NwAvGuy’s Objective 2 by JDSLabs and Epiphany Acoustics

April 4, 2012 | by Lieven | $100-$300, Desktop Amps | Epiphany Acoustics, JDSLabs

“The Objective 2 is an open source amplifier designed with emphasis on benchmark performance and low cost”, that’s how the O2 is described by JDSLabs, the makers of the C421 portable amp we reviewed a couple of weeks ago. JDSLabs and Epiphany are, as far as I know, the only two bigger O2 “dealers” and they were kind enough to supply us with their version of the banned Head-fi’er Nwavguy’s O2 amplifier.

Lots of people consider the Objective 2 to be a portable amp, mostly because it can also run on rechargeable 9V NiMH batteries but mesuring 108,50 x 80 x 29.5mm you can hardly call it a real portable amp, it’s more transportable as it is portable. I don’t see myself taking out this amp during public transport, but hey this is coming from a guy who doesn’t use full size cans in public either. Anyway, I categorised it under “Desktop Amps”.

The designer, Nwavguy, is about mesurements, and Headfonia is, well, let’s just say we’re not. We use our ears the way we always use them in our reviews. This is our way of reviewing, you like it or you don’t, so please don’t start about Nwavguy’s Objective and Subjective Challenges, etc. We are just giving our idea of the O2 amplifier and don’t have any intention to disrespect the designer and his development/review methods used.

Just like the C421 this amplifier has the input and output jacks, both 3.5mm, on the front just like the power button, gain button and even the AC connector. The Objective 2 uses an ALPS dual Analog Potentiometer which I think is great, I can’t say anything wrong about it in this design at all. Inside there are two JRC NJM4556AD Opamps and one JRC NJM2068D Opamp but I’ll let Mike talk some more about the technical aspects.

To start, the O2 amp is dead silent at all time, there is no hiss whatsoever (not that I expected it to) and turning the ALPS pot doesn’t make any noise at all. You immediately notice the big soundstage this amp has and its transparancy. There is no coloration what so ever, it is very neutral sounding and has a lovely detail retrieval for a mini amp. And with the excellent balance and instrumental separation it also has it makes it one, if not the best amp of that size I have heard so far in regard to these specific characteristics. The Objective 2 has more power as you’ll ever need (Dual Gain Switch (2.5x and 6.5x)), as a matter of fact I never had to use the highest gain setting, of course I did, but it wasn’t necessary. I know that JDSLabs offers to modify the gain settings to your liking when you order, I’m not sure if Epiphany also does that but it’s good to know in case you have a special headphone laying around you think will need an adjustment.
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Jeff Kong

haha the 4th paragraph got me giggling, especially later on when mike compared it to the asgard XD
Interesting review guys, thanks for the write up, enjoyed reading this quite a bit since i was well…. ill stop there.
- http://www.headfonia.com/ L.
  
  That actually is a coincidence. really. Don’t stop, tell us what you are thinking
  - Jeff Kong
    
    i think mike covered what i was thinking quite well in his section, the whole technical not necessarily translating to what you get. Personally i was moderately skeptical about this amp, yet very amused by his project. I have to say though, it is still a some what interesting product.
    
    On a side note, his current project is actually much more interesting…well to me at least….
  - http://www.headfonia.com Mike
    
    Yes I had no idea the Asgard was so closely related to NwAvGuy. I was just comparing it based on price, it’s the closest priced desktop amp I can think of.
http://www.facebook.com/profile.php?id=100002513160192 John Seaber

Pg. 3: ”
The chassis is too light and it moves around a lot. ”

It should be noted that we now include a set of stick-on bumpers (feet), so the O2 can’t slide around. Headfonia’s O2 sample shipped before we spotted this inconvenience…
- Zac Caslin
  
  I agree, I put them on my C Moy and 421 and they stay put.
  - http://pulse.yahoo.com/_AXN2QA2GHWOXATFZ45F2HV7QLI Gummy
    
    Almost missed this in comments – can you stick it as a note in review please?
    - http://www.headfonia.com Mike
      
      Made the change on the review. *thanks L*
- http://www.headfonia.com Mike
  
  Yes that should help a big deal. Thanks, John!
http://www.audioexcursions.com/ Austin Morrow

That’s quite a bummer. No synergy with the HD650? Anyway, I’ve heard people over at Head-Fi say that it’s literally the second coming of cheap amplifiers, as its glorious sound really outweighs its price point. After reading this review I can now see some of the potential caveats and it looks like the O2 may have been a little overhyped and farfetched.
- Zac Caslin
  
  I’d try it out before you dismiss it after one review. I like the reviews here but this just seemed like a review to generate page hits.
- http://www.headfonia.com Mike
  
  Well as I’ve said the clean black background is indeed very impressive, and a lot of people do enjoy that aspect immensely. It’s like listening to a planar headphone: clean grainless black background.
  - http://twitter.com/larryzang La-chan
    
    It was the same feeling as when I first heard my pair of Fostex T50RP’s. Black. But now I can have that feeling with the Z1000 and the AD2000 :3
http://www.facebook.com/silvestro.pomes Silvestro Pomes

But… my Fiio E10? Is more musical of THIS??

However… if it’s absolutely neutral, O2 + Beyer 880-600 ohm is the king of monitoring

I’ll remain with my Fiio and Hd598…
- http://www.facebook.com/silvestro.pomes Silvestro Pomes
  
  But O2 + Hd598… how it sounds?
  - http://www.headfonia.com Mike
    
    I didn’t feel the magic with the HD598.
    - http://profile.yahoo.com/M4TRTRL2SDVVBTYR55PD4757PE Tom
      
      Uh oh… my HD598 is recabled, though, with a Cardas 4×24; it sounds a little different from the stock.
Trent_D

You are just saying this because you don’t want to tick of your sponsors by saying this amp is better then amps many times the price. You guys are clearly bias and have let the price dictate what you say. In a blind test, you couldn’t tell the difference. Not that I believe this, but I figured I would save Nwavguy and his groupies the trouble and post it for them. Sad this isn’t a more musical amp
- http://www.headfonia.com Mike
  
  Sad cynical dude are everywhere on the internet these days.
- http://www.headfonia.com/ L.
  
  You had me fooled there for a bit
- sicgoat
  
  And those measurements dictate your brain not to trust your own ears.
  Yeah, right.. -__-’
  - http://www.headfonia.com Mike
    
    Trent was being sarcastic there, sicgoat.
  - Cola Bear
    
    Ears are easily fooled and untrustworthy as devices. Eyes and memory are likewise. Eyewitnesses of events have proven many many times untrustworthy. Memory changes the shape of a room, the color of a car, what someone wore, the first letter of a name (as in “I can’t remember but it begins with a J, only to find out it was Paul).
    
    Ears are important, yes, even untrained ears can tell the difference between “Live or Memorex”. However, ears are not very good test instruments and your brain forgets a sound character in mere seconds. While audio can be subjective in regards to instruments, headphones and speakers (I just don’t like the sound of a steel guitar) the electronics used to drive those acoustic peripherals should add as little change to the signal as possible (Do No Harm To The Signal).
    
    While all electronics (and speakers to a far greater extent) add “something”, some designs like the Benchmark, Violectric and the O2 in particular, their additions/distortions are below your perception threshold and are so-called “transparent”. A colored amp or preamp is like having tone controls or EQ that is always on and ever changing depending on what you plug in. Is that really how you want your electronics to be?
    
    To me, “synergy” is an ill-formed amorphous word people throw around when Product A & Product B just happen to sound good together. You cannot tell anyone that either A or B will sound good with C. That’s a crapshoot. With transparent electronics, you can be assured that the sound you hear is the basic sound character of your headphones (a whole other matter).
    
    Not all audiophiles like the Senn HD650′s and perhaps someone (Mike and/or Lieven) doesn’t like their true nature when hearing through a truly transparent amplifier. Point being, if you want to add some EQ or tone to a recording, so be it, use it and apologize to no one, at least with transparent electronics you can turn it off when no longer suitable.
    The fundamental problem with the review is not that the O2 was regarded as “meh”, it is that IF Mike truly likes the Violectric V200 (a measurably transparent amp) or the Stereophile “Class A” rated Benchmark DAC1 (another transparent amp) and NOT expectation bias, he should have held the O2 (a measurably transparent amp) in the same regard to a great extent. Then all transparent amps should be regarded as “meh” by Mike/Lieven and since this is not the case, it is tantamount to intellectual dishonesty. At this point, how can any of their reviews be considered accurate and/or honest? This is the Pandora’s Box of subjective-only reviews because neither Mike nor Lieven can reliably recall from memory the sound of any amp they have ever heard. The brain just does not work that way.
    - http://twitter.com/Original_Ken Ken Stuart
      
      “some designs like the Benchmark, Violectric and the O2 in particular, their additions/distortions are below your perception threshold and are so-called “transparent”.”
      
      And how do you know that ?
    - dalethorn
      
      “Ears are important, yes.” — Well, no, they’re not just important. They are everything, without exception. You can provide me machines to measure sound as a guide to my analysis, but that’s it. You can’t have your machines tell me “This is it, end of story.” Do you understand why that is?
- Cola Bear
  
  “Sad this isn’t a more musical amp” so, you have an O2 or even listened to one? Or are you just propagating the view(s) of someone else? The rhetoric here goes against the vast majority of reviews of the O2. Otherwise, I agree with your post.
http://profile.yahoo.com/CYFK5CWHIAFH5BDXAXPHXZ3LMY Mikhael

What source and headphone did you use for this review?
- http://www.headfonia.com Mike
  
  I used all sorts of stuff.. sorry for missing that out.
  
