds of music. If mid-to-high-end hifi buyers were primarily driven by music concerns rather than gear, or what’s cool, or whatever makes the best success statement, or whatever else you’ve got that isn’t strictly endorsing of objective music replay, the entire market could be served by just two speaker makers: Audience with their ClairAudient line, and Zu Audio. I wish I could say otherwise, but these are the only makers of speakers fully delivering authentic music fidelity today, i.e. replaying music orthosonically. There are a few additional contenders who nearly get it right, at various price strata: JohnBlue, Voxativ, 47 Labs’ Lens, Quad with their electrostatics, and Konus are some who cover between 270° and 330° of the full 360° circle of fidelity. Which is great, and that much completion of the circle can deliver beautiful sound. But only Zu and Audience have mastered making speakers that can effortlessly deliver altogether holistic music fidelity, authentically.

Send your Magicos, YGs and KEF Blades to the smelter. Torch everything Wilson, Focal, Devore, Maarten, Revel and Dynaudio, let alone those horrible JBL Century 100 reissues we see rising from the dead now. Throw every crossover-intensive speaker into the woodchipper and send the ground-up mulch to your local toxic waste facility. Fake news is mostly a trumped-up distraction, but fake fidelity – that’s real. The orthoscopic authenticity cornered by Zu and Audience is rooted in both companies having developed, within any practical considerations, uncompromised full-range drivers coupled to insightfully-engineered cabinets. In loudspeakers, adroitly-chosen materials, along with astute mechanical, resonance, acoustical, structural and construction decisions, preserve the essential simplicity of a full-range driver design, emitting music without exaggeration.

And that’s the whole distinction, because let’s face it -- most of the supply side of the hifi realm is in the exaggeration business. Moreover, much of the consuming public likes it that way! For every “hungry-ear” buyer who seeks the artificiality of being in the band or inside the piano, or gulped down by the singer to be a swallowed resident inside the body’s resonant cavity, there is a designer and manufacturer willing and eager to tilt the ratio of transient-to-tone, or the inverse, away from real and aggressively toward spectacle. It’s endemic, and buyers are as much at fault as the designers & sellers in the industry. For people who want more transient detail than is actually present in a performance or from an instrument, orthosonic speakers aren’t for them. If you want a Fender guitar amp running 6V6 tubes to sound like a Marshall stack, or if you think Johnny Cash sounding 12 feet tall is authentic, you don’t want a true-sound, orthosonic, hifi speaker.

If you need or want a surprisingly convincing speaker that can be held in one hand, buy a pair of ClairAudients. But if you want something with room-filling shove, you want Zu. So, I will leave Audience behind here, since this commentary is about Zu, particularly the Druid 6.

This year marks my 15th year of continual Zu in my hifi systems. I started with a pair of used Druids that had been updated by Zu to 2004 configuration. They turned out to be one of the first ten pair of Druids made back in 2000. Those Druids were the first convincing find in my then 30+ years quest for a convincing crossoverless speaker. The 2004-spec Druid was certainly not perfect, but it was a revelation. Imperfect because it was a bit of a narrowcaster, and was soft on the top end. A revelation for its completely coherent presentation, octave-to-octave balance, consistent transient behavior, striking intimacy, pinpoint imaging, absence of crossover-point pinching, plus it was a tone monster. Druid was effectively a dynamic driver Quad ESL-57 but with dynamic range, energy and willingness to be abused. It was the first speaker to ever pass my test for reproducing specific electric guitar/amp combinations with true fidelity. I immediately added an early pair of Definitions to another hifi system but kept those Druids on my secondary system until Druid 5 was introduced, along the way getting periodic upgrades installed, culminating in Druid 4-08.

In parallel, I made the Definition > Definition 2 > Definition 4 migration, yet the Druid never lost relevance. Definitions favored scale; Druids favored intimacy and they both overlapped on tone, coherence, speed, holistic transient and tonal behaviors and both excelled in delivering shove – that quality of musical dynamism that gives music projection and reach. In Zu’s case you get shove without gobs of power.

Druid 5 updated and expanded on the core Druid proposition but extended the top end for more harmonic completeness (courtesy of the Radian compression supertweeter replacing the older Zu tweet), deepened bass response, added greater agility and speed to the main driver, upped transparency, broadened the spatial presentation, boosted shove and put the Druid form factor in league with Definition by further killing cabinet talk. Druid 5 was the first Druid that had sufficient scale to double as a movie speaker, if the room wasn’t too big. Frankly, when Druid 5 debuted, it struck me as nearly perfect in practical terms, and about as much as one could expect from that form factor. Beyond Druid 5 lay incrementalism.

Or so I thought, then.

