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December 2012
Enjoy the Music.com Review Magazine
Don Garber's Magical Fi X4 Stereo Amplifier
A stunning 1.5 watts with Tung-Sol 46 for only $1095!
Review By A. Colin Flood


Best Audiophile Product Of 2013 Blue Note Award  For the golden elixir of musical nuances, for the roaring majesty of mountainous crescendos, for the exotic delicacy of female vocals, nothing comes as close to the joy and feeling of reality as the magical coupling of low-powered Single Ended Triode (SET) amplifiers and ultra-high efficiency horn loudspeakers. Horns love tubes! The combination is the pie and ice cream of practical audio nirvana.

The key to the success of this singing and dancing duo is the incredible efficiency of the horn speaker and the angelic purity of candle-bulb power. Your typical cone speaker needs a huge and clean 512-watt amplifier to drive its petulant 86dB/W/m efficiency to realistic musical volumes. In contrast, my incredibly efficient 104dB/W/m bookcase-size horns (see Enjoy Tthe Music.com biography) need just 8-watts to reach the same ear-ticing music peaks!

What this means is that the bizarre-looking, 1.5-watt tube amplifier can provide all the texture, sweetness and detail, at normal volume levels, that almost any music passage needs. With Garber's wonderful new $1k amplifier, in many Enjoy the Music.com categories, the combination provides some of the best sonic qualities that dream money can buy (see "Deprecating the Gifts of the G-ds"). I don't know of any other speaker and amplifier combination that can perform the sexy female intonations, the great dynamics and peaks of big orchestras and chorus and the beat-bounce of rock with as little compression and distortion as horns and tubes. The duo easily fills a room with vibrancy and verve. The combination reproduces detail, accuracy, coherence, dynamics and color in a way I have never heard before.

I have auditioned a dozen amplifiers and speakers for Enjoy the Music.com in my own home. Nothing I have heard works as startling, enticing and downright charming as well as the Garber X4 on the mid and upper-range of my Big Ole Horns. I will never forget the time when Garber's X4 came to visit. These are the best sounding amplifiers I have heard. This includes the wonderful Nelson Pass X250. I heard various Pass monster amplifiers on multiple loudspeakers. They are always impressive on all speakers. For a lot less money, the X4 comes ear-ticingly close in some respects. The X4 is a single-ended, direct-coupled design with two 46s, two 6SF5 tubes and a 5Y3 rectifier. The Tung Sol 46 is a power tube supplying undistorted output to a loudspeaker. It is a human-frequency range output tube. Tung-Sol was a manufacturer of lamps and vacuum tubes in Newark, New Jersey. They developed the first successful car headlight in 1907. In 1955, they created the classic 6550 vacuum tube. The Tung Sol brand is now owned by the New Sensor Corporation, which provides Sovtek, Electro-Harmonix, Genelex, Gold Lion, Mullard and Svetlana brands! Many popular tube brands it seems, come from the same source. Production of Tung Sol tubes is by their Reflector company, in the Ukraine.

The triode was the first electronic amplification device enabling amplified radio technology and long-distance telephony. They have a clean, clear, detailed sound, but low-power compared to other audio tubes. Triodes are used in high-end and professional audio applications, as well as in microphone preamplifiers, electric guitar and high power radio amplifiers and transmitters.


Awkward Lincoln Looks
The single, most obvious feature of the Fi X4 is its X-shape chassis. It is heavier, cruder and simpler looking than its pictures. Where most amplifiers are stark, rectangular boxes – fancy buttons and knobs, their only decoration – the X4 is a 1930s, futuristic, steam-punk, retro design sitting up high, tubes jutting side-ways in the air, with eight walls of silver aluminum sheet edged with strips of silver screens. The X4 stands – without a cover, bare tubes and parts sticking out in all directions – divided into four quadrants. The quadrants of the X chassis contain the major components, and behind the vertical walls, hide the minor electronics. One quadrant contains the power transformer and the rectifier tube; another has the filament transformer, a pair of chokes, an standard power connector and small black speaker binding posts. Yet another quad section has the signal and power tubes, and standard RCA input jacks. The final section has the output transformers. The Fi logo is small and simple black letters.

You will either love the futuristic retro look or hate it. The X4 doesn't look like any other amplifier, certainly not the typical slim solid-state box, or any other tube amplifier either. It is hard to decide which is front, back or side. Yet this is very smart marketing; you can easily identify an X-shape Garber amplifier at first sight. The X-shape certainly drew instant curiosity at my local audiophile meetup. Like the Klipsch copper cones, people spotted the X amplifier from across the room. I love the glow of tubes and the X4's awkwardly charming shape.