  Source: Dacport LX, Kingrex UD384, Fiio E10, Ipod, Altmann Tera. Headphones: Gosh so many. LCD-2, HD580, HD800, HD650, Philips Fidelio, MSPro, HD661, HD25-1, ATH M-50, Goldrings, PX100, HD200, Beyer T1, and a bunch of IEMs. I can’t even remember them all.
  I’ve had the amps for a few months and so I don’t really keep track of what I tried it with.
http://profile.yahoo.com/M4TRTRL2SDVVBTYR55PD4757PE Tom

I’ve been noticing that some people are remarking that the O2 is lacking microdetail… I don’t need power nor authority, since I have an easy-to-drive HD598 and everything else is universal/custom IEMs, so I really appreciate its ability to convey a black background, but someone tell me I’m not better served by saving up for a Leckerton UHA-6 Mk. II or something… Oh, and I don’t need portability. I never amp on the go.
- http://www.headfonia.com Mike
  
  Sounds like the O2 may be a good amp for you Tom.
  - http://profile.yahoo.com/M4TRTRL2SDVVBTYR55PD4757PE Tom
    
    Yeah, that has been my suspicion for a while; I’m just concerned about some peoples’ grumblings about not having enough detail as other TOTL amps… should that even be a concern?
    - http://www.headfonia.com Mike
      
      It’s not a big concern. You only need so much detail after all.. I was just saying that if we’re going to brand this as a technical amp, it needs to do better on the micro details.
      
      I mean I can listen to a Cmoy and not complain about detail levels.
      - http://twitter.com/larryzang La-chan
        
        Do you feel like your perception of the micro-detail is also related to the level of grain? Or rather, a bit of grain adds a bit of ‘sizzle’ to the lower/upper treble, and thus treble micro detail is easier to hear. To my ears, the actual level of detail of the O2 is quite high especially considering there is no noise floor, but the lack of grain means that the treble lacks the kind of ‘edge’ that something like the Asgard has.
      - http://profile.yahoo.com/M4TRTRL2SDVVBTYR55PD4757PE Tom
        
        That’s my suspicion as well — Regarding: La-chan’s comment
      - http://www.headfonia.com Mike
        
        La-chan, if there is one thing with grain and micro detail is that they tend to obscure it. Like on a photograph, a grainy photo can look romantic but you’re not going to see the small details. That’s why Ansel Adams shot his monumental landscapes in low ISO film so you can see the detail.
        
        And on the treble part, I can only say that micro detail is different from treble.
http://profiles.google.com/shrimants Shrimant Saxena

Its
a rough subject. On one hand, there are plenty of measurements saying
that this is “the best” amp. However, do perfect measurements guarentee
it will sound good? Absolutely not. i was just having this convo earlier
about how everyone’s ears are shaped
different, thus having different resonant frequencies, thus having
different preferences for things such as sound quality and IEM’s. Look
at ATH-m50. WAY overblown bass, but some people LOVE it. A friend of
mine demoed my rig. He got REALLY into Stairway To Heaven. When I got it
back, I was horrified: ATH-m50′s with bass boost 2 on Fiio E11. WTF?!
But that is “good” to some people. So is the O2 a bad amp? Certainly
not. Is it the RIGHT amp for the reviewer? Certainly not. However, are
there those who will claim it to be the best amp for them? Certainly.
Sound is both subjective and objective and no matter how objectively
well your amp performs, subjectivity will always bleed into the
measurements. Even if you plug it in and test it on a dummy head, you
wont get any measurements that are worthwhile to a human audience. Its
about trial and error as much as it is about design in the audio world.
Thats not to say design by ear is the only thing to go by. There are
certain measurements that should be guarenteed from a circuit (noise
floor, power down transient, decently flat frequency response) but where
people err is to think that 100% perfect measurements guarentees a 100%
perfect sound. I challenge anyone to find or build an earphone with a
perfectly flat frequency response, listen to it, and tell me it sounds
good to them. Thats not how ears work. Every ear is different, every
mind is different, and everyone will find their own slice of audio
nirvana. The O2 is simply not an end-all be-all solution to amps, and
although NwAvGuy did a great job in design and such he cant design
peoples ears to like his amp. Thats all there is to it.
http://twitter.com/larryzang La-chan

Just wanted to say, as an O2 owner I think this is a fair enough write-up. Although the O2 measures well and isn’t particularly coloured, the neutrality does mean that you aren’t going to find any special synergies with any particular headphone. In a way, that is both the selling point and the downside of the amp – the thing has been designed to be a tabula rasa of sorts, a ‘blank slate’ amp that will, with its low output impedance and low noise, deliver exactly the same sound to every single pair of headphones you own.
If you have a single favourite pair of headphones, this might mean a swing and a miss for synergy. If you like to collect headphones like I do, you might value the idea that you are comparing all your headphones on an electrically similar level – or rather, the electronics are not holding back any particular pair. No matter the impedance, sensitivity, etc of the headphone (except say some certain exotic models) the amp is going to deliver, and that is pretty impressive for a $150 amp. It means I can spend less time worrying about potential synergy issues and more time thinking about the actual ‘basic’ signature of the headphones I’m listening to. I switched from an Asgard to an O2 because of a low level ground loop or related problem I was getting through the Asgard, and upon the switch I was impressed by the lack of noise and grain in the sound. I’m happy, and I’m looking forward to the desktop version
http://www.facebook.com/negakinu Erik Wijnands

I think this is one of the most polarizing reviews you two have ever done and I believe this review is the perfect example of the Headfonia identity. I really loved reading the review exactely for this reason because it illustrates perfectly what audio-enthusiast, opposed to audio-technicians, look for in an amplifier. And dare I say the word I’m looking for is “musicality”?

This amp is all about the angle from which you look at it. In my opinion, it’s created solely as a proof of concept. I think of it as a grown-up, DIY wire-with-gain. I can’t comment on it’s signature because I CAN’T HEAR the Objective2. It disappears in my rig, completely. It’s a true amplifier. It amplifies my signal (DAC) for my headphones. That’s all it does. And it does that effortlessly.

Compared to other amplifiers out there, I think it’s important to remember that the Objective2 is originally meant to be DIY’ed for around $50 (excluding fancy enclosure). It wasn’t created to be mass produced and sold for $150. Objectively (pun intended) anyone with basic solder skills can build an Objective2. If you understand this, it suddenly becomes a much more interesting product. The intentions of it’s designer were to prove that it’s possible to create a very functional amplifier with a small footprint, for a fraction of the cost of more respected amplifiers in the market right now. One that MEASURES really well too!

Measures… Those brings us to, what I think, is the true crux of reviewing the Objective2. Inherent to an amp that measures like the Objective2 is the lack of colouration and colouration is, like we learned from, for example, tubes and equalizers, an audiophile’s best friend. It’s an audiophile’s dirty secret too. The neutrality we strive for stands paradoxal on the musicality we crave. The Objective2 is neutral and transparent and, as opinions on the O2 show, when we are confronted with true neutrality, it might not be as satisfying to our ears as we thought it was.
- http://profile.yahoo.com/M4TRTRL2SDVVBTYR55PD4757PE Tom
  
  Erik, I’ve been meaning to ask you, but how does the O2 compare to the HeadStreamer’s output? I’m strongly considering the O2 as the output for my D7, as I really feel the D7′s output is colored.
  - http://www.facebook.com/negakinu Erik Wijnands
    
    Like I said in my previous post, I can’t really comment on the difference in sound signature. I can only say the Headstreamer’s output is more suited for low-impedance cans. The O2 is more versatile in this regard. :)
- http://www.headfonia.com Mike
  
  The question that I’m asking really is, is the O2 really the superior design it’s meant to be? I’m referring to the bit where I’m talking about how the amp behaves at high gain.
  - http://openid.anonymity.com/pgx75 Guest
    
    At high gain, what you were likely hearing was the input stage clipping. High gain is not meant for more volume with sources like the DACPort, but to allow low-voltage sources such as iPods to be boosted to a level to drive difficult headphones.
    
    Doesn’t JDS/Epiphany mention this in their documentation? It’s prettymuch the most common misconception regarding the O2.
    - http://www.headfonia.com Mike
      
      Clipping is different than a loss of black background.
      - http://openid.anonymity.com/zsihrf Willakan
        
        I have personally done blind, volume-matched comparisons of the amp clipping and not clipping: it does not necessarily manifest itself as obvious distortion, dependent on the severity of the clipping. Indeed, the abrupt rise of both odd and even-order harmonic distortion products creates an impression of harshness and loss of clarity; However, you don’t immediately go “Ah hah! This amplifier’s input stage is clipping.”
        
        It is reasonably audibly obvious under direct comparison: several people unaware of the real purpose of the gain switch over at Head-Fi ended up with horribly clipping O2s. In each case, they were unaware that their amplifiers were clipping and instead wrote of a mysterious degradation in sound quality on high gain.
        
        I was, however, confused by your mention of rising noise levels. The O2′s noise is completely imperceptible under all possible circumstances AFAIK. If any noise is heard, it must have come from the source.
        
        http://www.headfonia.com Mike
        
        As I’ve said, clipping is different than loss of black background. What else can I say?
      - http://openid.anonymity.com/bayrtt Willakan
        
        OK, what exactly *do* you mean by a “black background”?
        (In response to bottom post by Mike)
        
        http://www.facebook.com/people/Fred-Maxwell/1307740682 Fred Maxwell
        
        “Black background” is like a “dry sound” — it’s applying a term from another sensory realm (sight, taste, etc.) to audio, as if it somehow makes sense. It’s akin to saying that chocolate pudding has a somewhat blue taste with hints of acoustic feedback.
- itineranti
  
  This is the healthiest and most honest comment I’ve read in a while: ” The neutrality we strive for stands paradoxal on the musicality we crave. The Objective2 is neutral and transparent and, as opinions on the O2 show, when we are confronted with true neutrality, it might not be as satisfying to our ears as we thought it was. ”Much needed indeed. Cheers!
- Cola Bear
  
  Very good post. I eschew coloration (distortion) in amps and electronics in general but not opposed to using some EQ on tracks that may need it because I can turn it off when I want to. A colored amp will always bring its inherent distortion (EQ) to any set of ‘phones you plug in.
  
  ‘Synergy’ is not a good thing because it is so random. Any combination that has ‘synergy’ cannot be said to work with a different combination of gear. The consumer is left to spend hard earned money on products that may not allow the best performance of the headphones.
  Another problem is many (most?) boutique manufacturers can’t even properly measure the gear they make. Or, they neglect to provide the real specs. Look at the fiascos NuForce & Schiit have found themselves in for example. Both of these companies have been caught with their pants down. Inexcusable. Do we even know their engineering qualifications? Unaware consumers led by spurious anecdotal subjectivism spend money on sub-grade half-baked gear thinking they are getting something great.
  
