ALO Audio Studio Six Tube Headphone Amplifier

Pros: Awesome performance, not wavering in the slightest even driving 4 pairs of headphones. Tubes are inexpensive to roll. Excellent build quality.
Cons: A pair of speaker taps would make it perfect for near-field listening too, as it has enough power for speakers. Stock TAD 6V6 tubes aren't the best.

(Scroll to the bottom to see the video review)​
The courier, towel wrapped around his neck and sweating profusely arrived at the door with the huge box. Not at all new to such things arriving at my door, he handled the box as if it only contained a feather, unlike myself as I carried it carefully through to my room. The big, black aluminium beast was easily extracted from the neatly cut foam to my rack.

Six sockets and … more than 6 tube boxes. 4 kinds of tubes and a few minutes of pulling tubes out and figuring out where they go, with only the skinny OB2 rectifiers being obvious, I had the amp ready to go. But not myself, as I had to head off to work. I did leave it and my DAC switched on so I could return later and they would be nicely warmed up, ready for listening. 
A manufacturer once said to me, that being a dedicated audiophile isn’t about owning gear that is good enough, it is about gear that is better than good enough.  To design an amp, or any piece of gear for that matter, that sets itself truly above the many that are available, not just in price, requires great skill and dedication. Head-Fi members insist that such equipment lives up to its price as well. Thus a top-of-the-line amp from ALO Audio was both unexpected and raised many questions. The answer was that the amp is designed by Thomas Martens in conjunction with ALO Audio, and has been in development over the last two years.
So, listen I did for some days, swapping tubes around as I did so.  Now I am at the point that I have a good picture in my mind of the amp, but am stuck at finding a way to describe my impressions. What I am hearing is excellent -- the music -- but delivered with a high level of detail and in a manner I would describe as absolute, that is, with an unapologetically accurate attitude that shows you exactly how the music is from the lowest bass note up to the highest treble. Not only the capabilities and flaws of the music but of your headphones as well. 
Top-quality SET amps have a reputation for their ability to deliver music with a delicious authority and the Studio Six is no exception. Initially I thought that the soundstage was smaller than my regular reference amp, the Audio-gd Phoenix. However, comparing them showed that it was the other way around: The Studio Six was delivering the music so precisely that I was hearing the music exactly as it was and exactly as everything else in the rest of my system was capable of delivering it.
With well-recorded small jazz or classical ensembles the exact position of every instrument is there in your mental vision. One of my favourite jazz albums, David Chesky's The Body Acoustic, an album of dark latin jazz is delivered with a precision that doesn't slack off for a single note. If the venue was small, then, within the limits of your headphones, the impression is of that. If it was in a concert hall, then a concert hall you get.
Poor recordings are spared nothing, and I was sad that Martha Argerich's performance of Sergei Rachmaninoff's Piano Concerto No. 3 in D minor was not spared having the so-so quality of its recording revealed. Van Halen was going to be out of the question too. Any even moderately compressed pop, such as Jack Johnson was going to reveal itself clearly as such. I love Elbow's The Seldom Seen Kid, but some of it was a bit harsh. 
The treble, which I'd already determined was delivered well with the NOS tubes and my Magnums was equally so with the HD-800s. It was the bass notes I was more interested in, however, as I wanted to know if they were as tight as with other headphones. The cello on What Am I Gonna Do With You Aime? (Kenny Rankin on Chesky Records 10th Anniversary album) was delivered with the kind of clarity I expect from high-end speaker systems. 
Playing very fast and complex, yet very well recorded music, such as Friday Night in San Francisco (available from HDTracks), the unrelenting detail, without the slightest let-up was overwhelming.  Because the amp doesn't lose even the minutest amount of composure during complex music, the extreme details even during complex musical passages -- super fast guitar riffs, fast drumming, multiple instruments playing all at once, everything is elevated to yet another level, with the Studio Six delivering the full degree of textural information. 
Binaural recordings from Chesky Music, such as Amber Rubarth’s album, were phenomenal, with every sound produced in the entire venue, down to the birds chirping outside, were delivered with absolute precision. Changing any component in my system, I could hear precisely how it affected the overall experience.  
Of course, Chesky's latest binaural recordings are perfect for this high level of headphone rig, but I didn't expect the waves of echo from the room walls to hit my ears so clearly as they did from C.C. Colletti singing You Shook Me (All Night Long).