Power tubes, even only 1.5-watts, need plenty of air space around them to operate coolly and efficiently. The rule of thumb is about one to two feet of breathing room around them. In addition to an eye-catching and brand creating design, the unique upright X-shape of the Garber amplifier forces ideal placement for tube amplifiers. The X amplifier don't fit into the typical component slot on the stereo rack very easily and nor should it. It is okay that the X4 doesn't look like any of the black boxes on the equipment rack; it doesn't sound like them either. Visually unique, this amplifier is something different. For this and other reasons, the X4 should sit proudly atop your equipment rack; an antediluvian monument to hand-made craftsmanship.

At 1.5-watts, it does not seem as the Tung Sol 46 tubes are over-driven, which some amplifier designs do to provide more power. Even so, there wasn't an estimate on the longevity of the tubes. The X4 did not seem inordinately hot. Most of the smooth jazz, easy listening time, it wasn't working very hard. Despite always-on Class A mode, the output transformers were only slightly warm to the touch. There are small black binding posts on one of the quadrants. The posts are too small for the thick spades of my Coincident CST-1 rattlesnakes, but standard speaker gauge cables are not a problem. My posts were not marked, but the top of each pair is the positive (+) connection. I did not receive the normal letter inside the box either. The letter states that the top pair of binding posts is the left side and the top post of each pair is positive.

The posts are good enough and inexpensive, keeping with the concept of the $1095 design. For $57 extra, you can have Cardas posts. There is also an option for an upgraded output transformer, but unless otherwise specified, the connections are for an 8 Ohm output. I connected with standard gauge, generic copper speaker cables, without connectors. It is easier to set-up the X4 by putting the small tubes in first. Like all tube amplifiers, the power tubes are hot in operation, especially the rectifier. There is no cover. KEEP OUT OF REACH OF CHILDREN AND PETS.

The tiny, silver flip power switch is on the same small quadrant panel as the power cord. It is a bit tricky to find. It is ‘on' when the switch is in the outward position. The fuse is a 2A 5 x 20mm slow-blow type. Because I power up every night, and then leave my tubes on when I am around for the weekend, the quadrant with the power switch became the front side of the face-less amplifier, which meant that the least attractive side faced the audience. The X4 comes in two boxes packed with paper. A plastic wrap would make a better moisture barrier. Warranty is for two years to original owner covering parts and labor of any repairs necessary due to defective parts or workmanship. Modification in any way voids warranty – creativity is the owner's responsibility.


Don Garber is the heart and soul of the diminutive amplifier. The Fi is his own brand. The X shape is their unique form factor. Garber has about two dozen products, ranging about one to eight thousand dollars. He makes mono and stereo amplifiers, pre-amplifiers and phonograph or line stages. Tubes are 2A3, 45, 46 and 300B in 120 or 230-40 volt versions. Phono stages are for moving magnet or coil cartridges. X-shape 300B amplifier is less than three grand, with a choice of options. I would love to hear anything and everything he makes. This is Garber's day job, but he says orders are backed up a little over a year – "not just for this one but for anything I make." He makes all his amplifiers by hand. In this day of free web sites and Facebook pages, strangely he does not have a web site! As a business writer and internet marketer myself, this sin is akin to not having business cards. Garber says he "hasn't had time."

The X4 is a new model of the X series. The original amplifier was a 2A3, followed by the X3, the 300B version. Ian White in Enjoy the Music.com reviewed the X3.*

He says his unique X-shape does not take that many more hours to construct than the typical tube amplifier, which is merely one flat metal plate in a box with tubes and transformers on top. The X-shape though "does separate all the functions nicely and make for an extremely short signal path. I think it's also interesting to look at."

"The last ‘strange looking' comment," he remembers, "was the customer who called up to apologize for selling his X and Y [pre-amplifier] because his wife made him do it. She just couldn't take any more ribbing from her friends about the "funny looking stereo". Garber choose the 46 tube because it was recommended by Gerry Engoren, who had converted a 45 amplifier with a 45-to-46 adapter. "I was aware of the tube," he says," but had never done anything with it since the excellent 45 was very similar and didn't have the dual grid of the 46. And Gerry was right," Garber said "it's a better (not to mention, cheaper) tube. It sounds incredibly good, at least to me, and it's still cheap."  Same for the Hammond transformer. "They're good and they're cheap. The idea behind the X series is good, cheap (relatively) amps." There are a few other tubes that will fit in these sockets, but not many that will work in this amp. The retail price of the X4 model with Tung Sol 46s is $1095, with the little Hammond transformers and $1595 with Hashimoto ones. I've previously described the original 2A3 X and the X3.