Enter Druid 6. Why has it taken me seven months to write this commentary? Because Druid 6 may as well be ground zero for a new vector of Zu. It completely unshackles the single-FRD / no-sub form factor of the Griewe – Druid configuration from the physical limits of its original form. Definition 1 had scale and a lot of cabinet talk. Definition 2 sacrificed some spatial scale to slay the cabinet talk. Definition 4 restored the spatial scale and tamed the cabinet talk to deliver a notably more objective speaker. Druid 6 has the spatial scale of Definition 1, which original Druids couldn’t come close to. It has the tone density trademark of all Druids and beyond what any Definition delivers. Snap and dynamic shove set a new Zu standard. Nuance and transparency Windex the entire presentation. Druid 6 is unbelievably quick, with the dynamic agility of Tiny Archibald confusing basketball opponents in his prime. And there is a fairly dramatic improvement in bass depth, character, impact and texture. I never had a real impulse to add subwoofers to any of my Druids, but then I had another system with Definitions and their powered sub-bass modules to satisfy deep bass cravings. Still, it just seemed counter to the simplicity and elegance of Druid to clutter the room with more boxes or towers to get bass fundamentals few recordings actually include. It’s probably only a half-octave further bass extension over Druid 5 but it sounds so convincing and fundamental that a sub is really only called for by a bass fetishist. All this adds up to a speaker that is a larger improvement over Druid 5 than Druid 5 was over v4-08. Which is saying quite a lot.

If you’ve traipsed through the Druids sequence as I have, that might not be your first conclusion, because on everything most obvious – high frequency response, neutrality, greater shove and improved bass, Druid 4-08 was left behind and there wasn’t a single aspect in which Druid 4-08 was better than Druid 5, other than you could buy a pair for much less cash. Druid 6 improves all these particular aspects over Druid 5 somewhat less so than the last generational shift, but that all sums, along with a specific and new Druid quality, to a new speaker that makes the greater leap over its predecessor. The new quality is “vividity." “ Yeah, that’s not a word, but I’m using it here. My TL;DR for this assessment is “Vivid.” And that is what slams your mind when you wire up Druid 6, especially after the 100 – 200 hours burn-in period needed when new.

Basil Hayden bourbon is 80 proof. Technically, that’s a little short for the category. But if I’m having whiskey before the sun is down, I often start there. It’s easygoing and doesn’t front load you for the evening. Druid 5 was like Basil Hayden. Forgiving, convincing, mellow. Works with almost any mood, music, room, aesthetic, amplification. Druid 6 is more like a 137 proof George T. Stagg bourbon. You need to be ready for it, and it’s going to seem a little loud on your palate. If you leave everything the same and just wire ‘em up, a pair of Druid 6 will hit you like a hot whiskey. Burning, flavorful….vivid. And unfailingly revealing. Druid 6 is a deity’s-honest truth of music presentation. So much so, some of you Druid aficionados out there might (will) prefer Druid 5. Depending on what you have today, Druid 6 will force upgrades, or at least changes in your system, upstream of the speakers. The most likely change Druid 6 will force is in amplification. Depending on how your DAC is voiced (don’t kid yourself, they’re all voiced) you’ll be contemplating a change there too. Phono cartridge? Could be, but less likely than DAC. Preamp, least likely to require a change unless a change in power amp argues for it. In my case, Druid 6 brought to a halt 15 years of Audion SET amplification with Druids, and really a total of 20 years of continuous SET listening in my secondary system. Why? Because the extra half octave or so of bass response is just a bridge too far for really clean, bloat-free bass from any zero-feedback SET amp I know of. SET works well with the deeper-plunging the Definition series because in the Def, a solid-state plate amp has a grip on the sub-woofer driver(s). The tonal qualities of the sub bass are derived from the power amp outputs (and characteristics) but the actual sub driver control is a product of the plate amp’s damping and grip. In Druid 5, the ~34 Hz bottom limit doesn’t reveal the limitations of low-damping factor, SET bass. My Audion Black Shadow 845 amps have excellent bass on Definitions and Druid 5. On Druid 6, bass extension is just enough further to bring SET deep bass control deficiencies to the forefront. Same with SET & PSET 300B.

So, I have to replace my beloved Audion Golden Dream monoblocks (300B PSET) to enjoy Druid 6 without distracting and illusion-undermining, zero-negative-feedback bass bloat. More on that near the end of this commentary.

But, if you’re forced into an electronics revision once in 15 years because of a significant loudspeaker advance, one can’t really complain. For the first time since first exposure to Zu Druid, I recommend alternatives to single ended triode amplification. As I will outline in a topical addendum at the end of this, I recommend single-ended pentode/tetrode, push-pull triode and some high-coherence push-pull tetrode and pentode amplifiers. Or if you’re tube-phobic, some solid-state amps one might want to consider include, Pass, First Watt, 47 Labs Gaincard, M2Tech Crosby, etc.

Druid 6 is the first Druid to serve as a convincing transducer for symphonic music. With the right amplification it will even play viciously intense metal without choking like you’re trying to squeeze toothpaste from its tube too quickly, forcing the tube itself to burst. No prior Druid could quite do that. On the other hand, Druid 6 loses nothing to prior Druids in the lone-performer-with-guitar genre, in fact drawing you into closer intimacy with the tone and textures of expression while maintaining the right spatial distance. It doesn’t exaggerate like the bulk of this industry’s loudspeaker offerings, inflating definition like you’re inside the instrument to feign intimacy.