  The O2 has been extensively tested and shown to the world for examination. Even the slightly compromising sections (e.g., half-wave ps) have been disclosed and the rationale behind using it was given. Even so, it has been shown to be utterly satisfactory. Some of the specs even beat out the venerable DAC1 by a good margin. Anyone is free to test the amp on their own and some have, showing the results to confer with the designer. No other amp in the hobbyist world has been under such scrutiny as the O2. The designer would be insane to publish false or misleading documentation, as some here have suggested.
http://pulse.yahoo.com/_UGJ3SZR3YRF4O4IZBPFIOIVFII Eugen

The truth is you need a colored amp to sinergize with a colored headphone, there’s NO one amp that fits all. That’s why it’s better to err slightly on the side of bass / midrange with headphone amps, it’s the compromise that works with most of the headphones on the market.

That’s also why tube rolling is such a great tool for headphones, it’s a easy and non-damaging EQ tool. Most people have no idea how to use actual EQ without damaging the sound, so at least they can use tubes.

So, it’s not the O2 that’s bad, it’s the premise it was built from. If there was a neutral headphone the O2 would be great. As there isn’t, I suspect it’s only good with the ones that get close to neutral, like the HD600, or the ones that err on the side of bass like HD650 and LCD2.
- http://twitter.com/larryzang La-chan
  
  I’m not too sure a mythical “neutral headphone” would be the right way of thinking about this. It would be more “if only there was a headphone that I was completely 100% satisfied with the sound with, and the O2 wouldn’t change anything about it.” Of course that’s a meaningless statement when people’s preferences and tastes for sound change over time, and sometimes even in the same day.
  - http://pulse.yahoo.com/_UGJ3SZR3YRF4O4IZBPFIOIVFII Eugen
    
    Not only that, people’s hearing changes over time and the mastering style of music changes (degrades) over time.
    
    That’s not an argument against a neutral headphone (which is NOT possible, even moving a headphone a little over your head completely changes its frequency and phase response).
    
    Tip: if you have a bright headphone move a little forward on your ears, towards your nose.
- http://www.headfonia.com Mike
  
  Lacking bass impact is different than being neutral. Lavry DA11′s headphone out is very neutral but the bass impact is very powerful. Likewise amps like the Beta22.
  - http://pulse.yahoo.com/_UGJ3SZR3YRF4O4IZBPFIOIVFII Eugen
    
    The DA11 and the Beta22 have a better PSU with more voltage swing, they control the bass better. They might have also have higher output impedance which gives an impression of bass weight (not verified).
    
    We are sensitive to even a 0.1dB increase in sound, well inside the linearity performance of most DACs, nevermind that of amplifiers which is way worse usually. If that increase is spread over a significant frequency range, it’s even more important.
    
    Also, different amplifies have different phase response, especially in the bass region.
    - http://www.headfonia.com Mike
      
      The PSU is not a valid excuse since you can get a Cmoy build with 18V that again would have more bass impact than the O2. (though not exactly a neutral sound)
      - http://openid.anonymity.com/zsihrf Willakan
        
        Are you sure that more bass impact is not simply the opamp in a CMOY getting incredibly upset at having to drive low impedance loads directly? Many of the “audiophile” opamps that people opt for are likely unsuited to driving headphones directly.
        
        http://www.headfonia.com Mike
        
        Are you suggesting that bad pairings = better bass impact? Sorry I don’t understand.
      - http://openid.anonymity.com/bayrtt Willakan
        
        (In response to bottom post by Mike)
        
        Defining it as better or worse is entirely up to you. My opinions on the matter are very strong and unlikely to be perceived as constructive
http://twitter.com/larryzang La-chan

By the way, did you two have any opinions in terms of which build (Epiphany or JDS) you preferred?
- http://www.headfonia.com Mike
  
  The Epiphany is a tad more solid and is a little heavier.
http://www.facebook.com/people/Rūdolfs-Putniņš/100001284307683 Rūdolfs Putniņš

Ok, here’s my take on the whole subjective/objective nonsense.

First of all measurements DO matter and designing amplifiers/headphones/dacs/… is not an art as some would like us to think. It is a an artisan craft that relies on technical knowledge and repeatable products as that is one of the signs of good craftsmanship. Mike , I think, will concur when I say that the difference between a professional photographer and an amateur is that a pro will always deliver a quality product whilst the amateur has much left to chance. Also the artist seeks to express an emotional message through his production while an artisan goes for quality [re]production.

Returning to the false dilemma of measurements vs ear. Again I will remark that modern microphones and other measurement equipment are far more potent of picking up data than any human ear. Not to mention that equipment leaves out the human factor of hearing. However it takes real human knowledge and experience to associate the measurements with psychoacoustic phenomena. Also it takes some listening experience to associate the documented and agreed upon psychoacoustic phenomena to personal qualia of sound perception (i.e. how does sibilant sound to you?). If we could successfully do that then Mike could just take some ultra nice photos of the gear in question and just slap some graphs under them. Maybe a remark here and there about ergonomics and a review would be done. Everyone could then translate the raw data into personal listening experiences and all would be well. However as it seems from what I’ve seen- there is very little knowledge on how to successfully translate measurements into psychoacoustic phenomena. Otherwise we would not have Nelson Pass designing high THD amps that sound pretty nice and the O2 sounding rather… meh.

Also one must keep in mind that music listening is a purely emotional practice, sure better gear will give you more of the artist’s hard work (not to mention the invisible cohort of tech guys who don’t have the fame and glory they deserve), but it takes very minor annoyances to ruin the listening experience. It might be a nasty ringing in the upper registers or the sense that there’s something better out there that need buying. Or rumbling stomach after that one particular purchase. I’d say for music listening it’s all about happiness if gear can make you happy then it’s good. If it gets in the way of happiness then it must go. For critical applications, however the measurements may reign supreme.
- http://www.headfonia.com Mike
  
  Rudolfs, check out my reply to Erik’s comment below.
- http://www.headfonia.com Mike
  
  Actually a good mic just zooms-in to the instrument better but your ears are still capable of capturing more.
  - Cola Bear
    
    That is quite a statement, what proofs do have to back that up? Are you learned in psychoacoustics and have a medical background? Or, are you just a general know-it-all shade-tree kind of reviewer? I wonder if you would post the results from your own hearing tests, so we can see where your hearing is deficient. Really, what makes you so capable a reviewer? So many points I see made here seem to be off-the-cuff knee-jerk reactions with no real understanding or education in any of the sciences, medical, psychological, engineering. Many have opinions but opinions not based on any real education are not worth much. Beware who you listen to for advice.
    - dalethorn
      
      Funny thing – when I was a teenager the thought that the entire universe could be squeezed down to something smaller than the head of a pin was unthinkable, absurd, would get you banned from academia forever. Now there are people still clinging to the notion that certain steady-state measurements contain all of the info our ears and brain can detect. And then it gets worse. There’s a small but growing contingent of science that believes our perceptions are not entirely contained in measureable atoms and molecules within our bodies, but may share bigger spaces on the quantum level. These are not witch-doctors any more than the crazies who understood that the entire universe was just a hologram and “solid” matter just an illusion. It does invoke a primitive sort of in-the-mother’s-womb comfort to see people so confident that measurement is beyond human perception in such things as cables and amps, but then reality sets in eventually and we get back to exploring.
    - http://twitter.com/Original_Ken Ken Stuart
      
      It is well known that the best microphone connected to the best amplifier connected to the best speaker, cannot reproduce a musical instrument accurately. We know this by comparing to the original instrument.
      
      This is all that Mike was saying.
      
      People who listen only to electric music (rather than acoustic music) might not be aware of this.
      - Cola Bear
        
        What Mike said was this “…your ears are still capable of capturing more.” My statement stands as is. He shows no proofs of such a thing nor a statement of his own hearing acuity.
http://www.facebook.com/n.phectt Miles Mchugh

Is it good for dubstep, rap , or heavy metal? Thats what i listen to. *falls on floor laughing hysterically making baby goat noises*
- http://www.headfonia.com/ L.
  
  Video, or it didn’t happen
edwel

Conduct a several loop recording test, if the O2 is being a plain “wire-with-gain”, then it should be compared to a plain “wire-WITHOUT-gain” and see/read/hear the difference refer to the original track. Of course you need a “transparent” DAC/ADC and DAW setup to get the job done.
- http://www.headfonia.com Mike
  
  Actually unaltered recording, if you just listen to it from straight from the mixing console, is always very close to the real thing. Problem is that any recording is always bound to have far more colorations than the majority of amps.
lorriman

What’s the output impedance of the Asgard? If it’s too high for the phones then what you are hearing is a bass boost at the cost of losing bass tightness and extension, plus a likely treble roll off. Boomy and flabby, in all likely hood, compared to an O2 with a bit of bass boost equalisation (with a decent equaliser, ie. not the ipod but rockbox is good), tight and crunching. I do this with my etymotic HF2 and my modded Fostex T50rp . Excellent results.

That bass boost, if that’s what’s happening, is going to give poor quality bass compared to an O2 with good equaliser bass boost (ie. on rockbox try low-shelf 80Hz +3db q=1. Withm y etymotics I et great bass with no discernible distrotion at +6db
- http://twitter.com/larryzang La-chan
  
  The Asgard used to be listed on their website with a 1 ohm output impedance figure. At some point this published figure was removed and has not been replaced, and its hard to say whether the figure was removed because:
  a) It was a typo (seems like a rather unlikely typo to have on the website for a few months. I am not sure if the spec was also listed in the manual as I no longer have mine).b) It was an incorrect measurement (this is troubling if a basic figure can be measured wrong).c) A 1 ohm figure makes the 1.5ohm figure of their upcoming mid-fi amps look a little awkward.
http://www.facebook.com/profile.php?id=100000455411784 Dietmar Gsell

As my main headphones are HD 650,I sold the O2 after 2 weeks of trying hard to like it!The amp is JUST amplifying and doesn’t add anything of the things I like ,be it detail retrieval,being engaging etc. Add to that the lack of punch/bass and you have the O2.Great measurements apparently but sounding like a DEAD DUCK to my ears!
Hype of the Year!
- http://www.headfonia.com/ L.
  