X-cellent Design
The differences between the 2A3 and 46 in both sound and in construction is that the "46 has an old-style single plate. Many contemporary 2A3s are single plate, but with a plate structure similar to a 300B. The 46 has two grids. One of them is strapped to the plate in this application. Garber says he doesn't "do verbal sonic character descriptions. Some people have a talent for this but I don't. It would seem to be a requirement for a critic. You can listen to music" he says, "or you can listen to sound. The overlap between the two is almost total, but if you separate out one, the other is gone."

As unusual as the X-shape is, it has a very simple circuit design. There are no resistors or capacitors in the signal path. Garber said he had "been planning a good cheap 2A3 amp and didn't want the standard Budd-box look but couldn't quite figure out how to lay it out. One day it came to me on the subway and I sketched it out on a paper I was reading and everything fell into place -- power supply in one wing, filter sections in two others and the amp section isolated by itself in the last. The signal path from input to output transformer is just a few inches, and it's direct coupled. Just a little bit of wire and two tubes.

He no longer uses the Magnequest output transformers. The driver tubes are 6SF5, "it's a high mu (gain) simple triode. Perfect for driving a 46 (or a 2A3 or 45)." There are zero passive components in the short signal path of the unique X-shape. The X4 is direct coupled. "The output tube's grid voltage is raised to be the same as the plate of the driver," Garber said, "eliminating the need for a DC blocking capacitor. It's an attempt to be as simple as possible. The black/clear twisted wires carry the signal from the input RCAs to the 6SF5 grids. The clear insulated wire carries the signal from pin 5 of the 6SF5 (the plate) to the grid of the 46. The plate of the 46 connects to the output transformer. That's it."

Some upgrades and modifications are available: silver wire in the signal path is an additional $15, a volume pot can be added ($75). There is also an option for an integrated version, with three inputs, selector switch and volume control ($250). It is available with a 220-40V power transformer, for $60 additional. Garber recommends ultra-high speaker efficiency and sensitivity. "Sensitivity should be 105-dB/W/m or higher, impedance the higher the better, but 8-ohms with no dips is fine."

"There will be people that will be happy with less efficient speakers," he says. "Room size, listening habits, musical taste, all play a part. But to recommend less efficient speakers might lead to a lot of returns. Not good. If you'd had anything less than Klipschorns I wouldn't have sent it, but I was curious how it would pair with them." Wattage into 8 Ohms is "somewhere around a watt and a half." He does not recommend 4- ohm speakers for this amplifier. Compared to the boxy and beefy Cayin and ASL tube amplifiers I have reviewed,* the X4 is relatively light and though awkwardly shaped, small at about 7.5 inches tall by 9 inches across. The tubes stick out sideways past the edge of the wall plates.

Because of its diminutive power, this is a review only a lover of ultra-efficient loudspeakers, such as my Big Ole Horns, can write. Big Ole Horns are like big wheels on a bicycle, you can use low-watt gears with them to cover a lot of ground. Playing Cassandra Wilson from CD on my 104dB/W/m efficient Klipschorns without the bass bin amplifier, the X4 gear was immediately effortless, easy and smooth. At normal volumes in my RealTrap* treated room, the X4 is powerful enough for the lean Khorn bass. The combination displayed what I love about horns and tubes: dynamic, fast attack, quick rise time, percussive, holographic image, wide soundstage, ringing horns and bells, soft clipping, no hard edges, no harsh or strident notes, no clinical dryness and copious details. Only a small lack of force in notes requiring oodles of energy, like drum whacks. Yet on vocals, the X4 has all the power and sweetness that Big Ole Horns need. There was no background noise, not even when warming up. I noticed textures that I hadn't noticed before. Like only the very best equipment does, the X4 made me want to run through my disc collection. The dial on my Dynaco tube pre-amplifier indicates relative power usage. With Patricia Barber at eight o'clock on the dial, the X4 brought out as much as treble details as the $12,000 Jaton A3 loudspeakers.


Other Speakers And Amplifiers
Living with the X4, my habits changed; I fired up the musical combination almost daily. With more conventional speakers, the Carnegie Acoustics CST-1s*, the X4 was warmer and deeper, with little indication of how low wattage the 46 tube is. There was no sparkling high-end; the X4 was more mellow in the treble. Though muted and veiled on Sade's Love, the combination still led to late-night listening sessions indicative of enticing musical qualities. I also listened to Red Wine's original Clari-T battery-powered amplifier. I choose Dire Straits' classic Brothers in Arms as a recognizable album that has some very difficult passages to reproduce on all but the best amplifier and speaker combinations. With the Clari-T, the crescendos were thin, light, tight and crisp. With the X4, the crashing guitar on "The Man's So Strong" is natural, organic, with attention to treble details. It managed to keep instruments separate if not solid, but with less body in the lower ranges. The crescendos lacked the cake-size weight of solid-state or more powerful tubes, such as the blooming bass of the Delta Studio 6s33s*, but the delicacy of sugar cookies was in every holiday morsel of music. I loved percussion with the X4, especially on the uber-dynamic Big Ole Horns, of course. The X4 had the whack of the kick drum, though the doo-dads of brass, bells and snares were sometimes light and airy.

