Inspire by Dennis Had IHA-1 Dragon Version

Average User Rating:
4.625/5,
  1. Currawong
    4.5/5,
    "The Dragon Inspire amp is both versatile and good-souding and can scale up with better tubes."
    Pros - Drives headphones well. Scales up with a better power tube. Good variety of options depending on budget.
    Cons - Front panel is not the most attractive. No gain setting options.
    [​IMG]

     
    A couple of years ago I happened to be in North Carolina, visiting friends who live near Moon Audio, so I took the opportunity to visit and try out some of the gear there and spend some time chatting to Drew and his wife Nichole. It was also a chance to pick up a reasonably-priced (ie: in the hundreds of dollars) set of custom-length silver interconnects, something that would normally cost in the thousands from companies nowadays. 
     
    I already own one Moon Audio cable, a Silver Dragon for the MrSpeakers Ether. I bought it second-hand as I only had a prototype DUM cable for them as I had bought one of the original first-production models. Like the Black Dragon, I didn't find the cable particular remarkable -- nothing jumps out about the sound when using them. That experience became a precedent for my experience with the Dragon IHA-1 Inspire.
     
    The IHA-1 was designed by Dennis Had, previously of Cary Audio, and very well-known for his tube amp designs. I had only seen Cary Audio gear in various high-end stores, but never auditioned any systems using them, so this was to be my first experience with one of his amps. 
     
    The IHA-1 is a relatively straight-forward design, with one power tube, by default a Electro Harmonics 5Y3GT, but compatible with any 5U4 type rectifier or 274B tube. Headphone (or optionally pre-amp) drive is provided by 2 6SN7 tubes, one per channel, and output is via transformers. 
     

     
    The amp can be ordered with upgrades: Lundahl transformers and/or NOS (New Old Stock) tubes. While the former is obviously a factory option, people with existing tube collections may not need the latter. For review purposes, the model sent had the NOS tubes included and a rolled a couple of my own collection in for comparison. 
     
    I've found that every amplifier manufacturer has its own "house sound" of sorts. For those of you who already know their way around tube amps, the Moon Audio "house sound", which is apparent both in their NOS tube selection for the amp, as well as their cable designs, can be best summarised by the chrome-top Sylvania 6SN7 that came with the amp -- a smooth, even sound that doesn't jump out at you, where the detail is there, but presented in a manner without drama.
     
    What was most lovely about the Inspire IHA-1 was the almost total lack of noise (it took using IEMs to find any, and then it wasn't at all a problem with the less sensitive pair) and the general even-handedness with which it drove everything from the Sennheiser HD800 to HiFiMan HE1000 V2. It doesn't present the music with warmth, as in the manner of the almost syrupy sound the Woo Audio WA8 had, but if something like FiiO's X7 is "steel", Audio-gd is "black opal" and the WA8 is "brass", then the Dragon Inspire might be "marble".
     

     
    I didn't have enough tubes or adaptors to do a lot of rolling, but I dropped a pair of GE red-base 5692s in place of the chrome-tops, which gave a more lively, if a bit more aggressive presentation. For the power tube I had a spare Mullard metal-base 5AR4 that I had bought as a pair.
     
    I'm pretty much a fan of the High Definition Tape Transfers jazz albums, some of which are magical. The Mark Colby Quartet in DSD256, decimated by Audirvana into PCM and fed to the Yggy as 178.6k is wonderful stuff, much of the dynamics present in the instruments despite the original recording age. Listening with the HE1000 V2, my Mullard metal-base GZ34 seemed to open up the soundstage and deliver more of the dynamics of the instruments than the RCA 5U4GB, while keeping the smoothness and liquidity of the Sylvania 6SN7s.
     

    NOS selection RCA 5U4GB on left. Mullard metal base GZ34 on right.

     
    Even with the Mullard the amp doesn't quite have the big-iron relaxed and spacious sound of my ALO Audio Studio Six with the HE1000 V2, even after I'd rolled Sylvania 6V6GTs in to even up the comparison.  What might be an interesting battle would be with all upgrades against the similarly-priced Apex Sangaku, though that amp, from memory, was most enjoyable with planars and less inspiring with the HD800.
     
    As my loaner had the optional pre-amp outputs included, I used it with my ADAM ARTist 3 speakers. While not the same as using it with a proper system, I can usually get a fair idea of how an amp’s pre-amp functionality this way. Flipping the switch on the back to change to pre-amp mode, the result was as satisfying as it was using headphones.
     
    The smoothness didn't detract at all from the dynamics of the San Antonio Symphony Orchestra performing Concierto Andaluz for 4 guitars & orchestra from the Mercury Living Presence CD set. The amp brought through both the fine detail of the instruments as well as demonstrated much of the capabilities of my Schiit Yggdrasil in this mode. It did this to a sufficient degree that I could switch the USB converter that I was using with the Yggdrasil and easily make out the subtle different in how the music sounded as a result.
     

