# Review: JDS Labs O2 (Black edition) + O2/ODAC discussion



## ostewart

[size=medium] *JDS Labs Assembled O2 Black Edition Review*[/size]
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 [size=medium] I would like to thank JDS Labs for sending me this sample for review, and to use as my reference amp.[/size]
 [size=medium] I will write as honest a review possible, supposedly this amp needs no burn-in as there are no capacitors in the output stage, even so it has quite a few hours on it.[/size]
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*Photos by Felix Speller:*
*www.felixspeller.com*
*www.flickr.com/felixspeller*
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 [size=medium] *Gear Used:*[/size]
 [size=medium] IPod Classic 160gb (rockboxed) > DIY Silver LOD > JDS Labs O2 > lots of different headphones[/size]
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 [size=medium] *Packaging, Build Quality and Accessories:*[/size]
 [size=medium] Packaging, well JDS are a more DIY company, so what you get is the amp, instructions and some rubber feet. I didnt get an AC adapter as i'm in europe, so i had to buy one. I think the package is simple but effective, the package was well protected by bubble wrap and the amp comes in an anti-static bag. Dont expect fancy packaging, but do expect great value and customer service.[/size]
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 [size=medium] Build quality is excellent, the metal enclosure feels very solid, the on/off and gain switches are spring loaded, the volume pot is smooth to operate and the input and output jacks are stiff and good quality, the amp is hand assembled in America, and you can tell by the quality of it, I did open it up to see the board, and the solder joints are great, and it is very neatly made.[/size]
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 [size=medium] I got the new black edition which looks better than the standard version in my opinion, i also got custom engraving which they provide free of charge with any order, and the engraving is expertly done. The edges of the amp are slightly rounded so it feels good in your hands.[/size]
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 [size=medium] *Design:*[/size]
 [size=medium] I will say a little about the design, this was not really made to be portable, more transportable as the size is a bit big to fit in your pocket but it does have 2 rechargable 9v batteries inside so it works without being plugged in, and the battery life is supposed to be around 8-10 hours.[/size]
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 [size=medium] The amp has all inputs and outputs on the front, and I think that in the future they may make a full desktop version, as this only has 3.5mm input and output, I would like to see RCA inputs on the back, with the AC jack on the back too, with only volume, gain and headphone out on the front.[/size]
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 [size=medium] This amp comes with variable gain, the standard is 2.5x and 6x, however you can customise this when you order it, I find the stock gain to be almost perfect, I think 1x and 6x would be good.[/size]
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 [size=medium] It has a built in headphone protection circuit which stops it outputting too much power into your headphones, also you can leave it plugged in and it does not get hot amd the batteries get trickle charged so no need to worry about damaging the batteries or the amp. When turning the amp on there is a slight audible click and when powering down there is a slight thud, but not loud or anything capable of damaging the drivers of the headphones.[/size]
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 [size=medium] I really think a lot went into the design of this amp, its a really nice shape and size, the only thing I would change is the layout of input/outputs, but that means more design and tweaking.[/size]
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 [size=medium] *Sound:*[/size]
 [size=medium] A lot has already been said about the O2, so I can't really add much. What I will say is that this amp is incredible, it is transparent, what goes in comes out clean and purely amped, not modified in any way.[/size]
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 [size=medium] You can plug any headphone in and its just so clean and clear, this amp is also very powerful, I had the chance to test it with the HD650, HD700, T1, HE6 and more... It managed to drive all of them, the T1 sounded excellent out of the O2, the HE6 was powered nicely with the O2 but I did prefer the HE6 out of a nice tube amp, the HD700 also sounded great out of the O2 and it had no problems with power.[/size]
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 [size=medium] With the T1 I had to use high gain, and the volume was about 10 o'clock on the pot, but it had plently of power and the sound produced was incredible.[/size]
 [size=medium] I was impressed by the power such a small amp can produce, and also the clean sound it produced, I really think this amp can drive most headphones quite well, and pairs well with most headphones as it let's the music shine through, not the amp colouring the sound.[/size]
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 [size=medium] I think that anyone looking for a budget amp, or even just a great transparent amp that can power nearly all headphones should check this out, it really is excellent value for money, the build quality, the sound, the power, everything is just very well thought out.[/size]
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 [size=medium] Thank you for reading[/size]
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 *Tracks Used:*
 Skrillex – First Of The Year (Equinox) (320kbps MP3)
 Paramore – Franklin (320kbps MP3)
 Diana Krall – The Girl In The Other Room (FLAC)
 Deolinda – Passou Por Mim E Sorriu (live) (ALAC)
 Suicide Silence – Unanswered (FLAC)
 Massive Attack – Angel (ALAC)
 Eat Static – Dzhopa Dream (ALAC)
 The XX – Crystalised (FLAC)
 Funeral For A Friend – Bend Your Arms To Look Like Wings (ALAC)
 Mumford & Sons – Little Lion Man (FLAC)
 The Scene Aesthetic – Humans (259kbps MP3)
 A Hero A Fake – Swallowed By The Sea (254kbps MP3)
 Vivaldi – The Four Seasons, Spring Allegro (ALAC)
 Johnny Craig – Children Of Divorce (161kbps MP3)
 Deadmau5 + Kaskade – I Remember (Caspa Remix) (320kbps MP3)
 Black Uhuru – Utterance (ALAC)
 We Are The In Crowd – Never Be What You Want (226kbps MP3)
 Silverstein – Discovering The Waterfront (320kbps MP3)
 Concept Of Thought – Our Thought (FLAC)
 Nirvana – Something In The Way (Unplugged) (ALAC)


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## wolfetan44

You got rubber feet with your O2? I didn't.


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## TheKillerPiglet

Randomkid,
  I see you also own the C421, could you contrast the two, especially with the T1?
   
  KP


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## ostewart

T1 is driven better with O2 as the O2 has more power and also the C421 is not as transparent as the O2, it sounds slightly warm in comparison. C421 wasn't made to drive the T1 really.


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## antberg

Nice thoughts Random,finally my second shipping may come home in a week or less,i hope.My HD650 will be very happy,haha!
  Quote: 





wolfetan44 said:


> You got rubber feet with your O2? I didn't.


 
  Well,maybe they did send them as gift,i did ordered one pair for the O2 and another pair for the ODac.But i did paid for them nonetheless,just a 2 dollars each,though.


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## TheKillerPiglet

Quote: 





ostewart said:


> T1 is driven better with O2 as the O2 has more power and also the C421 is not as transparent as the O2, it sounds slightly warm in comparison. C421 wasn't made to drive the T1 really.


 

 Thank you. I am considering a"'tweener" amp to carry with my laptop and will keep this in mind.
   
  KP


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## ostewart

I got rubber feet with my O2 and C421, I thought they came as standard, but I did put different feet on my O2, slightly bigger as it's not really portable so it doesn't matter.

KP the O2 would be perfect as a transportable for your laptop


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## ostewart

I didn't like the HD650 out of anything, but the O2 drives them fine and actually brings out some detail in them.
What sounds good is the music being amplified not the amp colouring the sound


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## spaark

Quote: 





sohnx said:


> I had the O2 & the HD650's at one point and I found that the O2 was terrible with them. I don't know why but people love to claim that this amp sounds great with everything without really explaining what "sounds great" means. Anyhow, I did like how the O2 drove my HD448's. It's a decent amp for some kinds of headphones.


 
  What's important to remember is that the O2 is transparent. It let's you hear headphones the way they were meant to be heard.


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## AKG240mkII

Quote: 





sohnx said:


> I had the O2 & the HD650's at one point and I found that the O2 was terrible with them. I don't know why but people love to claim that this amp sounds great with everything without really explaining what "sounds great" means. Anyhow, I did like how the O2 drove my HD448's. It's a decent amp for some kinds of headphones.


 
   


 Since the amp is '_Transparent' .._
_Don't you think it's the *sound-signature* __of the HD650's causing your 'problem' ??_


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## HamilcarBarca

Quote: 





akg240mkii said:


> Quote:
> 
> 
> 
> ...


 
   
  Either that or the source material. I don't know why people complain that a transparent amp sounds bad. They can't even hear it.


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## MrMateoHead

Great Review -
   
  I have the black O2 and now the Black ODAC as well. It costs a bit more, but I like the idea that I can use them as separate components in the future if I wish. It would be nice to move the jacks around, and maybe even redesign the amp so that the ODAC could easily "dock" when its mating to the O2.
   
  I can confirm that the battery life is pretty close to all-day long, but I don't like how the amp just stops playing when the batteries quit - a low battery indicator wouldn't be a terrible thing. A power light on the ODAC would also make sense, should one have an issue with it (like, forgetting to change their settings in windows, but assuming that their ODAC is "broken").
   
  I can also confirm that the sound quality is just above and beyond what I expected. There is ZERO noise emitted from the pair, at max volume, nothing playing. Total black background. That said, it took a few minutes to get used to the new sound, as my on-board audio, while noisier, might have been a touch on the "warm" side. That and, the 2V output of the ODAC is noticeably stronger than the 1V computer. There was a "thinness" to my ears which reminded me of hearing my HE-400s for the first time. Now the spaciousness and black background are just awesome.
   
  If you spring for the pair, I would recommend considering a gain of 1X and 6.5X (for non-ODAC sources like phones or Mp3 players). Given the relative variety of source inputs that you might use with the O2, it is a good idea to have fairly low, and fairly high gain modes. 2.5X is probably higher than needed with the ODAC, but not high enough for weaker sources.


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## ostewart

Thanks for the comment, yes it takes a while to get used to if your used to a warmer source.

Look out in February for more from me on JDS labs products, including the ODAC


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## wolfetan44

Wait, what do I have to do in windows to make my ODAC work? I thought it was just plug in and use.


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## ostewart

It should be plug and play, but sometimes you need to open your audio devices controls and select ODAC as the default audio driver/device instead of pc speakers or normal headphones out.


