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O2 AMP + ODAC - Page 4

post #46 of 5403
Originally Posted by mikeaj View Post


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.

 Ah, makes sense.  After I posted that conclusion came to me as well.

post #47 of 5403
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? 

I'm not expert enough to answer that.

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. 

I really don't know about headphone soundstage or what its provenance is. There is a notion that open headphones have more soundstage as the audio is making its way around the head to the other ear, but some sealed multi-armatures have plenty also?!?!?!

For bass extension:

If the HD598s are at 300 ohms then you almost certainly won't be having serious output impedance issues (but you may be having volume issues). At a shocking 50 ohms output impedance, the Galaxy SII would be starting to affect the frequency curve but not by much. At a pinch, if the phones are in the vicinity of 80 ohms then also you probably won't be having laptop output impedance issues since it does seem that most high output impedance sources don't go above 10 ohms, and the rule is multiply by 8 for the impedance of the phones to be a healthy match.

However if the phones are more like 30 Ohms then it's worth testing the laptops output impedance, which they have like everything else. You'll need a DMM (about $5), a 33ohm resistor and a 3.5mm diy jack. Details on NWavguy's site (the resistor goes in parallel, which isn't clear from his instructions). It's not just a loss of extension but that the bass becomes 'flabby'.

The easy option (and cheapish) is just to get a fiio5. It measures well and will correct the output impedance whatever it is. If you find you really can't hear a difference then maybe the output impedance was low all along. My dell D430 (from 5 years ago) has a surprisingly healthy .5 ohms output impedance, and I'm having trouble distinguishing it from my ODAC (apart from low-level noise)!!
P.S. I thoroughly enjoyed your analysis of 'improvements' involving amps. 

I'm re-writing my will as we speak.

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. 

Well, I go with nature and nurture. However some things are just genetics, which is evolutionarily helpful, for example if a wipe-out plague breaks out that kills everyone except those who can't stand Brussel Sprouts. I reckon the division between loud and quiet listeners is likely genetics. I've moved from mainstream to alternative to progressive. I think that's taste/learning/priorities. Taste is a nice general word that covers a lot of possibilities.
post #48 of 5403

Some one mentioned earlier that the Fiio E5 cannot be used while charging.  This is untrue, the E11 cannot me used while charging, but the E5 can be. 

post #49 of 5403
Originally Posted by Zophiel View Post

Some one mentioned earlier that the Fiio E5 cannot be used while charging.  This is untrue, the E11 cannot me used while charging, but the E5 can be. 

Very good to know that. I was mislead. I don't have the FIIO5.

In that case the Behringer UCA202 DAC + FIIO5 is a viable desktop/laptop solution. All for $45. Bargain!
post #50 of 5403

I have had a JDS Labs version of the O2 amp for a few days now. Ordered the ODAC its on backorder, 1-2 weeks out...so far with a HRT MSii+ USB Dac this amp has surpassed anything I have heard to date.


For the $144 assembled its the deal of the century to me.


Add the $99 assembled ODAC...gee for $250 you have a really outstanding setup...$250 is CHEAP for what this does compared to lots of other stuff.


When I get the ODAC in I will post my findings...


My poor old LYR is just sitting there, when I A/B' it with several tubes it sounded muddy to me ...before the O2 arrived i enjoyed it very much.


I am listening with LCD2's and it drives them to painfully high levels more than enough to cause ear damage...beware....I hear no difference with the AC adapter plugged in or out while listening...


I also have a set of Grado 325i's....which before this amp were ok, bright etc....the match between the grados and the O2 amp makes me want to listen to them instead of the LCD2's at times!! go figure..the Grados with the amp are very, very clear and crisp....wonderful soundstage, you hear the decay of a drun beat into the background etc...absolutely allows these cans to show what they really 'can' do...


