Head-Fi.org › Forums › Equipment Forums › Headphone Amps (full-size) › O2 AMP + ODAC
New Posts  All Forums:Forum Nav:

O2 AMP + ODAC - Page 3

post #31 of 1504
7/11/12 at 6:24pm
I forgot to add some critical info: so how do you know an amp is any good?

There are two camps: subjectivists and objectivists. The first listen with their ears and the latter make measurements.

Any scientifically minded person is liable to lean towards the objectivist camp. The O2 was designed by measurement. Essentially you know an amp should be good if the published specs say so *and* are adequate (some specs leave out essential details). After that you need a decent hifi mag or 3rd party to test and measure the amp. Then you really know.

There is a problem, however. Has every sonic characteristic been measured? Are all these measurements enough? Perhaps 70 years ago some one them were not measured. Perhaps there are unknown qualities to audio yet to be discovered. This plays straight in to the subjectivist camp and is unanswerable.
Reply

Gear mentioned in this thread:

post #32 of 1504
7/11/12 at 6:31pm

The answer is yes. The doubt is only raised to support a BS argument with no facts behind it.

Reply
post #33 of 1504
7/11/12 at 7:01pm
Quote:
Originally Posted by Satellite_6 View Post

The answer is yes. The doubt is only raised to support a BS argument with no facts behind it.

Logically there is no answer. It's rather like trying to prove there isn't a god. It's not logically possible: even if there isn't a shred of evidence of a god as some claim that still doesn't prove the matter. [Edit: a no one has come up with a logical argument that hasn't a flaw against the existence of a god; usually attempts are made with free will but they never hold up].

You may think you have every quality of audio nailed, but only a divine being can tell you that for sure. smily_headphones1.gif

Anyway, I myself am firmly in the objectivist camp but the above is a genuine weakness. Having said that: double blind testing is enough to satisfy me that objectivist equipment is not bested by subjectively designed equipment and that is as good as it gets for now.
Edited by lorriman - 7/11/12 at 7:10pm
Reply
post #34 of 1504
7/11/12 at 7:09pm
I also forgot to add that the FIIO5 amp measures well and is very cheap (other FII0s don't). Quite a few headphones that need the extra power will be just fine with a FIIO5. It also corrects output impedance. All for $15. If you want a DAC that measures well for your laptop then Behringer's UCA202 is cheap. (The ODAC measures wonderfully but strictly speaking it's overkill.) The Behringer has very high output impedance so you will need an amp unless you have very high impedance phones. That FIIO will do but keep in mind it doesn't work when charging so it's not the ideal desktop/laptop solution.
Edited by lorriman - 8/29/12 at 1:10am
Reply
post #35 of 1504
7/11/12 at 7:55pm
Quote:
Originally Posted by OJNeg View Post

It's not space on my desktop that I lack, it's space below it. I have all my cables very neatly networked to be out of sight. I could live with running an external power supply but it's an annoyance.

 

And moreover, I've had bad experiences with poor external power supplies when used with audio components. Some cheapies don't deliver anything close to the rated wattage. Power supplies are important to keeping line noise out and it's best to have a quality, reliable PS feeding your amp board. Might as well build it into the device and be able to run it off the mains.

 

It's not really an external power supply that the O2 uses.  The external unit the O2 uses is just a transformer, to step down the voltage from the wall to something like 13.5-20V AC.  Hence you'd need a different transformer in a country with 115V power as opposed to 230V power.  I think for size and weight concerns, maybe regulatory too (?), the transformer wasn't put inside the chassis.  You can get an upgraded transformer if you really want though; in fact, it's recommended for bench testing or running the planar magnetics run at a loud volume.  Difference in price is only like $5.

WAU12-200

WAU16-400

 

The power filtering is on the PCB inside the amp.  There are some filter caps and 7812 / 7912 linear regulators.  Power consumption of the O2 is in general pretty low—it's not class A, it only runs off of +- 12V rails, etc.—if it were a power hog, batteries would go out really fast, so it's not.  If the power supply were inadequate, then you think that there would be performance issues under high load, right, or maybe some noise?  I don't think there's evidence of that.  So I think that concerns over power supply quality are not really that well founded.  