Druid 6 is also easier to set up than any prior Druid. It might be more demanding of amplifier matching but the formerly-fussy floor-to-plinth gap height adjustment is much less hyper-critical now, for attaining correct bass. Because of its dispersive scale, getting a convincing soundstage is a less obsessive proposition in placement and toe-in. There will be rewards for taking the obsessive route, but you don’t have to. And one of the best small touches is that Druid 6 default footers are flat discs, layered with a thin polymer, and attached via a ball-mount that threads into the plinth. You can spec the plinth to be drilled through so the height of the feet can be adjusted from above with a hex wrench! Fantabulous. But the big advantage sonically is that the ball mount acts as a bearing for resonance dissipation. You can get spikes to anchor the speakers to a firm flooring under thick carpet, but for hard floors the default ball-mounted, top-adjustment, polymer-interfacing flat-disc footer is the bee’s knees, sonically and ergonomically. And it’s kind to your floors.

The design and execution emphasis on Druid 6 was the cabinet. The full range driver is improved and I won’t say that’s not important, but the complete revision to the cabinet materials, construction and the mounting of the drivers (including the FRD’s torque-tensioned anchoring to the rear of the cabinet, complementing the baffle attachment and its beefier surround), and the massive plinth are collectively a major advance in Druid resonance control, energy channeling and, by extension a murderous spree annihilating cabinet talk.

Figuratively Druid 6 wastes nothing from the signal in its transducing obligations. Of course it does waste something, but compared to what’s come before, it sounds like it doesn’t. Druid 6 is direct, declarative, clear, orthosonic. It snaps and crackles like real life sounds. Instruments and people have body and breath in correct proportion. Vocal fry sounds exactly like its coming from the Millennial voice behind it. Real acoustic guitar (if amplified, microphoned, not piezo-electric) sounds authentic in tone and in attack : resonance proportion. Voices, instruments and people are sized realistically. Everything is in high resolution in a natural way, without faked detail. Presentation is bursty and serene, strong and laid back, as is authentic to the performance.

It sounds perfect, but there’s a backside to the coin. Druid 6 is not forgiving of bad recordings, cheesy mixes, idiotic mastering. It lays bares faults in performance, recording decisions by the engineer, mastering, pressings (if vinyl). It is intolerant of runaway digititis. The manic sawing of digital compression loses the loincloth producers try to cover it with. The nasty bits of degraded fidelity traded away for expense reduction are naked for all to see.

You can ameliorate the relentless truthfulness of Druid 6 by choices upstream. A more forgiving phono cartridge or more sonically elastic phone preamp or DAC. Get the right tubes for your new configuration. Back off sheer resolution a trace with Zu Mission cables instead of Event 2. Or not. Go for the unmitigated, all-nude, vivid Druid 6 experience. Hear the beauty and the beast in modern recordings. You’ll thrill to music recorded in the pre-multi-track, pre-all-solid-state studio era. Recordings from the days of vacuum tube consoles and mics, with performers in the same room, have a holistic, tuneful sound mostly lost today, except for recordings from a few performers. Those recordings have a vividness perfectly transduced by Druid 6 and projected into your domestic space. With Druid 6, a modern, congested, over-processed, excessively-compressed assault is revealed for the noisefest it is. If you can’t handle that, you need Druid 5 or you need an obfuscating amp for poor recordings, and another amp for great ones.

Which means Druid 6 isn’t for everybody, and that’s a good thing. Because Zu can’t make as many of them as it can build Druid 5 in the same period of time. And Druid 6 costs about twice as much as its esteemed predecessor. Hence both are in the line concurrently. And this makes sense. In my TL;DR I noted “Sean built one for himself.” Sean has visited me often enough that I’ve had many hours of listening with him present. I’ve seen Sean spin vinyl of music he loves irrespective of recording or pressing quality, able to note the sonic offenses and still set them aside to let himself be infused by the tunes. And when the worst disk is done playing, he thinks about how to get more out of it.

This makes Druid 6 its own contradiction. It is the least forgiving Zu speaker ever, and yet the most fun. It’s seductive and off-putting in equal measure, depending on the quality of the source material. And yet its uncanny PRaT pulls you in to ignore what’s wrong with the source and revel in what’s right.

Zu’s finish quality is higher than ever, running with the best. The jewelry adorning the cabinetry is all functionally mandated, designed to look fab and is perfectly machined. While it sounds like this is as good as Druid can get, there’s no doubt Sean will take Druid further in coming years, but Druid 6 is a high plateau on which it can be parked, bought, enjoyed and admired while another speaker in the Zu line gets the new foundation of materials and build techniques laid down by Druid 6. In the meantime, in Druid 6, Sean Casey is making the one, true, full-range, orthosonic speaker. It doesn’t exaggerate, nor does it shade the truth. It neither spotlights nor romanticizes. It doesn’t make rough, wooly music silken, and it won’t make velvet sounds abrasive. Druid 6 presents Tom Waits and Maria Callas with equal authenticity. Yo Yo Ma and Joe Satriani are equally convincing. Frank Sinatra and Hound Dog Taylor are nothing but themselves.

A (lengthy) note on amplifiers for Zu.

If you’ve read anything prior I’ve posted here about Zu, you know I regard the amp-speaker interface and combination the fulcrum of fidelity for any Zu-based system. As I referenced earlier in having to abandon SET amps with Druid 6, buying this speaker requires careful consideration about the mated amplification. In the past 18 months another development required a complete revision to my power amplification in my Definition 4 system as well, so I have put extended effort into surveying alternate amps for both Zu systems over the past year or so.