Extreme dynamics -- extreme micro-detail dynamics. Because the amp doesn't lose even the minutest amount of composure during complex music, the extreme details even during complex musical passages -- super fast guitar riffs, fast drumming, multiple instruments playing all at once, everything is elevated to yet another level, with the Studio Six delivering a degree of textural information that is overwhelming. 
The performance of the amp is so unwavering that even if one plugs 4 completely different pairs of headphones in, even IEMs, the performance through any single pair does not change in the slightest. The question I had at the end of it all was not about whether the amp is worth it, but why it didn’t have speaker outputs. Ken Ball’s reply to this question was to send me a custom cable with a headphone plug on one end and speaker banana plugs on the other.
In fact, initially I didn’t like the presentation with my LCD-3s or HD-800s. However, swapping the interconnect I regularly use with tube amps, Van Den Hul The Orchid, which is Nordost-like aggressive, to ALO Audio’s own Reference 20s changed the character subtly but enough to make the other headphones enjoyable. 
What’s more, the amp is a tube-rollers delight. The tubes range in what they can potentially cost, from the inexpensive OB2s and 6V6s to the 6SN7 and 5AR4 which can range from cheap to highly expensive. Despite this, the amp really comes to shine the most when at least NOS 6V6s are used in place of the included TADs and good choices are made with the other tubes. The main benefit of this is more towards clarity and a lack of harshness, as the amp isn’t “tubey” sounding as such, being more precise-sounding than any solid-state amps I’ve owned.  However, the stock TAD 6V6s, whether due to needing more use, sounded somewhat harsh to me, so NOS tube selection is definitely necessary to get the most out of the amp. 
Not surprisingly, ALO Audio, as well as Audeze, offer a complete package of headphones, amp, tubes and cables (if not source). For a high-end one-stop kit for someone already with a high-end source it most definitely delivers as good as you can get, and you can have fun rolling tubes to your tastes too. 
Thanks to Ken Ball at ALO Audio for kindly lending "Team Tokyo" the amp and cables. 
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Reactions: Admiral Kolchak
GREAT job @Currawong!! Was SO psyched to hear you had the amp kickin!! GREAT job on the review brotha!  I'm about to get some of those Mullards from Ken that he posted for it! Psyched to dig deeper into more tube-rolling discussions on it w/ ya. I'm currently rockin a JJ 5AR4, Sylvania OB2's, a vintage RCA 6SN7, and Tung Sol 6V6's.  WHOA!!
such a great review,
I read it again!! Just got the McIntosh D100 headphone DAC/amp/line-stage (I HATE when they call a line-stage a "pre-amp" - a pre-amp, technically, has a phonostage on-board) but its KILLER ahead of the Studio Six!
Check it out
SP Wild
SP Wild
Great video review!  For an amature video the contrast and quality is far better than those other youtube videos.  I'm a huge fan of Judo and I think the analogy with Aikkido is an excellent way to put it.  Yeah something about SET amps that seem to be able to extract the very best of soundstaging and imaging, I loved my headphones driven with SET.  Must be a testimony of the 2 year development to have the confidence to supply 6 jacks and the unpredictable load this might induce - this is definitively an indication of innovation.  Gosh I wish I had such disposable income.  I always wanted a more refined SET amp than the one I had.  You guys who can afford this are lucky, I can't imagine wanting any more tube amps if I had this one. 