 

I can understand the reservations about having another fat plug-in thing to deal with though.


Edited by mikeaj - 7/11/12 at 7:57pm
Reply
post #36 of 1504
7/11/12 at 8:03pm
Thread Starter 
Quote:
Originally Posted by lorriman View Post

I also forgot to add that the FIIO5 amp measures well and is very cheap (other FII0s don't). Quite a few headphones that need the extra power will be just fine with a FIIO5. It also corrects output impedance. All for $15. If you want a DAC that measures well for your laptop then Behringer's UCA202 is cheap. The ODAC measures wonderfully but strictly speaking it's overkill. It has very high output impedance so you will need an amp unless you have very high impedance phones. That FIIO will do but keep in mind it doesn't work when charging so it's not the ideal desktop/laptop solution.

I know Nwavguy wrote a pretty favorable review of the FIIO E5. I'll look into that. Though can I take his word for it? And I thought the ODAC was designed so it could be used with headphones of any impedance? Or was that just the O2... 

Reply
post #37 of 1504
7/11/12 at 8:15pm
Thread Starter 

I have done numerous research on this new hobby of mind, including reading all of Nwavguy's articles, Headfonia's review of the O2/ ODAC (lolz), double-blind tests, etc. 

 

So am I to take it that everything that people praise about amps is simply a myth? Not necessarily being skeptical here considering how easily the mind fools itself when sound is involved. The reasons why I wanted an amp before are: improved soundstage, greater damping factor (tighter bass), greater extension, more clarity, wider dynamic range, etc. Or at least, that's what the reviewers always seem to rave about. 

Quote:
Originally Posted by lorriman View Post


There's quite a lot of info, properly backed up, on this topic at nwavgy's "More Power?" page. Google for the two terms: I can't post a link.
There's a lot of talk of amps 'improving' the sonic quality, but really that shouldn't be happening: they should only be increasing volume. Unless there's a problem....
High output impedance of an older source, ie older ipods/iphones (or not so old Galaxy SII) is perhaps the most common. A decent amp can correct that.
In some high end, low-impedance, high-current headphones the source can distort as its basic amp is overloaded. An amp with adequate power can avoid that.
But really, perfect hifi amping has been a settled technology for more than 20 years and is not expensive. Expensive amps are more marketing than reality. Solid State changed the world. It's even got to the stage where talk of class A or class AB is absurd: a properly made, modern class D amp is much cheaper and genuinely hifi (and cheap on electricity). No one needs class A amps.
So why, then, are amp reviews so often 'expansive' beyond what the above can explain? It's as if the reviewer is saying that the amp adds to the audio, or improves it. Apart from the above issues, that shouldn't happening. Unless there's a problem...
Very few know that amp tech is settled and cheap. Magazines certainly won't tell you. Some premium amp manufacturers build in a bit of distortion increasing with cheapness of the model. Can you imagine why? It's sometimes justified with "2nd order harmonic distortion improves audio", which playing with a multi-order distortion plugin on my laptop: I can tell you it does not.
No wonder then, that old fashioned tube amps don't sound so bad, even though they also distort: the competition is worse. Some even have issues that give a 3D effect (which the reviewer will experience as a 'bigger soundstage'). In the headphone amp world there is another factor: consumer amps based on popular but flawed DIY designs (Mini3 being an example of one of those designs). These are very common, as are dodgy DIY amps sold on ebay.
People moving from one of these amps to another are going to experience different sonic qualities, sometimes improvements. In the highly subjective world of audio all this passes for normality. And all this chaos is further obscured because there are legitimate sonic improvements due to the common issue of sources having high output impedance.
The O2 was an attempt to address this by showing that you can build a perfect ('wire-with-gain), powerful, portable amp for $70 in parts. It's been an anti-climax because there is nothing for the reviewers to say beyond: it just increases the volume. Which is exactly all that it should do.
To summarise: source output impedance aside, not many headphones actually need amping. You can tell if they do simply because you can't get the volume.
I wish it was as simple as that, but with those rarer low-impedance, high current phones (ie. LCD2s, HE-500 etc) potentially causing distortion: how do you measure that as an end user? You'll be trying to guess whether your audio might have distortion that might be fixed by amping.
Reply
post #38 of 1504
7/11/12 at 8:47pm