     
    Noteable that with my speakers set at the centre "0" volume setting, with the Yggdrasil as source, I had the volume, which starts at the 6 o'clock position, at around 9 o'clock. I expect this might be higher with speakers that aren't in near-field as mine are.
     
    Functionality-wise, my only complaint might be that the gain might be set a bit low for some people, or some equipment, as I had the volume up at 3pm, though that was with the above-mentioned jazz, and other music had it closer to 12 o'clock.  I'm also not a fan of the locking version of the Neutrik headphone jack, though it might save someone accidentally shorting the amp for an extended period of time should the plug be yanked half-out.
     
    When I first visited Moon Audio, I tried out a custom tube amp that Drew had in his showroom. At the time it, along with Black Dragon cabled HD800s was too smooth for my tastes, much as putting all green-label chrome-top Sylvanias in my Studio Six was. But now I've had a chance to get used to this with a variety of headphones, I appreciate it more than before. 
     
    Overall, the Dragon Inspire drove headphones effortlessly, from IEMs up to top-of-the-line full-sized models and is a highly capable amp. In my system, it was only bested by an amp that is far more expensive. It’s not the kind of amp for someone looking for warmth and lushness, but for good, all-round tube performance, with the option for a bit of variety, and even a bit of a sound upgrade, via tube rolling.  Given the price of the amp, I'd thoroughly recommend it.
     
    Thanks to Drew from Moon Audio for lending me the amp for review. 
     

     
     
     
  2. Frank I
    4.5/5,
    "The Return Of A Legend"
    Pros - transparent and nothing between you and the music
    Cons - need to be matched with the right source for volume levels
    [​IMG]
    Back in 1997 I visited my brother-in-law in Rochester, NY and not having much to do (because of the frigid weather in the region) we decided to go listen to some high end gear in a few local audio boutiques. Two-channel audio was king in those days and I had been looking for a new amplifier, so we decided to venture out and explore.
    There was a shop in Rochester that was carrying B&W speakers and Steve McCormick’s DNA amplifiers. We made that our first stop and it became my first introduction to an amplifier designed by Dennis Had. The main system was playing Holly Cole. The speaker was a B&W floor standing model. The vocal was seductive and lifelike. The baby Cary 300B mono amplifiers were being used in the system.
    I remember that the sound was liquid and palpable and was unlike anything I had ever heard or experienced before. Little did I know at the time it was the beginning of a love affair with tubes (and that passion still burns in my heart and soul as strong today as it was then). The amplifier really made realize what was possible in music reproduction. The baby mono amps were priced at $3500 pair (not inexpensive) and unfortunately were not in my budget at the time.
    When Drew Baird (of Moon Audio) had told me that Dennis Had was coming out of retirement and was inspired to do a headphone amplifier, my head start buzzing. Those feelings and fond memories of those early day auditioning the Cary sound immediately came to mind.
    Dennis Had has been building and designing amplifiers since he was a young boy. His time with Cary produced products that are in still in production today and have achieved a legendary status. The newly created Inspire Dragon is old school in design philosophy. Dennis believes in single-ended topology in his designs and still builds amplifiers the old-fashioned way; using simple circuits and minimal parts. The Inspire IHA-1 Dragon was designed after Dennis realized that there were lot of people using headphones and the designs had matured to where they needed good and clean amplification to bring out the best sound and musicality. After listening to various headphones, Dennis became so excited and decided to build his own amp.
    [​IMG]

    Design

    The Dragon IHA-1 is a simple circuit that Dennis designed to provide the purest output available. There are no parts in the signal path. The amplifier sports two 6SN7 driver tubes driven by a 5Y3GT rectifier. The rectifier acts more like a power tube.   The features of this amplifier are available from the Moon website and listed here: http://www.moon-audio.com/headphone-amplifiers/dragon-inspire-iha-1-tube- headphone-amp.html.
    The amplifier is is painted in a high quality clear coat attractive paint finish that resembles a fine Merlot. The Dragon has a DACT 100K attenuator that runs a pair of 6SN7 tubes and puts out 1W of power. The Electro Harmonic 5Y3GT rectifier is included as part of the standard tube package, which also includes two Russian 6SN7. Tube rollers will be able to substitute any 5U4 type rectifier or 274B tube.
    There are two headphone outputs in the front. One ¼ inch singled and a 4-pin XLR output as well. The amplifier is transformer coupled allowing for the use of just about any dynamic or planar headphones available today. The amplifier weighs a hefty 15 pounds.
     