In 2017 I had solar panels installed on my roof, and then later that year added Tesla Powerwall batteries. The panels were installed on the area of the roof directly over my living room where the Zu Definition 4 system lives. It’s a one-story rancher, wood construction house, so not much other than air, wood and sheetrock umbrellas my Definition 4 system from the shower of solar RFI. Apart from any RF emissions from the panels, the system has two wireless internet connections: a Wi-Fi connection to my mesh network by the Tesla Powerwall controller, and a cellular connection by the solar system inverter. At the same time, to accommodate the exterior Wi-Fi needs as well as prepare for wireless Roon endpoints to two separate systems, I changed my house Wi-Fi from a Google wireless router to an Eero mesh network.

The result was that my SET amps in the Definition 4 system proved perfect antennas for the shower of RFI bathing my living room, and no tactic for quieting that worked. The first step was to get an active preamp out of the system, so I sold off my crazy-good Melody p2688 tube preamp, which removed about half the problem. It was replaced by the splendid Luxman AT-3000 TVC from the early 1990s – a real work of magnetic art. Once that was added, I had quiet with push-pull tube and solid-state amps. At the time, I still had Druid 5 on the other system, and its location sharply contained the new RFI problem, so my Audion SET amps could still be used there. Then Druid 6 arrived to undermine my commitment to Audion SET. So, now what, for amplifiers?

About a year ago, after years of great difficulty finding a phono preamp that can make an Allnic Puritas phono cartridge sound correct (Allnic’s own phono preamps do not), I ventured a radical experiment to try the M2Tech Joplin Mk2 phono ADC, which I mated to the M2Tech Young Mk3 DAC, both powered by the Van der Graaf linear power supply. For this signal, The ADC converts analog to 24/192 digital and the DAC converts the processed phono analog digital signal to analog at 24/192 decoding. With RIAA done in the digital realm, and gain adjustable by 1 db increments, and a good range of options for cartridge loading, I finally got the Puritas to sound musically convincing. This led me to take a flyer on the M2Tech Crosby power amplifiers as a temporary fix to my Definition 4 power problem so I’d have something good to listen to while I took my time trying alternate tube amps. I bought two Crosby to run as bridged monoblocks. These are Class D amps using ICE modules with an M2Tech proprietary input section for better sound than most ICE-based amps. Into 8 ohms, one Crosby outputs 60w/channel. Run as a bridged monoblock, Crosby outputs 180w. Into the Def4’s 6-ohm load, Crosby should be good for ~270w each.

With a pair of Crosby amps and the Luxman TVC in the Def4 system, I had a quiet system again. In fact, dead-quiet. Quieter than ever! Without the RFI-induced gurgling, sputtering, spitting and whirring coming through my RF-antenna SET amps, I could listen in peace and embark on a tube amp odyssey as I had time.

Chalk up the M2Tech Crosby Class D amp as wonderfully-Zu compatible. This is the best Class D sound I’ve heard, period. Maybe only rivalled by the 47 Labs Gaincard, which has much less power. I prefer these to most bi-polar solid-state amps, only a few of which have somewhat better musicality, usually at less output. Such amps are generally associated with Nelson Pass. So if you are tube phobic or have any other reason to need or prefer a smooth, bursty, dynamic, musically-convincing, high-definition, solid state amplifier for Zu, consider the relatively affordable M2Tech Crosby.

Back to tube amps. At the same time I was considering tube amp alternatives to my long-time Audion SET amplifiers, I also have to note that I regularly am contacted for advice on affordable tube amps for Zu speakers as well. Now, I have a pair of Quad II Jubilee monoblocks, which were the last edition of Quad II amps produced in the UK. They sound quite good on any Zu speaker, so when I got Druid 6 and found them not ideal for SET in the bass region, it was easy to slip them in the Druid 6 system, or to move them over to Definition 4 when I wanted some tube-amplified music. The Quad II pair are always a great backup amp for me, and the closest-to-SET seamlessness I’ve heard in a push-pull amplifier, simple circuit and all that.

But Quad II is built for KT66, with 6L6 an alternative. I had mine pretty tweaked through tube selection: Tubestore Preferred Series 274B rectifier, Mullard mesh plate EF86, Sylvania NOS 6L6 long ago sourced from Mesa Boogie in the form of their legendary STR-415 power pentode. As an alternative I also used cryo’d Tube Doctor KT66. The Quad II sound seriously good but still only 12-15w and the pair could be more elastic. I would love them to have more of the Plasticman kaPow! reach & slam that my Audion Black Shadow 845 SET amps muster.

My system racks are setup for monoblocks, so all stereo amps are ruled out. Meanwhile, as I started my tube amps odyssey, more requests for affordable amp recommendations trickled into my email. Which is why I want to let you know about Ling Xiao Nan and his hand-built, affordable, amplifiers. Xiao Nan designs and builds his amps in the Guangzhou region of China. He is self-taught on the subject of vacuum tubes and amplification, and been building amps for over a decade. He’s also a guitar player, but he’s proud to point out that he is a “full-time amp builder.” You can find Xiao Nan offering amplifiers on eBay under his Tube Fantasy brand, but that’s only a fraction of what’s possible with him.