I wouldn't call it myth. They believe what they're hearing and sometimes what they're hearing really is there. An amp can be designed to sound more analogue (distortion/noise) or have an emphasis in certain parts of the the frequency response curve. It may "jive" better with the sound signature of their headphones or just appeal to their subjective tastes. I am holding out for the ODA/ODAC. I feel it's the cheapest guarantee of getting an unmolested signal to my headphones or speakers. With other similarly priced gear I won't know if I am missing something... as in you don't know what you don't know!

 

edit: ...and as a side note, I keep reading the high gain on the O2 is for higher impedence phones. On other amps this is the case, but on the O2 the low gain is for all phones from IEMs to the HD650. The gain switch is only for low output sources like an ipod etc. With the ODAC the output is 2V and the it will clip if the O2 is set to high gain.


Edited by muad - 7/11/12 at 8:51pm
Reply
post #39 of 1504
7/12/12 at 2:33am
Quote:
Originally Posted by NimbleTurtle View Post

I have done numerous research on this new hobby of mind, including reading all of Nwavguy's articles, Headfonia's review of the O2/ ODAC (lolz), double-blind tests, etc. 

So am I to take it that everything that people praise about amps is simply a myth? Not necessarily being skeptical here considering how easily the mind fools itself when sound is involved. The reasons why I wanted an amp before are: improved soundstage, greater damping factor (tighter bass), greater extension, more clarity, wider dynamic range, etc. Or at least, that's what the reviewers always seem to rave about. 

Well, NwAvGuys mention of double-blind testing busting the cable myth (ie. it turns out that cheap cables do the job just as well as expensive ones) is telling. However, even with that the fact is that I have some defective cables that sound completely awful. Even NwAvGuy mentions poor quality connectors potentially causing issues. I remember at school soldering a new plug on to my cheap headphones only for the audio quality to be catastrophic; I threw them away. (The reason was probably that I didn't know how to solder properly; doing the same job now I have no issues). So it's quite possible that there are sonic improvements under certain conditions: but that shouldn't be happening but for a flaw.

But my own argument leans more towards the fact of non-ideal amps masquerading as hifi mixed in to the fact that music/audio is such a subjective experience; even more so than photos/pictures. People are hearing real differences but not for the right reasons. For example, another factor I didn't mention is people not listening to the same tunes when auditioning equipment. I have tracks that are mastered with quite a bit of 3D DSP work. Others lack it. I can get the same effect by using the 'stereo width' setting in rockbox (set 'channel configuration' to 'custom' to enable that). I prefer it; I personally dislike in-the-audience recordings and prefer to be immersed in the middle of the band. Phase issues can do that with amps: give a 3D effect. The reviewer will be exulting the soundstage. Another reviwer will prefer in-the-audience, in which case poor channel separation will be an advantage. A proper amp should have no effect on soundstage. Impedance interactions can also 'improve' audio by their negative effect: for example a bass weak headhone gets a boomy lift at about 100Hz; some will like that since tastes/genetics vary so much. Some phones will have their characteristics helpfully moderated, but only by virtue of two flaws improving on one another is this happening (a hot treble being attenuated by high output impedace, for example, or vice versa, I can't remember; as well as the taming of an overly bassy headphone).

It's a heady cocktail of factors and a constant moving target. Magazines and profit motives don't help to dispel it.