    Sound

    The Dragon was setup with the Chord Hugo driving mostly lossless files from my iMac. The majority of my listening was done with my LCD X and HD 800. Also used were the Hifiman HE560 and the Alpha Dog planar headphones. The Oppo PM-1 saw some listening time as well. The Dragon volume control was used with the Oppo BDP 105. While using the Hugo as a source I used its digital volume control. The Hugo had sufficient gain and was able to drive the Dragon to loud levels.
    Michael Buble’s “Close Your Eyes”, from the album To Be Loved, is a beautiful song. The track immediately will draw you in with its wonderful lyric and the song is a personal favorite that reminds me so much of my wife. Michael vocal is pristine and the Inspire Dragon made me feel the song. I became intensely involved with the lyrics.
    The Dragon emotionally drew me in and had me thinking of that special person who is so important in my life. Buble’s voice is inspirational and brought tears to my eyes. I completely forgot about the gear and connected emotionally with the lyrics. Shelby Lynne’s vocals on “Just a Little Loving”, is well recorded and the vocal is one of my favorites in evaluating amplifier performance. The Dragon was articulate and had her vocal centered in the front of the soundstage. Shelby voice was clear and had body and you could feel her delicate and deliberate phrasing while singing this beautiful track.
    The Dragon, utilizing the stock rectifier with the upgraded Sylvania 6SN7 chrome top tubes, delivered the right amount of texture. The sound was clean and dynamic. The bass line was very identifiable with the Electro Harmonic rectifiers. Using the Sophia 274B, I felt that the bass was not as defined and far less dynamic. The Sophia tubes were simply less enjoyable.
    [​IMG]
    The midrange delivery of the Dragon is classic “Had” design. I was transported back to that time in Rochester when I had first heard the magic Cary 300B sound. This amplifier has that wonderful midrange tonality. Listening to Chris Botti’s trumpet on Impressions, “Prelude No. 20 in C minor” has that rare sense of “you are there” feeling. The trumpet was dead center and slightly up front with air around the instrument, which made it stand out in the performance.
    Closing my eyes, the performers around Botti were defined and focused in their own space with excellent separation. The delicate lyrical tonality of his trumpet was all there. The instrument sounded live and realistic. There were no artificial or electronic glare or glaze. The music was so delicate and inviting and the Dragon brought out the best in Botti’s performance.
    On the second track “Per Te”, with Andrea Bocelli, I became focused on the trumpet in the opening of the track because it was so delicate. The tonality was beautiful and absent were any hard or harsh sounds coming from the trumpet. The trumpet started to fade and Bocelli’s vocal started coming in and was inspiring. The beauty of the lyrics, although sung in Italian, felt universal as the Dragon disappeared into the music. All that was left was the beauty of Bocelli’s vocal and exquisite musical tonality. Never did I feel there was anything missing, the midrange was special and the treble was also musical. The magic that tube amplifiers provide with tonality usually is only heard in live performances. And the Dragon had that magic.
    [​IMG]
    Bass with the Dragon is excellent. The use of the stock rectifiers brought out a well-defined and tight bass. Much more than the Sophia 274B rectifier, which I found, was a little light in bass delivery. Kenny Barron’s, The Art of Conversation, has Dave Holland playing acoustic bass. On the opening track, “Oracle”, I could hear the texture of the bass notes with excellent extension and definition. The instrument was focused and spooky in realism while rendering its own space within the soundstage. There was separation and space between Holland bass and Barron’s piano. Kenny was to the left and you could hear and feel his involvement with the instrument as his hand was moving across the keys and Holland’s bass was in its owns space and had excellent extension.
    Pat Methney’s masterful work with Charlie Haden on Beyond the Missouri Sky – an album filled with terrific melody and tonality – is exceptional. Pat acoustic guitar is beautifully placed in the forefront and his delicate playing on “Waltz for Ruth” is something special. Haden’s bass is almost behind Methaney and on some lesser equipment it is hard to notice the separation of the two performers.
    The Dragon did not disappoint in being able to distinguish the separation and I was able to visualize some distance between the performers in the soundstage. Haden’s playing is exceptional and the Dragon was letting it all come through in a defined space within the soundstage.
    Listening to large-scale recordings like Copland’s majestic Fanfare for the Common Man, the Dragon was able to deliver a terrific performance. It had sufficient speed and dynamics to make this track come to life. The performance was all there and the soundstage was layered and I could hear every section of the orchestra. The Inspire Dragon was able to make it a believable performance. The Dragon never clipped while playing this wide dynamic recording. Many amplifiers I have used have struggled in reproducing this track.
    The Hugo volume control was being used with the Inspire dragon. I noticed I was getting more volume at higher levels with difficult to drive headphones. The Hugo added more gain and could drive the little Dragon to concert hall sound levels.
    The amplifier performed well with any headphone. Whether I was using the Alpha Dog or the HD 800, the Dragon did not have difficulty in driving either headphone. The Alpha Dog can be difficult with some amplifiers because it is not as efficient as some other planar designs and loves power. The Dragon easily drove the Alpha Dog and is a synergistic and good match.
    [​IMG]

