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

[cheapskateaudio]

Quote:

@Anaxilus
Driving headphones is maths. How the hell do you think you work out how to drive a headphone to a given SPL? Wizardry? There is absolutely nothing more to driving headphones.Anything else is simply BS.
As it happens, the HD800s are a relatively easy drive for the O2. Yes, this observation is based on maths. It's not "rudimentary," it's right. It can also drive the crap out of the HD650s and the K701s. What exactly do you think sensitivity ratings are for?
 
cheapskate:
NwAvGuy has measured the currents across the capacitors when the amp is operating to ensure they don't wreck performance. Whatever you've done, you've either degraded the performance of the amplifier to sound different or you are a victim of involuntary bias.
You can lob around accusations of religious fervour all you want, but it doesn't change the facts.

Ok, we have that standoff, and you say that but you still haven't heard or tested my specific amp. So you're assumptions are as good as mine from an absolute standpoint, the difference is you've probably rightly taken the side of the person who knows more about this amp than I do.
 
I just have my own opinion of why things are the way they are. Whether it was marketing, whether it was ego, whether it was a biased obsession with a specific number, I think this amp is hobbled in some manner...
 

 

[Willakan]

The thing is, for an amp to sound thin it requires a seriously dodgy frequency response - by which I mean huge audible frequency response error. The problem you are reporting is of such a serious nature (makes a headphone sound unlistenable) that it suggests that the amplifier has some huge measurable flaw (and I mean huge) which seems rather unlikely. I think someone else is using them with the HD650 and they reported good sound.
 
I would be interested, however, to see how you thought the O2 sounded fed from a non-uDAC source.

 

[mikeaj]

I would be very careful relating impulse response, frequency response, and so on, to what different specific people perceive as "fast" or "thin" or whatever (and some of those things likely to vary from person to person).  IMHO it's very difficult to argue against well-understood measures of electrical performance for what they describe; subjective classifications of sounds are much less well defined.  And that's even without considering the variability of perception even when comparing samples from the same person, and all the usual biases.

 

[SobbingWallet]

Quote:

 
you don't have a clue as to what DIY is about.
 
 

Okay, maybe I don't, but how will I know that if you don't elaborate and tell me where I'm wrong?  It's not like I've never done DIY projects before in the domain of other hobbies (which don't require soldering), and my opinion comes from my own experience and observations.  I'm no stranger to it, but maybe my experience differs from yours.  I didn't make some kind of hit and run, "LOL, DIY is for monkeys," post.  I made a post that explains, to the best of my ability, why the DIY ethic as I see it is not entirely applicable to this amp.  If you disagree with what I said, tell me why.  The least you can do is explain yourself when you make a blanket "you don't have a clue" attack.
 
This is the second time in this thread that I've been attacked by an established member for what I've said in this thread with NO real explanation or counterargument.  In Anaxilus's case, I reread my comment, agreed that I overstated my case, and restated what I really mean.  In this case, I have nothing to go on.  In what way am I wrong?  Am I actually wrong, or did what I say just upset you?  I don't actually know.  I may be a "noob with opinions," but I'm not here to spout tripe endlessly.  I'm here to learn and call things like I see them, and if I'm wrong, I want people to correct me instead of hurling generic and useless insults at me, ***.
 

 

[SobbingWallet]

Quote:

Is it stupid? Or am I simply the guy who isn't a dumb sucker for psuedo objective hyperbole?
 
Somebody actually change the coupling caps (YES IT HAS THEM, LOL), and tell me if you think it sounds *better* with the HD650's, I certainly don't hear any noise or distortion.
 
People like you are a danger to communities like this, communities where it is essential that we question everything we are presented with as part of our journey. And to avoid being taken for joy rides by lunatics with a rabid intolerant religious following.
 
Don't be surprised if "NwAvGuy" suddenly comes out with a new and improved amp, that is patented and *FOR SALE*. lol.
 

