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

O2 AMP + ODAC - Page 2

post #16 of 3668
Thread Starter 
Quote:
Originally Posted by lorriman View Post


Probably you are aware, but just in case: keep in mind that the combo means NO BATTERIES and so no portability. If you want this to do everything for you then it should be separates.

I actually did not know that. But either way, I decided to wait for the ODA to come out, and hopefully a combo of ODA and ODAC. The sound coming out of the bigger jack is better than the 3.5 mm one right? 

post #17 of 3668
Quote:
Originally Posted by NimbleTurtle View Post

I actually did not know that. But either way, I decided to wait for the ODA to come out, and hopefully a combo of ODA and ODAC. The sound coming out of the bigger jack is better than the 3.5 mm one right? 

 

No.

 

Well, after plugging / unplugging a 3.5mm jack a lot of times, it may start to go loose and fail on you. The larger jack may take longer to start failing. As long as there's a reasonably secure connection, it's the same. Er...okay, a larger jack may also have a smaller impedance (note that the ground connection is shared between L and R channels), so you would get lower crosstalk with the larger jack. With the 3.5mm jack and 15 ohms headphones, a worst-case scenario, crosstalk is -65 dB with the O2. For 600 ohms headphones, it's -95 dB. I don't think many people would consider that a real concern.

post #18 of 3668
Quote:
Originally Posted by NimbleTurtle View Post

I actually did not know that. But either way, I decided to wait for the ODA to come out, and hopefully a combo of ODA and ODAC. The sound coming out of the bigger jack is better than the 3.5 mm one right? 

As Mikeaj says, it really makes no difference (the O2 designer has even said that there is a - very slight - sonic advantage to a 3.5mm jack on the ODAC, interestingly) but the life span of the jack is a factor. The 3.5mm is rated to 2,000 inserts. Not very many really; enough to confidently cover a 1 year warranty but I want mine to last 15 years. I use a short extension purely to avoid using the O2's jack itself. Since I'm already using the Odac I don't bother with an extension lead for the 'in' jack.

Also, it's worth knowing that the ODA will have almost identical electronics to the O2. Effectively it's an O2 in a bigger case including internal power supply....at extra cost and no batteries?!?!?! hmmm, that makes no sense for me. The one convenience that might have made it an option is more switcheable gain options, ie three rather than the O2's two. A 1x, 4x and 12x would have everything covered, for example. But that's not on the ODA spec: just two switcheable gain options as with the O2.

As it is the O2 is effectively a desktop amp already (ignoring the external PSU). The only (non-stats) headphones it can't power are obscure and probably provide no real increase on modern headphones anyway. That's one powerful amp. It's also quite big for a 'portable' amp. If you get one in a B03 case (adds some height over the standard B02) then it has a desktop presence about it and has room for 1/4" jacks as you can see in some pics where people have done this.

If you really don't need batteries then the o2 in a B03 case may make you happy for slightly less money than the ODA which doesn't exist yet and of which the designer says it may be late summer or later before the design is released. You could be looking at Christmas before you get one. Even my O2 in a B02 box has small rubberised feet that make it behave like a mini-desktop amp on my desk.

There is one other option worth a mention but you would have to get a 'special build' of an O2: slipping the ODAC underneath the O2 circuit board. The designer didn't realise this possibility. This is how I have it (it's a self-build). There is actually room there. So I have it all in one box: O2, Odac and batteries!!! Yum.
post #19 of 3668
Quote:
Originally Posted by Zophiel View Post

 You are more interested in the interplay between impedance and sensitivity of the headphone rather than just the Ohms WRT Gain.  Just FYI the O2 is designed to be able to produce appropriate mW accross a LARGE (16-600) range of impedances.  what gain you want to use is your preference.  Once the music is playing at acceptable (your taste) levels, then you want to use the lowest gain you can do achieve this.  the O2 comes default with a 2.5X and 6.5X gain modes, but can be easily customized to 1X/2.5X/6.5X (pick any two).  Youre not going to really need 6.5X except for voltage HUNGRY headphones like HD 650 or the higher end Beyers.  

 

Impedance, sensitivity, hungriness or your tastes have nothing to do with O2 gain structure. Once again here are the key figures for the resulting kindergarden math.

 

Only thing you need to know is your source/dac maximum output voltage. Usually portable daps >0.5V, Fiio E10 1.6V, standard desktop stuff 2V (hello ODAC), some even more. Read the specs.

 

O2 on AC usage, simply divide 7 / V = max gain. With batteries it's lower, 4.5 / V. Anything over this can and will cause distortion. Hungry headphones or not, do not go over this limit, there is no need. 1V source with 6.5x gain is the same as 2V source with 3.25x gain. This is the maximum output O2 can do and it's enough for pretty much anything out there.