    Conclusion

    The time I had spent in 1997 up in Rochester audio boutiques had opened my eyes and ears to tube amplification. Dennis Had’s baby Cary amps forever changed my life with how I would listen to audio components. The sound was more musical than any solid-state amplifier I had heard in audio at the time. The sound was magical and for me made me want to explore and eventually purchase tube amplification.
    My lifelong love affair with tube amplifiers is still as strong today as it was back then. The Dragon delivers clean sound with nothing getting in the way of the performance. The musicality and tonality of the amplifier is there with nothing left out. The design is simple with no parts in the signal path and nothing in the way of musical delivery. Headphone enthusiasts can utilize just about any efficient headphone with either a XLR-4 or singled ended cable. The Dragon delivers for me everything I look for in a good tube design; it always had me involved and never left me wanting for anything during my listening sessions.
    The Return of the Legend was well worth the wait as Dennis Had has brought an affordable music lover’s product to the marketplace. So if you want to see what the fuss is all about with the Dennis Had design, call Drew Baird over at Moon Audio to arrange an audition. The Dragon is the triumphant return of a masterful artisan designer and is highly recommended for any music enthusiast. It’s a well-designed product that offers both performance and excellent value and an easy recommendation.
    - See more at: http://headphone.guru/inspire-ha1-amplifier-return-of-a-legend/#sthash.XTGZwUkz.dpuf
    Butler and ButtUglyJeff like this.
  3. BlakeT
    5.0/5,
    "Magically H O L O G R A P H I C"
    Pros - Sound Quality
    Cons - ?

     
     
     
    I’ve had my Dragon Inspire IHA-1 now for a sufficient time period to post my thoughts. I will use a subjective 5 point scoring system.
     
    Setup:
     
    Power Conditioning:  Blue Circle Audio FX2 XOe and Blue Circle Audio PLC Thingee FX2
     
    Power Cables: Sablon Audio Gran Corona
     
    Audio Chain: MacBook Pro running Audirvana Plus > TotalDac D1 usb cable/filter > iFi iUSB > Light Harmonic 10G split usb cable > Berkeley Audio Alpha usb/spdif converter > Siltech HF9 aes/ebu > Bel Canto DAC 2.5 > Siltech 220i interconnect > Jeff Rowland Capri preamp > Siltech 220i interconnect > Dragon Inspire IHA-1 > T1’s/TH900/3000ANV
     
     
    Build Quality:  4.5 out of 5
     
    The IHA-1 is a relatively heavy (for the size of the chassis) unit and appears robust.  Everything is tight, knobs have no loose play, the unit sits flat on a flat surface, no issues whatsoever. 
     
    The paint job is terrific and you need to see it in person to really appreciate it.
     
    The tube sockets and headphone inputs are very solid and I believe they will last a very long time and continuous tube rolling and plugging and unplugging of headphones should not be a problem.
     
    When using my TH900's or my 3000ANV's and there is no music playing, I can hear a barely audible faint hum in the right channel.  It disappears when music is playing.  It does not bother me, but I wanted to mention it.  With my T1’s, I can’t hear the hum at all.  Out of curiosity (not concern) I corresponded with Dennis Had and Moon Audio about this and it is not a defect.  It is a counterpart to the design of the amp and the sonic goals for this amp.
     
     
     
    Aesthetics:  4.0 out of 5. 
     
    The faceplate of the IHA-1 has a bit of “old school” “no nonsense” look to it.  I like it, but think it could be improved a bit with perhaps a different faceplate.  The terrific paint job makes up for the rather utilitarian looking faceplate.  I do like the overall size of the chassis.  Let me state again- the paint job is outstanding!
     
     
     
    Sound Quality:  5 out of 5.  I'd like to give it a 6 [​IMG]
     
     
    I don’t believe one can review the IHA-1 without mentioning the tubes being used.  The IHA-1 is very transparent and if your headphones are of sufficient quality, you will very easily be able to tell differences when rolling in different tubes.  After a bit of experimentation, I settled on a NOS Brimar U52 for the rectifier tube and NOS Sylvania 6BX7’s, which provide a bit less power than 6SN7’s, but I find them to be the most enjoyable (I understand the 6BX7’s are Dennis Had’s favorites, and I can see why).  If you need more power, you can swap in different tubes.
     
    If I had to summarize the sound of the IHA-1 in one word it would be “magical”.  I don’t mean to sound like a new age hippie (because I’m not), but this amp transports me to another planet.  On the planet are two things- me and the music, and after a while, it is just the music.  Everything around me… all the possible distractions melt away from my consciousness.   My tendency to analyze the sound tends to drift away as well.  I get swept up in the emotion of the listening experience.
     
    Breaking the sound down into separate aspects, I would say the IHA-1 earns a solid 5 in every single sonic aspect I can think of, except for the bass, which I would give a very good 4 or 4.5, which is down to tube designs vs. solid state designs and not a design issue with the IHA-1.  I would personally take the IHA-1 over any solid state amp without hesitation.
     
    Forcing myself to analyze the sound, I would describe it as very holographic.  The sound is exceptionally three-dimensional, round, full, highly detailed, airy and slightly warm.  And by “warm” don’t take that to mean “rolled off”.  It is not rolled off at all- it seems quite extended.  Treble and midrange are spectacular.  Bass is very nice as well.   Bass is perhaps not as hard hitting as a top level solid state amp, but still quite good.  For context, I listen to EDM more than any other music genre and the IHA-1 is able to keep up in the bass department.
     
