[TheShaman]

Hey, I'm all about measurements and blind tests. That's why if one says that the better bench numbers of The Wire don't mean anything, I'd like some proof (= blind test) about that.
 
Btw, I don't think the designer of O2 even suggested that he hit the "measurements-sweetspot", where everything that measures worse, sounds worse and everything that measures better, sounds the same - or that such a spot even exists..  
If he did, I'd personally like some objective data to back that up as well.
 
I should note I'm only looking for a desktop amp (so I don't care about battery operation and such) and I prefer working with SMD components for various reasons. 
I already have the older Wire boards but I need one SE amp and was waiting for O2 Desktop. Now that I saw the numbers of the SE-SE version The Wire, I don't see why I should invest in the O2.
Even if it does sound the same as the O2 (which has to be proven), I consider The Wire an easier build, which doesn't seem to cost much more and performs better on the test bench - so a better amp objectively, which for us measurement guys should be important, all other things being equal.
 
I'll stay tuned just in case such a blind test takes place.

 

[mikeaj]

Well you can find some apples-to-apples comparisons (measurements) at "that" place between the O2 and Benchmark DAC1 Pre, for example.  The Wire does better than the DAC1's headphone output, but the DAC1 is mostly similar to the O2.
 
He claims his own ABX testing shows he (and others) can't tell the O2 from the DAC1 headphone out, but I wouldn't really take a negative result on an ABX too seriously from somebody who is expecting a negative result.  Also The Wire performs at a higher level anyway, if you believe that that will make the difference.
 
 
But as DRUB kind of mentioned, most headphones (and speakers) have THD figures that can hardly break 0.1%, certainly not 0.01%.  Check the docs on InnerFidelity for HD 800, LCD-2, HE-6, SR-009, or whatever else you want.  Well, that's assuming that the test setup can actually provide enough resolution to accurately capture what is going on.  Is 0.002% on the amp going to make a difference vs. 0.0005%?  I would guess that even were you listening very loud and had super hearing, the difference would be masked by the headphones...
 
http://www.innerfidelity.com/headphone-data-sheet-downloads
 
Of course I'm be interested in testing to prove one way or the other, anyhow.

 

[Willakan]

NwAvGuy offers $500 to the charity of choice for the person who can distinguish his amp from any other well-measuring amp in a blind test.
Whilst I'd be the first to admit the difficulties involved in setting up such a challenge make it perhaps a little unlikely to be fufilled, there is nothing wrong with the O2 that could be audible that I am aware of. For example, the most uber-radical studies into THD audibility still conclude the audible levels are considerably above what the O2 exhibits. The traditional figure for THD audibility is 1% - NwAvGuy suggests the latest studies show (locked behind an AES paywall annoyingly) that 0.01% THD in the midrange is a number to keep below to be safe. The O2's THD ( easy load at 1khz) is something like 0.001%. You can do better, but not audibly so.

 

[wakibaki]

 

Wait, if a reference design sounds the same, blind, as a cheaper design, what exactly is the point of the reference design? Better amps are all well and good, but I don't have the money to lavish on things that sound the same under blind conditions and would question the plausibility of taking as fact that those who do enjoy a superior experience.
Just to prevent any conclusion, I absolutely agree that it is possible to beat the O2 measurably by a pretty large margin, but would question the value of doing so if all you want is a transparent amplifier.

Quote:

Originally Posted by wakibaki /img/forum/go_quote.gif
 
You can still have competition between designs.
 
You can compete for features, style, miniaturisation, efficiency, battery life, ergonomics, design philosophy, aesthetics, robustness, ingenuity, value for money and doubtless other characteristics all considerably more healthy than the current set of values....

 
That's the whole point. To shift the argument beyond a load of meaningless and ultimately fruitless agonising over the third decimal point of 1% of some specification and beyond any considerations of a superior sound and to concentrate on the multiple other characteristics that make an amplifier desirable and which are being largely ignored in favour of a dispute that offers no possibility of reconciliation because it's based on characteristics that cannot be verified repeatably by any known technique.
 
The O2:-
 
For:
 
Cheap.
Thru hole.
Battery/mains
Open source
Robust
Headphone protection circuit (for some faults)
Short circuit tolerant
Simple user interface
Low output impedance so flat response
Drives the very large majority of phones
Published specs produced on industrial-grade testgear
 
Against:
 
Bulky, esthetically primitive
Cheap (no snob appeal)
Not SMT (20th. Century)
Battery life could be better, there is unused space in the enclosure
Primitive charging regime
Limited connectivity (only 2*3.5 jacks, in and out)
Limited range of adjustments (no tone, balance)
Rail-rail swing could be improved to further increase range of phones driven
Current output capability could be higher
Can and does radiate some interference in some circumstances (according to the designer)
 
w

 

[estreeter]

What is going on with the quoting button atm ? I have tried several times to quote an earlier post, and it keeps quoting a different post ...
 
