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O2 Build Complete: Let the objective, subjective listening tests commence! - Page 12  

post #166 of 721
Hey sounds like your having alot of fun and its nice to hear you improved the sound im actually trying to start diying things now and im interested in ur upgrades id love to know where i could find the parts for the upgrades that u did to the obj02 thx for your input
post #167 of 721

If you're looking for mods (some of them may be difficult to call as an "upgrade") that make a little more sense and are better documented, I'd suggest taking a look at some of agdr's interesting-looking suggestions on diyaudio:

http://www.diyaudio.com/forums/headphone-systems/

 

If you want legit improvements in accuracy, most mods are going to be sidegrades (or very slight upgrades that would be hard to pick up with audio instrumentation test gear, let alone ears) or downgrades.  Certainly there are different features to add or improvements in battery life to be had.

post #168 of 721
Quote:
Originally Posted by mikeaj View Post

Mine's been done for a while.  I get the feeling that many builders just don't feel the need to post impressions since it has been documented so much already and given a few reviews before the large group buy was even finished.

 

If you want them...impressions:  it works well.  I'm not sure about sound quality, but I certainly don't hear anything wrong (including noise).  The end.



That's one of the best amp reviews I have ever read :-)

post #169 of 721

The perfect objective review: "nothing is wrong" beyersmile.png

post #170 of 721

Is it normal that the Voltage regulator are burning hot ?

post #171 of 721
Quote:
Originally Posted by WhDemon View Post

Is it normal that the Voltage regulator are burning hot ?



On mine, they never get past slightly warm to the touch.  I am only using the ac adapter though.

post #172 of 721
Quote:
Originally Posted by shadow419 View Post





On mine, they never get past slightly warm to the touch.  I am only using the ac adapter though.



 

Im using also the ac adapter only. Battery clips are not installed yet. Voltages are fine. WAU16-400

post #173 of 721
Quote:
Originally Posted by WhDemon View Post

Is it normal that the Voltage regulator are burning hot ?


 

Quote:
Originally Posted by shadow419 View Post

On mine, they never get past slightly warm to the touch.  I am only using the ac adapter though.


 

Quote:
Originally Posted by WhDemon View Post

Im using also the ac adapter only. Battery clips are not installed yet. Voltages are fine. WAU16-400


This is probably an indication of a fault somewhere. Despite the fact that you report no other symptoms, excess current is leaking to ground. If there was a simple short the current would be high enough to trip the regulator's overcurrent (thermal) protection, so the current is through something with resistance. You may be able to find it by feeling around on the board for another hot-spot.

 

w

 

post #174 of 721

I finally built mine. It sounds marvelous!!!

post #175 of 721
I'm not sure LFF how the O2 is supposed to actually sound like anything. But no matter, it is a very fine piece of amp! I'd use it more if my LOD hadn't broken...
post #176 of 721


 

Quote:
Originally Posted by estreeter View Post

Thanks for the feedback guys - I'm perfectly happy with 'it works well'. We have enough amps that 'make the magic smoke come out of your headphones' on Head-Fi .....   rolleyes.gif

 

Well, here's another vote that it works well. biggrin.gif  I bought mine from aerohoff at diyAudio, since I've never soldered before, but it was everything I was expecting so far.  I don't have any high-impedance or low-sensitivity headphones to test yet, so I have nothing to say regarding the improvement over unamped listening.  I'll be able to informally test that once my FA-011's arrive, since they require an amp for maximum performance.

 

For anyone needing more, I think the O2 is just difficult to subjectively review in detail, because it's easier to go into detail about coloration than lack thereof and neutrality:

What I can say is that my low-impedance HTF600's and Re-ZERO's seem to sound very similar to the way they do without the amp.  The O2 actually might be making them sound a bit clearer, but if that observation is "real," it's probably because the O2 lets me use full volume output from my computer instead of using digital volume controls to drop 40 dB (which loses tons of precision).  I definitely can't detect any coloration, noise, or distortion though.

 

Still, that's pretty much to be expected from any O2 that's built properly:  The O2 measures well by design, and any amplifier that measures well across the board will necessarily sound the same as another that measures well across the board.  (If the load doesn't require amplification, well-measuring amps should also sound the same as an unamplified signal, once volume-matched).  A well-measuring amp like the O2 is inherently neutral, which makes it more of a reference point that colored amps can be contrasted with.  That's different from saying "all amplifiers sound the same," because the vast majority don't, but that's a direct result of coloring the signal in measurable ways.  To say otherwise would imply that electrical signals have esoteric (or magical) properties that can only be detected by headphone or speaker drivers in combination with the human ear, and which cannot be detected by any other objective tests or instruments.  (That doesn't mean we can directly measure a complex phenomenon like soundstage, but an amp's effect on soundstage still results from the interaction of simpler, measurable characteristics like distortion and crossfeed.)