Online, Xiao Nan generally sells clones of vintage circuits, particularly pre-war and post-war German cinema amplifiers, the Quad II and the Williamson designs. The circuits are faithful with only a few component value deviations for modern speakers, particularly in cathode capacitors. When he is cloning an amp circuit, he builds his transformers to the original electrical spec but uses his own preferred winding techniques. Xiao Nan machine-winds his transformers on his least expensive amps, and hand-winds them in everything else not-very-much-more expensive. He keeps cost down first by building in China, but also by keeping to a Quad II-sized chassis for most of what he offers, in black or natural aluminum, or a similarly-proportioned upsize for designs with larger transformers. Ling Xiao Nan builds monoblocks.

I first learned about Tube Fantasy when I was out on my patio on a cold-for-Los-Angeles night in December with a glass of Corbin Cash Rye, Tidal on my iPhone through my i.am+ Buttons, idly flipping through tube amps on eBay. A listing for a Quad II clone pair at a ridiculously low price stopped me cold, especially since I had gotten a request to recommend a cheap tube amp for Zu earlier that day. They were so inexpensive I decided to do the Zu community a public service to evaluate them. If someone was selling a pair of Quad II clones for a few hundred bucks, I had to hear them, for better or worse.

I’m going to comment on those Quad II clones shortly, but in email correspondence about the sale and in asking some questions I had about the amps, I quickly got to know Xiao Nan beyond the usual eBay transaction, and in doing so I learned about other amps he makes. Perfect. I now had a custom amp builder to let me affordably tour circuits and tube types to bracket myself and zero in on where to finally land in replacing my Audion SET amplifiers. This led to me acquiring the following monoblock pairs in the span of 3-1/2 months: Quad II clone, Williamson push-pull, 2a3 triode push-pull, Klangfilm KLV-204 clone (F2a beam power tetrode-based) single-ended tetrode, LS50/GU50 single-ended pentode, 300B-or-2a3 push-pull. And I am considering getting a pair of Telefunken V69 clones.

At some point, some of these amp pairs will be sold, but the luxury of auditioning a range of circuits and tube types on a relatively modest cash outlay is considerable. And you know what? Xiao Nan might make you a pair of stepping-stone amps, or he might make you the last pair you need. He certainly can. Xiao Nan tends toward simpler circuits, high quality parts, emphasis on transformers and pentode/tetrode designs, though he builds triode push-pull anytime you want. He is quick to build, his soldering is clean and careful. Nothing is needlessly bulked up for faux masculine appeal.

Ling Xiao Nan and Tube Fantasy are in many respects the Sean Casey and Zu Audio of tube amps. Both represent strong points of view, are music-driven and constantly tinkering for better sound, and delivered value is high.

Here’s a sampling of Ling Xiao Nan / Tube Fantasy prices, monoblock pairs, shipped to USA (DHL), amps only, no tubes:

QUAD II Clone (18w), $499

Williamson Clone (25w wired triode / 45w wired pentode), $688

2A3 push pull triode (13w), $688

Klangfilm KLV204 Clone, single-ended-tetrode (10w), $688

LS50/GU50 Direct Coupled, Single-ended Pentode (13w), $1000

In cases where Xiao Nan supplies any of the tubes, he specifies so. Otherwise, you source tubes and stuff the amps when you get them. Every amp Xiao Nan builds gets burned in and listened to for five hours before shipping. All my amps have arrived trouble-free electrically. One had stripped transformer cover threads due to customs overtightening during disassembly-reassembly under inspection, and they also damaged a faceplate. Xiao Nan immediately ordered replacements for me.

Xiao Nan does not pot his transformers both for maintainability and because potting compromises high frequency performance. You may hear a trace more mechanical hum up close than from, say, a true Quad II. But music-on, this is irrelevant. The amps are quiet electrically. Common to all of Xiao Nan’s amplifiers is exceptional transparency, very high definition, fast transient speed, exceptional soundstaging and depth. For whatever reason, with any of his amplifiers, I am getting more spatial depth in the soundstage than with any amplifiers I’ve had connected to my Zu systems, regardless of price, and that includes the many amps visitors have brought to audition on Zu speakers. That fast, transparent, dynamic, tuneful sound I valued particularly in Audion SET is here. Further, in the push-pull amps, crossover notch grunge is vanishingly low. Some notes on specific amps:

Quad II Clone: Fast, open, dynamic sound. Because Xiao Nan winds the output transformer differently than Quad did, this also changes the feedback behavior somewhat. The result is greater audible difference between KT66, 6L6 and EL34 in the clone compared to genuine Quad II. With EL34, the clone is relentlessly revealing, hi-def and blindingly fast, which is great for excellent recordings/masters/pressings, but not forgiving of flawed wax or digitalis-digital. With KT66 the clone is closest to the original Quad II sound, which was not strictly romanticized but does possess some vintage warmth. The perfect balance is found with the NOS 6L6. With this power tube, the clone is smooth, defined, dynamic; delivering Druid-like tone density and lots of dynamic punch for its power. The amp takes some time to burn in and bloom. About 120 hours will do it. It will sound thin in the bass region until then, but progressively less so.