Let's go through your list:
  1. improved soundstage: phase issues faking 3D
  2. tighter bass: corrected high output impedance
  3. greater extension: on the lows, again corrected output impedance
  4. more clarity: phase issues, as 3D is sometimes experienced as greater clarity (thinking of recent review I read here)
  5. more clarity: higher treble due to high out-put impedance
  6. wider dynamic range: noisy source corrected by whacking up the volume to max (in the quite common case where the noise itself doesn't increase with increased volume)
  7. Greater detail: as with 6, Windows XP bit stripping for volume control; where only max volume gives you all 16 bits. An amp helps here: max vol on XP, vol control on the amp
  8. (and one I am adding: sweeter audio: correction of subtle distortion when using weak amp with high current phones)
  9. (more bass: boomy 100Hz bass boost from high output impedance)
  10. (less bass: high output impedance attenuating an overly bassy phone)
  11. (in-the-audience effect, that some prefer, on tracks mastered with strong spatialisation: poor channel separation)

These are all real effects. Some caused by poor amps, some caused by decent amps helping to correct source flaws (ie. older ipods/iphones and galaxy sII high output impedance). Some caused by poor amps attenuating or boosting exagerrated or inadequate phones.

A good amp with a good source should be adding nothing but volume. Ie. clip+ and FIIO 5.

Here's how deep the rabbit hole goes: when I connected my ODAC to my laptop I had expected to be able to use digital volume control on the laptop as since it has 24bit it is immune to XP's bit stripping issue. However, I discovered some time later that Windows selected 16bit/44Khz by default!!!!!! Obviously I changed the setting immediately. Had a reviewer had max volume when testing one DAC and much less volume on testing the ODAC: the ODAC would have been objectively producing poorer audio, FFS!!!!!!!!
Edited by lorriman - 7/12/12 at 2:48am
Reply
post #40 of 1504
7/12/12 at 2:40am
Quote:
Originally Posted by NimbleTurtle View Post

I know Nwavguy wrote a pretty favorable review of the FIIO E5. I'll look into that. Though can I take his word for it? And I thought the ODAC was designed so it could be used with headphones of any impedance? Or was that just the O2... 

The ODAC only has a line-out which is not headphone compatible. It has to be plugged in to an amp to work.
Quote:
Though can I take his word for it?

His open sourcing of the O2 and no-payment for the ODAC pretty much guarantees that his motives are not split. And why would he give such a good review to such a cheap item. It he were trying to make money then he wouldn't have but rather binned the review and reviewed an expensive amp instead.

Taken as a whole: NWAvGuys materials prove in themselves that he can be trusted. But in any case reviews of his stuff would appear to confirm his claims as does the deference given to him now on diyaudio (which I've inhabited due to my self-build of the O2).

It's a pretty amazing feat, but the critical factor is that he is not making money out of this.
Edited by lorriman - 7/12/12 at 2:57am
Reply
post #41 of 1504
7/12/12 at 3:13am
Oh, and I forgot to mention one other thing: quiet listeners vs loud listeners.

Quiet listeners often do not dislike spikes in the audio spectrum: a spike at around 800Hz for example, is a 'forward mid'. But for a loud listener it is a shouty honk. A spike in the treble is a 'shimmer' or a 'sparkle', but for loud listeners it is a painful jab in the ears. A track mastered with vocals given boosted volume, for understandable though mistaken reasons, is hard for loud listeners and must go some way to explain the loudness wars, as strong compression/limiting can remove this problem. Spotify uses limiting most judiciously and to our advantage generally. So personal tastes/genetics really screw up the whole business of reviewing-equipment/music-production.


I discovered some of the above when I started sine wave sweeps to equalize my headphones.. Equalized, the cheap Denon AHC260s sound like my etymotics. Rockbox has the parametric equalizer one needs for this justifying a clip+ purchase even more.

[if anyone is interested: AHC260 equalisation is : -4 db 3220Hz q=3, -2.5db 6450Hz q=4.6, treble set to -10]
Edited by lorriman - 7/12/12 at 3:23am
Reply
post #42 of 1504
7/12/12 at 12:32pm
Quote:
Originally Posted by lorriman View Post


6.    wider dynamic range: noisy source corrected by whacking up the volume to max (in the quite common case where the noise itself doesn't increase with increased volume)

 I would just like to add that if you are listening to your headphones near the limit of your source (current or voltage), the source may not have the appropriate power for some of the peak notes, and this will come off as a reduced dynamic range. An amp will correct this by not clipping on these notes.  For what its worth, I think lorriman is spot on and I agree with im 1:1. 