 
The amp has caps on the board, and I can see them myself plain as day (and I assume they're coupled, because you say so), but according to the designer there are no [EDIT: electrolytic] caps in the signal path.  I'm not an electrical engineer and know little about circuits themselves, so I don't know if that's a legitimate difference or not.  Can someone tell me if I'm wrong here, and explain why?  (Actual question).  I'm going by the information on the designer's page, where he contrasts his design with capacitor-coupled output designs and explicitly states that there are no electrolytic caps in the signal path.  Is that information simply outdated, or are you misunderstanding the way the design works?
 
I base my opinion on the O2 on the objective tests - which I have no reason to believe are a lie - and my own limited subjective testing with it.  I'm willing to accept evidence that I'm wrong, but one person's "I don't like the sound with the HD 650 unless I mod it" just doesn't cut it for me.  If I'm wrong, I want to know why.  My mentality is isn't about lunacy or rabid intolerant religiousness; it's based on the simple assumption that IF an amp measures correctly, it's perfectly neutral.  (In the case where I DID go overboard on my comments, I retracted and restated.)  I'm on pretty safe ground there, given the alternative is that audio signals are special and magical and completely unlike other electrical signals, and these invisible signal differences can affect insensitive instruments like headphone drivers but no other test we can come up with.  Frankly, I'm not prone to believing in magic without evidence, which IS a quasi-religious belief.  I have no doubt that EddieE is the same.

 

[SobbingWallet]

Quote:

Well, there is a reason for the desktop amp and it's not to power Stax.  People seem to be claiming some of the hardest to drive phones out there can all be driven to optimal levels out of the portable version using their rudimentary math skills, even though a desktop is in the works.  Should tell you something.  Though this is just speculation as I haven't heard it yet.  I'll be sure to hook up my easy to drive HD800s w/ it and see how transparent and dynamic it is compared to my overkill desktop amps.

To my understanding the desktop version is more about increased functionality and utility than increased power output.  The portable version is crammed together in such a way that the front panel is a mess, with two buttons, a volume pot, and three cords coming out.  The desktop version is apparently large enough to fix that, add 1/4" output, get rid of the power on/off transients, etc.  It also has a clearer sense of purpose IMO, because the "portable" version is just too big to be easily used as a portable (unless it's kept in a backpack compartment or something).  The designer seems to be throwing around the idea of addressing the input overloading complaints and possibly upping the power a bit as well, and he's also planning a DAC daughter board.  I don't doubt the desktop version will be more powerful to give more headroom for extreme cans like the HE-6, but the portable version isn't exactly weak in that department either, so I doubt he'd be making a desktop version if the only improvement regarded power output.

 

[samsquanch]

 
Circled in red are directly in the signal path
Circled in green are in the feedback portion of the signal, arguably in the signal path
Circled in blue are in a debatable part of the signal path
 

 

[Maxvla]

Still waiting for a desktop version, something as close to the original as possible, but not shoe horned into a tiny box with all the controls/ports smashed together.

 

[SobbingWallet]

Quote:

 
Circled in red are directly in the signal path
Circled in green are in the feedback portion of the signal, arguably in the signal path
Circled in blue are in a debatable part of the signal path
 

Thanks.  That seems to contradict what the designer says on his page, so that's very interesting.  He mentions only once that his design doesn't include [EDIT: electrolytic] caps in the signal path, so that comment could be outdated and based on a scrapped design, but it seems more likely that he misspoke entirely (given the sheer number of capacitors you made an argument for).  Perusing his site some more, he actually defended using caps in the signal path in another passage...so I think it's safe to say he misspoke entirely when he said his design doesn't have them.  Either way, I was clearly mistaken.  (EDIT:  Actually, I'm mistaken here, lol.  See below.)
 