  I agree, the HD650 is no fun with the O2
http://www.facebook.com/marco.bardoscia Marco Bardoscia

What about genre bandwidth?
http://www.facebook.com/profile.php?id=837240051 Julio Cesar B

O.k I’m here sitting and agreeing with the people that is saying this amp doesn’t sound exciting with 650′s.
Now, I plugged my AKG’s 272 HD and boy, that was jawdropping. I was actually hearing bass punch out of those that i never experienced before except when I plugged them to some Audio Technica HA5000 which is 10 times more expensive.

Then I quickly reach for my 701′s and… guess what. yeah, audio bliss.
This actually has me confussed because as a matter of fact, I always liked the 650′s over the 701′s.

This amp really has some strange sinergy with the AKG’s I can’t really describe.
- http://www.facebook.com/people/Francisco-Silveira/100000950183466 Francisco Silveira
  
  The goal of the amp, or at least the objective approach, is to avoid creating any sinergy at all. I’m not saying this won’t match perfectly with some pair of headphones out there, and it probably does, but that’s not the point. An amp is supposed to amplify a signal without adding anything.
http://www.facebook.com/people/Hari-Susetyo/1211480515 Hari Susetyo

But to get amp like this with just $100 or less, hmmm.. good item to have isn’t it.. can’t complain more…

but yeah.. it’s not as good as people keep talking out there… HYPE!!! especially people who said that O2 can beat a desktop amp with higher price… it doesn’t have a big sound that I get from a real desktop amp, but for small sensitive IEM it’s actually good..

I have O2 with black PCB…black enclosure… so cool.. decided to keep it…
dalethorn

My experience with the JDS O2 is similar. With the HD-800 I thought it sounded very good, but with the lesser-bass headphones like the Shure 1840 and 940, the Beyer DT-48A and DT-1350, and a few others, not so good. The treble became harsher and the bass leaner when it was already pretty lean.
- http://www.facebook.com/jeffreytang71 Jeffrey Tang
  
  Well, I’m enjoying the O2 with my DT48A, at first I felt the Meier Arietta was on par, but it seems that the O2 is not as limited in the frequency range span. I have also tried them with my DT48S Nagra and you can only imagine what i hear. Very Hi End sound. Simply amazing….have been posting less and enjoying the music more since i got the O2.
belligero

Being the experienced reviewers that you are, you would of course have no difficulty in repeating these observations in a blind listening test, right?
alejandro vidal

if the amp really lacks “musicality” and “micro detail” how come no one has taken the DBT challenge proposed by nwavguy himself? if the amp really sounds so different it surely would be easy to identify by sound alone.
http://www.facebook.com/profile.php?id=100001174173334 Scott Boyer

The O2 is built off of sound science. Unfortunately, music is both an art and a science. Nwavguy not only left out the art part, he ignores it’s relevance altogether.
- alejandro vidal
  
  Music is an art, and we should leave that to the artist (musicians).
  Amplification of signals is NOT an art, at least not if what you look for is fidelity to the original signal.
  - http://www.facebook.com/profile.php?id=100001174173334 Scott Boyer
    
    Not necessarily. How do you explain people’s love of tube amplifiers. They inherently add distortion, but in a musical way.
    
    Music is to provoke a human emotion. If the O2 comes up flat then it is not musical. Some people strive for measured accuracy…great. But others want to be moved by their music.
    
    If you simply want a calibrated instrument, the O2 is your choice.
    - alejandro vidal
      
      “…
      at least not if what you look for is fidelity to the original signal. ”
      
      if you need distortion to be moved by the music you hear that’s fine, but you should know that you are actually loosing fidelity to the original recording.
      - http://www.facebook.com/profile.php?id=100001174173334 Scott Boyer
        
        I’m simply stating that “a wire with gain” is not everyone’s ultimate goal.
        
        Kinda like spending time with Spock. He’s interesting and scientifically logical, but I wouldn’t want to live with him.
        
        Live long and prosper. :)
    - l_e_e
      
      You are right: _music_ is to provoke a human emotion, but if you need coloration, distortion etc. to provoke that emotion I’d suggest switching the artist, not the amp. Else your own statement doesn’t make any sense.
      - http://www.facebook.com/profile.php?id=100001174173334 Scott Boyer
        
        I am referring to the presentation of the music.
        
        Sometimes it’s just that intangible thing that gets your toe tapping. When you get a system right, it’s easy to tell. On Headfonia they sometimes call it PRAT.
        
        One must also look at the overall system as well. I’ve tried it with my Sennheiser 650HD as well and it’s just not for me. (My comments on the O2 mirror Mike’s). But on other phones, it could definitely be a good match.
        
        Not bashing those in favor of a scientifically, perfect neutral tone, it’s just that unless you are recording your own live, acoustic music, I’m not sure it’s going to happen. Personally, I like the Sennheiser house sound for headphones, but for full size speaker listening I prefer a more neutral sound.
        
        Everyone has their overall system goal. I just don’t think everyone’s ultimate headphone setup necessarily sounds, by definition, perfectly neutral. If it were, then we’d be throwing out most of the “ultimate” headphones available today.
      - l_e_e
        
        (The like below was me trying to reply to Scott.)
        So you’re saying that it’s the presentation of the music that is to provoke emotion, not the music itself? I wholeheartedly disagree.
        
        What makes me toe tapping is the music, not the (re-)presentation/reproduction or the gear. Whether I listen with a nice headphone setup or a kitchen radio doesn’t change if I like the music or not.
        
        What is not going to happen? A neutral reproduction of what is on the recording? Oh it certainly is. You have to differentiate between what is on the recording (the music, the art …) and what is happening between what’s on the recording and the sound reaching your eardrums aka reproduction.
        This reminds me of the misunderstanding many seem to have with EQing. When I say I use an EQ, many people ask if I’m trying to fix flaws on the recordings – no, absolutely not. I use a fixed EQ curve for a given headphone that stays the same regardless of the recording, so all I fix are the flaws of the headphone (reproduction), not the music.
        
        It’s obvious that not everyone is into neutral reproduction, and that’s great because there are headphones with intentionally boosted bass or treble and so on and effects processors, DSPs such as EQs etc. But building a reproduction chain with “flawed” components (a DAC with treble roll-off, noisy, non-flat, distorting amplifier, expensive silver cables trying and failing to brighten up the sound again …) is just a stupid way to waste money.
      - http://www.facebook.com/profile.php?id=100001174173334 Scott Boyer
        
        I think I’ve been misunderstood. There are many factors that make a musical experience special. Presentation is just one of them, of course.
        
        I’d like to say that the O2 is extremely impressive when you look at the measurements. So why isn’t it working with the 650HD? Hmmmmm…
        
        I guess what I’m trying to nail down is the “synergy” and emotion in a musical experience. When you listen to music, what is it that makes your toe tap, gives you goose pimples, and just plain puts a smile on your face?
        
        I can appreciate a musician whether I hear them on my headphone system or a clock radio, but a clock radio doesn’t put that smile on my face, much less give me goose pimples. Why is that? Do scientific measurements play a part? Absolutely! But once you reach a certain level of audiophile quality, synergy comes into play.
        
        Does synergy come into play for everyone? Maybe not. But once you feel an emotional connection to your music, it’s wonderful.
        
        Can synergy be scientifically measured? I’m not so sure. How do I know I like a certain food. Do I only read the nutrition label and ingredients? Will that tell me? What’s your favorite color…blue? How do you know? Have you ever been in love? Can you measure that?
        
        If you’re getting synergy with a neutral/uncolored presentation….great! But others don’t. That’s one reason tube amps and opamp rolling are popular. Some people call it “preference over reference”.
        
        If you’re going after a perfectly neutral system and presentation, once again, unless you’re recording your own live acoustic or vocals, your store bought recordings ARE colored. As best, you are getting the artist’s intention. Which I can fully respect.
        
        My loudspeaker system has been calibrated using Audyssey MultEQ XT32 with a Pro Kit using the full 32 measurements. It measures flat and I thoroughly enjoy it as my main course. But listening to my headphone setup is my dessert and I have chosen a warmer Sennheiser based bias.
        
        Again, for many people, it comes down to the synergy of their system. For me the combination of the O2 and the 650HD don’t work, but other headphone combinations could be wonderful.
      - l_e_e
        
        NwAvGuy designed the O2 using the HD650 and compared it with other people to the DAC1. The lack of “synergy” you’re talking of does not exist. My guess is it’s a lack of coloration or distortion or high output impedance or a combination of the former that you experienced. Or maybe the HD650 just isn’t the right headphone for you, dunno.
      - http://www.facebook.com/profile.php?id=100001174173334 Scott Boyer
        
        “…the lack of synergy…does not exist…”
        Wow, that’s quite a subjective statement. If the O2 is purpose built off of measurements, how’s that measured?
        
        I absolutely love my 650HD. I’ve tried them with many amps and have not found them lacking in the least. It’s truly reference headphone.
      - l_e_e
        
        Nope, it’s not quite subjective. You might want to read up on some O2 articles on NwAvGuy’s blog before continuing this discussion, otherwise you wouldn’t be asking how to measure an amp’s ability to drive headphones or ask for specs or graphs. And before you ask for independent measurements: Google is your friend.
      - http://www.facebook.com/profile.php?id=100001174173334 Scott Boyer
        
        Yes, I’ve read his blog.
        
        I’m not questioning the O2′s ability to properly drive headphones. Let’s keep this discussion on course.
        
        I’m stating that the O2 has no synergy with the 650 HD. You said “The lack of synergy you’re talking of does not exist.” So, if you’re trying to prove your point scientifically, do it.
        
        Let’s get scientific. Charts, graphs, and third party verification or it didn’t happen. Otherwise it sounds like common internet hearsay and therefore subjective by definition.
        
