ALO Studio Six headphone amplifier review


A waggish reviewer buddy recently observed: “So, here’s the problem with headphones. How do you lure a girl back to your room with the promise of a Django Reinhardt album? And what the hell will you do if she actually wants to hear it? Music is a social activity. No set of cans can give [you] that.” Music is a social activity? Not for (most) head-fi-ers it isn’t. The song that sings inside your head is for you and you only. It’s private – a sealed-in listening experience that might be awesome for you it’s not easily shareable.


Alone in a crowd. Remember those iPod flash mobs of the early noughties? Organised via forums, iPod wearers would convene in a public place at an agreed time to dance [almost] silently to whatever was being piped into their heads by their Apple player. The flashmob would disburse as quickly as it formed, usually after ten minutes or so, leaving passers by suitably bemused. These were private audio parties that offered almost no common musical experience; gatherings that held non-participants at arm’s length. There was no exhortation to “come on in, the water’s lovely”.

Taking things a little further in 2013 are the organisers of Silent Disco: a DJ’s song selection isn’t wired direct to a PA system but piped wirelessly to each headphone-set-wearer in the room. It’s an odd sight for onlookers: you see a DJ and you see people dancing but it’s a club space where only the occasional awkward sing-a-long and the shuffle of feet puncture the eerie silence. It’s a private listening experience, common only to fellow headset wearers. Silent Discos are kind of a halfway house between private audio and good old-fashioned loudspeaker sociability.

A manufacturer can develop a product via tight consultation with its potential customer base; design and development by committee. That’s how Michael Goodman played it on Head-Fi with CEntrance HiFi-M8 development and customers seem largely delighted with the end result.


Another way to skin the same cat is for a manufacturer to plough its own furrow, working behind closed doors, peanut gallery be damned. This is how ALO Audio took a couple of years to bring the Studio Six to market. Echoing the late Steve Jobs’ approach to product development, ALO Audio haven’t asked us what we want, they’re telling us what we need: a single-ended (no balanced!) headphone amplifier with zero feedback, all run from an ‘overbuilt’ power supply.

The Studio Six is an all-tubular belle with six insertions of glass and gas: 2 x TAD 6V6 for output, one JJ 5AR4 for rectification, one Electro-Harmonix 6SN7 for voltage-gain and a pair of NOS Raeython OB2 for regulation. Those listeners wanting to extrapolate the NOS vibe to the output tubes should know that ALO offer such options: JAN Phillips 6V6 or Bendix 5992 (6V6), both sold as matched pairs. Silver or black are your colour choices. A deeper dig into specifications can be found over at the ALO website.

Breaking. ALO Audio’s production process streamlining has this month (October 2013) lopped a sizeable chunk from the Studio Six’s sticker. It’s down from $5k to $4k with Teflon caps a $200 option. Connectivity: three inputs (out back) and four 1/4″ output sockets (on the front). Yes, the Studio Six can drive four pairs of headphones. Simultaneously. Without quality loss. Holy HiFiMan.

However, I doubt ALO mainman Ken Ball and the amplifier’s chief engineer/designer Thomas A. Martens had sociability at the top of their agenda during the Studio Six’s development process. ALO Audio made the Studio Six with four outputs because they could. Martens provided the schematics. ALO took this (ahem) ball and ran an all point-to-point prototype into the end zone. Like all the best product inception stories, the chassis is a design Ball first sketched out with pencil and paper. Ball’s team designed the enclosure “to look as good as it sounds” and then worked harder still on the associated engineering work required to have the whole shebang built on home turf. I’ll call it early: I think they did a bang-up job on all fronts.


Ken Ball explains: “Total time for everything was around two years and was quite expensive. I can only hope to break even. It’s not really about profits for us. First and foremost we wanted a tremendous tube headphone amplifier under our banner. The first time we heard the Studio Six we immediately fell in love with it, so getting it to market under our brand was the goal. We made many prototypes of the Studio Six during the development process… until we got it 100% right.”

You can see early enclosure sketches on ALO’s Studio Six-dedicated Tumblr here, here and here. The prototype can be seen here.

Ball on the ‘overbuilt’ power supply: “They [the transformers] are not hand wound. Instead they are ones we selected measured well and were made in the USA. We found custom hand wound transformers not in the end all being something that was needed. These sounded terrific. The power transformer was special made to order but not a hand wound type.”

Martens on tube rectification: “I do realize that yes, most often the first impulse of many (most?) Electrical engineers upon seeing a tube rectifier in use is to say: ‘Hey, why don’t you just use some good fast diodes in there and a timed soft-start circuit? You can get rid of that big, hot and wasteful tube rectifier!’ Well… the virtue of a properly implemented tube rectifier also makes itself known in the resulting sound of the amp.”


Vroom vroom. I really dig my daily headphone drive, a Burson HA-160, but the Studio Six plays in a whole different league. Strike that – it plays in a different dimension. Moving from the former to the latter brought better channel separation, considerably taller and wider staging, more detail, better-saturated tonal colour and – surprisingly – demonstrably faster rhythmic snap. The Studio Six’s strongest suits are layer separation and transparency. Music breathes from large and healthy lungs.