Headphoneus Supremus
Pros: KILLER headphone amp. Grabs you by the...
Cons: no balanced inputs
I just experienced one of the most incredible listening sessions I can remember with the ALO Studio Six!  I'm still in a sort-of sonic shock.
I haven't experienced that sensation since I first heard the Genesis One Loudspeaker System (250k) in Harry Pearson's house (Founder of
The Absolute Sound magazine) for the first time.
This is a single-ended triode amplifier that utilizes 6SN7, 6V6, 5AR4 and OB2 (2) tubes with an over spec'd power supply.  The beefy power supply is important here, as this amp delivers such velocity and authority that it's gestalt reminds me of some of the best in-room single-ended triode designs (like the OG Antique Sound Labs Hurricanes for example (but in smaller form).
I've driven my Audeze LCD3, an Audeze LCD1 on-loan, Sennheiser HD800, and V-MODA Crossfade M-100's at the same time without any noticeable loss in harmonic structure or overall gain!! I ran different lengths of cable so I could hear each headphone individually and not be interfered by the sound coming from the other cans.
My Audeze LCD3's were equipped w/ Moon Audio's latest Silver Dragon LCD3 cable w/ new Furutech connectors for this (formal review coming ASAP). This cable brings out the emotion in music playback like no other on the LCD3's that I've heard- and I've been using Cardas Clear as my reference (and have heard most ALO cables - which are also very good).
The ALO Studio Six is in a class all it's own. This from a proud owner of an E.A.R. HP4, which I considered THE reference for me in high end personal audio. The reason? Not the bass response, or clarity, coherence, and transparency (all the audiophile buzzwords it possesses). Nope. I loved (and still love) the E.A.R because it was the only headphone amp that brought me to tears when listening to music, until now... The Studio Six handles everything from Miles Davis to Daft Punk, Ella Fitzgerald, Aphex Twin, James Blake, Burial and Shlohmo with finesse and authority. It's quiet, allowing for the music to shine through. Even the tactile experience of the amplifier is satisfying, like your money really went to something substantial. Also: With this particular selection of tubes - I suspect Ken Ball and his team experimented on perfecting this design for as long as they deemed necessary to convey music transparently.
After nearly twenty years listening to high end audio I can say that using the ALO Studio Six headphone amp with these components (UPDATED): My Audeze LCD3 magnetic planar headphones - Studio Six - MYTEK Stereo192-DSD DAC - MacBook Pro SSD running Audirvana - is like experiencing my good friend Dan Meinwald's (importer of E.A.R, Marten Audio Loudspeakers, Townshend, and more) incredible high end, full-range in-room stereo system! The only difference? His system, in its current iteration, cost in upwards of 250k!!
I'd say this system has far more dynamic velocity than my room reference system, especially in terms of it's impact on all my senses. If I close my eyes while crankin' this amp and my Audeze LCD3's (or HD800's) I can imagine myself at club Twilo in New York in the mid-nineties (w/ the right underground DJ mix) or in the Hamptons rockin' to Bob Marley in the Summer with some of my best friends since the first grade. The system connects me to the music in ways I've only heard in stereo systems all costing over 100k!
Now, I know the headphones, wire, and amp are all contributing their own sonic characteristics, which is why I always describe the experience of the music with the addition of a new component. But here, in personal audio, with an amplifier this robust, I can say with confidence that old school high end stereo rules apply here: The amp is half the system. In that case, if you can afford this (in life some of the better things cost more money - my Beemer costs more than my Kia) I believe the ALO Studio Six provides the greatest musical experience in personal audio today - because it sounded terrific across all my cans!
That's something special indeed.
I am never giving this amplifier up. I haven't quite figured that out, YET.
A Class-Defining product! Nothing less.
Thanks mfaoro and I'm so sorry to hear about your wife! We're both in nurse-modes! Yes the LCD3's do LOVE a clean watt, but I have enjoyed them numerous times being driven by headphone amps with less power (like the HRT microStreamer believe it or not - that's just silly, but it sounds GREAT), so I think all of this is similar to high end two-channel in terms of trial and error. Sometimes a sonic pairing that makes no sense on paper creates a glorious musical experience! It's part of the magic of music playback that I LOVE. The Studio Six drives the LCD3's very well for me. Their midrange is clean and coherent (not too aggressive or laid-back) the highs are extended and airy, while the bass thumps with authority. I dig that combo.
I submitted my review to Positive Feedback today gents! I sincerely hope you dig it. I'll ping the URL here as soon as it's published
forgot to add my full review of the ALO Studio Six for Positive Feedback in this comments thread!! Sorry bout that guys. HERE'S THE LINK FOR YOU