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## gikigill

Good job on the review mate, ignore the troll and enjoy your amp.
   
  I have the O2 running MadDogs, JH16, JVC S500 and ,MDR-F1.
   
  With the exception of the F1, it sounds great with all of them.


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## ostewart

I am happy to accept people's opinions, as you can see above, this forum is great, I see no need to argue with someone over taste, it's futile.

Glad to see everyone enjoying their O2's, I really am impressed at how I can plug nearly any headphone in and it just sounds clean and clear.

Keep enjoying the music guys! That's what it's all about


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## wolfetan44

Quote: 





ostewart said:


> I am happy to accept people's opinions, as you can see above, this forum is great, I see no need to argue with someone over taste, it's futile.
> 
> Glad to see everyone enjoying their O2's, I really am impressed at how I can plug nearly any headphone in and it just sounds clean and clear.
> 
> Keep enjoying the music guys! That's what it's all about


 
  Yep, I did a O2 vs. FiiO E11. No contest


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## ostewart

Fiio E11 is a great beginner's amp, but no contest vs O2 or C421

I do like the fact that the O2 is backed up with objective specifications, it leaves us to do the subjective listening and describing


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## gikigill

I use the O2 to power the Maddogs ortho and they sing beautifully. You obviously dont know what youre talking about as I am an ex owner of the 650 and they do not pair well with all amps. Its the nature of the beast in this game.Theres no single amp that goes well with every headphone and its not their fault.


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## proton007

Quote: 





gikigill said:


> I use the O2 to power the Maddogs ortho and they sing beautifully. You obviously dont know what youre talking about as I am an ex owner of the 650 and they do not pair well with all amps. Its the nature of the beast in this game.Theres no single amp that goes well with every headphone and its not their fault.


 

 Everyone is entitled to their opinion. There's no need to attack someone just because he doesn't agree with you.


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## ostewart

As I said before, this is all subjective, each to his own


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## gikigill

No attack here but just explaining that not everything is compatible with everything. There is a thing as synergy. My hifiman He-6 are proof of that.He should different headphones and see for himself. No silver bullets in audio.


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## ostewart

Actually it's 18v... And yes the HD650 is crap IMO, outdated, veiled and too warm. Complete opposite to what I like, I enjoy a accurate sound.

This is my opinion, I didn't even really like the HD700, I also found it a little warm, but more detailed.


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## xnor

Quote: 





lorriman said:


> Sure, the HD650 may not pair well with an O2 for the sound signature you prefer (*which is probably not neutral despite your going on about neutrality*) but in reality the O2 is merely demonstrating the true nature of the HD650: and you don't like it.


 
  This seems to be the problem. If someone doesn't like the sound of a headphone with a flat, low distortion amp the person doesn't like the headphone. Saying it's the amp's fault is absurd.


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## lorriman

xnor said:


> This seems to be the problem. If someone doesn't like the sound of a headphone with a flat, low distortion amp the person doesn't like the headphone. Saying it's the amp's fault is absurd.




Yes, it really does help to have a clue as to what neutrality sounds like. It was one of my motivations for getting the etymotics. All the headphones that I've heard (including my orthos) warble in volume all over the frequency range. 

Putting an increasing frequency sine wave tone through etymotics and what you hear is a outrageous flatness. The frequency graphs don't do them justice: they are as flat as pancakes except at their very limits. A technological tour de force.

And they are cold and thin (until you get used to them). Personally, I prefer a bit of bass boost, and since etymotics have almost no distortion even at high volume, they equalise marvellously, 7db at 50Hz. Banging bass. 

Warmth? Just boost the mid bass a bit.

Until you have heard a genuinely flat headphone out of a transparent/neutral source then one's opinion is meaningless and uninformed.


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## HeatFan12

Been keeping up with this thread, again great job randomkid.  With all this different talk about neutrality and whatnot with the HD650s, I just have three questions for you guys and hopefully the OP would not mind since it is relevant to the thread.
   
  1) Does this amp drive the HD650s efficiently/properly?
   
  2) If #1 is "yes" do they synergize well with this amp (not too much of anything in the spectrum and clean sound)?
   
  3) What sources are you guys using with the O2 & HD650?
   
  Thanks in advance...
   
  Cheers!!!


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## ostewart

heatfan12 said:


> Been keeping up with this thread, again great job randomkid.  With all this different talk about neutrality and whatnot with the HD650s, I just have three questions for you guys and hopefully the OP would not mind since it is relevant to the thread.
> 
> 1) Does this amp drive the HD650s efficiently/properly?
> 
> ...




1 - yes it can drive the HD650 fine and properly

2 - synergy depends on what sound you like, I'm not a fan of the HD650, but did find that they sound alright out of the O2 as they are a little warm and veiled, O2 makes them sound a little cleaner and detailed than a warm tube amp (too warm then)

3 - ipod classic LOD playing lossless most of the time, untill I get a good DAC


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## adydula

funny seeing how nwavguy choose the hd650's as his favorite??? wow!
   
  Alex


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## HeatFan12

Thanks very much randomkid.

Cheers!


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## miceblue

Quote: 





ostewart said:


> Actually it's 18v... And yes the HD650 is crap IMO, outdated, veiled and too warm. Complete opposite to what I like, I enjoy a accurate sound.
> 
> This is my opinion, I didn't even really like the HD700, I also found it a little warm, but more detailed.


 
  Hey I'm in with you on that. Every time I've tried the HD650, whether it be SS amps, Schiit Amps, Woo Audio amps, Bottlehead Crack amp, I have not liked its sound. To me it remains a mystery as to why so many people like it. For the ~$300 street price nowadays it sounds pretty good though, although I prefer the sound signature of an AKG K 701.
   
  That being said, the O2 drives the K 701 quite well from my experience. It definitely sounds more detailed and the soundstage is to its maximum potential with it versus Woo Audio and Schiit products. When I brought the O2/ODAC to the last local Head-Fi meet I went to, people were mighty impressed with how the O2 sounded. People said it could drive an LCD-2, but not to its full potential in the bass department.


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## ostewart

Yay, thread open again, now lets not let it go down the same road again, discussions regarding the O2 amp, and not perceived neutrality please


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## wolfetan44

Quote: 





ostewart said:


> Yay, thread open again, now lets not let it go down the same road again, discussions regarding the O2 amp, and not perceived neutrality please


 
  THANK GOD. I don't feel like editing my  post on O2 + ODAC so I'm going to leave it there. Anyways, I thought it was a great review, I would lend my ODAC to you. But your just too far away for my comfort.


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## ostewart

JDS said they would send me one either this month or next month, or Epiphany Acoustics as they have one wkth RCA outputs, and may send me one.

Thanks


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## wolfetan44

Quote: 





ostewart said:


> JDS said they would send me one either this month or next month, or Epiphany Acoustics as they have one wkth RCA outputs, and may send me one.
> 
> Thanks


 
  For free?


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## DemonFox

Great review Random. So if I was looking for a upgrade to my little e11 I was thinking the new e07k, O2, or C421 black... I do like warmer sounding so would I be better off with the other two vs the newer O2? They'll be paired with my iPhone 5, Old School iPod, or MacBook Pro source. Cans D5000's, JVC s500 (maybe), and DT990/250 Pro's


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## ostewart

C421 is warmer, wait until February and keep an eye on JDS, don't jump on the C421 just yet.
The O2 is transparent, so if your headphones are warm it won't make them bright they will stay warm.

Im waiting for the Fiio E12 which I hope to be reviewing when it's officially released.

Wolf: I'm finally making it as a reviewer, so its a sample, no commercial value. But yes it's free.


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## HeatFan12

Now I'm confused....
	

	
	
		
		

		
		
	


	




.......What exactly is neutrality?....
	

	
	
		
		

		
		
	


	







...............Just kidding of course...
	

	
	
		
		

		
		
	


	



   
   
  Mine is shipping today........
   
  Cheers!!!!!


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## adydula

I would hope that all the O2 fans and people that are looking to buy or DIY one would really read the designers blog, not for the diatribe but for the technical design points and what things seem to really affect an amps being transparent etc....
   
  The guy has done a wonderful job of exploring many of the specs that seem to possibly have an impact on the source signal etc....here is the list of audio specs that he identified as the point of diminishing returns:
   

 Output impedance less than 2 ohms
 Input impedance >= 10K
 Frequency response +/- 0.25 dB 20 hz – 20 Khz 400 mV 16-600 Ohms
 Phase response less than +/- 2 degrees error 100 hz - 20 Khz 16-600 Ohms
 Absolute phase: Preserved
 Slew Rate greater than 3 V/uS using 10 Khz square wave near full output 600 Ohms
 Distortion under 0.01% 20hz – 20 Khz into 16 – 600 ohms from 10 mV – 400 mV RMS
 Channel separation better than -40 dB @ 16 ohms and –60 dB @ 150 ohms 400 mV RMS
 Channel balance error less than 1 dB at any setting down to –45 dB below max volume
 Noise under –105 dBv (103 dBu) unweighted (5.6 uV or -97 dBr referenced to 400 mV)
 DC offset under 5 mV typical, and ideally, under 20 mV worst case
 100% stable with any realistic reactive load from 16 – 600 ohms
 Transient ringing and overshoot tightly controlled with all realistic headphone loads and 0.01 uF
 166 mA per channel, both channels driven, peak current capability at < 1% THD
 6.25 volts RMS on AC power at < 1% THD into 150 ohms
 4.5 volts RMS on DC power (nominal battery voltage) at < 1% THD into 150 ohms
 
 Take some time to read why "he" thinks these are the minimum req's and also know that the O2 delivers in these areas.....
   
  Alex


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## HeatFan12

Quote: 





adydula said:


> I would hope that all the O2 fans and people that are looking to buy or DIY one would really read the designers blog, not for the diatribe but for the technical design points and what things seem to really affect an amps being transparent etc....
> 
> 
> 
> ...