Anyway, to the poster who claimed that he is 'still waiting for a proper review of this amp' as no-one has written one, you clearly havent read the earlier impressions given in several threads on HF. No, you wont see anything about 'lush mids' or 'saucy treble', but you might be happier with another amp if you want people to wax lyrical about a wire-with-gain. Even 'The Wire', by all account an exceptional amplifier, doesn't get reviews like that, and you wont see that kind of hyperbole around Kevin Gilmore's designs.

 

[upstateguy]

Quote:

What is going on with the quoting button atm ? I have tried several times to quote an earlier post, and it keeps quoting a different post ...
 
Anyway, to the poster who claimed that he is 'still waiting for a proper review of this amp' as no-one has written one, you clearly havent read the earlier impressions given in several threads on HF. No, you wont see anything about 'lush mids' or 'saucy treble', but you might be happier with another amp if you want people to wax lyrical about a wire-with-gain. Even 'The Wire', by all account an exceptional amplifier, doesn't get reviews like that, and you wont see that kind of hyperbole around Kevin Gilmore's designs.

Quote button worked for me....
 
And +1 on your post.

 

[i_djoel2000]

Quote:

What is going on with the quoting button atm ? I have tried several times to quote an earlier post, and it keeps quoting a different post ...
 
Anyway, to the poster who claimed that he is 'still waiting for a proper review of this amp' as no-one has written one, you clearly havent read the earlier impressions given in several threads on HF. No, you wont see anything about 'lush mids' or 'saucy treble', but you might be happier with another amp if you want people to wax lyrical about a wire-with-gain. Even 'The Wire', by all account an exceptional amplifier, doesn't get reviews like that, and you wont see that kind of hyperbole around Kevin Gilmore's designs.

i have read ALL o2 reviews in head-fi, including short impressions in the comment as well

 
at least one can compare it to a highly regarded branded amp like schiit lyr or burson. not just short impression or saying 'good', 'nice', or 'it drives high impedance headphones just fine' without making further justification (does it have better treble extension than burson? or smoother than lyr? etc.). something like that doesn't just go without saying, so i think someone needs to make that kind of review
 
why won't we get proper review in this kind of DIY amp? even skylab wrote wonderful review about AMB Mini3
 
*just my 2 cents
 

 

[khaos974]

Quote:

Wait, if a reference design sounds the same, blind, as a cheaper design, what exactly is the point of the reference design?

Bragging rights and feeding your inner subjectvist because your hearing may still be influenced by *knowing* you have a measurably better amp

 
 

 

[fishski13]

Quote:

i have read ALL o2 reviews in head-fi, including short impressions in the comment as well

 
at least one can compare it to a highly regarded branded amp like schiit lyr or burson. not just short impression or saying 'good', 'nice', or 'it drives high impedance headphones just fine' without making further justification (does it have better treble extension than burson? or smoother than lyr? etc.). something like that doesn't just go without saying, so i think someone needs to make that kind of review
 
why won't we get proper review in this kind of DIY amp? even skylab wrote wonderful review about AMB Mini3
 
*just my 2 cents
 

the amp hasn't been out that long.  i don't think those that genuflect to measurements are likely to bust out into flowery prose, and from that point of view, i'm not sure how much room there is for subjective impressions for an amplifier designed around objective benchmarks.  i'm not sure that this amp is lighting up the subjectivist camp either, especially with an opamp for the output device. 
 

 

[qusp]

how about linearity/phase? i admit i havent studied the O2 measurements, but i expect due to the design that it will fall down here against what is essentially perfect on the wire due to no caps. for me it has a lot more going for it than just the better measurements. its a much more compact amp, for me even the balanced version would take even less time to build (i believe most peoples aversion/fear to/of smd is in their minds)
 
actually as far as reviews of 'the wire' i think my short review and a couple others like it are about as close as you'll get to using descriptive language and i only illustrated that it could be whatever the source demanded
 
the wire
 
For:
 
reasonably priced
available in SE-SE, BAL-SE and BAL-BAL
SMD
Small number of parts
Easily attainable BOM ie. no difficult to find obsolete semis
Very compact
Technically and aesthetically appealing
Essentially perfectly linear
Almost identical performance into varying load
Large current output even on the SE-SE, Doubled on BAL-BAL
Battery/mains
Open source
Robust
Short circuit tolerant (hmm)
Simple user interface
Low (essentially no) output impedance so flat response
Drives multidriver iems with ease, something many people seem to incorrectly assume is easy
Drives all headphone loads right up to small speakers
Published specs produced on industrial-grade testgear
Very handy little adjustable power supply for multiple projects
no integrated volume control, so perfect channel matching can be attained with digital control
 