    The IHA-1 also excels at timbre, fullness of tone, dynamics and soundstaging.  With the right recordings, the ability of the IHA-1 to recreate the recording venue is breathtaking. I can’t point to any weakness or sonic shortcoming.   It just sounds “right”.
     
    I really don’t know what more I can say.  Dennis Had is a genius.
  4. atubbs
    4.5/5,
    "Holographic Sound, Great Microdynamics"
    Pros - holographic sound, fantastic microdynamics, solid build, limited production/hand-built, legendary audio designer, perfect ergonomics
    Cons - price, visual aesthetic is "love it or leave it," not the best pairing for ultra-sensitive (noise) or ultra-demanding (power) cans
    BACKGROUND 
     

     
    You may not have heard of Dennis had, but you've likely heard of his products.  Dennis Had and his wife Donna founded Cary Audio Design in 1989, but the story I've been able to piece together (go Google a bit, I'll wait) is also rich and fascinating. As he mentions in his eBay listings, he built his first single-ended 6V6G amplifier for a 7th grade science fair and has been hooked ever since.
     
    Had left Cary a few years ago, but he continues to design and hand build single-ended tube audio components as a hobby. His "retirement hobby" is our gain. Had releases a handful of his designs on eBay semi-regularly (I've seen quoted a figure of 1-2 per week but have seen far less than that recently), usually consisting of amplifiers (stereo and mono pairs), integrated amplifiers, and headphone amplifiers. True to his original beliefs, they are all single-ended designs focusing on simplicity and the listening experience.
     
    Had's affection for single-ended designs are well-explained in a 1995 Stereophile interview:
     
     
    THE AMPLIFIER
     

     
    The Dragon IHA-1 is a custom version of the Inspire IHA-1 offered irregularly on eBay. It is distributed exclusively through Moon Audio and as I understand it was inspired by Drew's introducing Dennis to some Audeze headphones. There's a quick video with Baird and Had about the amp if you want to learn more at Moon Audio's site.
     
    The Dragon Version has some changes versus the model that most commonly appears on eBay. I'm not aware of the internal changes if there are any (and I don't have the heart to crack mine open), but externally some differences are readily apparent. First, the front plate is black and the paint job is a copper-red metallic finish that would feel at home on a vintage American muscle car (versus walnut veneer on white). Second, the LED is blue instead of read. Third, the output jacks are upgraded, with professional locking 1/4" and 4-pin XLR connections (this is a single-ended design, but the 4-pin jack takes its connections from the output taps of the output transformers; my listening has been exclusively via the 4-pin jack). These take the place of a pair of 1/4" inputs and are mounted to the chassis rather than through the faceplate. Fourth, the potentiometer has been replaced with a dual DACT stepped attenuator.
     
    On the back of the unit there are two pairs of RCA inputs, a fuse holder, and an IEC inlet. The amplifier comes with a standard power cable.
     
    The design leverages dual triode 6SN7 tubes in class A single-ended mode with zero feedback. Had recommends the (lower gain) 6BX7 but any 6SN7/SBL7 should work (e.g. the RCA 5692). The tube rectifier is 5Y3/5U4/274B types as well as 5AR4, though Had recommends against indirect heating in this application.
     
    The design is direct-coupled and output is via custom air-gap output transformers. It produces just over a watt into 32 ohms and a bit under a watt near 600 ohms. That should make it powerful enough to drive most loads.
     
    AESTHETICS & OPERATION
     

     
    Make no mistake, this is a low-production bespoke product: The fit, finish and polish are good but this unit will not win any design awards. The front panel is connected to the chassis with some sort of adhesive and bits of hair and fuzz around it remind you of that fact under any close scrutiny.  The output transformer sheet metal bends aren't particularly uniform and the labels on top of the transformers are crooked. The RCA inputs in the back aren't labeled 1 or 2 (they do have channel indicator rings, however), though it's easy to figure out which is which. There are at least four different styles of type on the front face and they look like they were placed without any real thought to design and layout. The amplifier's packaging is "toss it in a box wrapped in 100 feet of bubble wrap. The entire bottom of the amplifier is covered in Dennis's scrawl, except for the part obscured by the rubber foot (no joke). I happen to thing it's a nice touch on a very personal product, but others may not. The blue LED looks sort of like an awkward afterthought; I'm pretty sure I prefer the red of the stock unit. Those looking for the attention to detail and incredible fabrication of e.g. a Woo or HeadAmp will sneer in disgust. It's not that the Dragon IHA-1 is outright ugly, but it looks a lot better in the dark.
     