 
   
   
  Hey Alex,
   
  I'm guessing you are referring to ..WavMan?


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## adydula

Hi Heat...
   
  yup thats a good guess!
   
  Lots of great stuff lurking on that blog...each time I read the techie stuff I learn something neat about this little gem of an amp...
   
  Alex


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## wolfetan44

Quote: 





ostewart said:


> C421 is warmer, wait until February and keep an eye on JDS, don't jump on the C421 just yet.
> The O2 is transparent, so if your headphones are warm it won't make them bright they will stay warm.
> 
> Im waiting for the Fiio E12 which I hope to be reviewing when it's officially released.
> ...


 
  Wait, wait till Febuary for? Also, lucky!


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## ostewart

wolfetan44 said:


> Wait, wait till Febuary for? Also, lucky!




Wait and see, that's all I can say


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## wolfetan44

Quote: 





ostewart said:


> Quote:
> 
> 
> 
> ...


 
  But, I just bought a O2/ODAC. Mistake?


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## adydula

wolf!!
   
  no!!!!
   
  Alex


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## ostewart

Not a mistake, I was referring to the purchase of a C421


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## adydula

I dont want to tell you not to buy a c421...if thats what you want.....
   
  If you do get one let us know how you like it..
   
  Alex


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## ostewart

Yes, C421 is excellent, my personal portable amp, but wait till February, that's all I'm allowed to say for now


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## adydula

do we need to sign a NDA?
   
  lol
   
  Alex


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## adydula

sorry double post...listening to some old Joni Mitchell stuff via the O2/ODAC and my LCD2's....audio heaven here...
   
  Alex


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## ostewart

Yes something like that... Sorry guys


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## adydula

np...what i take is JDS labs might be coming out with a new amp?
   
  Gee, maybe the nvavguy went to Portugal and has been in hiding putting his ODA together and now JDS is ready to anounce in Feb!!
   
  wow what a story that would be..
   
  Alex


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## moshen

Quote: 





adydula said:


> np...what i take is JDS labs might be coming out with a new amp?
> 
> Gee, maybe the nvavguy went to Portugal and has been in hiding putting his ODA together and now JDS is ready to anounce in Feb!!
> 
> ...


 
  +1 to that.


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## wolfetan44

ostewart said:


> Yes something like that... Sorry guys


Could've told me not to get the O2!


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## ostewart

It's not ODA, nor anything like O2,


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## wolfetan44

ostewart said:


> It's not ODA, nor anything like O2,


Is it a JDS original? Or is it made by another modder?


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## ostewart

JDS original I think, I know hardly anything, please, just keep an eye on them in February, that's all I can say.

Back to the O2  anyone else enjoying their O2?


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## antberg

/l\
  / l \
    l
  Well,right now the second unit they send me is on my country income offices (since 26 December),i hope until the end of the next week the combo will be rocking out with my HD650.hehe


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## adydula

ok random...didnt mean to put you on the 'spot'....
	

	
	
		
		

		
			




   
  My O2 i bought frm JDS started 'blipping' last night....shocked the heck out of me.....was using my Grado 325is...and it was really a loud popping sound....i immediately powered off the O2.
   
  This was that battery low warning thing.....i never got this low before...put the ac adapter in and popping gone, charge overnight and all is good.
   
  But this poping to me seemed quite 'violent' with these Grados....must be listening louder than i think.....
   
  Alex


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## willmax

adydula said:


> ok random...didnt mean to put you on the 'spot'....
> 
> My O2 i bought frm JDS started 'blipping' last night....shocked the heck out of me.....was using my Grado 325is...and it was really a loud popping sound....i immediately powered off the O2.
> 
> ...




I've also had this popping noise and it scared the hell out of me, I wish there was a way to mod the amp so it doesn't do that and instead just switches off when the battery is low.


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## MrMateoHead

That pop is the amp shutting itself off, basically.
   
  I usually get a kind of "bump" and then just silence until I plug it back in. Nothing scary.


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## adydula

This isnt any small inaudible thing,...its a very loud pro-nounced popping that I believe is moving the element in the cans to extremes....I avoid it now by not letting the batteries run down!! keep the ac adapter plugged in....if i use batteries only then i only do it for a hour or so etc..
   
  Alex


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## ostewart

will have to check this. But I think the newer ones may not have this problem.


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## HeatFan12

Any of you folks tried the UCA202 with the O2?  I believe wavman tested and measured it with good results.  I've had mine for years and use it as a usb to spdif converter as well as a dac.  I'll try it out when my O2 arrives which should be Mon. or Tues.  For $29 it's a steal...
   
  Cheers!!!


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## miceblue

Quote: 





willmax said:


> Quote:
> 
> 
> 
> ...


 
  Yeah I have heard the O2 "pop" when the battery gets low, but I also hear that "pop" when I have my headphones plugged-in and I turn off the O2. Actually, when the O2 is on and my headphones are plugged-in, when I plug the ODAC into my computer's USB port, I get a "popping" sound or two from that as well. I'm not too concerned about it though as long as my K 701 doesn't experience some weird driver warping effect (from too much voltage?) like a certain other amp.


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## ostewart

miceblue said:


> Yeah I have heard the O2 "pop" when the battery gets low, but I also hear that "pop" when I have my headphones plugged-in and I turn off the O2. Actually, when the O2 is on and my headphones are plugged-in, when I plug the ODAC into my computer's USB port, I get a "popping" sound or two from that as well. I'm not too concerned about it though as long as my K 701 doesn't experience some weird driver warping effect (from too much voltage?) like a certain other amp.




Hum... I wonder which amp that could be, Schiit I can't remember the name


----------



## adydula

Hmmm, I never get popping sounds when plugging in the USD ODAC? But I dont even think of doing that often at all...I just tried it about 10 times and no popping sound here at all.
   
  Alex


----------



## ostewart

I wouldn't worry about the popping too much as the O2 has a built in headphone protection circuit.


----------



## lorriman

ostewart said:


> I wouldn't worry about the popping too much as the O2 has a built in headphone protection circuit.




...hmmm, but it sounds like that's what's not working.

I haven't ever run down the batteries, but all the other stuff (turning off, etc) only causes the usual quiet thump...into my etymotics. 

At a guess one of the mosfets is malfunctioning.


----------



## ostewart

Best thing to do is ask John at JDS Labs


----------



## Shazb0t

My O2 doesn't make any popping noises when turned on/off.  I would contact JDS Labs and ask them.


----------



## MrMateoHead

I do get some stutter / static occasionally. But It could be Foobar, it could be my computer, I am not sure. Seems to happen when I engage in some serious multi-tasking / PDF downloading and viewing.
   
  This occured through the normal HP jack as well as the O2 + ODAC combo.


----------



## proton007

Quote: 





mrmateohead said:


> I do get some stutter / static occasionally. But It could be Foobar, it could be my computer, I am not sure. Seems to happen when I engage in some serious multi-tasking / PDF downloading and viewing.
> 
> This occured through the normal HP jack as well as the O2 + ODAC combo.


 

 Stutter means a memory buffer underflow.


----------



## adydula

If your doing some serious multi-tasking well...thats the issue...
   
  You either put up with it or get a bigger ie faster system etc....
   
  I have a HTPC i do most of my listening on with the cans....and I do multi-task and every once in awhile i detect stuttering or a skip...
   
  If I stop, it stops....for the most part i can listen and browse with no issues at all..
   
  Its what it is....
   
  Alex


----------



## xnor

Check your DPC latency using LatencyMon. It should be below 1000us, better yet below 500us. Even occasional latency spikes can cause glitches.


----------



## lorriman

xnor said:


> Check your DPC latency using LatencyMon. It should be below 1000us, better yet below 500us. Even occasional latency spikes can cause glitches.




Nice tip, xnor.


----------



## adydula

A great idea!
   
  Alex


----------



## HeatFan12

Well, the O2 has landed.


----------



## ostewart

Nice, post impressions when you can


----------



## lorriman

Half decent pics. 

So, presumably that's an older ipod and you'll be getting the benefit of decently lowered output impedance.


----------



## proton007

Quote: 





lorriman said:


> Half decent pics.
> 
> So, presumably that's an older ipod and you'll be getting the benefit of decently lowered output impedance.


 

 Why would you call it half decent?


----------



## antberg

Pardon my ignorance,are you using Beyer "Cushions" with your Ultrasones HeatFan?
   
  BTW,great rig,that's the rig i am looking for,i got a pair of HD650,my ODac and O2 combo did not leave income taxes offices yet ,and i am saving some money extra to get an IPod.


----------



## ostewart

Quote: 





antberg said:


> Pardon my ignorance,are you using Beyer "Cushions" with your Ultrasones HeatFan?
> 
> BTW,great rig,that's the rig i am looking for,i got a pair of HD650,my ODac and O2 combo did not leave income taxes offices yet ,and i am saving some money extra to get an IPod.


 
  dont forget to get the ipod classic 7G and rockbox it


----------



## adydula

Nice pix!
   
  thanks for sharing!
   
  Alex


----------



## HeatFan12

Quote: 





ostewart said:


> Nice, post impressions when you can


 
   
   
  Thanks!  I see now why all the discussions on neutral, transparent, clarity etc.  My initial impression is this little amp will let the headphones "be" the headphones (and I'm a tube freak...lol).  Very pleased with the purchase and still have to try out other phones and sources but definitely a winner.  Going to spend a good amount of time with it today (day off) and will come back later tonight with other thoughts...
   
  Thanks to all that share their experiences with this little amp.
   
   
   
  Quote: 





lorriman said:


> Half decent pics.
> 
> So, presumably that's an older ipod and you'll be getting the benefit of decently lowered output impedance.


 
   
   
  Lol...Well, I have a half decent camera and less than half decent picture taking skills...So, I'll take that as a compliment...Cheers!!! Thanks!
   