Williamson (Triode-Mode): Dynamically stronger than the Quad II or its clone. Refined, smooth, high definition, solid deep bass on Definition 4 or Druid 6. Same basic sonic difference between EL34, 6L6, KT66, as in the Quad Clone. Again, I settled on NOS 6L6. In the Williamson, the Quad II and QII Clone, my preferred rectifier is the Tubestore Preferred Series 274B. It gets the most tone, space, definition and dynamic punch from all three amplifiers. This is an exceptional tube amp, that lives up to the Williamson amp legend from shortly after WWII. In fact, it’s the best Williamson implementation I’ve heard and easily walks over a Marantz 8B.

2a3 Push-Pull: Inexplicably bursty and elastic for its 13 watts. And my pair have only 8 ohms windings. On 16-ohm Druid 6 they sound dynamically huge. Excellent bass discipline compared to any SET amp, while retaining all the triode magic, though still quite objective. No slow, lazy, old-school triode amp sluggishness. This amp, Xiao Nan’s custom circuit at my request, gives up nothing in definition, speed and punch to the tetrode and pentodes in his other push-pull amps. The rectifier you want is NOS 5v4.

Klangfilm KLV-204: This is an early post-war German cinema and studio amp. It was used as a monitoring amp in recording studios (so high definition required) and as a reserve amp for cinemas using the larger KLV-402 & 502 amplifiers. It lives up to its high definition requirements. I have known about the F2a tetrode tube for decades and never managed to get my hands on any of the Klangfilm or Telefunken amps that used it. I was excited to get a chance to hear the Shindo Cortese, which promptly disappointed me like most other Shindo amps I’ve heard. But this KLV-204 clone is exciting to listen to! Only 10 watts (I had my pair wound for 16 ohms to use with Druids), it sounds dynamic beyond its means. No detail gets past it. Midrange is tone-dense like a great triode but burstier. Among the quickest, most agile amps I’ve heard at any price. Like Druid 6, this KlangClone is vivid, tonally, dynamically, and spatially. With Druid 6 it is musically amazing on an excellent recording, but the x-ray truth of the combination can render a poor recording too distracting to listen to. Badly recorded or mastered bass, particularly, shunts the illusion of musicality. This is one of my favorite amps ever heard, but it is a specialist and Xiao Nan builds it affordably enough to use it selectively. The F2a tube, btw, is a German Post power tetrode built for 10,000 hours of life. They often go longer. As NOS and vintage tubes go, they aren’t cheap, but they aren’t ridiculously expensive, either, given how long they last.

LS50/GU50 Single-ended Pentode: More like the sound of the Klangfilm KLV-204 than any of the others. Crisp, clear, fast and transparent. Also dynamic beyond what’s expected from its mere 13 watts output. Clean top-to-bottom. A little bass shy compared to the push-pull amps but there’s a remedy. In most tube amps, particularly those with cathode bypass caps, there is a trade-off between ultimate bass performance, and ultimate top end. When faced with this, Xiao Nan prioritizes top end linearity over bass linearity. But making adjustments to the chosen values for cathode bypass caps can land you in your zone. You can do this after getting the amps or if you communicate to Xiao Nan your general preferences, he can reliably adjust for the right value. You just have to communicate effectively. Overall, Xiao Nan’s LS50/GU50 single-ended pentode monoblocks are sonically in the same realm as the F2a-based Klangfilm KLV-204 clones, but not quite so MRI in unsparing revelation. The LS50 has more latitude in acceptable recording quality than the KlangClone. Given the Definition 4 sub-bass extension, Xiao Nan suggest snipping the cathode bypass cap on the E180F driver tube to bring bass performance into better balance with the speaker. But I have to say before doing that, the intrinsic bass from this amp on Def4 maybe a little light, but it is very well presented in terms of character, definition and attack.

300B/2a3 Push-Pull: I commissioned Xiao Nan to build for me a pair of monoblocks that can use either 300B or 2a3 output tubes, in push-pull configuration. I have a quad of KR 300B Balloon tubes held back from my recent sale of my Audion Golden Dream 300B monoblock amps, which I wanted to use in push-pull configuration with either my Druid 6 or Definition 4 system to make continuing use of those magnificent tubes. Xiao Nan indulged me with a custom design. Those amps are arriving in the next day or two. Comments pending if anyone is interested.

Telefunken V69 Clone: Probably last in my series of bracketing amps from Xiao Nan will be a pair of clones of the legendary Telefunken V69 Cinema amp. This is a full Class A, push-pull, tetrode amplifier using a pair of the F2a tetrode tubes in each monoblock. Like the Klangfilm KLV-204, input and driver tubes are the equally-revered EF-12 small-signal pentode. Class A output is 25 watts per monoblock. I will decide in the next day or two whether I will order these, put them in the mix and then vet the whole shebang for what stays and what goes.

You can find Ling Xiao Nan on eBay as seller “fatkit83-8.” If you private message me, I can offer his direct contact information for amp inquiries.