    The tube sockets are solidly anchored; I have no concerns when changing valves. For that matter, everything about the amplifier is solid. The transformers aren't going anywhere, the RCA jacks are firmly installed, and there's no play, wiggle, or shake in the amp. Despite the entire previous paragraph, everything mechanical and functional about this amplifier is clearly sorted and well thought-out. Had may not be a champion of the visual aesthetic, but his design shows mastery of the physical and functional. The input selector switch has a firm and positive throw. It's never going to be triggered by accident and it's obvious when a change has been made. It's intuitive that going left is the left input and going right is the right input, and that mute is in the middle; operation of the amp in pure darkness reminds the listener that this amp's ergonomics were designed for somebody using it ... not somebody looking at it. The attenuator knob has perfect knob feel and was left pleasantly small. For me this is important; I find large knobs to have enough size and mass that positive identification of detents becomes difficult as attenuators age. The rectangular shape of the knob makes it easy to identify and turn with a couple of fingers in the dark.
     
    I'm not a huge fan of locking connectors for headphones. They feel great, but they increase the risk of destroying a cable, headphones, or the amp itself if I do something clumsy (I regret this happens more often than I'd like).
     
    The form factor itself is deceptively small; it's about 2/3 of the depth and width of a typical (~17") stereo component. This isn't that weird since there are a lot of goofy sizes in head-fi. The unit has tall feet and can take up a lot of vertical space when coupled with a large rectifier. The layout is rather compact with the three tubes, capacitor, and three transformers all packed together in pretty close quarters. The three transformers provide a substantial amount of mass, but I would not call the unit heavy as much as solid.
     
    Operation is easy: Plug in the tubes, flip the on switch, wait a few seconds, roll the input selector, and listen to some tunes. At least, I think that's how it works as there aren't any instructions included. I can imagine Had saying "why would you need any instructions? I made this thing as simple as possible, you can't mis-use it!" Or, maybe not, but that's what I'd like to imagine.
     
    Included by default are a Sovtek 5Y3GT rectifier tube and a pair of EH 6SN7s. In that trim, the amp runs $1599. The upgrade tubes optioned are NOS Sylvania 6BX7 output tubes ($100) and a Sophia 274B ($160) rectifier.
     
    For those new to tubes, the output tubes don't look like much when they're running; in some cases (like the Zalytron 5692) the getter in fact completely hides any sort of illumination. They can run hot, however, with surface temperatures around 250 degrees. There's no tube cage on this thing, so be careful. The rectifiers range from mildly interesting-looking to downright gorgeous under operation; the giant Sophia tube is more in the gorgeous direction, with its bright direct heaters and stamped "mesh" plates. It's nowhere near as warm on the surface and could probably be handled during normal operation if somebody was particularly weird.
     
    With both of my signal paths, I find I'm using the volume knob roughly from 9 to 3 with the majority pretty close to noon. I feel like there's an appropriate level of gain gradation in this range and don't feel the amp suffers from the stepped attenuator plague of wanting a setting in-between a particular set of detents. Where in other amps with stepped attenuators I often have problems finding the goldilocks level, this has not been a limitation in use with the HD800/LCD-3F.
     
    THE SOUND
     

     
    This brings us to the only thing that should really matter for those considering the purchase of this amplifier: How does it sound? Well, that's a good question! I'll offer my initial impressions, but will caution that these are at best preliminary: I reserve the right to update this as I have more time with the amp, roll more tubes, and rotate more headphones through it. 
     
    I've spent about 20% of my time listening to the amp with Sennheiser HD800s and the remainder with Audeze LCD-3Fs. Both cans were wired with Moon Audio Silver Dragon cables and terminated with 4-pin Neutrik connectors. I did not (and indeed may never) try the 1/4" output yet. I like both, but I love the Audeze cans on this amp especially; the pairing is special.
     
    Before I continue, one final disclaimer: My desktop headamp listening experience is most extensive on the HeadAmp GS-X (mk II modules), Woo WA7/WA7tp, and the Oppo HA-1. When I used blanket generalizations like "compared to other amplifiers" I'm referring more to this canon than the entire universe of headamps. 
     
    It's for me somewhat difficult to describe how this amp sounds; the easiest way I can really describe it is that it's a very good lens through which one can listen to music through a certain set of tubes. If the tubes sound a certain way, the amp sounds a certain way. In rolling several different valves I never latched onto a sound signature of the amplifier itself. I don't mean to be evasive about this, but I remain struck by a notion that this amp is all about getting out of the way and letting the tubes do their thing -- good or bad. 
     
    So, the problem then is I have a hard time latching on to the common refrain about such a design that the amp sounds warm. With certain tubes it sounds a little warm, I guess, but I don't think warmth is an intrinsic property of this amp. Instead I would describe the sound signature of the amp and tube configuration having more the characteristic of "not dark" than "warm." The presentation strikes me as having a neutral mid-range, with austere bass and neutral to just shy of neutral treble.  While the bass does not have incredible slam and impact, the precision of the attack and release more than make up for it: There is plenty of low-range extension and it doesn't leave me thirsty. The low-end signature of the amp reminds me of that of the HD800s; the pair combined amplifies the effect. Whether or not I'd call it "accurate" bass I think the word that comes to mind most is "realistic."
     