The bass is a soft thump rather than a sharp and hard thunk. X4 bass is a slow Southern drawl instead of a fast NY clip. While the low bass had the notes, it did not have the feel. The CSTs however needed something a little more powerful than 1.5-watts. In my set-up, dual (passive) bi-amplification provided all the solid bass I needed, though the bass amplifier was rarely used. My ACI Titan* sub was also used infrequently on big ole horns, even for action movies. I simply preferred the naturalness of X4 music over the thrill of movies while the X4 was in the house. I would love to hear the X4 on a 100-dB single driver system, like the Supravox Carlas* or the Omega TS1s*, but backed by a powerful sub-woofer.

The X4s were instant-on the first time. They didn't seem to need warm-up. The Fi 46 on my big ole horns provided the micro-resolution that the CSTs didn't have, but the Carlas and the Jaton A3s did. Even with movies, I never felt like I was listening to an under-powered amplifier. On the CSTs, horns on the X4 had blare without ring, bite without rasp. On Patricia Barber's Companion, there was plenty of texture for the bass of late night jazz sessions. Integration between mid and low bass was smooth. The line driver Axiom M80Ti* arrays were one of the better loudspeakers I have reviewed (see "The Best I've Ever Heard Loudspeaker Round-Up"*). Compared to the CSTs, the M80s had stronger bass but I remember it as hard and unrefined, more electric bass than string tone. Treble, though not as sparkling as the M80s or as shimmering as the A3s, was delightfully sweet with the X4.

I also heard Garber's X4 drive a pair of Soundfield Audio's big 1812 Overture prototypes ($7500?) at our local audiophile Meetup (seen at AXPONA 2012). This meeting was in a horribly hard, large concrete block room at a local community center. With big 15" cones, the Overtures are wonderfully efficient and dynamic. With a NAD 1700 preamplifier on Oscar Peterson's live Verve classic (1961), The Sound of the Trio, the X4 got the piano weight, made treble easy to listen to, had quick attack, felt natural, though sometimes lean in the mid-bass and thin in the vocals. With serious equalization from the high-impedance output, it sounded almost solid state in the vocals; NOT as rich and full, but treble was subdued and relegated to background effects. Though the X4 sounded obviously delicate and sweet in the mid-range, it clearly did not have the oomph for the bass or the treble in such a large room. A DIY solid-state Class A 15-watt amplifier put it to shame on these exciting loudspeakers. Garber fans should explore active and passive dual and tri-amplification with all but the highest-efficiency loudspeakers if they want maximum musical peaks and/or loudest volumes in large rooms.

Still I agree with appellations heaped upon Garber's amplifiers for ultra-high efficiency loudspeakers, at normal sound levels, in typical-size living rooms. The X4 is indeed liquid-smooth, always pleasant, never fatiguing, with excellent musical detail. The X4 was delightful on my Big Ole Horns. It certainly was everything most music and movies in my smallish listening room required. They are a perfect amplifier for passive dual-amplification on my hyper-efficiency of my mid and high end horns.


In my own Enjoy the Music.com category, the X4 is easily five Blue Notes – as best it can be, money no object. I was very pleased with most aspects of its performance. I would award it a sixth Extra Merit note if possible. I strongly recommend Don Garber's X4 with Tung Sol 46 tubes for uber-efficient loudspeakers, preferably with solid-state bi-amplification or sub-woofer. I really did enjoy the music.



Sub-bass (10Hz - 60Hz)

Mid-bass (80Hz - 200Hz)

Midrange (200Hz - 3,000Hz)

High Frequencies (3,000Hz On Up)



Inner Resolution

Soundscape Width Front

Soundscape Width Rear  
Soundscape Depth Behind Speakers

Soundscape Extension Into Room


Fit And Finish

Self Noise

Value For The Money


Type: Vacuum tube stereo power amplifier
Power: Approximately 1.5 Watts
Input impedance: 470 kOhms
Output: 4, 8 or 16 Ohms
Input Connection: Two RCA
Output Connection: Four-way binding posts
Price: $1095 ($1595 with Hashimoto output transformers)


Company Information
Mr. Don Garber
Brooklyn, NY

Voice: (718) 625-7353
E-mail: dgfi@earthlink.net













































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