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Reviewer: Srajan Ebaen
Source: Zanden Audio Model 2000P/5000S
Preamp/Integrated: ModWright SWL 9.0SE; AudioZone PRE-T1 [on review]; Music First Audio [on review]
Amp: 2 x Audiosector Patek SE run one channel each, the other shorted out; Canary Audio CA-308 [on review]; Fi 421A [on review]; Yamamoto A-08S [on review]; WRAD 300 [on review];
Speakers: Zu Cable Definition Mk 1.5; Gallo Reference 3; Ars Aures Sensorial [on review]; WLM Viola [on review]
Cables: Zanden Audio proprietary I²S cable, Stealth Audio Indra (x2), Zu Cable Ibis, Zu Cable Birth on Definitions; Crystal Cable Reference power cords; ZCable Hurricane power cords on both conditioners
Stands: 1 x Grand Prix Audio Monaco four-tier
Powerline conditioning: 2 x Walker Audio Velocitor S
Sundry accessories: GPA Formula Carbon/Kevlar shelf for transport; GPA Apex footers underneath stand, DAC and amp; Walker Audio SST on all connections; Walker Audio Vivid CD cleaner; Furutech RD-2 CD demagnetizer; WorldPower cryo'd Hubbell wall sockets
Room size: 30' w x 18' d x 10' h [sloping ceiling] in long-wall setup in one half, with open adjoining living room for a total of ca.1000 squ.ft floor plan
Review Component Retail: $3,075 + shipping

Sighting a 421A Fi amp is about as rare as a white elephant. Massa good aim. Bwana big shot. Bagged hisself one. Ayee! I'd feel terrible if we were talking some endangered species. Granted, the dual triode power tube -- which explains why this amp is more single-ended than most by sporting one lone output bottle for a stereo amp -- isn't made anymore. Still, <$100 samples can be found without too much trickery. See? This 4-watt amp isn't endangered or extinct at all. Anyone wanting one merely need to contact designer Don Garber. But seeing one in the flesh in all its four-storied cleverness doesn't happen every day. In fact, to the best of my knowledge, even a savvy googlist won't chance upon a photo of it anywhere. Until now, that is. To celebrate the occasion, the actual review hereby kicks off with the usual big game trophy photos. Insert grand tales with your imagination until hard listening data become available.

"The 421A is a double triode, originally made by Western Electric as a series regulator. As I learned about tubes, I wondered about the number of double triodes, of which there are many, essentially two tubes in a single bottle. If I were more thorough, I'd do the research to find out how this idea arose, but I haven't. I was aware of the 6AS7, the tube all the OTL guys use. When I saw a 421A, the idea of a three tube amp (rectifier, double triode driver, double triode output) occurred. So I experimented a bit and here it is."

"It's been sort of a sleeper in that I haven't pushed or promoted it - but it's been a favorite of mine. It has the advantage, for very high efficiency speakers, of being quieter than directly heated triodes (2A3, 300B, 45 etc.) since it's indirectly heated, with a heater that is ensheathed by a tube which serves as the cathode. Beyond that I'm not going to say much. Listen to it and see what you think."

"The driver tube is a 6SL7 but I've included a 6SN7 too. The 6SN7 will provide a little less gain and a slightly different sonic character. I'd be curious to hear your reaction to the difference between the two if you have the time." How refreshing. No psychological profiling for his product; no claims of superiority. Don's brief e-mail was a poster child for how to deal with reviews. Let the reviewer call it as she hears it. Avoid gratuitous salesmanship or anxious manipulations. If you have a good product, it'll speak for itself loud and clear.
Garber's legendary Fi shop has been covered in detail in these pages before. In brief, it can rightly be regarded as the birthplace of the American HiFi triode culture after transistors had wiped out audio's tubular beginnings to achieve dominance (if arguably not supremacy).

Though triodes -- and pentodes, both single-ended, push/pull and OTL -- have long since reinvaded the market, the micro-power genre remains an esoteric fringe phenomenon. It is only slowly gaining domestic momentum. That's due to the growing availability of copasetic speakers with the necessary high efficiencies. This is true for flea power of both solid and hollow state architectures.

While most modern valve amps either go the Harley route -- knee-deep chrome -- or the wood/metal two-tone chic, the open architecture of the 421A is a definitive throwback to Bauhaus minimalism with its "form follows function" mandate. It insures adequate ventilation and provides the owner with visual reassurance of what is and is not inside the amp.

Simple is best. No doubt about it, this Fi amplifier wears its persuasion flamboyantly on its sleeve. Add the John Hancock of the designer and a serial number deeply engraved into its skin like a proud cattle stamp. Marks of bespoke ownership.

Reiterating that we're here dealing with a single-ended zero feedback Class A design is nearly redundant. When simple is best, that's the only ticket to bliss in valve land. And simpler than three tubes for two channels plainly ain't feasible if you insist on tube rectification.

With associated parts minimalism in blatant view on this quadruple sandwich, we can be assured that the Fi 421A is an archetypical manifestation of an extreme vision - how to subtract complexity and parts until nothing is left that could be removed without rendering the amp broken.

Those who would speculate before listening -- or who'd let their assumptions influence their ears -- would undoubtedly criticize the output device. They'd predict that channel separation during complex passages could be compromised if one half of the tube pulled down the other. A similar argument is held against paralleled SET architectures.

It does make for a compelling case, especially in an audio culture reared on dual mono. How dual is this tube, really? How would the designer of the 421A stereo amp respond when faced with this line of questioning?

Personally, I was far more curious about the power equation. The lowest I've stooped to in the past were 5 and 6 watts by way of the FirstWatt F2, Red Wine Audio Clari-T, Art Audio PX25 and Decware Zen Taboo. With their 101dB sensitivities, my big-rig speakers don't need power to go loud. Alas, power doesn't just equate to decibels. It also affects control. How would four-or-so watts of go juice translate? For context, I'd have the 2wpc Yamamoto A-08S based on the 45 triode; the 8-watt 300B Canary Audio CA-308s; and the mondo-charged 160wpc Western Reserve Audio Design WRAD 300 with its four push/pull KT88s per channel. One way or another, I'd get a handle on this scenario. To hold you over until then, a few more factoids from the designer's pen below.

Incidentally and as far as power goes, the passive Audio Zone PRE-T1 passing on a 1-volt signal from my Zanden DAC (while itself being set to the +6dB option) proved more than sufficient without calling for more active gain on the preamp front. Regarding noise, Garber's right on the money - this creative etagière of aluminum plates is radically quiet. Perfect for its intended high-efficiency mates.

While we're leaking inside info, do four watts sound bleached, anorexic and bereft of bass heft? Not! There's distinctly more here here. But the fine distinction between here and there shall remain a trump card to be played out in the review proper. Also, I had to turn the Definitions' bass attenuators down after coming off the 300Bs. Golden-eared honest truth.

This sleeper shall awaken in due time. For now, however, back to Don Garber's final comments on vital stats and such:

Power output: 4 watts or so (contingent on driver tube choice)
Input sensitivity: 0.65V for full output
Input impedance: 250K
Output impedance: 8 ohms (4 or 16 upon request)
Plate voltage: 250V
Plate current: 60mA

And what more does one really need to know - except for how this very unconventional custom creation sounds? Indeed. Let's get to that next. On the subject of dual tubes, Don remained silent. "You figure it out" seemed the implied gesture to any would-be doubting Thomas. Trust your ears? Now there's a thought...