        So the question is quite valid and still stands.
      - l_e_e
        
        >I’m not questioning the O2′s ability to properly drive headphones.
        But in the next sentence you claim it has no synergy with the HD650? This makes no sense. You talk about synergy, yet you don’t even seem to know what exactly you’re talking about. The O2 has ~0.5 ohm output impedance (no need to measure this, look at the schematic) and therefore does not alter the frequency response of the HD650′s due to their non-flat impedance (it doesn’t add bass like many other amps would). Measured frequency response is flat. Distortion has been measured to be lower than a beta22 (not by nwavguy, but I’m not going to do the Google search for you).
        
        What question still stands, how to measure synergy? Here’s my answer: If you don’t know what synergy is, cannot define it or it only is in your head, how do you expect me to come up with a measurement for it?
        
        Let’s be honest. Saying it has no synergy is a subjectivists way to say “I don’t know.. I don’t like this amp”.
      - http://www.facebook.com/profile.php?id=100001174173334 Scott Boyer
        
        Actually, I do know what synergy is. I explained it in a previous post below. Please reread.
        
        A set of headphones can certainly be driven properly and have no synergy. I use the O2 as a prime example. Others on this site agree as well.
      - l_e_e
        
        I don’t see where you explained it, you just said something like either there is synergy or not and are not sure if it can be measured.
        To me it seems that “synergy” is a certain amount of coloration or distortion that makes certain recordings or headphones sound different (of course always nicer subjectively). From that standpoint I can see how you’d talk about a lack of synergy.
        Still has nothing to do with accurate, neutral reproduction which this amp is about.
        
        It seems there are two ways to build an audio reproduction chain:
        a) Using components whose colorations (objectively flaws) make up for one another (subjectively synergize) that result in combination with the headphones in a objectively inaccurate but subjectively nice sound. You don’t hear every detail that’s on the recording, but a subjectively prettified version.
        b) Using components that are flat, neutral (subjectively boring? lacking synergy?) that result in an accurate reproduction chain (excluding the headphones). The headphones plus optional EQ/DSPs are used for the desired (distortion-free) coloration. You hear every detail that’s on the recording with whatever tonal balance you chose.
      - http://www.facebook.com/profile.php?id=100001174173334 Scott Boyer
        
        Well, I’m glad that we can agree that there’s more than one way to build one’s system. It all comes down to choice and what the engineer’s goals and listener’s goals are.
        
        Guess that’s why there’s more than one flavor of ice cream.
        
        dalethorn
        
        I think choice is good when I have a clear choice. But does a manufacturer of a device that’s intentionally made colored to please certain users who somehow “know” about those colorations bother to inform the rest of us who don’t want colorations that his/her design is deliberately colored? My guess is no. My guess is they don’t want to advertise that because it would make them look stupid. I think an amplifier that has “flavors” like ice cream is an absurd notion. Personally I don’t even know of any. I have headphones that are bassy, bass-light, midrange-centric, etc. And obviously so. But all of my amps sound flat and measure flat. Did I miss those bass-heavy amps somewhere? I want to be sure of where they are, because I sure don’t want to buy one!
    - http://www.facebook.com/people/Fred-Maxwell/1307740682 Fred Maxwell
      
      It’s not the job of an amp to produce music, it’s to accurately REproduce it. If you aren’t moved by your music when played through high-fidelity audio equipment (i.e., equipment that does not color the sound), blame the performer, producer, and engineers.
    - Cola Bear
      
      There is a propensity of some audiophiles to wax nostalgic and think back to a time when tube gear was prevalent. It invokes certain emotions they may find favorable. Tube distortion is definately NOT musical, ANY added distortion is NOT musical. Musical instruments (non-electronic) do not create distortion. It is the reproduction chain that creates distortion artifacts. The O2′s distortion is below you ability to hear it. It is magnitudes lower than tube gear.
      - dalethorn
        
        The O2′s distortion is below most people’s ability to hear it with the music tracks they have. You have to be sure that applies with higher resolution tracks, or be sure you can’t hear the higher resolution. I’ve made that mistake.
      - http://twitter.com/Original_Ken Ken Stuart
        
        If it were true that ” Tube distortion is definately NOT musical,” then
        all guitar amplifiers used on platinum rock albums would never have
        existed, and the whole history of rock music since the 60s would never
        have existed either.
        
        If we are talking about music reproduction, then the reason people think
        that tube amps “sound good”, is because they add back harmonics lost
        previously in the chain by some less than perfect components.
http://www.facebook.com/profile.php?id=793059760 Paul Leskinen

For a site that values listening tests and eschews measurement comparisons, I’m troubled by the lack of ABX testing. With the amount of money spent on headphones and amplifiers, a simple ABX box would seem to be essential for comparing amplifiers. This perhaps could be more revealing of differences between amplifiers, but it’s also possible that you would wind up not using it, as suddenly many good (i.e. non-distorting) low output impedance amplifiers would sound exactly the same. Can you offer an explanation for NOT using ABX as a tool in your toolbox (other than you’re afraid it will invalidate much of the differences between amps that you hear)?

As for the lack of bass, assuming it’s not a psychological bias effect stemming from the description of the design goals of this amplifier (“objective,” “measurement-based,” etc.), leading you to expect thin bass and “analytical” sound, it seems more likely that it is a result of the O2 being compared to amplifiers with higher output impedance, causing a boost in bass response in headphones with an impedance bump in the low frequencies. This is a result of the multiple problems with high output impedance, not a fault of the O2. The O2 has been measured flat from 20 Hz-48 KHz, and seems unlikely to be lacking in bass control due to its <1 ohm output impedance. Again, the ABX testing would help clarify that there actually is a bass difference between the O2 and the Cmoy (which also has a low output impedance).

I would be very surprised at audible noise on the high-gain setting that was not due to the source. I have never heard any noise at any volume or gain setting attributable solely to the O2. Perhaps there's an issue with your O2, or else you are boosting the source to the point where the noise is finally audible?
Fabio_Rocks

Lieven you got a BIG response from nwavguy’s blog. What he said:

“Someone could set up a blind test between the O2 and an accurate amp Leiven really likes, and he would no longer be able to tell the amps apart because his brain wouldn’t know what to expect”
- Jeff Kong
  
  thing is…people can think what they want to think about a product…why all the fuss? It’s not like nwavguy is fussed about it anyways, hes just using headfonia as an example, his tone is exactly the same as how hes been writing his other writings (ie i dont think what he wrote was intended to be negative nor is it BIG). He probably wouldnt have cared, but people kept posting stuff and asking questions about it on his blog.
- antonius wijaya
  
  Agree, Video answer in youtube will be nice
- http://www.headfonia.com Mike
  
  I guess all the violectric amp users are fooled by placebo then.
  
  Luckily I’ve gotten rid of that Zana Deux. I bet it would measure very bad next to the O2.
http://www.headfonia.com Mike

I don’t understand why people are so mad about the review. Me and L clearly acknowledged its good technicalities. I even said that the black background is unheard of on any portable amps (and that includes amps from ALO our sponsor among others). So we don’t like the mids and the bass is not impactful enough for us, is that wrong?

Seriously, read the review again before you get all defensive about the O2.

Unless you guys are expecting a perfect 10 review which is not going to happen. Read all my amplifier reviews, I never give a perfect 10 review on any amplifier even the $6,000 ones.
- Ory Zaidenvorm
  
  edited
- http://ancientwisdom.pip.verisignlabs.com/ AncientWisdom
  
  I believe the reason might be one or more of the following:
  1. In all my time reading Headfonia reviews this is the one that I perceive as the most negative one (honestly can’t think of a worst one although probably one exists). I even remember in one review a commentor asked Mike how come most if not all the reviews on this site are so positive and Mike replied something along the lines of “I can’t help but write about the stuff I like”… Well you made it quite clear you don’t like this amp, but it is unclear why (and I don’t mean your “explained” why, I mean we are wondering if there is a another hidden why and what it might be).
  2. I don’t think I have read many of your reviews rating cheaper gear higher than more expensive gear (I’ll be happy to be corrected!). In this instance the O2 is probably one of the cheapest amplifiers on this earth (bar Chinese brands) and as expected it scored a pretty lousy review. I understand that usually you get your money’s value but there should be at least some products that pounce much heavier than their price, that’s just the nature of worldwide commerce and competition.
  3. This review is in contradiction to allot of other reviews out there which stress how transparent it is. How can it be transparent and lack some aspects of sound at the same time? Make no mistakes, lack of bass (or mids) is coloration! True naturality does not (should not) sound like anything at all…
  Assuming you knew about the amp’s reputation before reviewing it, it looks very suspicious that your observations on it nailed exactly what some people would consider “natural” and “sterile” to supposedly mean.
  4. Unlike allot of the gear you review, I actually own an O2. And my impressions are very different than yours (coupled with a pair of DT-770 it rocks my world all day, every day at work. There is absolutely no bass missing. And I listen to electronic music with lots of bass. It compares excellently with my home Asus Xonar STX + FA-011!). Now I understand that different people experience things differently but the magnitude of difference between my experience and yours, in my opinion, cannot be simply attributed to different taste/subjectivity. this has really caused me to question how much can I trust the rest of your reviews on gears that I have not heard (and might not get a chance to hear before making a purchase decision)? Can I trust them on a $500 piece of kit? what about $1000? and what about $90? you get my point.
  5. Unlike allot of the other gear reviewed here, the O2 has no financial backing. I’ll leave any possible implication out of this comment, but it does raise some questions (not meaning to open any huge discussions on this, but just didn’t want to omit this).
  