Of course the genuine Quad II remains a highly-viable tube amp for any Zu speaker. It is coherent, musical and also delivers more dynamic shove than its diminutive specifications might lead you to expect. Ling Xiao Nan gives you alternatives, and plenty of them, for less cash. And similar to like-minded Asian originators like mhdt (DACs), Jasmine Audio (phono preamps and amplifiers), and Melody (preamps and amps), all of Ling Xiao Nan’s implementations are informed by music listening and in-depth inquisitiveness seeking more fidelity than he previously delivered at any given time. Just like Sean Casey.

Ask questions if you have them.

Phil


213cobra
Phil, I get it.  I'm doing somewhat the same with a few other guys (although likely a tad more expensive per hour than the gent you've found).  I'm very intrigued by your findings so far.  Xiao Nan's amps are insanely low priced even if using simple schematics, so his parts list must also be extremely modest.  Even inexpensive transformers add up, but if he's winding his own that certainly helps cost-wise.  If these have the promise of beating high-end SET, at least on these speakers, I'm game for the science of it and look forward to being able to hear for myself and learn from your experiments.  Great stuff and thank you.

After re-reading your write-up again, I must admit I don't think I feel the same regarding that last 1/2 octave of bass being an issue with SET, although I understand your argument.  I am using an Undertone, and I feel that properly configuring it with each amp, while a tad painful the first time, is more than adequate to be additive to the 6s and allows a great SET to do all those things a great SET can do.  I even use the Undertone successfully with the Atma-Sphere M60s--amps that probably don't need it--but still seem to work well with the Undertone to go even lower than the 6s can muster and improve the overall presentation.

Also, I might suggest that the tube selection for the Druid 5s/Soul Supremes might be too much of a good thing when moving from the 5 (or in my case, Soul Supreme) to the 6.  I think a more "laid back" tube in the same family might reveal the softer details through the 6 that might otherwise come off as too "in your face" with the extra transparency and speed and detail offered in this speaker vs. the previous.  In a couple of my SET amps, some NOS beauties provided some real nuance that some of the bigger bully modern tubes ended up stomping on a little on the 6s.  But these same tube selections may have been too laid back and not as exciting and emotionally alive on the Soul Supremes.  Similarly, I think my Decware SEP and SET amps to be phenomenal with the 6s, but maybe are a little too chill sometimes on the Supremes.
Xiao Nan doesn't just wind his transformers. He builds the cores too. Materials are very inexpensive, even copper, where he lives, compared to the West. He uses premium parts but on the other hand he is not going for overkill where it's not material. He also sells most of his amps tubeless unless a customer wants him to supply, so that cost isn't in his standard pricing. And he's using a spectrum of basic commodity chasses for his various amps and preamps. He tends toward simpler designs, but compared to his triode p-p and the Klangfilm klv204 clone, the Williamson and the Telefunken v69 are not so simple. They cost more but are still low by US standards, keeping in mind he also has no middlemen margin in his pricing, and he is acutely aware that he has no pricing power intrinsic to his brand so he prices to make a living but still get people who are music-first to take a chance.

My comments on SET compatibility with Druid 6 bass are not inclusive of using Undertone with them. I actually don't think Druid 6 is best with subs. Not that there's any harm in it, but doing so somewhat degrades the orthosonic character of the speaker and using a pair with D6 costs as much as Definitions. That's an aside. More to the point, Undertone works with SET for the same reason SET works with Definition: The SET amp is not controlling the driver. That's handled by the built-in solid state subwoofer amp, which maintains an electrical and dynamic grip on the driver that the scant-damping factor SET amp cannot. If you are feeding the Undertone from the output of the main SET amplifiers, you are getting the tonal and transient character of the main amp's bass input to the solid state sub amp, but the actual driver motor control is a product of that directly-connected Class D amp. Obviously, your AS M60s work equally well with Undertone for this reason, even though they would outperform the SET amp on bass discipline if driving a deep bass-capable driver directly.

If your preamp has dual outputs, have you tried driving the Undertone via line-level inputs so you are getting only the preamp's + Undertone amp's character in the sub output? I wonder which you'd prefer?

Now, the question then is, what are you doing to limit the Druid 6's bass response to 50 Hz or so when you tap the SET main amp for the sub input? Nothing? Then you are getting the Druid 6's lowest bass characteristics layered into or onto the the Undertone's output. Unless you set up the Undertone to roll in at or slightly below the Druid 6 roll-off, all you are doing with the Undertone is extending bass response deeper than the Druid 6 will go alone. You'll still have the Druid 6 bass / SET problem between about 45 to 28 Hz. Now, this isn't a problem in Definition because in that speaker, the lower response of the Zu main drivers are limited by the sealed chamber implementation. Turn off a Def's sub and you will hear that the Zu FRD as implemented there will not match the lower extension of the Zu FRD in Druid 6 with its Greiwe loading. I suppose you could limit the lower extension of the Druid 6 by closing off the bottom cabinet outlet and adjust Undertone upward accordingly, and that might actually be the best way to use the two together, seamlessly. I have to think about that.

I generally agree that moving a tube amp from D5 > D6 may require a change of one or more tubes. I have a wide selection of 845s for my Audion Black Shadows but in that case, I did not find a change to be useful. The two most objective 845 tubes in my stash have the same value to both speakers. What I did do is revert the driver tube from the very assertive Bendix 6900 to Tung-Sol NOS 5687 and that put the amps and speakers in the zone. Except for that portion of the D6's lowest response that extends beyond D5's.