Reply
post #43 of 1504
7/12/12 at 12:48pm
Thread Starter 

So the ODAC is not as versatile as I thought if it has to be paired with an amp. But then again, I presume this is due to its high voltage? 

 

So is soundstage and imaging (for headphones) simply an "unnatural" manipulation of the mechanics? People say my HD 598 has great soundstage, and I certainly agree it gives that perception of space. Sorry for asking so many questions but what I really want to improve with my HD 598 is the bass extension. I'm using this straight out of the laptop. Do laptops have an "output impedance" like amps do? I just want the bass to be extended as far as possible. 

 

P.S. I thoroughly enjoyed your analysis of 'improvements' involving amps. 

 

Is there really any proof that genetics have an influence on musical "taste"? I don't even like that word... "taste". I prefer the term "priority". I think people differ from each other in their priorities - what they want out of music - and these things are easily changeable, not fixed like it's some sort of genetic quality. 

Quote:
Originally Posted by lorriman View Post


Well, NwAvGuys mention of double-blind testing busting the cable myth (ie. it turns out that cheap cables do the job just as well as expensive ones) is telling. However, even with that the fact is that I have some defective cables that sound completely awful. Even NwAvGuy mentions poor quality connectors potentially causing issues. I remember at school soldering a new plug on to my cheap headphones only for the audio quality to be catastrophic; I threw them away. (The reason was probably that I didn't know how to solder properly; doing the same job now I have no issues). So it's quite possible that there are sonic improvements under certain conditions: but that shouldn't be happening but for a flaw.
But my own argument leans more towards the fact of non-ideal amps masquerading as hifi mixed in to the fact that music/audio is such a subjective experience; even more so than photos/pictures. People are hearing real differences but not for the right reasons. For example, another factor I didn't mention is people not listening to the same tunes when auditioning equipment. I have tracks that are mastered with quite a bit of 3D DSP work. Others lack it. I can get the same effect by using the 'stereo width' setting in rockbox (set 'channel configuration' to 'custom' to enable that). I prefer it; I personally dislike in-the-audience recordings and prefer to be immersed in the middle of the band. Phase issues can do that with amps: give a 3D effect. The reviewer will be exulting the soundstage. Another reviwer will prefer in-the-audience, in which case poor channel separation will be an advantage. A proper amp should have no effect on soundstage. Impedance interactions can also 'improve' audio by their negative effect: for example a bass weak headhone gets a boomy lift at about 100Hz; some will like that since tastes/genetics vary so much. Some phones will have their characteristics helpfully moderated, but only by virtue of two flaws improving on one another is this happening (a hot treble being attenuated by high output impedace, for example, or vice versa, I can't remember; as well as the taming of an overly bassy headphone).
It's a heady cocktail of factors and a constant moving target. Magazines and profit motives don't help to dispel it.
Let's go through your list:
  1. improved soundstage: phase issues faking 3D
  2. tighter bass: corrected high output impedance
  3. greater extension: on the lows, again corrected output impedance
  4. more clarity: phase issues, as 3D is sometimes experienced as greater clarity (thinking of recent review I read here)
  5. more clarity: higher treble due to high out-put impedance
  6. wider dynamic range: noisy source corrected by whacking up the volume to max (in the quite common case where the noise itself doesn't increase with increased volume)
  7. Greater detail: as with 6, Windows XP bit stripping for volume control; where only max volume gives you all 16 bits. An amp helps here: max vol on XP, vol control on the amp
  8. (and one I am adding: sweeter audio: correction of subtle distortion when using weak amp with high current phones)
  9. (more bass: boomy 100Hz bass boost from high output impedance)
  10. (less bass: high output impedance attenuating an overly bassy phone)
  11. (in-the-audience effect, that some prefer, on tracks mastered with strong spatialisation: poor channel separation)
These are all real effects. Some caused by poor amps, some caused by decent amps helping to correct source flaws (ie. older ipods/iphones and galaxy sII high output impedance). Some caused by poor amps attenuating or boosting exagerrated or inadequate phones.
A good amp with a good source should be adding nothing but volume. Ie. clip+ and FIIO 5.
Here's how deep the rabbit hole goes: when I connected my ODAC to my laptop I had expected to be able to use digital volume control on the laptop as since it has 24bit it is immune to XP's bit stripping issue. However, I discovered some time later that Windows selected 16bit/44Khz by default!!!!!! Obviously I changed the setting immediately. Had a reviewer had max volume when testing one DAC and much less volume on testing the ODAC: the ODAC would have been objectively producing poorer audio, FFS!!!!!!!!
Reply
post #44 of 1504
7/12/12 at 1:14pm
Quote:
Originally Posted by NimbleTurtle View Post