  Yes, that is a 5.5G iPod video (rockboxed).
   
   
   
   
  Quote: 





antberg said:


> Pardon my ignorance,are you using Beyer "Cushions" with your Ultrasones HeatFan?
> 
> BTW,great rig,that's the rig i am looking for,i got a pair of HD650,my ODac and O2 combo did not leave income taxes offices yet ,and i am saving some money extra to get an IPod.


 
   
   
  Thanks!  No, those are the stock 750 pads.
   
   
   
   
  Quote: 





proton007 said:


> Why would you call it half decent?


 
   
  Thanks!
   
   
   
  Quote: 





adydula said:


> Nice pix!
> 
> thanks for sharing!
> 
> Alex


 
   
   
  Thanks!


----------



## ostewart

enjoy, look forward to further impressions.


----------



## lorriman

proton007 said:


> Why would you call it half decent?




Oops! It's a UK colloquialism for 'quite good'. Forgot the international flavour of this forum. 

It would be used when the something is much better than normal though not pro/amazing. So really I was giving my appreciations of the good pics.


----------



## miceblue

Quote: 





ostewart said:


> Quote:
> 
> 
> 
> ...


 
  Can it?
  From Rockbox's website:
  Quote: 





> *Apple*: iPod 1g through 5.5g, iPod Mini, iPod Nano 1g


 
  I have an iPod Video (5th gen) and it's pretty fantastic.


----------



## HeatFan12

Quote: 





miceblue said:


> Can it?
> From Rockbox's website:
> I have an iPod Video (5th gen) and it's pretty fantastic.


 
   
   
http://www.head-fi.org/t/532426/ipod-classic-rockbox-its-happening


----------



## proton007

Quote: 





miceblue said:


> Can it?
> From Rockbox's website:
> I have an iPod Video (5th gen) and it's pretty fantastic.


 

 I've rockboxed my iPod, its possible and works alright.


----------



## HeatFan12

Well, spent a good amount of time with the O2.  Tried various phones as well as different sources including the Behringer UCA202 to give the O2 some Foobar love.  For the most part portable sources were my go to.  The last few months I have been really interested in battery powered amps with a bit larger footprint than the traditional portable amps.  I still love the desktops though, but trying out new things keeps it real.
   
  The phones I was most interested in trying with the O2 were the D5000s.  The O2 tightened everything up nicely with no bass bloat while retaining that sexy, smooth Denon love.  I listen to a variety of music- rock, metal, dubstep, house, trance, hip etc. and the combo delivered.  Very clean and clear.
   
  I guess I can touch up on this without breaking any rules..lol.....---  For those newer members, the designer of this amp used to be a member.  Many head-fiers sparred with him on some of his claims on a certain 'thread', myself included (all in good fun of course..
	

	
	
		
		

		
			





).  Back and forth we all went...lol...
   
  Well, all I have to say is that the wavman talked the talk and he walked the walk in designing a great amp.
   
  Cheers!!!
   
  Gotta get ready for the Heat game and a little Youthanasia always gets the juices pumping....


----------



## antberg




----------



## adydula

Great..glad its working out good for you!
  Alex


----------



## ostewart

adydula said:


> Great..glad its working out good for you!
> Alex




I agree, enjoy!


----------



## ostewart

Double post


----------



## miceblue

Quote: 





adydula said:


> Hmmm, I never get popping sounds when plugging in the USD ODAC? But I dont even think of doing that often at all...I just tried it about 10 times and no popping sound here at all.
> 
> Alex


 
   
   


> A pop upon connecting ODAC is normal. Will reply to your longer message in a moment.
> 
> Thanks,
> John Seaber JDS Labs, Inc. | Tel: 314-252-0936


----------



## TheKillerPiglet

Quote: 





ostewart said:


> I got rubber feet with my O2 and C421, I thought they came as standard, but I did put different feet on my O2, slightly bigger as it's not really portable so it doesn't matter.
> 
> KP the O2 would be perfect as a transportable for your laptop


 
   
  I got one this past Monday. It is indeed a perfect laptop amp. It's small enough to still be easy to carry, but it has enough power to handle full size cans. The original intent was to drive DT990's or K550's at the office and T1's when I used my laptop in front of the TV. 
   
  As it turned out, it did such an excellent job on the T1's I found myself taking the Beyers into the office all week. $150 dollar amp on $1200 'phones. Heh. I don't think I can bring myself to throw the T1's into my laptop bag for travel, but it is tempting.
   
  Source from laptop is HRT MS II, FLAC, JRiver WSAPI Event, no DSP.
   
  Build quality is excellent, which is what was expected after receiving a C421 earlier this year from JDS. Do wish the cover to get to the 9V batteries did not require screw driver to remove, as it'd be nice to be able to easily drop a couple of non-rechargeable batteries in there in a pinch.
   
  KP


----------



## ostewart

thekillerpiglet said:


> I got one this past Monday. It is indeed a perfect laptop amp. It's small enough to still be easy to carry, but it has enough power to handle full size cans. The original intent was to drive DT990's or K550's at the office and T1's when I used my laptop in front of the TV.
> 
> As it turned out, it did such an excellent job on the T1's I found myself taking the Beyers into the office all week. $150 dollar amp on $1200 'phones. Heh. I don't think I can bring myself to throw the T1's into my laptop bag for travel, but it is tempting.
> 
> ...




I also thought it drove the T1 really well, I was very impressed. Glad your enjoying it.


----------



## adydula

It drives my LCD2 just wonderfully....as well as AKG Q701's,,,,,
   
  Alex


----------



## ostewart

Impressive power from such a small amp.


----------



## TheKillerPiglet

Quote: 





ostewart said:


> I also thought it drove the T1 really well, I was very impressed. Glad your enjoying it.


 
   
  By a happy coincidence, the AC plug on the O2 is the same as the one for my Asus laptop. Carrying charger for O2 is now optional. Yay.
   
  KP


----------



## mikeaj

Quote: 





thekillerpiglet said:


> By a happy coincidence, the AC plug on the O2 is the same as the one for my Asus laptop. Carrying charger for O2 is now optional. Yay.
> 
> KP


 
   
  Even if the plug is the same, how does this alleviate the need to carry the other wallwart?  It's not like the laptop AC/DC adapter (well, it's a SMPS) outputs AC for the O2.


----------



## adydula

Make sure its a AC adapter not a AC to DC adpapter! 
  Alex


----------



## TheKillerPiglet

It outputs 19V AC so it is within the power range suggested at JDS.
   
  KP


----------



## miceblue

adydula said:


> It drives my LCD2 just wonderfully....as well as AKG Q701's,,,,,
> 
> Alex



I personally haven't heard the LCD-2 with the O2, but when I brought the O2 to a local Head-Fi meet, some of the members said the O2 did a pretty good job at driving the LCD-2 but lacked a bit in the bass department.

A newer K 701 sounds absolutely fantastic with the O2 though. I couldn't be happier with my O2 purchase.



adydula said:


> Make sure its a AC adapter not a AC to DC adpapter!
> Alex



Since my AC adaptor is dead at the moment, I asked my dad if we had one lying around. Apparently AC adaptors aren't very common in our house, hahahaha. He graduated with an electrical engineering degree so he kind of explained to me why having an AC adaptor would be beter in some cases versus using an AC/DC adaptor. Cool stuff and it definitely fits what the O2 is trying to achieve.


----------



## mikeaj

Is there any laptop that seriously uses an adapter with AC output?  Why waste space and weight doing AC/DC conversion inside the laptop?  All the internal components run off of various levels of DC (so there are DC-DC step-down converters), and you want DC to charge the battery anyway.  Desktop computer ATX / BTX / whatever spec are all DC power.
   
   
   
  If you're getting (buying) a new AC adapter, you may as well spend a few dollars extra on the beefed-up part, WA16-1000:
  http://www.mouser.com/ProductDetail/Triad-Magnetics/WAU16-1000/?qs=sGAEpiMZZMtpkqKkT5w3uqH3NkAtJ%252bfiB%252bEoemwjDP0%3d
   
  That's way overkill, but default WAU12-200 is a bit marginal if charging the batteries and running high power outputs.  It's probably plenty okay for most uses, which is why it's default, but it's just to save a few bucks.


----------



## adydula

There are many happy LCD-2 users using the O2. It has power to spare to drive the LCD-2 to hearing damaging levels and beyond.

 The LCD-2 hits 110 dB with about 1 volt of input. Peaks of 110 dB are considered plenty loud by most people (hearing damage starts past 85 dB). 110 dB is standing on a sidewalk next to a jack hammer tearing up concrete.

 Even if you plan for 115 dB peaks, which is extremely loud, you only need about 1.7 Vrms which is 0.048 watts. The O2 can provide 5+ Vrms which is good for 124 dB SPL with the LCD-2. And that's running from battery power.

 So just on batteries alone the O2 will dirve the LCD2's to their limits and ear damaging levels.
   
  There is not shortage of bass with the O2....if its there in the recording it will get amplified and if your cans can reproduce these low frequencies you will hear them!
   
  Alex


----------



## miceblue

Quote: 





adydula said:


> There are many happy LCD-2 users using the O2. It has power to spare to drive the LCD-2 to hearing damaging levels and beyond.
> 
> The LCD-2 hits 110 dB with about 1 volt of input. Peaks of 110 dB are considered plenty loud by most people (hearing damage starts past 85 dB). 110 dB is standing on a sidewalk next to a jack hammer tearing up concrete.
> 
> ...


 
  Interesting. Maybe the listeners were used to a warmer-sounding amp then. The meets here in Seattle tend to have a lot of tube amps (from Schiit to Woo). I'll have to try it out whenever the next meet is! ^.^


----------



## ostewart

Yes I agree most use tube amps for the LCD, so going to a transparent amp will sound like there's a lack of bass until they get used to real sound of the headphones.
Saying that I did try a very nice icon audio tube amp with upgraded tubes (don't know which) and that sounded incredible, very detailed without adding a lot of warmth, I was expecting the typical tube sound, but that's not what I heard.