With a Studio Six and AKG K-702 one-two, it proved a cinch to pick how the AURALiC Vega smokes out lesser able-bodied DACs. Talk about bringing knives to a gun-fight. Next to the Vega, the Astell&Kern AK120 running in DAC mode sounds diluted; a facsimile several times removed from the Vega. The point? This ALO statement will let you know quickly and cleanly the shortcomings of your source. It’s a reviewer’s dreamboat. Moreover, if you’re the kind of guy who likes to compare headphones directly, the Studio Six is your new best friend.

It’s also the ultimate store demo amp – give your customers 1) the option of connecting four headphones simultaneously with a view to more readily picking their favourite and 2) hearing each headphone at its very best. Every headphone store owner worth his/her salt should consider one. And then there’s your girl and that Django Rinehart album. The ALO amplifier will allow the two of you to dig it privately, together, alone. You’ll need similarly specified ‘phones though; a Grado and an Aude’ze might not bring the romance. Instead, hearing damage for the Grado wearer.

An ability to dance with four partners simultaneously runs secondary to the Studio Six’s unerring stability with current delivery, even under duress. This head-fi fellow gives some indication of how the Studio Six plays when torture-tested at one possible limit of real-world scenarios.


The ALO amplifier didn’t play so well with (my) custom IEMs. A pair of C-Ear X (review here), gave me a low-frequency hum coupled to a high-frequency whine that was still audible during quieter musical passages. No such noise presented with other ‘phones.

A pair of Mr Speakers Mad Dogs then entered the fray; Fostex mongrels with that pack a powerful bite and possibly the finest $300 headphone on the market today. They’re seriously comfortable too. The ALO silver machine afforded the Mad Dogs an abundance of ambient information that I couldn’t replicate with other amplifiers. Not even the venerated Yamamoto HA-02 (US$1200) – which bettered the HA-160 on separation and overall transparency but was lighter on with bass weight – could get close to the ALO unit. The Japanese shoebox sounds ‘pretty’ next to the Portlandian, which offers so much more wam, bam, thank you ma’am.


And there’s the rub: the Studio Six will make a man out of any ‘phone you throw at it. Even budget models. Conversely, such game-lifting bites hard when heading back in the other direction. As one reader smartly opined on a photo of this amp on DAR’s Facebook page: “How do you ever go back to budget?”. Returning the Mad Dogs from Planet ALO to the Burson moon sounded – and felt – like a demotion. The soundstage walls drew in closer and what was previously separated was now more congealed. Heed this warning: don’t audition the Studio Six unless you can afford it.

As a rule, I don’t normally go in for emotionally-driven dribbles. I tend to prefer more sober and sure-footed commentary, both when writing my own and reading others’. Too much sweet talk rots teeth. However, so deeply-nourishing is the sound of this American that I’m saying, “fuck it…rave on!”

Touched for the very first time. I still recall the first time I heard The The’s Infected. I was 15, behind headphones driven by a Sansui AU-217 and Dual turntable. No, I don’t remember the brand/model of cartridge or headphones but the forty-minute cerebral electrical storm that fired inside my head throughout that first spin remains unforgettable. As much a function of my own adolescence as Matt Johnson’s creative vision, it still ranks as the most profound music listening experience of my life. Infected was the album that got me hooked me deep into collecting records, then CDs and – later – into maximising sound quality with better playback equipment.


Hearing Infected in 2013 via the Studio Six stirred memories of that formative first listen. To whit, the ALO tubular command centre is a record collection re-virginiser. It makes everything sound as fresh as the first time you heard it.

Do note: if the slightest thought of tubes renders you glass-y-eyed and wobbly-kneed, it’s time to sit down and sober up. Don’t think you’re getting a gooey, romanticized delivery with the Studio Six. Instead, exceptional transparency combined with oodles of tone furnishes the listener with both high and low volume satisfaction. It won’t bend or buckle under the strain of higher impedance cans. That’s its bare essence.

You’re also buying into confidence and eliminating doubt. Doubt that there’s a better amplifier out there for your favourite ‘phones, doubt that such a beast could make them sound even sweeter, more three-dimensional, more tonally saturated. Make no mistake, ALO pack these sonic attributes into the Studio Six for an endgame product with few rivals.


No comparisons! I fantasised about wrapping this review with a play on that tired and toothless cliché: that the Studio Six competes with units two or three times the price. Ha! Does such a product even exist? Kinda: the freshly announced 234 Monos from Woo Audio (US$15k) contrast the Studio Six as childs play. Except it isn’t. Its sound is as epic as it is sumptuous.

What I heard from the ALO Studio Six and Aude’ze LCD-3 combination back in June still ranks as the greatest sound I’ve heard to date, with the Sydney-side Mad Dogs scratching at the door for second place. Even at a $4k price point, ALO show that – physicality and soundstaging aside – you still get far better bang-for-buck behind cans than you’d ever realise from your room-compromised loudspeakers. And if you’re finding it hard to puncture the bubbled-world of head-fi, I urge you to give the Studio Six a whirl – if it doesn’t turn you onto headphone listening, nothing will.