He slams on capacitor-coupled output a whole lot more though.  Would that circuit also be considered an example of capacitor-coupled output, contradicting his explanations again, or do you know of a subtle difference?  He appears to characterize his circuit as direct coupled instead, which is not supposed to have those kind of problems.  (The measurements themselves still hint to me that cheapskateaudio is mistaken about the nature of the O2's coupling, since the designer is so adamant about capacitor-coupled output rolling off the frequency response depending on impedance, and cheapskateaudio made similar comments that they prohibit neutrality.  I've read the same elsewhere as well.)
 
(EDIT:  Simpler explanation from samsquanch below:  The caps are not electrolytic, so the designer did not misspeak, and I paraphrased him correctly to cheapskateaudio yesterday.  Still, my argument tying the electrolytic caps comment to capacitor-coupled output was a non-sequitur.  Since O2's capacitors are coupled in the first gain stage but not the output stage, I'm not sure yet if cheapskateaudio was right or wrong about the implications.)

 

[samsquanch]

They're not electrolytics.   For capacitor coupling in ac circuits you typically use non polarized film caps.  The headphone output is not coupled, but the output from the first gain stage is.
 

 

[SobbingWallet]

Quote:

They're not electrolytics.   For capacitor coupling in ac circuits you typically use non polarized film caps.  The headphone output is not coupled, but the output from the first gain stage is.
 

Got it.  Thank you for clearing that up.  Would that be liable to cause problems or a lack of neutrality (rolloffs, etc.) as cheapskateaudio argued, or was he mistaken after all?

 

[fishski13]

SB,
i mean this as no disrespect to the O2 or the designer, but measurably "perfect" amps have been around for decades.  some people don't feel that perfect measurements = musical enjoyment.  i've owned and enjoyed my BM DAC1 for 5 years as a DAC but despite the measurements, i don't rate the HP amp highly - it is serviceable with darker/thicker sounding HPs like the HD650 or T50rp though.  i cannot reconcile why i like the DAC but not the HP amp.  telling myself that since it measures great therefore i should like it doesn't cut it.  
 
as to the DIY comment you made: The "spirit of DIY" is usually to hack things together and see what works, because nobody usually knows quite what they're doing, everyone's flying blind, and throwing darts at an invisible target to feel out its shape (and getting a decent result from it) can be a lot more fun and rewarding than paying out the butt for a professionally built but hugely overpriced product.
 
this is really off the mark.  spend some time on diyaudio.com.  you have a lot of great designers that are not just slapping things together with capacitor fetishes hoping it will work.  if anything, criticisms against over-priced commercial gear, marketing b.s. and audiophoolery is the norm.  generally speaking, DIYing isn't about saving money but developing an understanding of why a signal can sound the way it does.  sure, i wish a dScope or Audio Precision was more affordable to bring more data to the DIY table, but $10K will buy you lots of wanky wire and NOS tubes 

. 
 
i should have my O2 parts ordered by the end of the week.

 

[SobbingWallet]

Quote:

SB,
i mean this as no disrespect to the O2 or the designer, but measurably "perfect" amps have been around for decades.  some people don't feel that perfect measurements = musical enjoyment.  i've owned and enjoyed my BM DAC1 for 5 years as a DAC but despite the measurements, i don't rate the HP amp highly - it is serviceable with darker/thicker sounding HPs like the HD650 or T50rp though.  i cannot reconcile why i like the DAC but not the HP amp.  telling myself that since it measures great therefore i should like it doesn't cut it.  
 
as to the DIY comment you made: The "spirit of DIY" is usually to hack things together and see what works, because nobody usually knows quite what they're doing, everyone's flying blind, and throwing darts at an invisible target to feel out its shape (and getting a decent result from it) can be a lot more fun and rewarding than paying out the butt for a professionally built but hugely overpriced product.
 
this is really off the mark.  spend some time on diyaudio.com.  you have a lot of great designers that are not just slapping things together with capacitor fetishes hoping it will work.  if anything, criticisms against over-priced commercial gear, marketing b.s. and audiophoolery is the norm.  generally speaking, DIYing isn't about saving money but developing an understanding of why a signal can sound the way it does.  sure, i wish a dScope or Audio Precision was more affordable to bring more data to the DIY table, but $10K will buy you lots of wanky wire and NOS tubes 

. 
 
i should have my O2 parts ordered by the end of the week.