----------



## Currawong

Quote: 





adydula said:


> There are many happy LCD-2 users using the O2. It has power to spare to drive the LCD-2 to hearing damaging levels and beyond.
> 
> The LCD-2 hits 110 dB with about 1 volt of input. Peaks of 110 dB are considered plenty loud by most people (hearing damage starts past 85 dB). 110 dB is standing on a sidewalk next to a jack hammer tearing up concrete.
> 
> ...


 
   
  When you listen to complex music with the LCD-2s, do you get compression? Whether or not an amp can drive a pair of headphones capably isn't just about the numbers, it has to be able to maintain a linear flow of power to the circuit despite the widely fluctuating voltage it has to deliver.


----------



## HeatFan12

Quote: 





mikeaj said:


> Is there any laptop that seriously uses an adapter with AC output?  Why waste space and weight doing AC/DC conversion inside the laptop?  All the internal components run off of various levels of DC (so there are DC-DC step-down converters), and you want DC to charge the battery anyway.  Desktop computer ATX / BTX / whatever spec are all DC power.
> 
> 
> 
> ...


 
   
  Hey Mike,
   
  For mainly using the O2 plugged in (with batteries installed) the WAU16 is a better option down the road?


----------



## RustA

Quote: 





currawong said:


> When you listen to complex music with the LCD-2s, do you get compression? Whether or not an amp can drive a pair of headphones capably isn't just about the numbers, it has to be able to maintain a linear flow of power to the circuit despite the widely fluctuating voltage it has to deliver.


 
   
  The one who designed the amp possibly knows more about audio and electronics than all people discussing here on head-fi together... Technical excellence of his amp has even been proved on innerfidelity. So if he claims (on his blog) that the amp is more than suitable for LCD-2, I would definitely trust him. Definitely.
   
  However, one should be careful when using batteries... there could be clipping under certain conditions. More info is available on his blog, of course. And that's what I like - you can get all the info you need in order to drive your headphones with near-to-100% confidence.


----------



## RustA

Quote: 





heatfan12 said:


> Hey Mike,
> 
> For mainly using the O2 plugged in (with batteries installed) the WAU16 is a better option down the road?


 
   
  WAU12-200 should be suitable unless you are going to use them with low impedance headphones, or phones that need a lot of current... Generally speaking. There are other conditions which require better transformer - for example sine wave testing...
   
  You will be absolutely safe with WAU16-400 or WAU16-1000... I personally recommend 14-16V and 500+ mA to be 100% sure.


----------



## HeatFan12

Quote: 





rusta said:


> WAU12-200 should be suitable unless you are going to use them with low impedance headphones, or phones that need a lot of current... Generally speaking. There are other conditions which require better transformer - for example sine wave testing...
> 
> You will be absolutely safe with WAU16-400 or WAU16-1000... I personally recommend 14-16V and 500+ mA to be 100% sure.


 
   
   
  Thanks RustA,
   
  Been using the O2 mostly with Ultrasones and Denon, so definitely an investment worth making.  Both are about the same price, so your recommendation 400 or 1000?


----------



## RustA

Quote: 





heatfan12 said:


> Thanks RustA,
> 
> Been using the O2 mostly with Ultrasones and Denon, so definitely an investment worth making.  Both are about the same price, so your recommendation 400 or 1000?


 
   
  To be 1000% sure => 1000 mA... So WAU16-1000.


----------



## ostewart

Mine is 15v 500ma thinking that's pretty safe


----------



## RustA

Quote: 





ostewart said:


> Mine is 15v 500ma thinking that's pretty safe


 
   
  Yes... Mine is 15v 650ma though!


----------



## miceblue

Quote: 





rusta said:


> WAU12-200 should be suitable unless you are going to use them with low impedance headphones, or phones that need a lot of current... Generally speaking. There are other conditions which require better transformer - for example sine wave testing...
> 
> You will be absolutely safe with WAU16-400 or WAU16-1000... I personally recommend 14-16V and 500+ mA to be 100% sure.


 
  I know absolutely nothing about AC chargers and the correct voltages and current for gear. T_T
   
  JDS Labs is going to send me a stock O2 charger (WAU12-200) free of charge since mine apparently died somehow. I use a 32-ohm V-MODA M-100, Shure SRH940, and 64-ohm AKG K 701 with my O2...as well a 16-ohm Sennheiser CX300 and MEElectronics M9 on occasion (I probably don't even need the O2 for those). Is the stock charger OK for my case, or do you think a different one would be more suitable?


----------



## RustA

Quote: 





miceblue said:


> I know absolutely nothing about AC chargers and the correct voltages and current for gear. T_T
> 
> JDS Labs is going to send me a stock O2 charger (WAU12-200) free of charge since mine apparently died somehow. I use a 32-ohm V-MODA M-100, Shure SRH940, and 64-ohm AKG K 701 with my O2...as well a 16-ohm Sennheiser CX300 and MEElectronics M9 on occasion (I probably don't even need the O2 for those). Is the stock charger OK for my case, or do you think a different one would be more suitable?


 
   
  I would definitely consider a better one, especially for K701... As I said above, get something like WAU16-400 or WAU16-1000, or anything with 14-16V and 500+ mA at best.
   
  It's not that you are going to experience BETTER sound but you will not get clipping or partial distortion even at the worst cases. For common usage, you are most likely not going to experience a difference - that's why JDS labs offer WAU12-200. I personally tried both WAU12-200 and WAU16-400 and they "sounded" the same to me, completely. So it's more about mitigating any possible problem that could occur.


----------



## ostewart

miceblue said:


> I know absolutely nothing about AC chargers and the correct voltages and current for gear. T_T
> 
> JDS Labs is going to send me a stock O2 charger (WAU12-200) free of charge since mine apparently died somehow. I use a 32-ohm V-MODA M-100, Shure SRH940, and 64-ohm AKG K 701 with my O2...as well a 16-ohm Sennheiser CX300 and MEElectronics M9 on occasion (I probably don't even need the O2 for those). Is the stock charger OK for my case, or do you think a different one would be more suitable?




Sure is nice of John, I think that they have the best customer support I've ever come across, another reason to go with JDS. I remember sending my C421 in for a ferrite change as mine was from the old batch, he did it for anyone that wanted it free of charge


----------



## adydula

I am one of those more than happy LCD2 users with the O2. I have listened for hundreds of hours with the LCD2's R2's with the 2 O2 amps I have and ODAC's and two other amps and 2 other dacs....

 The O2 amp is totally inaudible....evidenced by the specs it meets and it totally transparent....garbage in ...garbage out. If you put in compressed source material into the O2 you will get crappy compressed source sound out of it....put in well recorded AND well mastered material into the O2 you will get sound out that comes out very, very well and its amazing at times how good it sounds with this amp. A good amp, like a straight wire with gain  just doesn not add or take anything away from the source....
   
  I beg to differ "its all about the numbers" ....if the specs that the O2 were designed against were not met or exceeded it would NOT be a transparent amp. It does deliver the voltage and power to excercise most headphones out there, including the LCD2's...with authority and control.
   
  I would much have an amp that meets or exceeds these specs...than one that does not....we can go from there,
   
  As far as the ac adapter I have tried all of them....and the best AC adapter is the WAU16-400. It is the best transformer for any headphone
   
  The WAU20-200 doesn't result in any higher output into high impedance headphones (because the O2 uses a regulated power supply internally) and it has less current for low impedance loads. The WAU16-400 is the best transformer for any headphone.

 The 18 and 20 volt transformers do put more of a thermal "strain" on the O2 as the regulators run hotter.
   
  I can honeslty say that with 4 transformers i have tried and even compared to the pure DC of the batteries I can not detect and real world difference with LCD2's, Q701's or Grado 325is...
   
  Alex
   
  Note there is a lot on this subject on the designers blog....take the time to read the stuff on AC adapters and his recommendations.. At first I was not a beliver and bought several AC adapters to see for myself.
   
   
  .


----------



## miceblue

Quote: 





ostewart said:


> Quote:
> 
> 
> 
> ...


 
  Yup for sure. I would definitely recommend purchasing things through JDS Labs again as their customer support has been very helpful, personal, and overall just a fantastic experience.


----------



## adydula

Yup, JDS labs support if first class...its good to see that.....
   
  Alex


----------



## HeatFan12

Great info on all the power specs.  Thanks to all...
   
  I went ahead and ordered the WAU16-1000 for peace of mind I guess down the road and to make my Grados sound like Senns....lol..jk of course..
	

	
	
		
		

		
			




   
  Now, let's say folks are using the O2 exclusively with batteries and using the WAU-200 (stock) to charge only with no load (headphones) connected.  Would this be a suitable plan B?  I'm assuming the O2 charges while powered off?  I'll have the WAU-200 as well, and instead of putting it in a drawer I would like to put it to work.
   
  Thanks!


----------



## shadow419

@Heatfan12  Correct.  As long as it's plugged into an outlet the batteries will charge.


----------



## adydula

Yes that would be fine....I actually do that myself...I uses the lower power one to charge batteries while I am away and unplug to listen with batteries only.
   
  My higher voltage on I use on my second setup.
   
  Alex


----------



## adamlr

after coming to the realization that my next set of cans are going to be "easy to drive", i finally decided on the O&O rather than the M&M, figuring *5 is a bit much for efficient, 30-40 ohm headphones. just placed the order - its back ordered, to ship on the 31st of january >_<
   
  anyway, can i take the batteries out and plug the O2 into the wall, using it as a desktop amp? id really rather get rid of all the battery business.
   
  many thanks


----------



## HamilcarBarca

Quote: 





adamlr said:


> after coming to the realization that my next set of cans are going to be "easy to drive", i finally decided on the O&O rather than the M&M, figuring *5 is a bit much for efficient, 30-40 ohm headphones. just placed the order - its back ordered, to ship on the 31st of january >_<
> 
> anyway, can i take the batteries out and plug the O2 into the wall, using it as a desktop amp? id really rather get rid of all the battery business.