Associated Equipment

  • AURALiC Vega
  • Astell&Kern AK120
  • Light Harmonic LightSpeed USB cable
  • Yamomoto HA-02
  • Burson HA-160
  • C-Ear X CIEM
  • Mr Speakers Mad Dog
  • AKG K-702
  • KEF M500
  • V-Moda Crossfade M-100


Audition Music

  • The The – Infected (1986)
  • Prefab Sprout – Crimson/Red (2013)
  • The Blow Monkeys – Limping For A Generation (2013 remaster)
  • Paul Simon – Graceland (2011 remaster)
  • AtomTM – HD (2013)
  • Lana Del Rey – Born To Die (2011)


Further information

Written by John H. Darko

John lives in the NOW + HERE = NOWHERE. He derives an income from the ad revenues of DAR. John is also an occasional staff writer for Stereophile, 6moons and TONEAudio.

Twitter: DarkoAudio
Instagram: DarkoAudio
Facebook: DAR


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  1. Great review as always. Thanks for giving me a glimpse of what this beast can do. But as you warned, I probably won’t try it as I can NOT afford it. Ignorance is bliss in this case. =)

  2. I always love reading your reviews but what is with the bias in this one? “you still get far better bang-for-buck behind cans than you’d ever realise from your room-compromised loudspeakers”. Don’t do that kind of thing in your reviews. Way too many reviewers now creating, sustaining, and engaging in some made up headphones VS speakers value confrontation. Its not necessary and it cheapens the good work you do in your reviews.

    • It’s not bias, it’s opinion. To quote fully, “…physicality and soundstaging aside – you still get far better bang-for-buck behind cans than you’d ever realise from your room-compromised loudspeakers”

      I really do believe you get better bang for buck with (say) $1k on a headphone rig compared to $1k on a speaker setup. However, my point in this review was that the ALO amp upholds this opinion, even at its higher price point.

  3. Thanks for the review, John. I realise you are writing for an international audience, but listing the price at ‘4K’ is misleading when you look at the Addicted to Audio price – I understand why it has to be higher, but 6K AUD is still well over 4K USD at ~92-94 cents (Oct, 2013). We seem to be getting back to the bad old days where you can add 50-60% of the USD price for Australia, and that’s one of the reasons I’m moving to Asia early next year. Re. Ken’s statement : ‘lucky to break even’ – IME, he hasn’t been backward about charging premium prices for everything ALO. I’m hoping to see a headphone amp from Line Magnetic in the very near future, at much keener pricing : somewhere in the 2-2.5K USD region with their characteristic build quality and I’m there.

    • The US price is US$4000. It is quoted as such because this is the amp’s country of origin.

      The AU$6000 A2A price might not yet account for the very recent (last week!) price drop at ALO (but that is a matter for them). Assuming they are still working at the old US$5000 RRP, it translates at today’s x-rates to AU$5196. Add import duties of AU$546 (yes, I saw the FedEx paperwork) and you’re at AU$5742. Hardly a return to the ‘bad old days’.

      I can’t comment on Ken Ball’s margins when I know nothing of ALO’s cost structure and the Studio Six’s R&D investments.

      • Thanks for the explanation John, but if AA paid 5K USD for that amp – and import duty on 5K – they must be one of a disappearing breed of retailers that buys their product at RRP from another retailer. That said, I appreciate that the cost of keeping a niche product like this in inventory would be prohibitive for most – kudos to AA for being willing to take a gamble on the amp.

        • I forgot to include the $500 shipping in my previous cost breakdown too! From what I saw at the Melbourne hifi show, A2A is thriving (not dying).

  4. Can you use different output tubes ? If yes, what kinds / which ones please ?
    What about EL34’s, 6550’s, KT88’s, KT120’s, and so on ?

    Also, when you say single-ended, is that in keeping with an “S.E.T. triode type circuit” or is it simply just using an RCA connector with one circuit per channel versus an XLR connector with two circuits per channel – 1 per phase as balanced has ?

    Is this purely single ended as an S.E.T. type amp would have or is it ultralinear ?

    I do not like S.E.T. sound. I never have, and likely never will. I like Push-Pull in ultralinear mode. I always have, and likely always will. Even when I worked at Cary Audio in 2004, I never liked any of their syrupy, slow, dull, lifeless, highly colored, S.E.T. amps. I like Audio Research, Atma-Sphere OTL, Conrad Johnson, Jadis, etc.

    Is there a tubed headphone amp that you would suggest, or the brand of at least please ?

    Thank you,


  5. The fact that the Mad Dogs comes that close to the LCD-3 at a fraction of the price speaks volumes about the humble Fostex drivers and additional engineering done to them by Mr.Speakers. I wonder how good the Alpha Dog or Smeggy’s Thunderpants would sound on this amp.