    I rolled with a few rectifiers and half a dozen output tubes, but fell into immediate love with the pairing of a Sophia Princess 274B (from Moon) and a pair of CBS-Hytron 5692s (from Upscale Audio) and haven't changed since. I wanted to love the Sophia 6SN7s just because they looked amazing next to the 274B, but it just wasn't meant to be. Stop looking when you find the one you love, or something like that? So, all of the feedback about the amplifier in this review comes from the Sophia/Zalytron pairing unless otherwise noted.
     
    Soundstage remains a nebulous concept for me with headamps: I wouldn't describe the presentation as particularly broad or narrow versus other amplifiers. Positional clarity or lack thereof similarly is not particularly unique or distinctive. The word that does come to mind is that the audio presentation is "holographic." It's not that the performers are suddenly in front of me on a stage and I can tell you how far away they are and how far they sit apart; those are the terms and sensations I still reserve for loudspeaker systems. Instead, the sound itself is incredibly three-dimensional and provides a great deal of texture and depth. I'll use the holographic term as somewhat of an analogy: A lot of paintings have a great deal of depth and texture and intrigue, but they look the same no matter how the light strikes them or how they're tilted. The hologram has more to it than that; one finds different things depending on what they're paying attention to and it can be somewhat overwhelming to try to take it all in at once. Good music is confusing and overwhelming and rewards careful as well as casual listening. This amplifier is not a scalpel for surgical analysis of music. It seems to be more designed to step back and say "look, there's all this crazy stuff going on that you never realized before!" Wow. Give me a few minutes...
     
    ... dear reader, I got lost listening to the amp for a few more hours, but I'm back again. Sorry about that.
     
    The holographic sound is what grabbed my attention with this amp, but I want to talk a little bit more about what retains it: More than anything, the microdynamic capability of this amplifier is astounding. I have not been exposed to an amplifier that delivers better microdynamics.  To all of those folks ready with the pitch forks, there are plenty of amps I haven't heard yet, especially in the high-end valve realm. The texture and detail capability is impressive. It doesn't matter if I'm getting slammed with loud beats, a pin drop is still distinct. The speed and precision of the amp is incredible. I listened to songs I've probably heard at least a thousand times, and with each one I was discovering new depth and richness of sound that I never experienced in the past. This didn't just happen when I was listening for it; the amp has a way of grabbing your attention and saying "listen to this, just get lost in this passage, you've never heard it like this before..."
     
    ... sorry, got distracted again. I'd say I lost a few hours of my life, but it was definitely a gain.
     
    If folks are interested I can try to comment on other aspects of the sound quality, but for me this part is the kicker: The amp is incredibly euphonic for me for the reasons listed above (holographic sound and microdynamics). It makes me want to listen to the music and it makes it incredibly hard to listen to the equipment. If there's a dragon to chase in head-fi, that's mine. I hate listening to equipment. Listening sessions that end with "I wish this X had more Y" just fill me with disgust. I'd rather end up with "okay, just one more track..."
     
    It could be said that everything I'm hearing is just second harmonic distortion and I'm in love with distortion and not signal. To that I say "that's entirely possible!" But, I enjoy it just the same. There's plain and there's French Vanilla, and I'm enjoying the French Vanilla with this amplifier. There is probably something intelligent that could be said about how the amplifier lacks clinical accuracy and 100% authentic reproduction, but I'm not the guy to say it. Count me as a believer in whatever it is this thing is doing to the music. 
     
    MORE OF THE SAME
     
    The capabilities and pleasure of the amplifier have continued as I've expanded beyond the HD800 and LCD-3F. 
     
    First up, the Oppo PM-1 puts on a good showing. These headphones are surprisingly sensitive, so the full range of the attenuator knob is not necessary. Volume levels quickly get into uncomfortable territory around noon or so. Still, I have not had any difficult finding the "right" volume level in the gradations available to me before 1 or so. I like the LCD-3F with this amp more because I like the LCD-3F more, but I think the PM-1 shows very well here. Due to their high sensitivity, Oppo's headphones make the low-level hum in the right channel more obvious.
     
    Given how the LCD-3F sings with this amp, it should not be much of a surprise that the LCD-XC also pairs rather well. I don't have too much to add beyond that they sound a bit more closed than the 3F. Go figure, right? Since they are closed, they also make the low-level right-channel hum ever so slightly more obvious when there is no signal present.  
     
    PLAYING WITH THE EXTREMES: A MIXED BAG
     
    Happy with how the HD800 sounds and very happy with how the LCD-3F sounds, I wanted to explore the amp with some of the more extreme cases I had in my inventory. In the grand tradition of "Will it blend?" and "but does it play Crysis?" we must also confront whether or not the amplifier can drive the HE-6. With the 6BX7 I have to max the gain to get to a "normal" listening level. The 6SN7 pulls things up just enough to have a couple of detents to play with, but I would have a hard time recommending this as being the go-to amplifier for the HE-6; it's just not going to get loud enough for many with that particular set of headphones. With that said, for the volume levels the amp is capable of, the headphones do sound great. So, more sensitive Hifiman models (I have no personal experience) may work better, or this could still be a great pairing for those that don't listen too loud.
     