 
   
  When you write "O&O", do you mean the ODAC+O2 combo? It doesn't take batteries, and only uses the AC transformer.


----------



## adamlr

Quote: 





hamilcarbarca said:


> When you write "O&O", do you mean the ODAC+O2 combo? It doesn't take batteries, and only uses the AC transformer.


 

 sorry, yes i do mean ODAC+O2, but separately, not in the same box. the ODAC is usb powered, but the O2 comes with rechargeable batteries, can i take them out, and only use the ac transformer?


----------



## ostewart

I'm not quite sure, I'd say yes but best ask JDS or Adydula, he seems to know his stuff, lent my O2 to a teacher who has Beyerdynamic DT770 pro 80ohm


----------



## xnor

Yes. But it's also safe to let the batteries in there.


----------



## adamlr

Quote: 





xnor said:


> Yes. But it's also safe to let the batteries in there.


 

 just leave them in even though the ac adapter is plugged in? doesnt that kill the batteries?


----------



## mikeaj

It's kind of a gray area.  Yes, it'll continue to charge forever, which is generally not good for the batteries, but once the batteries are at full charge then the current coming in is low enough that it's supposed to be okay.  If you never will use it on batteries, then take them out, but it's probably not a big deal.


----------



## xnor

From the blog that shall not be named: "The charge current automatically tapers off as they reach full charge and you can leave the AC power connected indefinitely if you want. But if you’re going to use the O2 mainly as a desktop amp for months at a time you should remove the batteries."


----------



## HeatFan12

Quote: 





shadow419 said:


> @Heatfan12  Correct.  As long as it's plugged into an outlet the batteries will charge.


 
   
  Quote: 





adydula said:


> Yes that would be fine....I actually do that myself...I uses the lower power one to charge batteries while I am away and unplug to listen with batteries only.
> 
> My higher voltage on I use on my second setup.
> 
> Alex


 
   
   
  Thanks very much guys...
   
  Cheers!!!


----------



## adydula

If you dont plan on using the batteries, remove them.
   
  Batteries like to be charged and discharges over and over and over.....
   
  Alex


----------



## AngryGuy

I just purchased a used jds o2/odac combo from someone and I love it but I'm having one issue with it. With some of my higher sensitivity headphones, the volume out of the O2 is simply too much except at very low levels on the volume knob. The problem is that at very low levels the volume pot gives me very uneven volume. By the time I get to where it sounds normal, it's at the absolute limit of how loud I would want to listen. Is there anything I can do about this without changing the gain? It has the default 2.5/6.5 gain on it. I wouldn't really like to change that since I have a wide variety of headphones and the higher gains could be useful to me. Is there a different volume pot that I could use that wouldn't have this issue?


----------



## proton007

Quote: 





angryguy said:


> I just purchased a used jds o2/odac combo from someone and I love it but I'm having one issue with it. With some of my higher sensitivity headphones, the volume out of the O2 is simply too much except at very low levels on the volume knob. The problem is that at very low levels the volume pot gives me very uneven volume. By the time I get to where it sounds normal, it's at the absolute limit of how loud I would want to listen. Is there anything I can do about this without changing the gain? It has the default 2.5/6.5 gain on it. I wouldn't really like to change that since I have a wide variety of headphones and the higher gains could be useful to me. Is there a different volume pot that I could use that wouldn't have this issue?


 

 I'd suggest to lower the source volume to a point where the O2's knob has sufficient variation of volume.


----------



## muad

Quote: 





angryguy said:


> I just purchased a used jds o2/odac combo from someone and I love it but I'm having one issue with it. With some of my higher sensitivity headphones, the volume out of the O2 is simply too much except at very low levels on the volume knob. The problem is that at very low levels the volume pot gives me very uneven volume. By the time I get to where it sounds normal, it's at the absolute limit of how loud I would want to listen. Is there anything I can do about this without changing the gain? It has the default 2.5/6.5 gain on it. I wouldn't really like to change that since I have a wide variety of headphones and the higher gains could be useful to me. Is there a different volume pot that I could use that wouldn't have this issue?


 
   
  correct me if i am wrong... but didn't nwavguy set the high gain up for lower input sources and not for less sensitive headphones? If you don't plan on using anything but the odac as the source you should never need the 6.5 gain. I cut mine to 1x for use with my BA iem's and the 1x gain is plenty for my hd650. So now I have 1x and 2.5x gain. I would assume that 2.5x gain should be enough to run most headphones. Maybe someone else can comment?


----------



## AngryGuy

Quote: 





muad said:


> correct me if i am wrong... but didn't nwavguy set the high gain up for lower input sources and not for less sensitive headphones? If you don't plan on using anything but the odac as the source you should never need the 6.5 gain. I cut mine to 1x for use with my BA iem's and the 1x gain is plenty for my hd650. So now I have 1x and 2.5x gain. I would assume that 2.5x gain should be enough to run most headphones. Maybe someone else can comment?


 
  You're probably right about this. 

 I think I'm just going to try 1x/2.5x. I just need to remove R19 and R23, right?


----------



## moshen

Quote: 





angryguy said:


> You're probably right about this.
> 
> I think I'm just going to try 1x/2.5x. I just need to remove R19 and R23, right?


 
  Yea, that's what I did. I clipped those two resistors. Very easy to do. 1x/2.5x gain works much better than stock.


----------



## proton007

Quote: 





moshen said:


> Yea, that's what I did. I clipped those two resistors. Very easy to do. 1x/2.5x gain works much better than stock.


 

 Either you can do that, or if you can solder yourself, solder a wire wrap socket instead of the resistors, and then you can just plug in/out the resistors without soldering/clipping.


----------



## lorriman

angryguy said:


> You're probably right about this.
> 
> 
> I think I'm just going to try 1x/2.5x. I just need to remove R19 and R23, right?




DON'T DO IT!!!! 

Clip the 2.5x not the 6X.

The 6.5x is needed for low-voltage sources like ipods and clip+'s when used with higher impedance phones (particularly if using equalisation). 

For example, as a loud listener my 32ohm headphones are right at the limit of the pot on the 2.5x gain setting when I set my rockboxed clip+ to 0dbs (with no equalisation). 

If I equalize 12dbs at 40Hz ( which gives me a flat bass response at normal listening levels) then this makes the clip+ lower the overall gain to accommodate the equalisation. I run it at -3dbs to give a touch of headroom (0dbs is the limit of gain before distortion sets in as the rockbox developers look up the particular device specs; the extra 6dbs above that is for the gung ho or those who do not seek the nirvana of hifi) then I totally run out of pot at 2.5x.


----------



## Currawong

Quote: 





rusta said:


> Quote:
> 
> 
> 
> ...


 
   
  This doesn't answer my question. You don't need an engineering degree to hear compression when listening. It's a simple test for those of us without $10k measuring equipment. FYI, the tests done in various places, with the exception of one I linked, didn't use headphones when they were done, so don't show the linearity of the circuit in actual use. One that did showed that the O2 starts to distort when IEMs are connected, compared to a UHA-6SII which didn't.


----------



## lorriman

currawong said:


> so don't show the linearity of the circuit in actual use. One that did showed that the O2 starts to distort when IEMs are connected, compared to a UHA-6SII which didn't.




...distort? You mean the frequency curve inaudibly dips, not actual distortion.

This is really academic. No one is going to hear the tiny dip in the O2's driving of a low-impedance balanced armature. The design principle was to aim for audible transparency (which pretty much defines true hifi) not technical perfection, which is in anycase impossible without a true Zero Z (output impedance) which is impossible if I remember correctly.


----------



## RustA

Quote: 





currawong said:


> This doesn't answer my question. You don't need an engineering degree to hear compression when listening. It's a simple test for those of us without $10k measuring equipment. FYI, the tests done in various places, with the exception of one I linked, didn't use headphones when they were done, so don't show the linearity of the circuit in actual use. One that did showed that the O2 starts to distort when IEMs are connected, compared to a UHA-6SII which didn't.


 
   
  So what's the conclusion if what you claim is true? That O2 is not perfect from the technical perspective? Well, it's not, you can read it on the author's blog as well... He is very aware of it.
   
  I cannot hear any audible distortion with my phones, including IEMs and low impedance phones from Denon or Audeze... The question remains - why do you need an amp for IEMs?


----------



## lorriman

angryguy said:


> You're probably right about this.
> 
> 
> I think I'm just going to try 1x/2.5x. I just need to remove R19 and R23, right?




I forgot to add that there is an alternative. You could get a splitter with individual volume controls. Seriously useful. Has no audible downsides.

Here's my own:

http://www.head-fi.org/t/627755/short-positive-review-iluv-headphone-2-way-splitter-with-dual-independent-volume-controls


----------



## adamlr

Quote: 





mikeaj said:


> It's kind of a gray area.  Yes, it'll continue to charge forever, which is generally not good for the batteries, but once the batteries are at full charge then the current coming in is low enough that it's supposed to be okay.  If you never will use it on batteries, then take them out, but it's probably not a big deal.


 
   
  Quote: 





xnor said:


> From the blog that shall not be named: "The charge current automatically tapers off as they reach full charge and you can leave the AC power connected indefinitely if you want. But if you’re going to use the O2 mainly as a desktop amp for months at a time you should remove the batteries."


 
   
  Quote: 





adydula said:


> If you dont plan on using the batteries, remove them.
> 
> Batteries like to be charged and discharges over and over and over.....
> 
> Alex


 

 thank you very much, cheers


----------



## adydula

There is "compression" in the source material....have to be careful here with words...to me being around for a LONG time on this earth things I have learned from this forum and others that the words we use ....well can be interpreteted widely....back to "compression"..
   