 

I use LCD-2 with 1x gain 95% of the time. My DacMagic has pretty high 2.3V output, so theoretical max gain is 7 / 2.3 = ~3x. If you already have O2 with default 2.5x / 6.5x gains, you can easily convert either to 1x by simply removing the resistor with small pliers (I guess this needs a bit more detailed documentation..). I have done it to get 1x / 2.5x. It's pretty perfect. For the lowest theoretical noise you want to choose the lowest gain that satisfies your volume. But you need to know the gain limit.


Edited by hekeli - 7/11/12 at 9:36am
post #20 of 3668
Quote:
Originally Posted by lorriman View Post


Probably you are aware, but just in case: keep in mind that the combo means NO BATTERIES and so no portability. If you want this to do everything for you then it should be separates.

 You can, of course, buy the ODAC and O2 separately and retain the "mobile" advantage of the O2, and like others have said, it is a competant desktop amp on AC Power anyway. 

post #21 of 3668
Quote:
Originally Posted by hekeli View Post

 

Impedance, sensitivity, hungriness or your tastes have nothing to do with O2 gain structure. Once again here are the key figures for the resulting kindergarden math.

 

Only thing you need to know is your source/dac maximum output voltage. Usually portable daps >0.5V, Fiio E10 1.6V, standard desktop stuff 2V (hello ODAC), some even more. Read the specs.

 

It was taken as an asumption that he was going to use either the typical .5V - 1.0V portable or the more standard 2V soundcard out.  In which case understanding how your headpones react to a given voltage at a given impedance (or a given power) is the only element left.  We have both stated that the majority of headphones fall well within the boundries of the typical source+O2 output combinations.  

 

The tastes has to do with how loud he likes it.  If he likes it quiet, he may be able to get away with 2.5X on all headphones (as i imagine most would any way)  otherwise he may want 6.5X if he doesnt appreciate his hearing!   It doesnt affect the mechanics of gain, but may affect the  "minimum gain to get it done".


Edited by Zophiel - 7/11/12 at 9:53am
post #22 of 3668
Quote:
Originally Posted by lorriman View Post


As Mikeaj says, it really makes no difference (the O2 designer has even said that there is a - very slight - sonic advantage to a 3.5mm jack on the ODAC, interestingly) but the life span of the jack is a factor. The 3.5mm is rated to 2,000 inserts. Not very many really; enough to confidently cover a 1 year warranty but I want mine to last 15 years. I use a short extension purely to avoid using the O2's jack itself. Since I'm already using the Odac I don't bother with an extension lead for the 'in' jack.
Also, it's worth knowing that the ODA will have almost identical electronics to the O2. Effectively it's an O2 in a bigger case including internal power supply....at extra cost and no batteries?!?!?! hmmm, that makes no sense for me. The one convenience that might have made it an option is more switcheable gain options, ie three rather than the O2's two. A 1x, 4x and 12x would have everything covered, for example. But that's not on the ODA spec: just two switcheable gain options as with the O2.
As it is the O2 is effectively a desktop amp already (ignoring the external PSU). The only (non-stats) headphones it can't power are obscure and probably provide no real increase on modern headphones anyway. That's one powerful amp. It's also quite big for a 'portable' amp. If you get one in a B03 case (adds some height over the standard B02) then it has a desktop presence about it and has room for 1/4" jacks as you can see in some pics where people have done this.
If you really don't need batteries then the o2 in a B03 case may make you happy for slightly less money than the ODA which doesn't exist yet and of which the designer says it may be late summer or later before the design is released. You could be looking at Christmas before you get one. Even my O2 in a B02 box has small rubberised feet that make it behave like a mini-desktop amp on my desk.
There is one other option worth a mention but you would have to get a 'special build' of an O2: slipping the ODAC underneath the O2 circuit board. The designer didn't realise this possibility. This is how I have it (it's a self-build). There is actually room there. So I have it all in one box: O2, Odac and batteries!!! Yum.

 

The O2 obviously can be used as a desktop amp, but I'd prefer to use an amp with it's own power supply. I don't like running a nasty power brick of questionable quality around my already cluttered desktop. An internal power supply is a key feature that makes a desktop amp IMO.

 

My big question is, can he keep the cost down with the ODA? $150 is a pretty sweet price point for a portable amp, but there's no way it'll stay that low if he's adding a step down transformer and all the components for a regulated power board and a larger case and the necessary case components. Do you think he can keep the assembled price under $300? $400? It'd be great if he could release a kit. If not, I'll make the beta22 my next build instead of the ODA.

post #23 of 3668
Quote:
Originally Posted by Zophiel View Post

It was taken as an asumption that he was going to use either the typical .5V - 1.0V portable or the more standard 2V soundcard out.  In which case understanding how your headpones react to a given voltage at a given impedance (or a given power) is the only element left.  We have both stated that the majority of headphones fall well within the boundries of the typical source+O2 output combinations.  