    At the other end of the spectrum, I plugged my 4-pin-terminated JH13Pros into the amp. I would not recommend this particular pairing; the general noise levels are too high for my taste with this particular in-ear monitor.
     
    Back in a very different direction of hard to drive, I plugged the AKG K701s into the 1/4" jack (good news, I can now confirm it works too). The amp is able to drive these cans and there's still a little room to play in the high end of the gain (more so than the HE-6). With that said, the sound lacks a bit of control compared to e.g. the GS-X in some quick comparisons. The pair sounds decent, but a little thin for my tastes.
     
    NITS AND CONS
     

     
    Let's talk about the downsides. Optioned out with some tubes for rolling, this amp is bumping up against two thousand dollars in the US.  That's endgame or well beyond endgame pricing for a headamp. It might be somewhat difficult to call anything in that league "a value." I would not say the amp is embarrassed by gear at a similar price point. To sum up, on value my feeling is that the amp punches within its weight class and I'm rather taken with it. For those interested in getting more bang for the buck, the eBay IHA-1 lacks the upgrades mentioned above, but it also comes in a bit cheaper at $1200. At the end of the day, this is an extremely low-production hand-built product and one is getting both the benefits and detriments of that.
     
    I think I've already beaten the amp up a bit in terms of looks and fit/finish so I won't go into that point further.
     
    It comes with zero functionality beyond being a two-source unbalanced headamp. There's no line out, pre out, or speaker out. There's no balanced inputs. There's no gain switch (the only real option to adjust there is in tube choice; the 6BX7 provides less gain than the 6SN7 types). About the only display or indication is the blue LED. I tend to prefer this sort of simplicity of focus and purpose, but it's important to keep in mind this terminates a signal path in one's system and nothing more.
     
    Finally, there is a very mild hum in the right channel; it starts when the amp is turned on and rapidly attenuates after the first few seconds of amplifier operation. After 15-30 seconds it's virtually inaudible and incredibly difficult to hear even with quiet passages in the music. Had responded to another member explaining this in detail in this post. I'd recommend reading that for any concerns on this point. I think this would only bother or impact people with extremely sensitive headphones/in-ear monitors, and it's really only noticeable when there's no signal present otherwise. I don't tend to listen to headphones without a signal present, so this has not been a problem for me! Had clarified in e-mail that it's down about 78dB from the music signal, so when I say mild, I mean mild. I was not clear on whether it's because of the circuit design or the physical layout; I attempted to get clarification on this point but did not hear back from Had. In my experimentation, this is less noticeable when using 6BX7 tubes than 6SN7; several other head-fi folks only notice it with the 6SN7. I did experiment with different power cords, isolation transformers, power regenerators, and other voodoo devices. None had any particular impact on this hum.
     
    ASSOCIATED EQUIPMENT AS REVIEWED
     
    Power Cables: Pangea AC14SE
    USB Cables (don't make a difference, but they look pretty): Wireworld Ultraviolet
    Line-Level Cables: Kimber Kable Timbre (digital: Ultraplate, analog: WBT)
    Phono Cables: Kimber Kable TAK-Cu
    Power Conditioner: Furman P-8 Pro Series II, Torus Power RM15Plus
    Digital Chain: Macbook Pro, Audiophileo1/PurePower, NAD M51
    Analog Chain: Sumiko Blackbird, Pro-Ject RM-10.1, Simaudio Moon 320S/310LP
    Headphones: Sennheiser HD800, Audeze LCD-3F, Hifiman HE-6, AKG K701, JHAudio JH13Pro
     
    CRITICAL LISTENING SOFTWARE
     
    The following are the recordings I focused on when listening critically; have put a lot of additional software through the amp when I was just listening to the music. Except where noted, I auditioned each in both vinyl and red book from my own CD rips.
     
    Opeth - Pale Communion, Ghost Reveries                           
    Porcupine Tree - Lightbulb Sun
    Steven Wilson - The Raven That Refused To Sing
    Nine Inch Nails - Hesitation Marks (Digital copy is direct FLAC)
    Aphex Twin - Syro
    Stravinsky - The Firebird Suite (Reference Recordings, analog only)
    Miles Davis - Sketches of Spain
     
    FULL DISCLOSURE
     
    I am a Moon Audio Ambassador, but that role has nothing to do with the purchase or evaluation of this amplifier. I purchased it with my own funds and reviewed it independently.
     
    UPDATES
     
    20141115 - a few clarifications, fixed a few typographical goofs.
    20141117 - added a few more headphones, clarified current state of noise understanding
    20141117 - further clarified hum concern, linked to BlakeT's information on this (thanks!)
    20141118 - added a brief section about the PM-1, LCD-XC
    20141130 - minor wording tweaks
    20141207 - minor wording tweaks, type-o squashing, admitting I might just like second harmonic distortion
     
    TODO
     
    These are things I'm still intending to explore, and may provide updates in these areas over time:
     
    1. Tube rolling!