Thanks, fishski13.  When I made my DIY comment, I definitely took a narrow view that overlooked the serious hobbyists and semi-professional designers building things from scratch (the O2 designer would also be in this category).  I was thinking more in terms of consumer-level DIY-ers who buy pre-designed kits or use trial and error (like trying to figure out the best way to mod the T50RP's), rather than the actual designers that come up with the kits in the first place.  The particular "spirit of DIY" that cheapskateaudio invoked seemed to be very different from the serious design approach that people at diyaudio take, and my aim was just to explain why cheapskateaudio's approach was fundamentally opposed to the O2's purpose.  In the process, I made too much of a blanket statement about DIY, and I didn't mean to belittle anyone or insult the diyaudio crowd with a crude mischaracterization.  Regardless, you're right about the journey and the self-learning process.  I didn't mean to overlook it, but that's a huge part of it too.
 
I don't begrudge your amp preferences either, and I'm sorry if I made it out like I do.  The most unique thing about the O2 is not that it's [AFAIK] measurably "perfect," but that it accomplishes that without a huge price tag.  It seems to be the first one that's in any way affordable to entry-level Head-Fi'ers (at least nowadays), so that's a pretty big deal.  I've argued pretty vigorously that well-measured amps show headphones "how they really are" in a way that others don't, so disliking them is more a statement about the headphones themselves than the amp, even when colored amps make the headphones sound much better.  That seems pretty self-evident to me, and I'm not sure where the resistance to that concept comes from.  Any definition of amp neutrality that does not rely on measurements just seems arbitrary to me.  I've also argued that neutral amps are more versatile than colored amps due to taking a source of error out of the equation, which is a bit of a generalization (given not all error affects frequency response, etc.), but that's pretty much where my strong opinions end.
 
There are definitely amps that sound better with specific headphones, and there are even "imperfect" amps that are versatile all-around and can still sound better to some people with all of their headphones, for various reasons (which contradicts the overstated post I made that set Anaxilus off

).  If colored amps make your music sound better to you, that's awesome, and I'd be an idiot to call you wrong.  Hell, a full-blown tube amp might sound better to me than the O2 with all headphones, for all I know (more harmonics means moar awesome?).  I just think that when it comes to neutral and measurably "correct" amps, it's more technically correct to approach dislike from the viewpoint of, "I don't like my headphones with this amp," rather than, "I don't like this amp."  Any amplifier sound signature will sound great with the right headphones and lousy with the wrong ones, but a truly neutral and uncolored amp will at least show headphones as they actually are.  That's really all I'm trying to say in this thread, along with the rest of the cult of objective fanatics.

  Taking this approach just seems like a better way for having an accurate reference point for "neutral" and determining your preferences from there.  (I'm interested in your O2 impressions, BTW.  Assuming the O2 measures as well as the designer says, I suspect you'll dislike it for the same reasons as your DAC1, and I'd be very surprised if your opinion on it differs.)

 

[mikeaj]

DIY means different things to different people:  that much should be apparent, I hope.  I'm only in it very occasionally for different things, either to save money or get something that couldn't otherwise be gotten at the time.
 
 
Anyway, if you're going to make tweaks of the design, it makes sense to read the documentation regarding why the part was chosen.  Then you can agree or disagree with the rationale and figure out if something else may be worth trying.  About the gain -> output stage coupling caps C13 and C14, different caps were already tested in various ways, and none of them tested were significantly different in performance.  Most selections that people would have concerns about regarding performance were tested, though I wouldn't be surprised if there were some aspects that are not detailed.