  I am not trying by any means to attack you, I am a close follower of Headfonia for over 6 months now (and have read allot of your older articles), I am just expressing my thoughts after reading the article.
  I do believe that you are expressing your honest opinion, and from nwavguy’s reponse it seems he also comes from that standpoint.
  BTW if you honestly encourage open discussion in the community it would be great if you could respond to his arguments and explain your point of view, although I fear for allot of people nothing short of a youtube video blind test would suffice
  - http://profile.yahoo.com/6FD75HR366LZD36QDBLT2RK7AU Hai
    
    1. Did you read his review about the nfb 12 ?
    2. He did said the c421 rival more expensive amp.
    3. I think the reason of people reaction coming from the old flame with nwavguy
    - http://ancientwisdom.pip.verisignlabs.com/ AncientWisdom
      
      I’ll answer one by one:
      1. I have actually read the review about the nfb 12 when it was published. I had no idea that was a $200 amp! definitely a much worse review than the O2 but still relatively at the bottom of the scale of high end audio.
      2. Yes he definitely likes the C421, but which actual more expensive amps is it better than?
      3. I have absolutely nothing to do with the flame war (personal opinions aside) and (gasp!) even visit head-fi every now and again
      
      BTW Lieven even says that the Fiio E10/17 have better mids than O2 which
      to me is the same as saying “I like my sound colored in this specific
      way”, doesn’t have much to do with the amp as an amp (at least that’s the way I see it).
      - DeliciousFlatFrequencyResponse
        
        I wonder how can Lieven says that the E10 have better mids than O2 when both of their frequency response are equally very flat. Even the E10 has quite a lot of more distortion compared to the O2 (altough it’s still well under audioble level).
        
        I believe the E10 should be transparent enough and should be unable to be distinguished in a blind test. The same should go with the Sandisk Sansa Clip+, which I actually have, and cannot be distinguished in a blind test with the E10 because both are equally transparent enough. (Call me “tin ear”, if you have to)
        
        About all of this “Subjective vs Objective”, in my opinion, it’s perfectly okay if someone like colored (“synergetic” amp) or neutral (“transparent” amp). I think I am belong to the neutral amp (more like, transparent sound reproduction) camp because I believe music should be enjoyed as how the artists & recording engineer means it, therefore adding coloration and euphonic distortion to the source will betray their expectation about how their expression should be conceived to the listeners.
        
        But all in all, can’t we just exists alongside peacefully?
        
        http://www.facebook.com/people/Fred-Maxwell/1307740682 Fred Maxwell
        
        The problem with subjective reviews is that they are comments on what the reviewer likes rather than the accuracy of the sound. Not to be rude, but I don’t care what sounds best to the reviewer. His ears, brain, headphones, and tastes are different than mine.
        
        The goal of audio reproduction should be accurate sound. The goal of audio production, in studios, should be pleasing sound. It’s not the job of my amp, headphones, speakers, preamp, CD player, etc. to change the sound that the artist, producer, and engineers created.
        
        Asking subjectivist and objectivist audiophiles to exist “alongside peacefully” is like asking faith healers and medical doctors to get along.
        
        dalethorn
        
        Partly agree, partly disagree. We need both. The reason for knowing whether the reviewer likes the sound in any respect is not because it’s random information – it’s because the reviewer has a track record and that info can be compared to many things. It’s more difficult than “purely” objective info, but reproduced sound itself is a long way from a perfected science, even in the so-called “straight wire with gain” that none of these amps really is.
        
        http://www.facebook.com/people/Fred-Maxwell/1307740682 Fred Maxwell
        
        You wrote “reproduced sound itself is a long way from a perfected science, even in the so-called “straight wire with gain” that none of these amps really is.”
        
        How better to measure whether something is a straight wire with gain than to use modern, state of the art test equipment? Claiming that you can hear things that modern audio test equipment can’t measure is like claiming your eyes have better resolution than a scanning electron microscope.
        
        If you can’t hear the noise or distortion products that an amp adds to a signal it is, audibly, a straight wire with gain. What actually happens is that accurate products are often rated more poorly by subjectivist reviewers who prefer some type of euphonic distortion to accuracy.
        
        “because the reviewer has a track record and that info can be compared to many things.”
        
        Really? What is his track record and how do you compare it? Reviewers are subject to biases just like the rest of us. Secretly put an O2 into a Red Wine Corvina $1000 headphone amp’s case and then ask a subjectivist reviewer to compare that “$1000 Red Wine Corvina” to a $144 O2 in a JDS Labs case. A large majority of subjectivist reviewers will claim that one or the other is audibly superior. Nothing makes the need for ABX testing more obvious than an experiment like that one.
        
        I’ll share a brief story to illustrate the point. I had a piece of sound processing gear in my listening room. A self-proclaimed golden ear audiophile claimed that it degraded the sound just by being in the signal path. So I switched it in and out multiple times at his direction. He was aghast that I could not hear how much better the sound was with it out. He suggested that I might not be as experienced a listener or that, maybe, I even had some form of hearing loss and should get it checked out by an audiologist. All I really was doing was muting the sound for a split second at each “switch.” The “offending” component was not even connected to the audio system — just AC power. When I revealed what I’d done, he stormed out, never to return (thank you, blind testing!).
        
        A top-notch amp should not sound good. It should be accurate.
        
        dalethorn
        
        I’m sorry but I’m not a “subjectivist” nor a golden ear audiophile. I’m just an ordinary person whose brain and auditory system is far superior to your stone knives and bearskins.
        
        dalethorn
        
        But I do agree that a lot of the people types you mention can be more of an obstruction to fidelity than wires made of less than ideal materials.
        
        http://twitter.com/Original_Ken Ken Stuart
        
        I agree that blind testing (such as putting an O2 in an RWC case) can point out bias and placebo effect, and/or eliminate them.
        The problem is when people respond to your bias example by then proclaming that a) there are no differences between amps, cables, CD players, etc. and b) measurements currently can point out all aspects of sound.
        For example you state:
        “How better to measure whether something is a straight wire with gain
        than to use modern, state of the art test equipment? Claiming that you
        can hear things that modern audio test equipment can’t measure is like
        claiming your eyes have better resolution than a scanning electron
        microscope.”
        Your logic there is false.
        Why? For example, spy satellites can see everything on the surface of the earth. Yet, things go unnoticed which national security people wish they had known about. How can this be? Because a human being has to determine what is significant amongst all those trillions of trillions of bytes of data.
        Similarly, it is possibly true that we are currently capable of measuring any one small sound quality, but we are far from creating tests that can predict the response of audio equipment to complicated groups of sounds.
        An even better example is weather.
        For $99, you can measure all the relevant atmospheric data at one particular point. Meteorologists have millions of these stations everywhere, and have been spending years developing competing computer models, yet they still predict rain when it does not happen and vice versa.
        You can put all the electrical test signals you like into an amplifier, and it won’t predict what will happen when you put The Beatles – Abbey Road into the input. And then when you have adjusted your design so that Abbey Road is reproduced poorly, it still might not work correctly with Skrillex – Equinox in the input.
        
        http://www.facebook.com/profile.php?id=100001174173334 Scott Boyer
        
        Love hearing all the “stories” that objectivists throw out there.
        
        Fact is, the amp is only one part of the overall system. So why put all the emphasis on the “wire with gain” when your headphones and recordings are not neutral in the first place.
        
        dalethorn
        
        One little suggestion for blind testers: Make it fair. Let the tester control the handling of the gear, but give complete control of the timing of the changes/swaps/etc. to the testee. If you think about this it will make sense.
        
        http://www.facebook.com/profile.php?id=100001174173334 Scott Boyer
        
        Seems that you’re more concerned with reproducing music, rather than listening to it.
        
        Also, the faith healer/doctor metaphor is neither appropriate or accurate.
        
        http://twitter.com/Original_Ken Ken Stuart
        
        When you say “I wonder how can Lieven says that the E10 have better mids than O2 when both of their frequency response are equally very flat.” How do you know that frequency response graphs indicate something about the midrange sound?
        There are two aspects of this that are ignored by many people:
        1 – How do you know that frequency response graphs indicate sound quality?
        2 – How do you know when the frequency response graphs are “good enough”?
        
        http://www.headfonia.com/ L.
        
        I said that?
        
        http://twitter.com/Original_Ken Ken Stuart
        
        If you read carefully I quoted directly from user DeliciousFlatFrequencyResponse’s post, that is why I surrounded it by double quotes.
        That is why at the beginning of my post, Disqus put:
        @ DeliciousFlatFrequencyResponse
        meaning
        “To DeliciousFlatFrequencyResponse – I am replying to the post you made right above mine”
        The discussions make no sense unless you read them in the context of the thread.
        
        AncientWisdom
        
        @twitter-432989079:disqus :
        Lieven did not actually say that, that was a mistake I made (if you read a few posts down..).
        
        It was Mike, and he said: “The mids are moderately thin in comparison to
        amps like the C421 or the Fiio E10/E11/E17 that Lieven and me both
        liked”
        
        http://twitter.com/Original_Ken Ken Stuart
        
        You completely distracted everyone from my point. So I have changed Lieven and E10 in the quote to ___ and ___ , since I am talking about the overall methodology.
        But now you understand why this discussion never ends – no one notices any actual points that should cause them to question their viewpoint.
        
        AncientWisdom
        
        @twitter-432989079:disqus : Sorry that was not my intention! I accidentally originally wrote what I wrote in regards to Lieven, but after he pointed out he said no such thing I corrected it and apologised. Disqus actually messes up the order of yesterday’s conversation, I did not bring it up again, I only commented after Lieven (look at the time stamps and you will see what I mean).
        
        Anyway, I completely understand what you mean, you have actually revived this conversation after a few of us (‘crazy objectivists’ as we are fondly known around these parts) have given up
        The point you are making is the point I originally made… or tried to make. I would love someone to take up the challenge of trying to differentiate between two flat measuring solid state amps in a double blind test… but I have a gut feeling it is never going to happen
        
        Cola Bear
        
        The FiiO E10 approaches audible transparency so long as the software volume control is set to MAX and you use the E10′s volume pot. This is not an ideal situation for some users.
      - http://ancientwisdom.pip.verisignlabs.com/ AncientWisdom
        
        @DeliciousFlatFrequencyResponse:disqus :I also tend to be skeptical that the E-10 can be distinguished easily from the O2. One way or another Mike and I think Lieven commented previously that the O2 is the better amp (simple economics at play). So how can Lieven now say the E10 is better in his opinion? I’m just a bit baffled.I also 100% agree with you in regards to coloration being ok and in fact all my kits are un-ashamedly colored. However the color is in the Headphones, not the source/amp.My gear: FA-011, DT-770, Shure DJ750 and more- none of them remotely natural.However sources/amps: Asus STX, Sansa Clip+, O2 – all of them strive to be transparent.I understand people have different opinions, preferences and views however this review feels like it’s more than that.”can’t we just exists alongside peacefully?”
        I sure hope so! After all we all share a hobby/passion!
      - http://www.headfonia.com/ L.
        