  When I hear the term in audio I immediatley think of crappy source material...a song that was recorded and the dynamic range was reduced from what the technology would allow....for whatever reason...
   
  In electronics like the O2 amp if we are talking about its "compression" to the signal being inserted into it, compared to the signal out....is that the "compression" your talking about?
   
  Distortion is another thing...and it is tied to the gain settings and the source amplitude in the O2....
   
  For the most part the standard gain settings are just fine....for me with three sets of cans, widely different, I find I never use the 6.5x gains settings with the ODAC and with a much hotter 2.25 Vrms HRT MSii+ asynch USB dac....
   
  With AKG 701's, LCD2's anf my Grados....the volume knob is never past the 1pm position....or my ears would bleed. LOL.
   
  I can easily get the O2 amp to distort and sound crappy...but you just dont go there....
   
  If its one thing that the O2 has an archilles heel its the gain settings implementation because many of us just dont really understand it, what it is, how it works etc...
   
  But the real technical beauty of it is that you can dial it in if needed...not like other amps...one new one that comes to mind....that the gain is set....fixed...story over....
   
  All the best
  Alex


----------



## xnor

I think the input/gain stage of the O2 perfectly fits the rest of the amp and is actually one of its strong points. Other amps clip a lot earlier, like the E9's input at ~2.1 V. That is regardless of the position of the volume control.
   
  With the O2 on AC power you can use:
  max_gain = 7V / input_voltage
  for example: 7V / 2.25V = 3.11x, so any gain setting lower than that is fine
   
  max_input = 7V / gain
  for example: 7V / 2.5x = 2.8V, so the default 2.5x gain is fine for sources up to 2.8 V


----------



## mikeaj

Quote: 





lorriman said:


> ...distort? You mean the frequency curve inaudibly dips, not actual distortion.
> 
> This is really academic. No one is going to hear the tiny dip in the O2's driving of a low-impedance balanced armature. The design principle was to aim for audible transparency (which pretty much defines true hifi) not technical perfection, which is in anycase impossible without a true Zero Z (output impedance) which is impossible if I remember correctly.


 
   
  Technically that's distortion, but almost everybody means "non-linear distortion" when they talk about distortion.  Mild FR changes are not non-linear distortion, as you say.  I wouldn't be confident enough to say "inaudibly dips", but I think it's at the level where it's not worth losing sleep over.  That said, it's a bigger deal than some other things that audiophiles worry about.
   
  Many devices have lower output impedance.  0 output impedance is like 0 distortion or 0 noise—impossible, as you say... unless you find me a wire with 0 resistance and much more.  It's meaningless in the grand scheme of things.  Most of it on the O2 comes from the output resistors, which are there mainly for safety / matching of the cheap output op amps.  A small tradeoff, like many things.
   
   
   
  If you wanted, you could adjust the gain on lots of other DIY amps, some commercial ones too.  Though beware of instability.


----------



## ostewart

Thanks guys, I'm learning a lot from my own thread, I might actually change mine to 1x and 6x gain, 2.5 is too high.


----------



## adydula

Kool!!
   
  Thanks for starting the thread...its good to see us all learning etc...
   
  Alex


----------



## muad

Is there any use for the 6.5x gain if I will only ever use an odac with it?


----------



## proton007

Quote: 





muad said:


> Is there any use for the 6.5x gain if I will only ever use an odac with it?


 

 With the ODAC, maybe not.


----------



## HeatFan12

Now that the proper power requirements and schematics have been taken care of, how about some pics?
   
  Show your sources, docks, LODs, mini cables connected to the O2.  I've already posted a couple but have to bling her up for the next go around...
   
  Cheers!!!


----------



## miceblue

Quote: 





lorriman said:


> Quote:
> 
> 
> 
> ...


 
  Woah that's a lot of volume. o.0
  I usually have my Clip Zip at -25 dB, 1.0x gain on the O2, with the volume knob as my volume adjustor, hooked up to my 36-ohm headphones (according to Innerfidelity's impedance measurement).
   
  Is the 6.5x gain thing true? I occasionally use my O2 with my Clip Zip, but not very often and I have the 2.5x/1.0x gain options.
   
   
   
  Quote: 





heatfan12 said:


> Now that the proper power requirements and schematics have been taken care of, how about some pics?
> 
> Show your sources, docks, LODs, mini cables connected to the O2.  I've already posted a couple but have to bling her up for the next go around...
> 
> Cheers!!!


 
  I don't have a LOD at the moment, but I'll probably get one from Amazon soon whenever I order something to get the "spend $25 get free shipping" deal thing.
  Anywho here are my setups.
   

  ^ Does anyone have a recommendation for a shorter mini USB cable? I don't like the length of the one that came with the JDS Labs O2, I don't like bending my cables very much (I tend to keep the cable as close to its original position as possible), and I don't want to lose sound quality (if the AC charger was carefully chosen, perhaps the USB cable was carefully chosen as well?).


----------



## lorriman

miceblue said:


> Woah that's a lot of volume. o.0
> I usually have my Clip Zip at -25 dB, 1.0x gain on the O2, with the volume knob as my volume adjustor, hooked up to my 36-ohm headphones (according to Innerfidelity's impedance measurement).




I've noticed that some of my friends usually set the clip to -24db when I would set it to between -9db and -15db (no equalisation). Others set it to my level. One of the -25db-ers told me that any higher was painful!! So that's not because they are quiet listeners; it's their volume/pain threshold (at least in that particular case). So, going on a conservative estimate, that's a 9db difference which is quite a lot. AFAIK, I'm not deaf. I had an ear test when I was a kid and had fine hearing. Progressive deafness usually affects the midrange the most, but listening to a sine generator rising from 100Hz to 12Khz on my etymotics (legendary flatness), I can't hear a volume difference; so I doubt I am deaf.

It would be interesting to know more about this difference. I'm going to test one of my -24db friends today to see if they have better hearing or are just more sensitive to pain (I suspect the latter because in this person's case they are very sensitive to physical pain-play, like how chaps punch each other for fun, or, in a boring chemistry lesson, my best friend and I would stab each other in the legs with biros to try to alleviate the boredom; that's a total no-no with this person).

If the latter then that would have a profound affect in relation to the loudness/frequency curves and necessary bass equalisations (to get flat bass all the way down to 20Hz from headphones that trail off in the lower regions as most do). In order to get the same bass response as myself they would have to go for even more than 12dbs gain at 40Hz. I've noticed from frequency/sine-tone testing that at low volume there is a 30db perceived difference between 100Hz and 30Hz which, which reflects those curves. Of course, with their volume so low, they are not going to get distortion with a 30db bass boost; except from a poor equalizer (like ipod nano 2 or Windows Media Player 11; both utterly awful).


----------



## miceblue

Quote: 





lorriman said:


> Quote:
> 
> 
> 
> ...


 
  Well I have -25 dB as the maximum volume level while riding on the bus, so that might be something to take-in to account. While walking around campus I lower it to -30 dB. At home, if I listen to my Clip Zip, I have the volume set at -60 dB. I'm kind of afraid to know what my threshold of pain is, but I know that with -25 dB at 1.0x O2 gain with 36-ohm headphones with the volume knob at the max volume, music is pretty loud to me while on a noisy bus.. >.>
   
  Oddly enough, or perhaps by coincidence, my sense of touch pretty sensitive too (I would say my sense of touch and hearing are my most sensitive senses). Hearing is a mechanical/electrical process via mechanotransduction so maybe that has to do something with volume sensitivity (just pondering out loud, it's probably not the case).
   
  I have yet to do frequency/sine-tone/pink noise testing since I'm not quite sure how to do it but I have read about the equal loudness contours.
   
  Interesting stuff.
   
  John at JDS Labs recommended I use the 2.5x/1.0x gain since I tend to listen to music at low volume levels, which is why I was asking about the 1.0x/6.5x gain thing. I can't really imagine using the 6.5x gain. XD


----------



## lorriman

miceblue said:


> John at JDS Labs recommended I use the 2.5x/1.0x gain since I tend to listen to music at low volume levels, which is why I was asking about the 1.0x/6.5x gain thing. I can't really imagine using the 6.5x gain. XD




With such extraordinarily low-volume listening (to my mind) it does make sense to choose 1x/2.5x . Then again, if you were to get a 300ohm headphone (HD600?) and clip+ with +30dbs 30Hz bass equalisation reflecting the loudness contour for a low volume listener, if that's how it works which remains to be seen (and with which the clip+ automatically lowers the overall gain by 30dbs), even you might run out of pot at 2.5x.


----------



## ostewart

i think its best to have 1x and 6.5x as i might get some quite hard to drive headphones in the future, which mau need the 6.5x gain, 1 and 2.5x are too close to be of any use to me i think


----------



## RustA

Quote: 





ostewart said:


> i think its best to have 1x and 6.5x as i might get some quite hard to drive headphones in the future, which mau need the 6.5x gain, 1 and 2.5x are too close to be of any use to me i think


 
   
  The best thing is to use "*Optional Gain Resistor Pin Sockets​*" = you can have whatever gain you want whenever you want... Search on the blog for more info.​   
If you do not have an option to do it, use 1x and 2.5x since 6.5x is too much for 99% of headphones. For ODAC users, 6.5x is even more out-of-reality.​


----------



## ostewart

using an iPod, rockboxed, i used 6.5 on beyerdynamic T1 and the likes, 1 is fine for most headphones in my opinion, especially if you used ODAC, then 6.5 for ipod and hard to drive headphones.


----------



## ostewart

more pics:
   
  Toxic cables DIY silver LOD, plus Toxic cables SPC DIY headphone cable


----------



## skamp

Using expensive "silver" cables with the _Objective 2_… oh the irony!