As I wrote earlier, I fully accept that some people may like and prefer the sound of a good SET amp's bass with Druid 6. But I'm not advising it when anyone asks what will give them the most natural sound, and am hence on a trek to trial alternative topologies. So far, single-ended tetrode/pentode and push-pull triode are leading.

BTW, there's a price to every choice. I love great & objective SET amps but they give up some discipline that's natural to tetrodes, pentodes and triode-push-pull. So wherever I end up, I am not likely to contend that any of these alternate topologies will replicate every favorable SET trait. But I expect to make the holistic presentation better, regardless what I lose. I'll also say that using supertweeters with Druids (5 or 6) makes a broader spectrum of amps more suitable with the speaker, including right down to the bottom of bass performance.

Phil
Phil, any more concrete news on Defs 6? Could I ask you once more to ask you to get Sean to contact me. I've tried twice thru Gerrit to no avail. It appears Sean has sorted one customer's subs hum issue. I'd like to be next. 
Phil, I honestly am super pumped at the research you’re doing. You totally had me at Klangfilm! He certainly sounds like an awesome "find" and I look forward to hearing his amp(s) at some point. I certainly will be watching for your continued findings.

As for my Undertone connection, I’ve ONLY tried it with the second line out, so I haven’t tried it the other way running off the amps (which I know is how many prefer it). I will try to figure out how to do that and let you know which I prefer (is it as simple as a second set of speaker cables?).

As for the mix, I’m not limiting the 6’s bass output at all, but I used a mic and REW and did sweeps over and over manually adjusting the PEQ, phase and levels on the Undertone to where it only barely overlapped with the 6 (as best I could from the graphs). It sounded awesome when I was done, and better than with Druid 6s alone. I’ve repeated that test many times with many amps and prefer it with the Undertone for all. I am also certain that I am not as skilled at listening for realistic bass as you, and it’s highly likely you would not be as satisfied with the bass my system is producing given your ear.

I didn’t think the 845 SET (many brands, 2 different amps) was the perfect match for the 6s. I’m just now trying different 300bs on my Audions, preferring Gold Lions over EML XLs, and just literally got 2 Takatsukis to put in 1 side (PSET obviously) and I might be in love (dang, may have to buy a second set). My two 45 amps were very good on the 6s, filling the room MUCH more than I expected for that low of a WPC. The Yamamoto does not have the range of my Radu Tarta 45 with NOS 45s, and so really only the Radu 45 and the Golden Dreams with Taks that are fitting the bill for me as top sounding with the 6s. I will be able to try a 71a SET in a few weeks when it gets delivered. I suspect it may not have the guts in this particular room.

I was sorely tempted to ask you about the super tweeters I saw in one of your Druid 6 photos a while back. My speaker side projects are strongly suggesting the benefits of super tweeter over top of a full range as well. Does the pair you tried have a higher range that what’s in the Druids?
Before you commit to Takatsuki 300B in your Golden Dreams, I encourage you to listen to the KR 300B globe glass. The standard tube is half the price of the Takatsuki and in my view twice as good. There's a newer premium KR 300B for the US market only that is still cheaper than the Tak but more than the std KR - I haven't heard it. I tried the Takatsuki. I found it smooth but totally lackluster compared the the KR, especially in view of the price. The KR bass is far more disciplined and defined. The amps have more slam than with the Takatsuki and more spatial information. Top end is more extended, too. I got the same comparative results in the Luxman Anniversary 300B (true 70s-style Luxman audio art). The Takatsuki sounded quite old school triode to me. The advantages were magnified by Druid 6 compared to Druid 5 and very much laid bare by Definition 4. Having already been using KR for almost 10 years, I was not impressed with the Takatsuki at all. But given the native sound of many Japanese triode amps, I understand its sound, which is very well regarded there. It is a materially and structurally well-made tube. But then, feel and examine a KR!

The supertweeters I have atop my Druids are a JohnBlue model since superseded. They have multiple roll-in frequencies and extend to 45kHz. I have them set up to roll in at the highest point, 17kHz. I am probably going to try a pair of Townshends on my Defs, which extend out to 90kHz or thereabouts, but I may wait until I get my Definition 6s. The point of the supertweeter is not to duplicate the Radian's work but to extend the speaker ultrasonically. For me it's a one way street -- once the improvement is heard, you can't unhear it. It's subtle at first, then the longer you live with it, the more obvious are the penalties of removing them.

Sounds like you did a good job integrating the Undertone with your D6s. There is no right answer about running the Undertone line-in vs. speaker-in. Yes, you can run a second set of speaker cables from the Golden Dreams to the Undertone, or if Undertones are near the Druids just run a short speaker cable from the Druid speaker posts to Undertone. It's clean if you are using the Speakon connector with Zu cable to get from amps to Druids. There are good reason to expect the preamp line out to Undertone line-in to be better, but not always, and a lot depends on your pre.

Good news today: My Telefunken V69 clones popped out of DHL Hong Kong, to arrive Monday. Now he has to get them to shove the LS50 PSEP and EL156 SEP out the door, and I can get writing.

Phil