        I’m not commenting on this thread in general but if you had read my part or the review more closely you would have seen I never made such a statement, I didn’t even mention the E10 as a matter of fact and I only spoke of the Violectric, so I have no idea where you’re getting this from. You can discuss all you want but please don’t go stating stuff mentioning my name if I never said it. It makes me wonder what else visitors misunderstood/didn’t read.
      - http://ancientwisdom.pip.verisignlabs.com/ AncientWisdom
        
        My Apologies Lieven!
        The sentence I was referring to is: “The mids are moderately thin in comparison to amps like the C421 or the Fiio E10/E11/E17 that Lieven and me both liked”
        This is under Mike’s impressions, I somehow thought I saw this on your part but was obviously confused (maybe because of the mention of your name in that sentence).
        Anyway I apologise again, it was not my intention to create false information.
        
        PS What do you mean by not commenting on this thread? why?
      - http://www.headfonia.com/ L.
        
        Well a last one then. I think Mike’s comment pretty much expressed my feelings too. That being said. 1. I can accept people preferring mesurements, but a lot of the “objective” guys seem to be unable to accept our point of view. I find that sad. 2. We even say the amp is great (but we don’t enjoy it because of the way we think the bass and mids are) yet we get critisized for not giving it a full 10/10 or for not following the ideology that it is the perfect amp. That’s it, I’ll get out of your way again now. Apology accepted btw
        
        http://www.facebook.com/profile.php?id=100001174173334 Scott Boyer
        
        Measurements definitely have their place and are helpful as a guide, but they are not to meant to be followed so blindly.
        
        In the end, one needs to try equipment out for themselves to see if it’s what they are really looking for. Nothing replaces first hand experience.
      - http://ancientwisdom.pip.verisignlabs.com/ AncientWisdom
        
        Leivan,
        The criticism is not due to you not giving a 10/10 score, it is not about objective vs. subjective and it is definitely not the preference of measurements over subjective impressions (nwavguy himself posts subjective impressions with his reviews). It is also not about not having measurements or any of that – we do not expect that of you. Allot such things got thrown here or responded to ‘objectivists’ posts without any connection with what people were actually saying.
        
        It is very simple: nwavguy claims the amp is transparent. You say according to your listening it is not. There is proof that expectation bias could very well change the way stuff sound to you.
        
        It all come down to this: you *should* do a blind test against another transparent amp (preferably one that you like such as the v200) and verify that you can still hear those differences, even when you don’t know what you listen to.
        
        If you choose not to do so that is of course OK, but know that your impressions are not reliable because you have not refuted the existence of bias.
        
        I am not expecting a response as it is obvious you and Mike decided it is better to opt out of the discussion, however you seem interested to know what the problem is, and it seems you still don’t get it so I am trying to explain it as clearly as I can.
- http://profile.yahoo.com/PN7EJS34TCX3UAZQDHPZFXHYWE Rian
  
  I think most people aren’t mad, but they felt this article doesn’t do a whole justice to O2, especially on the fourth part of the article which sounded like you had a problem with the ideology behind the amp(!) instead of the amp itself.
  
  It’s OK to critique the amp, but not the ideology behind it, as it ticks people off fast.
  
  Not only the criticism falls on deaf ears, it stimulated people into negative thinking.
  At that point basically you turned the whole thing into a subjectivist sermon.
  And now you wonder why people are posting their rebuttals.
  
  By the way, I respected Nelson Pass as much as I respected Bob Carver.
  - orta03
    
    I disagree. Mike’s point in the fourth part of this review is measurements alone do not necessarily guarantee a optimal sounding amp. It’s a different view point as many in the industry do not share NwAvguy’s philosophy.
    
    The bigger point is Mike and Lieven have a different philosophy(as stated in the article) on reviewing gear than NwAvguy. There’s nothing wrong with having a diferent viewpoint. And I think it’s a bit unfair to be critical of a subjective viewpoint on the O2, its simply the way Mike has every reviewed every piece of gear on the site.
    - alejandro vidal
      
      measurements can guarantee that an amp is audibly transparent an therefore its sound indistinguishable from any other transparent amp.
      if the “view” you talk about is that not all amp that measure well (no coloration) sound the same, a DBT should show that, such view would also imply some sort of unknown electro-acoustic effect to account for the differences in sound. If the view is that accurate gear sounds bad or is not “musical” enough then all accurate gear should sound bad and get similar bad reviews.
    - http://profile.yahoo.com/PN7EJS34TCX3UAZQDHPZFXHYWE Rian
      
      I think you completely missed my point.
      
      The problem is being a subjective (or objective) review doesn’t give the reviewer(s) a free pass to poke the standpoint of the product designer or lack there of.
      
      Keywords: a pair of good ears, good/bad sonics, strong belief, wrote so convincingly
      
      It is akin like suggesting an atheist to believe in the existence of God.
http://www.facebook.com/profile.php?id=793059760 Paul Leskinen

I could be missing something, but I still see no explanation in that link for NOT using ABX testing. No measurements required…ABX is just a way to validate that one is hearing a difference between two sources. If there truly is a difference, it should be easy to tell (i.e. you should get near 100% on the ABX trial). It should actually reveal more subtle differences than can be detected another way, since auditory memory deteriorates after only 0.2 seconds, and it’s basically impossible to switch cables that quickly.
- http://www.facebook.com/profile.php?id=100001174173334 Scott Boyer
  
  Sounds like you didn’t read the link thoroughly. Please reread.
  
  Their philosophy is clearly defined.
  - http://www.facebook.com/people/Fred-Maxwell/1307740682 Fred Maxwell
    
    I read it “thoroughly” and am a published author as well as being an electrical engineer in the aerospace industry. Paul Leskinen is correct. If you interpreted it differently, you are wrong. There is nothing presented in that article that argues against ABX testing.
    
    In fact, there is no valid argument against ABX testing, period. Arguing against it is as foolish as arguing against double-blind testing in the pharmaceutical industry. Stop rejecting science in favor of mysticism.
    - http://www.facebook.com/profile.php?id=100001174173334 Scott Boyer
      
      Glad to hear that you’re an engineer. I stayed at a Holiday Inn Express last night.
      
      Regarding ABX testing…please refrain from putting words in my mouth. You’re drawing the wrong conclusions.
      
      Headfonia doesn’t do ABX. Period. End of story.
      
      If you don’t agree with this review, use your publishing skills and write your own O2 review.
      - Trent_D
        
        Engineer nothing. I went to Yardale where I had a 4.0 GPA!
http://twitter.com/larryzang La-chan

As I said in a previous comment, I have an O2, and I like it a lot because I think it sounds clean and transparent. All Mike has said is that its a good, clean and transparent amp, but he didn’t like some of the pairings he listened to. Frankly the tone of some of these replies are a little disrespectful or juvenile.

I’m really not sure what people are calling for when they are calling for a blind test. You are asking him to compare the O2 in a blind test against another ‘audibly transparent’ amp because you believe he is making up the differences between the different amps he reviewed the O2 against? Who in these replies making the demand for a ABX test, actually has the equipment or understanding to verify whether the amps he was comparing against are actually ‘audibly transparent’? Who here can nominate an amp that is measured to be ‘audibly transparent’, and not just based on the manufacturers published specification? Has anyone here, with the proper equipment, actually even independently verified if Nwavguy’s design actually meets the published measurements and is indeed ‘audibly transparent’?

Nwavguy has called out people and manufacturers using blind faith and sighted listening to arrive at their conclusions and yet there are people here who are defending the O2 with the same unshakeable beliefs. Mike is allowed not to enjoy the sound of the O2, just as he expresses his opinion on other gear in any number of helpful reviews he has written here. If you feel that there is some error in his methodology, and you have the equipment to demonstrate there is no actual difference between Product A and Product B, then I suggest you post up your measurements and findings instead of calling for these ‘challenges’ from the sidelines. Otherwise, stop waving around an ABX test like a baseball bat.

Your belief that the O2 is measurably superior and therefore subjectively superior is as much ideology as anything else. As I said, I like my O2, but I don’t pretend that my subjective presence isn’t based on anything other than my brain telling me Nwavguy sounds like he knows what he is talking about, and my ears telling me I like what I’m hearing.
- alejandro vidal
  
  “Your belief that the O2 is measurably superior and therefore subjectively superior is as much ideology as anything else.”
  
  I don’t think anyone has stated that (the part about measurably superior->subjectively superior).
  
  The complaints are more about attributing coloration (lack of bass punch and “wrong” mids) to an amp that isn’t supposed to have coloration at all. Blind testing would be useful because it could confirm or disprove that the amp is in fact audibly
  transparent.
  - http://twitter.com/larryzang La-chan
    
    This is my issue. Which amp is he supposed to compare it to that is supposedly audibly transparent, so that he can do an ABX test to it? No one, except nwavguy and the manufacturers, have the equipment to actually prove that any of these amps are audibly transparent. As nwavguy has pointed out, most manufacturers provide insufficient or inaccurate measurements for their products. There is no credible, independent verification from anyone else that the O2 actually measures as well as it does. Under these circumstances, what ABX test can be performed to demonstrate that the amp is in fact ‘audibly transparent’? Yet there is an assumption that the O2 is in fact audibly transparent. That is an act of faith as much as anything else, because all you are doing is taking the designer’s word that the amp he has designed is better and superior. nwavguy has been more transparent about it, but in the end it is the same as any other manufacturer publishing specifications.
    