 

[fishski13]

Quote:

Thanks, fishski13.  When I made my DIY comment, I definitely took a narrow view that overlooked the serious hobbyists and semi-professional designers building things from scratch (the O2 designer would also be in this category).  I was thinking more in terms of consumer-level DIY-ers who buy pre-designed kits or use trial and error (like trying to figure out the best way to mod the T50RP's), rather than the actual designers that come up with the kits in the first place.  The particular "spirit of DIY" that cheapskateaudio invoked seemed to be very different from the serious design approach that people at diyaudio take, and my aim was just to explain why cheapskateaudio's approach was fundamentally opposed to the O2's purpose.  In the process, I made too much of a blanket statement about DIY, and I didn't mean to belittle anyone or insult the diyaudio crowd with a crude mischaracterization.  Regardless, you're right about the journey and the self-learning process.  I didn't mean to overlook it, but that's a huge part of it too.
 
I don't begrudge your amp preferences either, and I'm sorry if I made it out like I do.  The most unique thing about the O2 is not that it's [AFAIK] measurably "perfect," but that it accomplishes that without a huge price tag.  It seems to be the first one that's in any way affordable to entry-level Head-Fi'ers (at least nowadays), so that's a pretty big deal.  I've argued pretty vigorously that well-measured amps show headphones "how they really are" in a way that others don't, so disliking them is more a statement about the headphones themselves than the amp, even when colored amps make the headphones sound much better.  That seems pretty self-evident to me, and I'm not sure where the resistance to that concept comes from.  Any definition of amp neutrality that does not rely on measurements just seems arbitrary to me.  I've also argued that neutral amps are more versatile than colored amps due to taking a source of error out of the equation, which is a bit of a generalization (given not all error affects frequency response, etc.), but that's pretty much where my strong opinions end.
 
There are definitely amps that sound better with specific headphones, and there are even "imperfect" amps that are versatile all-around and can still sound better to some people with all of their headphones, for various reasons (which contradicts the overstated post I made that set Anaxilus off

).  If colored amps make your music sound better to you, that's awesome, and I'd be an idiot to call you wrong.  Hell, a full-blown tube amp might sound better to me than the O2 with all headphones, for all I know (more harmonics means moar awesome?).  I just think that when it comes to neutral and measurably "correct" amps, it's more technically correct to approach dislike from the viewpoint of, "I don't like my headphones with this amp," rather than, "I don't like this amp."  Any amplifier sound signature will sound great with the right headphones and lousy with the wrong ones, but a truly neutral and uncolored amp will at least show headphones as they actually are.  That's really all I'm trying to say in this thread, along with the rest of the cult of objective fanatics.

  Taking this approach just seems like a better way for having an accurate reference point for "neutral" and determining your preferences from there.  (I'm interested in your O2 impressions, BTW.  Assuming the O2 measures as well as the designer says, I suspect you'll dislike it for the same reasons as your DAC1, and I'd be very surprised if your opinion on it differs.)

thanks. understood.  i gotcha now.  

 
while i hate to place VFM judgements on commercial gears, i think that DIY cuts through the audiophoolery b.s. and can allow the end user to shell out less cash.  yes, DIY means different things to different people, but i'd like to think that DIY should be a large tent where ideas are shared and opposing opinions are respectfully argued.  i have problem with non-DIYers and DIYers that pit designs against one another in a disrespectful manner based on a set of beliefs or metrics. 
 
short of delivering the "actual event" (impossible), everything in the audio chain is colored.  if your goal is to try to deliver the "real thing", you're going to rely on your ears and subjective impressions since no number on a scope be able to tell you this.  if you want "what's on the recording", you'll probably genuflect to measurements.  no matter what, it's what you like the best in the end, and as a DIYer you get to have control over this.  DIY shouldn't be about marketing and brainwashing a la hIGH eND.
 
regards.