 

The tastes has to do with how loud he likes it.  If he likes it quiet, he may be able to get away with 2.5X on all headphones (as i imagine most would any way)  otherwise he may want 6.5X if he doesnt appreciate his hearing!   It doesnt affect the mechanics of gain, but may affect the  "minimum gain to get it done".

 

I'm not sure I can follow you. 2V x 6.5 would distort. 1V x 6.5 would not. If you want hearing damage, you don't need to spend money on O2 just to distort it.

 

(Or perhaps you meant "not the more standard 2V soundcard out"?)

 

 

Quote:
Originally Posted by OJNeg View Post

 

The O2 obviously can be used as a desktop amp, but I'd prefer to use an amp with it's own power supply. I don't like running a nasty power brick of questionable quality around my already cluttered desktop. An internal power supply is a key feature that makes a desktop amp IMO.

 

Do you usually keep your "power bricks", extension cords etc on your desktop? I certainly don't, they are well hidden. I want as little stuff on my desktop as possible, smaller the better. wink.gif

post #24 of 3668
Quote:
Originally Posted by hekeli View Post

 

I'm not sure I can follow you. 2V x 6.5 would distort. 1V x 6.5 would not. If you want hearing damage, you don't need to spend money on O2 just to distort it.

 

(Or perhaps you meant "not the more standard 2V soundcard out"?)

 

 

No sorry, I meant only to use that as a boundry case to say that, in almost any situation (sources from .5 to 2.0V) the O2 provides adequate output voltage (or power) to power just almost any phone.  It is up to you to dial in the correct gain, taking into account your headphones sensitivity, your taste in volume and the O2's output at the impedance of your particular headphone.  Of that large range of output powers, only a small subsection will be suitable for your particular headphone.  I wasn't stating anything novel, just reafirming that the O2 has more than ample output power for just about any phone, and that if you wanted to confirm that, you would have to do math beyond "will the O2 work with my 50 ohm phones".   Given his 7.7 Volt max output (IIRC) I agree that any source and gain combination that would lead to a peak voltage higher than this would just distort, but that was not the point of my statement.

post #25 of 3668
Thread Starter 
Quote:
Originally Posted by lorriman View Post


As Mikeaj says, it really makes no difference (the O2 designer has even said that there is a - very slight - sonic advantage to a 3.5mm jack on the ODAC, interestingly) but the life span of the jack is a factor. The 3.5mm is rated to 2,000 inserts. Not very many really; enough to confidently cover a 1 year warranty but I want mine to last 15 years. I use a short extension purely to avoid using the O2's jack itself. Since I'm already using the Odac I don't bother with an extension lead for the 'in' jack.
Also, it's worth knowing that the ODA will have almost identical electronics to the O2. Effectively it's an O2 in a bigger case including internal power supply....at extra cost and no batteries?!?!?! hmmm, that makes no sense for me. The one convenience that might have made it an option is more switcheable gain options, ie three rather than the O2's two. A 1x, 4x and 12x would have everything covered, for example. But that's not on the ODA spec: just two switcheable gain options as with the O2.
As it is the O2 is effectively a desktop amp already (ignoring the external PSU). The only (non-stats) headphones it can't power are obscure and probably provide no real increase on modern headphones anyway. That's one powerful amp. It's also quite big for a 'portable' amp. If you get one in a B03 case (adds some height over the standard B02) then it has a desktop presence about it and has room for 1/4" jacks as you can see in some pics where people have done this.
If you really don't need batteries then the o2 in a B03 case may make you happy for slightly less money than the ODA which doesn't exist yet and of which the designer says it may be late summer or later before the design is released. You could be looking at Christmas before you get one. Even my O2 in a B02 box has small rubberised feet that make it behave like a mini-desktop amp on my desk.
There is one other option worth a mention but you would have to get a 'special build' of an O2: slipping the ODAC underneath the O2 circuit board. The designer didn't realise this possibility. This is how I have it (it's a self-build). There is actually room there. So I have it all in one box: O2, Odac and batteries!!! Yum.

Would I be plugging in my headphone jack thru the ODAC or the O2? I'm a bit lost on how they're setup ifI get two of these separately. And are the "BO3" and "BO2" cases options available options on websites that provide the ODAC/ O2? 

 

Quote:
Originally Posted by mikeaj View Post

 

No.