The LCD 2's have a larger soundstage but its not as clear as the Grados and I paid a bunch of dollars for the LCD2's...the bass is better with the LCD2s for sure...the grados are lacking in that...somewhat...


Aint technology great!!



Edited by adydula - 7/12/12 at 4:55pm
post #51 of 5403

ODAC + O2 combo portable mod

As currently there are plenty of mobile phones/tablets
http://forum.xda-developers.com/showpost.php?p=27631058&postcount=10 and Apple devices supporting external DAC output it makes sense to issue a version of ODAC + O2 portable combo that can work from 9-8.4V batteries as original O2 design. I just did this mod using JDS Labs combo. The only additional effort is drilling one hole in O2 PCB (on unused spot) and moving USB hole on the back plate. Please see attachments. I think it will be useful for current and future ODAC + O2 combo users as well opens combo to new use cases.


post #52 of 5403
Originally Posted by adydula View Post

Add the $99 assembled ODAC...gee for $250 you have a really outstanding setup...$250 is CHEAP for what this does compared to lots of other stuff.

No question. Pure hifi for not much at all.
When I get the ODAC in I will post my findings...

looking forward to that.
post #53 of 5403

Hi, I am a noob here... but where can I buy an O2+ODAC box with external power (no need for batteries) and 6.5mm headphone jack?  Do I have to make one myself (which I am really not confident in doing)?  Please help me out here....


I just realized that it is exactly the ODA (Objective Desktop Amp) that is yet to be released ...

Edited by goforthepod - 7/15/12 at 5:57am
post #54 of 5403

What you are looking for is going to be in the O2 desktop amp/DAC combo, which I believe is still a while away from being released.

At this moment, if you want the 6.5mm headphone jack, you'll likely have to do it yourself, although it probably wouldn't hurt to ask one of the builders if it is possible to install it instead of the 3.5mm. I doubt it however as all the mass produced O2 enclosures out there have the 3.5mm.

post #55 of 5403
There is room in the standard B02 for both ODAC and 6.5mm jack if you are willing to give up the batteries. I expect that one of the manufacturers could wire up a 6.5mm jack and leave it within the case waiting for you or a friend to drill a hole. It's mostly plastic and a touch of electrical tape would avoid any possibility of a short in the meantime. An aluminium drill bit costs $3 off ebay. An auto punch costs a little more but you may not need the precision.
post #56 of 5403

You can wait or buy the O2 Amp and ODAC the way it is and wire it together OR you can buy the O2 and ODAC combo at:



Its on backorder due the ODAC.


You can use 6.5mm normal headphones as I do with a simple 3.5 to normal size adpater...


I didnt want to wait for the desktop version, theres not going to be any technical performance differences per say.


The batteries in the O2 amp your remove to install the ODAC board, a few wires and some nylon screwe to mount the board and you will have the same thing that the desktop is less the RCA's and larger headphone jack...



you can buy the assembled board and the ODAC and get your own cased etc and make your own.




Wait for the desktop version when it comes out.....



post #57 of 5403

This is my method of combining the O2 and ODAC in the O2's case, with the addition of RCA line outputs (direct from the ODAC). The front and rear panels are my own design, produced by Front Panel Express in Seattle (as recommended by NwAVGuy). As a few others have done, the ODAC  board is mounted upside down beneath the O2's PCB, which retains use of the batteries. This flipped over board is why the USB jack is so close to the bottom of the enclosure.





post #58 of 5403
Interesting. How did you get the RCAs to fit? The BOM's RCAs are too large to my eyes.
post #59 of 5403



Nice Job!!



post #60 of 5403
Originally Posted by bel201smi View Post

O2 AMP + ODAC is the oldest version i think the sound quality is not so very good i think express music is more batter then it...


If I understand you right, you prefer some other device's sound quality to the ODAC+O2. This means either you have a faulty ODAC/O2 or the other device is an imperfect DAC/AMP and you prefer your music with the 'adjustment' it makes to your music.
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