 

Some people actually do believe in "magical" signal properties, but this viewpoint essentially renounces the possibility of a true high-fidelity amplified signal or a pure "wire with gain amp."  By extension this viewpoint would imply that headphones cannot be tested or measured on their own terms, since their sound changes from amp to amp, and no amp is objectively "correct."  At the same time, no amp can be tested or measured on its own terms either, because the sound of an amp definitely changes depending on the load (headphones).  In short, if you believe that an objectively correct amplifier cannot exist, the O2 shouldn't hold any special interest for you.  It will just be another amp to test in combination with your particular headphones, so you can see if you personally like the combination of the two.

 

I fall into the camp that believes that an objectively correct "wire with gain" amplifier is possible, and that the O2 has accomplished that goal.  Aside from curiosity, there are two major reasons to specifically want such an amp:

  1. You may want an amp that delivers a high-fidelity amplified signal, regardless of whether genuine high-fidelity is actually your favorite cup of tea.  In this case, subjective impressions will be irrelevant to you, because objective measurements have the final say on whether an amp is high-fidelity or not.
  2. You may be looking for sheer audio enjoyment like most, but you'd rather limit your variables to just testing different headphones instead of testing different combinations of amps and headphones.  (It's definitely cheaper. wink.gif)  In this case, you necessarily believe that listening to your headphones through the O2 means listening to your headphones as they really are...so it would be a bit silly and redundant to subjectively comment on the amp's sound by itself.  Unless/until you become convinced that the amp is coloring the sound, there's not much to say beyond, "It works, and it sounds like my headphones."

 

Finally, a third camp seems to concede that a correct "wire with gain" amplifier is possible and that well-measuring amps will sound the same, but they've argued that the O2 designer has only published the results from a few handpicked objective tests.  These criticisms seem to be vague and speculative to me though, rather than genuine calls for specific additional testing.  (I could be mistaken, but they seem to come from a persistent emotional disbelief that an inexpensive amp could actually do the job correctly.)

 

Most O2 owners will ultimately fall into the second camp, so that should help explain the relative shortage of subjective impressions.  It sounds as neutral as it measures (unless you overload the input stage), so there's not much more to say.  It doesn't add extra warmth or fullness to my music, but it isn't supposed to.  It also presents the soundstage "as is" rather than augmenting it.  At the same time, my expectation bias will make me less sensitive to any kind of coloration anyway, so that just gives me even less to say from the perspective of subjective sound quality. tongue.gif  Most O2 owners probably fall into the same category.

 

Short of the expensive Violectric amps or the Benchmark DAC1's built-in amp, I'd say the O2 is basically the definition of a neutral reference amplifier.  (It has to be, unless the objective measurements are lies, omitting something, or unable to capture mysterious or magical properties of an electrical signal that somehow influence only drivers and ears.)  My ears agree with the objective measurements based on the only test I can perform, which is comparing easily driven headphones with and without the amp.  You're unlikely to get reliable subjective impressions with more detail:  If you read impressions that say it's too cold, it probably means the reviewer prefers warm amps to neutral amps.  If you read impressions that say it's too thin, it probably means the reviewer prefers full amps to neutral amps.  (If you read impressions that say it isn't neutral, it probably means the reviewer is using the wrong reference point for neutral, unless something just went wrong with the build process.)  The problem is, these impressions basically say more about the reviewer's preferences than the amp itself, and they'll be meaningless to you unless you know how your preferences compare with the reviewer's.

 

Bottom line:  If you want a stress-free neutral amplifier, you'll like the O2, and you won't have to worry about how it might be altering your music.  If you believe in the existence of a neutral amplifier but don't know whether you'd like it or not, the O2 is a great reference point, and it's the only one that won't cost you an arm and a leg.  If you already know that you want the fullest and most "euphonic" sound possible, the O2 definitely isn't for you, and you should look for amps with harmonic distortion and crossfeed instead.


Edited by SobbingWallet - 11/11/11 at 9:29pm
post #177 of 721

TL : DR tongue.gif  

Actually did read it and a well worded essay it was.

Finished building mine yesterday and I'm very pleased with it.  Plenty of power/volume even with the smallest gain settings for most headphones/sources.

 

 

 

post #178 of 721
Quote:
Originally Posted by Magedark View Post

I'm not sure LFF how the O2 is supposed to actually sound like anything.

That's why it sounds marvelous!

 

post #179 of 721

 

Quote:
Originally Posted by LFF View Post

That's why it sounds marvelous!

 

 

Do you still have a pair of Fischer FA-002W High Editions?  You said they were extremely picky about amps, so I'm curious whether a neutral amp like the O2 works for them, or if they actually require some special kind of coloration to meet their potential.

post #180 of 721
Thread Starter 
Quote:
Originally Posted by jacobthellamer View Post



 



 

 Yeah I am going to use 1/4 jacks, RCA input, off board switches and a nice alps potentiometer for the desktop version. I will be running the desktop build off a toroid too :D



Which ALPS are you using? I took a cursory look at some pot options but couldn't find anything at mouser.

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