 

Well, after plugging / unplugging a 3.5mm jack a lot of times, it may start to go loose and fail on you. The larger jack may take longer to start failing. As long as there's a reasonably secure connection, it's the same. Er...okay, a larger jack may also have a smaller impedance (note that the ground connection is shared between L and R channels), so you would get lower crosstalk with the larger jack. With the 3.5mm jack and 15 ohms headphones, a worst-case scenario, crosstalk is -65 dB with the O2. For 600 ohms headphones, it's -95 dB. I don't think many people would consider that a real concern.

Thanks for the info! 

post #26 of 3668
Thread Starter 
Quote:
Originally Posted by Zophiel View Post

No sorry, I meant only to use that as a boundry case to say that, in almost any situation (sources from .5 to 2.0V) the O2 provides adequate output voltage (or power) to power just almost any phone.  It is up to you to dial in the correct gain, taking into account your headphones sensitivity, your taste in volume and the O2's output at the impedance of your particular headphone.  Of that large range of output powers, only a small subsection will be suitable for your particular headphone.  I wasn't stating anything novel, just reafirming that the O2 has more than ample output power for just about any phone, and that if you wanted to confirm that, you would have to do math beyond "will the O2 work with my 50 ohm phones".   Given his 7.7 Volt max output (IIRC) I agree that any source and gain combination that would lead to a peak voltage higher than this would just distort, but that was not the point of my statement.

Ah makes sense. Thanks. I listen at a pretty medium volume so I think I will go with the 1x and 2.5 x gain. 

 

Thanks for all the wise words from the very knowledgeable technicians on this board! Much appreciated. 

post #27 of 3668
Thread Starter 

BTW I know this has been answered many times before but I feel the need to reconfirm this. 

 

What exactly does an amp do? Other than providing the potential to drive cans at larger volumes? And is there a way to scientifically prove these effects? 

 

And oh shoot I have one more question: does impedance affect how "much" it improves the headphones? Is there, for instance, a direct correlation between the improvements of an amp powering a 15 ohm headphone, as opposed to a 600 ohm headphone (other than perhaps, being able to sufficiently listen at preferred volume). 

post #28 of 3668

In short, amps provide additional power to headphones that may require it.   Go to NwAvGuy's website and read up on some of the more technical details behind impedance and other electrical phenomena.   Chances are, if you don't know explicitly that you need an amp, you probably don't.  Most headphones will benefit some from an amp with a lower output impedance (a cahracteristic of the amp itself) just due to the headphones damping mechanism, but this, as well, is subjective as to whether this change in sound is an improvement or not.  The vast majority of introductory headphones that can be had for $100 and less, likely dont need an amp; the output voltage from the player (be it a computer/laptop or Digital Audio Player {iPod, etc}) is sufficient to drive it to reasonable listening levels.  Some of the more advanced headphones require an amp for one of many reasons.  As the headphone's impedance increases, the voltage produced by the source provides less power, which depending on the sensitivity of the headphone, can lead to reduced or less dynamic listening volume. 

 

I wont go any further than that, and end with : Educate yourself on the topic, the basics are easy to understand and don't require much math.   If you have a high impedance or a low sensitivity hphone (Beyerdynamics and HiFiMan headphones respectivly as examples) then an amp will likely help, or even be rquired. 

 

 

The DAC  is another issue altogether, but basically bypasses what may be inferior components in your source with higher quality components.   The DAC/AMP combo is one way to ensure the electronics chain between your digital music files and the music you hear is as high quality and controlled as possible.  Its expensive, but if you are serious about htis hobby, it is a necessary step in acheiving the best possible sound.


Edited by Zophiel - 7/11/12 at 3:11pm
post #29 of 3668
Quote:
Originally Posted by hekeli View Post

 

Do you usually keep your "power bricks", extension cords etc on your desktop? I certainly don't, they are well hidden. I want as little stuff on my desktop as possible, smaller the better. wink.gif

 

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.

post #30 of 3668
Quote:
Originally Posted by NimbleTurtle View Post

BTW I know this has been answered many times before but I feel the need to reconfirm this. 

What exactly does an amp do? Other than providing the potential to drive cans at larger volumes? And is there a way to scientifically prove these effects? 

And oh shoot I have one more question: does impedance affect how "much" it improves the headphones? Is there, for instance, a direct correlation between the improvements of an amp powering a 15 ohm headphone, as opposed to a 600 ohm headphone (other than perhaps, being able to sufficiently listen at preferred volume). 

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.
Edited by lorriman - 7/11/12 at 6:03pm
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Headphone Amps (full-size)
Head-Fi.org › Forums › Equipment Forums › Headphone Amps (full-size) › O2 AMP + ODAC