    It’s reasonable to think that Mike could ABX test against another amp that he likes with the HD650, and see if under blind testing his preference changes. Even if it does or doesn’t change, all ABX testing tells us is that Mike prefers the sound of one or the other. It can’t tell us whether or not the O2 is actually neutral and uncoloured; it just tells us about Mike’s preferences in terms of sound and whether his impressions were coloured by everything else he knew about the O2 and its design. In the end, without a universal reference point the ABX testing process – which sounds like a very objective and scientific – is just going to return subjective information about what Mike prefers. In which case, does that really differ from the review as it stands – Mike’s subjective opinion on which amp he prefers?
    
    If you are asking for Mike to do an ABX test, in essence you are hoping or expecting that his opinion of the O2 might change – and this is a bias as much as any other hope or expectation. This review was conducted in the same way as every other review on this site. It speaks volumes about the subjective faith that Nwavguy has inspired from his objective design if this is the only review that was ever so scrutinised in the name of ‘objectivity’ because people are unhappy with the outcome. If you don’t want want Mike’s subjective opinion, then my suggestion is: don’t read his reviews.
    
    Let me repeat, I have an O2, and I like the sound. I like Mike’s reviews, and they are enjoyable to read. I’m not going to demand he change his way of reviewing things if he doesn’t like something that I do.
    - l_e_e
      
      That’s a lot of text and questions for a very simple answer: double-blind test.
      Like NwAvGuy suggested in his latest article, you should read it. Should also answer your other questions.
      
      You don’t seem to understand what transparency means.
      Mike would actually have trouble identifying which amp is which (O2 vs. V200 for example) in a blind test.
      - http://twitter.com/larryzang La-chan
        
        Please do not suggest I have not already read the article, and I have not understood it. I’d like you to actually read my comments and understand them. Since you feel that I have too much text, I’ll ask these two questions:
        
        1. Has anyone independently verified in a credible fashion that the O2′s published measurements are accurate?
        2. Has anyone independently verified in credible fashion that the V200, or any amp’s, measurements are accurate?
        
        I accept the idea that good measurement results should result in a amp that sounds transparent. What I am casting doubt on is that everyone has taken it as a given that the O2 meets its published measurements, and therefore they attack the review on the basis that the O2 is absolutely guaranteed to be transparent because Nwavguy’s measurements say so. You are taking him at his word, when Nwavguy has called BS on other manufacturers either providing false or inaccurate measurements without any verification. You are sanctimoniously declaring the review as deeply flawed because the O2 is definitely, 100% for sure, proven to be measurably transparent, without any basis to go on besides the statements of the designer!
        
        I am not saying that blind testing may not uncover that there is a difference or no difference in sound between the O2 and another amp. But “transparency” is as much of a relative buzzword as “coloration.” Without knowing if the O2 is actually measurably transparent, all a blind test will show is that Mike and L. were hearing differences that either were there or weren’t.
        
        ie:
        1. Under a blind test, the O2 sounds the same as another amp.
        2. Under a blind test, the O2 sounds different.
        
        At no point does the result of this test actually tell us whether or not the O2 is ‘audibly transparent’. It just tells us how the O2 sounds compared to another amp, and none of these amps are amps we know for sure have truthful or complete published measurements. And yet people are insisting that blind testing will demonstrate the O2 is transparent.
        
        “I can’t hear the difference between X and Y” is only relative transparency.
        “I can’t hear the difference between X and Y and both X and Y have been shown to be measurably accurate.” is absolute transparency.
        
        People are making the case that the O2 is absolutely transparent, when all the blind test will show is that the O2 sounds very similar to another amp. This is my problem with people calling for a blind test as if it somehow proves something empirical about the O2.
        
        I don’t think I am being unreasonable in having a degree of skepticism about how critical this amp’s defenders are being. I like the O2, I think the designer knows what he is doing, but I am not going to go making leaps of faith on that basis.
      - l_e_e
        
        @La-chan: I don’t know if “anyone independently verified in a credible fashion that the O2′s publish measurements are accurate” but I have made some measurements myself and I see nothing wrong if I compare them to NwAvGuy’s measurements. I don’t have access to an expensive audio analyzer but a couple of very well measuring A/Ds and D/As that can be used to measure the flat frequency response, low THD, IMD, crosstalk .. both with dummy and headphone loads. (Unloaded measurements are useless. see mini3, c421 …)
        
        Yes, I am taking him at his word that other manufacturers have produced bad equipment because nobody has shown otherwise. Even though RMAA is quite limited you can easily measure some of the flaws NwAvGuy has published. Take a look at the threads on some audio forums that discuss his articles. Nobody wrote: “hey look at this, I measured something completely different.”
        
        I am declaring this review is flawed because it makes claims that contradict both measurements and several other reviews spread over different audio forums.
        
        > 1. Under a blind test, the O2 sounds the same as another amp.
        vs. a V200? This would be enough to show that the reviewers approach is flawed.
        
        Also, you don’t need both X and Y to be measurably accurate in order to show “absolute” transparency.
        
        > And yet people are insisting that blind testing will demonstrate the O2 is transparent.
        How high do you think are the chances that two different amps sound identical without them being transparent, i.e. both have identical coloration/flaws? Very, very low I’d say. Of course, a single test wouldn’t prove anything and nor would 100 tests be 100% proof that it is transparent..
- http://www.facebook.com/profile.php?id=793059760 Paul Leskinen
  
  The bottom line: It is pretty well proven that measurements reliably predict transparency in an amplifier, via double-blind listening tests. If there is an audible difference, there is certainly a measurement that will show it using current technology. There is nothing “magical” about our ears–they are easily fooled. If Lievan and Mike claim that the O2 is not transparent (e.g. thin bass and midrange), I will stand up and call BS to their faces, as they are clearly biased, and refuse to even acknowledge that blind testing is a valid tool. If they want to purvey their biased, sighted listening tests to their gullible fanboys, that’s fine–buyer beware. I for one, am completely done with Headfonia, as it has absolutely lost all credibility in my mind. Face the facts: A sufficiently well-designed amplifier will sound EXACTLY like any other sufficiently well-designed amplifier: Any amplifier with sufficiently low output impedance, sufficiently low distortion and flat frequency response is “transparent.” End of story. All of your flowery adjectives used to describe multi-thousand dollar amplifiers prove NOTHING. You ARE subject to bias (regardless of your denials to the contrary), and that is a fact proven by multiple studies. If all of the rest of you who want to spend thousands on their “preferred” esoteric tube amplifiers that color the sound in a pretty way, well, there’s a sucker born every minute.
  
  Bye bye, Headfonia.
  - http://ancientwisdom.pip.verisignlabs.com/ AncientWisdom
    
    Yep that pretty much sums it up.
    
    Not to mention the fact that they have contradicted themselves; in the past they have expressed that it is a great amp (both on Facebook and in their comment section) well deserving it’s high praise but now somehow the opinion has changed with no given explanation.
  - http://www.facebook.com/profile.php?id=100001174173334 Scott Boyer
    
    “…If there is an audible difference, there is certainly a measurement that will show it using current technology…”
    Not necessarily.
    
    Also…
    Sorry you were not able to convince Mike and L to change the review style of their website. Their philosophy has already been clearly stated several times. If you are not happy with the direction of their review style, there are many other measurement based review websites out there. A few posters are determined to discredit their review style and the direction of their website and I’m still not sure why that is. Different strokes for different folks. Why all the fuss?
    
    Many of us are happy to see a site like this where reviewers use the tools that they were born with…their ears.
    - l_e_e
      
      > Many of us are happy to see a site like this where reviewers use the tools that they were born with…their ears.
      
      Ever heard of BIAS? Ah.. never mind.
      - http://www.facebook.com/profile.php?id=100001174173334 Scott Boyer
        
        And the other shoe drops….
        
        Guess you’ll be leaving too?
      - Trent_D
        
        One of the primary rules of film criticism (and this applies to all forms of criticism) is to know your bias. EVERYBODY has bias. Maybe it is favoring measurements over all else. It could be putting a lot of weight on how something looks. Perhaps you have a bias towards a certain sound, like MR JDSlabs who admitted to being a bass boost guy. I enjoy reading the reviews here. I come hear looking for their opinions. Mike and L are good about stating what sounds they like or why they like or don’t like something. If you don’t like the way they review, read elsewhere.
http://www.facebook.com/profile.php?id=793059760 Paul Leskinen

Yes, they listen. That’s fine. How do they remove bias from their sighted listening tests? Why do they not employ an ABX box for that purpose?
- http://www.facebook.com/profile.php?id=100001174173334 Scott Boyer
  
  Maybe you have an ABX box that they can borrow?
  - http://www.facebook.com/profile.php?id=793059760 Paul Leskinen
    
    No, I do not. But then, I don’t have a blog that reviews and compares headphone amplifiers—my point is that THEY should have an ABX box, or at least attempt some kind of blind test when comparing amps.
    - http://www.facebook.com/profile.php?id=100001174173334 Scott Boyer
      
      Oh, it just sounded like you had one from all of your comments.
      
      Have you ever ABX tested your own system? Just curious.
    - http://www.facebook.com/people/Fred-Maxwell/1307740682 Fred Maxwell
      
      Paul,
      
      If you say that you have done ABX testing and could not differentiate between products X and Y, then the subjectivists will immediately pounce, claiming that it’s proof that ABX testing is flawed, that you lack listening skills, that the rest of your system is somehow lacking, etc.
      
      It’s a no-win scenario — I know because I’ve been on the losing side. Most of the subjectivists who prod you to perform the ABX testing that you advocate will never agree to participate in such a test themselves. They will posit that product X is audibly superior to product Y — they “hear” the difference, so it’s real, not bias or imagination, and is not open to discussion. In essence, any test that fails to support their beliefs is at fault; their beliefs are not open to question.
      - dalethorn
        
        So who is doing the listening training? Challenging what someone hears is problematic unless you are well trained in listening yourself. It seems like you could miss all kinds of things by being tuned in to certain sounds more than others. Are there people so good at this that they are sure they have all the bases covered? My take on the reviews is that reviewers have to operate within a certain range of listening skills in order to not wander all over the place and get lost. But when critics weigh in with very different opinions, I wonder if they have a wider range of skills, a narrower range, or they just learned a different way completely? Since there does not seem to be a universal guide to learning critical listening.

NwAvGuy’s Objective 2 by JDSLabs and Epiphany Acoustics

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