So the ODAC is not as versatile as I thought if it has to be paired with an amp. But then again, I presume this is due to its high voltage? 

 

So is soundstage and imaging (for headphones) simply an "unnatural" manipulation of the mechanics? People say my HD 598 has great soundstage, and I certainly agree it gives that perception of space. Sorry for asking so many questions but what I really want to improve with my HD 598 is the bass extension. I'm using this straight out of the laptop. Do laptops have an "output impedance" like amps do? I just want the bass to be extended as far as possible. 

 

P.S. I thoroughly enjoyed your analysis of 'improvements' involving amps. 

 

Is there really any proof that genetics have an influence on musical "taste"? I don't even like that word... "taste". I prefer the term "priority". I think people differ from each other in their priorities - what they want out of music - and these things are easily changeable, not fixed like it's some sort of genetic quality. 

 The ODAC needs an amp for reasons i don't honestly know, but it isnt for high voltage. IIRC it outputs the redbook standard of 2 VRMS.  Which makes me wonder why exactly it NEEDS an amp, since that kind of voltage could run many a headphone.  If anything requires in amp, it is generally because the voltage it outputs is too low, so perhaps im incorrect in the 2 VRMS statement.   Perhaps lorri can ehnlighten us. 

 

 

Regarding genetics and taste.  Taste is a preferance, and like any preferance from food to clothing, it varies greatly from person to person; saying the cause is genetics is just a simpler way of stating this.  How you percieve sound is an impossibly complicated function of mechanical and psycological factors, starting with such things as the shape of your pene and ear canal and going on to such intangible idea's like childhood trauma (i knew a girl who couldn't listen to one song as it was the song she whitnessed her sister commiting suicide to, thusly adjusting her future musical preferances). So in the end, the golden rule of the "audiophile" hobby is: "If you like the sound of it, its good!" 

Reply
post #45 of 1504
7/12/12 at 1:36pm
Quote:
Originally Posted by Zophiel View Post

 The ODAC needs an amp for reasons i don't honestly know, but it isnt for high voltage. IIRC it outputs the redbook standard of 2 VRMS.  Which makes me wonder why exactly it NEEDS an amp, since that kind of voltage could run many a headphone.  If anything requires in amp, it is generally because the voltage it outputs is too low, so perhaps im incorrect in the 2 VRMS statement.   Perhaps lorri can ehnlighten us. 

 

Like all (audio) DACs with no headphone output, it doesn't have the electronics to handle high current.  It just has a line output, which is intended to be connected to a line input of another device, which is usually several thousand ohms or more (put simply, current is voltage divided by impedance, so high impedance means not much current is required).  You need a specialized design or at least some kind of headphone output / buffer to be able to provide enough current for headphones.  There are some other issues too, but it's mostly about the current.  You might have a nice clean 2V, but when you connect that to some headphones, it won't be nice and clean, and probably not even really 2V anymore.

 

Some line outputs can do okay driving headphones, but that's pretty much operating them way outside of specification.

Reply
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Headphone Amps (full-size)

Gear mentioned in this thread:

Head-Fi.org › Forums › Equipment Forums › Headphone Amps (full-size) › O2 AMP + ODAC