Against:
 
 
Battery life is short unless large/expensive polymer prism cells are used (although on the SE-SE this is probably much better)
BYO charging regime
Limited range of adjustments (no tone, balance)
No DC protection of any kind so common sense is assumed
Method of construction may be off-putting to some inexperienced builders
Some parts may be expensive at some vendors (element14/farnell i'm looking at you)
No integrated volume control
 
 

 

[Anaxilus]

Quote:

Anyone had a chance to compare O2 to The Wire?

Why?  By the logic applied here by some they sound exactly the same.  Just look at the measurements.
 

 

[Anaxilus]

Quote:

i believe someone should compare this to burson instead, since the designer believes this amp will blow any branded amp within 1000 bucks range. haha
 
still waiting for a proper review of this amp, though. so far none has come

Burson sounds pretty bad IMO, but that's just my subjective hearing which is basically worthless.  There must have been a scratch on the enclosure that colored my expectation bias.
 

 

[Head Injury]

Quote:

i have read ALL o2 reviews in head-fi, including short impressions in the comment as well

 
at least one can compare it to a highly regarded branded amp like schiit lyr or burson. not just short impression or saying 'good', 'nice', or 'it drives high impedance headphones just fine' without making further justification (does it have better treble extension than burson? or smoother than lyr? etc.). something like that doesn't just go without saying, so i think someone needs to make that kind of review
 
why won't we get proper review in this kind of DIY amp? even skylab wrote wonderful review about AMB Mini3
 
*just my 2 cents

Schiit Lyr vs. O2 from an objective standpoint wouldn't be a fair fight. But that's the nature of tubes and discrete designs. They aim to please the romantics, not the charts.
 
Quote:

how about linearity/phase? i admit i havent studied the O2 measurements, but i expect due to the design that it will fall down here against what is essentially perfect on the wire due to no caps.

 
There's phase measurements in the first O2 article on his site.

 

[cheapskateaudio]

 
Quote:

 
Also, how on God's earth is cheapskate still posting?

 
Thats funny coming from the second biggest troll in this discussion. 
 
It is legal, rational, and A-OK, as a DIYer, to make changes, make claims, and do nothing to back them up except to say, SOUNDS BETTER TO ME...
 
Anyone contending otherwise is a jerk who doesn't quite understand the point of this H O B B Y.
 
----
 
One source of my woes has apparently been U5/U6 which tend to get fatigued quite rapidly/easily. I noticed that both amps I built seemed to have reduced performance over time, especially when driving HD650's. Yes, it got *worse* sounding over time, one of the amps eventually started to clip and died completely. The issue was U5 which got too hot and died, it's only rated to 85C and most linear regs are rated to 125-150C. (Of course the minute I hear this amp making funny noises I unplug the HD650's, because I'm not ruining my headphones with this shoddy battery amp.) 
 
I don't think this amp likes to run on AC power, and I don't think the upgrades provided by the WAU16-400 are sustainable given the PS. I measure 18.1V from my WAU16-400 so I guess that's just too much for those poor little regs to handle. 
 
When I replaced U5/U6 the amp sounded quite good, and there were no pops and clicks on startup. Given that it's plausible that if you're getting pops or clicks of any kind, its probably because you've been running AC and your V-regs are starting to poop out.
 
One symptom of a dying V-reg is that a strong input signal will start to clip, and turning down the input will remove the clipping, until the V-regs completely toast themselves. 
 
Anyhow, I'm pretty sure the BOM v-regs are pure crap. Fair warning, be careful if you're running this amp on AC with demanding headphones. 
 
 
 

 

[deadlylover]

Quote:

 
Thats funny coming from the biggest troll in this discussion. 
 
It is legal, rational, and A-OK, as a DIYer, to make changes, make claims, and do nothing to back them up except to say, SOUNDS BETTER TO ME...
 
Anyone contending otherwise is a pompous jerk who doesn't quite understand the point of this H O B B Y.

 
Yeah I don't think those guys have any problem with that at all.
 
However, until proven otherwise, you didn't improve the amp (in a technical sense). And that's really what all those guys are making a big kick in the fuss about, which is akin to fighting over nothing. But that's what audiophiles do.
 
Quote:

Schiit Lyr vs. O2 from an objective standpoint wouldn't be a fair fight. But that's the nature of tubes and discrete designs. They aim to please the romantics, not the charts.

 
It all depends on the designer's goals, because the Blue Hawaii would like to have a word with you.