----------



## ostewart

not expensive, i only paid for the LOD connector and the Pailiccs jack, the cable i won in a competition


----------



## RustA

Quote: 





skamp said:


> Using expensive "silver" cables with the _Objective 2_… oh the irony!


 
   
  I have all the interconnection of my O2/ODAC desktop combo made of HQ silver ,-) Very cheap in reality since you do not need many feet in order to do them...


----------



## ostewart

true, you can make nice siver cables for cheap, im guessing this one would have cost around $30-40 to make.


----------



## adydula

Well at least they wont make the combo sound any worse!
   
  lol
   
  Alex


----------



## miceblue

Quote: 





ostewart said:


> more pics:
> 
> Toxic cables DIY silver LOD, plus Toxic cables SPC DIY headphone cable


 
  Do these cables actually make a difference in sound quality?
  When I hear "toxic cables" I'm inclined to not purchase them. XD


----------



## skamp

That's my point. NwAvGuy, the designer of the O2, would reply with a resounding "NO".


----------



## mikeaj

Got to get that silver power cord and silver resoldering job to complete the set!
   


Spoiler: Hm...



Silver transformer?  
	

	
	
		
		

		
			




   


Spoiler: Actually



That would be kind of cool.  Then again, maybe it's not good to give people funny ideas that might be taken in some kind of mistaken pursuit of sound quality.  Oh dearie.


----------



## RustA

Quote: 





skamp said:


> That's my point. NwAvGuy, the designer of the O2, would reply with a resounding "NO".


 
   
  I have quite a lot of upgrades on my O2/ODAC unit because I would like it to last for years as my benchmark tool for listening, composing, and testing/comparing other amps and DACs with it (have inputs and outputs to enable both). That's why I have OCC silver cables inside as well (to maintain the IC's quality over time), not because of SQ improvements.


----------



## tdockweiler

Quote: 





skamp said:


> That's my point. NwAvGuy, the designer of the O2, would reply with a resounding "NO".


 

 Just because there is not a measurable difference doesn't mean there isn't a slight change in the tone of how a headphone will sound.
  Just look at all these amps that sound completely different and measure the same. Yeah, I know it's all how it's designed and everything, but still.
   
  Here's a test. Try a K702 or a really bright headphone with the O2 or Magni and silver or a very low capacitance wire. It's not fun. I learned this the hard way when I got my ALO SXC cable for the Q701.
  It's just preferences. Sometimes crappy cable is actually better. What warmth the K702 had is kind of lost. Oh and how do you measure warmth? The 598 still measures fairly flat, but it's still warm.
  The Clip+ is warm and is ruler flat.
   
  To my ears it's all about capacitance. I prefer it to be somewhere in the middle. I guess most store brands are somewhere in the middle. Monoprice is a little higher I imagine.
   
  My belief is that the difference is how bright/thin or warm and full sounding the headphone will be. Then it all depends on the equipment too.
  The difference isn't huge despite what some want you to believe.
   
  Try a silver cable and then Canare. They're total opposite and the biggest difference you could probably hear (due to capacitance).
   
  BTW try to guess why people love the HD-650 with silver cables. Do you think they always say "ohh..it's so warm and full sounding". No, it's usually like..."it's so much clearer and it lost it's veil".
   
  note: I don't believe in expensive cables, but I do believe in some differences. I prefer to use anything that's cheap and has good shielding. 60 cents/foot Mogami is nice. So is the Monoprice stuff.
   
  Ohh and supposedly ultra low capacitance wire is always labeled as the most "transparent" 
	

	
	
		
		

		
		
	


	




 Doesn't mean I have to like it. I'll stick with my Monprice and Mogami.


----------



## HamilcarBarca

Quote: 





tdockweiler said:


> Quote:
> 
> 
> 
> ...


 
   
  I think that is what it means. The O2's designer agrees. If there's a "slight change of tone", the electrical difference will be measurable. Otherwise, there's nothing happening which might make the headphone behave differently.


----------



## skamp

The *Objective* 2 was designed precisely to make a point against the usual subjectivist rhetoric. That's why it's so ironic to see it used with silver cables that are supposed to improve the sound quality, by people who claim that what they hear isn't measurable.


----------



## adydula

If I bought all the stuff that has touted to "lift the veil" for me.....I would have the band or group playing live in my living room....
   
  Alex


----------



## skamp

NwAvGuy's reaction:


----------



## RustA

Quote: 





skamp said:


> NwAvGuy's reaction:


 
   
  Thank you very much for your contribution here, anything else to add to enlighten us? 
	

	
	
		
		

		
		
	


	



   
  As I said, quality cable with added silver (along with quality solder) will maintain its ability to properly conduct the signal in a long-term over cheap non-silver one. If it makes you happy, I use the stock Audeze cable and have no plans for change in this regard.


----------



## tdockweiler

Quote: 





hamilcarbarca said:


> I think that is what it means. The O2's designer agrees. If there's a "slight change of tone", the electrical difference will be measurable. Otherwise, there's nothing happening which might make the headphone behave differently.


 
   
  "electrical difference"? Of course that would be measurable and much different. Unless you're talking about frequency response measurements. The thing I don't get is why people can't believe there is a difference in tone despite frequency graph measurements being exactly the same. How do you explain the difference between say the Ipod Touch 2G and Clip+? Both sound totally different but both are ruler flat. I guess there's a lot more too it. What is it that makes the Clip+ sound warmer despite measuring the same?
  That's a serious question. Maybe it has more distortion.
   
  And no, I don't believe in cables offering that big of a difference. I don't really care and don't believe all cables are the same. Lately what's most important to me is it's capacitance and shielding.
   
  Right now i'm using Monoprice cables.


----------



## skamp

NwAvGuy, like any other objectivist, would say that the differences you hear would probably vanish in a proper double blind test. Haven't you read his blog?


----------



## tdockweiler

Quote: 





skamp said:


> NwAvGuy, like any other objectivist, would say that the differences you hear would probably vanish in a proper double blind test. Haven't you read his blog?


 

 Yes, and you'd also probably fail a blind test between an E9 and O2.
  I guess we should just go out and buy an E9 since it's cheaper...
   
  EDIT: ok i'm partially joking, but I wouldn't be surprised if 75% of us would fail that. No I'm not kidding.
   
  Honestly I could not live with silver wire on anything that's bright. If that's me hearing things, then so be it..
  If someone could live with the K702 with silver for a month, i'll personally mail you a check for $500. Not even a K702 fan could do it!
  It'd drive me crazy. The O2 or Magni would even make it worse.


----------



## skamp

The E9's high output impedance (that's measurable!) would probably have caused a high frequency spike of several decibels (that's measurable too!) with my balanced armature Shure SE425 IEMs. I wanted an amp/DAC combo that would work well with any headphones/IEMs, and with good build quality. My FiiO E7 developped contact problems on both headphone outs after only a couple of months, so I didn't want to risk buying anything more from FiiO.

Now that I have my O2/ODAC, I don't need anything else. And yeah, I probably couldn't differentiate it from some other, cheaper gear that measures well (e.g. a FiiO E7), but I don't claim that I could, and I don't care. It's fully transparent, and that's exactly what it was designed to achieve. Also, it gives me a warm fuzzy feeling of overkill.


----------



## tdockweiler

Quote: 





skamp said:


> The E9's high output impedance (that's measurable!) would probably have caused a high frequency spike of several decibels (that's measurable too!) with my balanced armature Shure SE425 IEMs. I wanted an amp/DAC combo that would work well with any headphones/IEMs, and with good build quality. My FiiO E7 developped contact problems on both headphone outs after only a couple of months, so I didn't want to risk buying anything more from FiiO.
> 
> Now that I have my O2/ODAC, I don't need anything else. And yeah, I probably couldn't differentiate it from some other, cheaper gear that measures well (e.g. a FiiO E7), but I don't claim that I could, and I don't care. It's fully transparent, and that's exactly what it was designed to achieve. Also, it gives me a warm fuzzy feeling of overkill.


 
   
  I agree with that, but it's a bit annoying how people claim every headphone under say 80 ohm is going to magically be altered. The Q701 doesn't change a bit with the E9's 10 ohm output impedance. I can't even get that to change with even my 330 ohm receiver. My 38ohm DJ100 is perfect too. I know the E9 is no transparent "wire with gain". 
	

	
	
		
		

		
			





 It still sounds pretty good, but the Magni is more accurate. Sometimes I don't need 100% accuracy.
   
  I know this sounds nuts, but I'd probably fail an extended blind a/b test with my Magni and E9, but am pretty confident i'd pass one between a headphone using silver wire and say Canare. Crazy right? To me the difference is like comparing an O2/Magni to a tube amp 
	

	
	
		
		

		
		
	


	




 It all depends on the amp/dac too. I've noticed it was easier to tell the difference between cables with my HRT MSII compared to the ODAC. Not sure why.
   
  The difference between my Micro Amp, E9 and Magni sure isn't very huge, but that's obvious. I still am tempted to try the O2 and compare it.
   
  I know this will annoy someone, but I do wonder if the O2 has maybe an ultra tiny touch of warmth. The Magni seems pretty cold and analytical. Well I guess they're both dead neutral/transparent.
  Some amps that are still very transparent still seem to have a little bit of warmth. I mean not enough to really change ANY headphone. My Micro Amp sounds very slightly warm compared to the Magni (and probably O2) and I thought that was impossible. It's actually less warm than my Clip+. I also never thought an amp could make my E9 sound warm.


----------



## skamp

tdockweiler said:


> I agree with that, but it's a bit annoying how people claim every headphone under say 80 ohm is going to magically be altered. The Q701 doesn't change a bit with the E9's 10 ohm output impedance.




That's not speculation on my part, I've measured it, though with a lower output impedance (5.5Ω). The variation in frequency response that I will witness with my IEMs as output impedance grows, is a boost in the high frequencies. Also, there's nothing magical about it, it's just basic physics. It might or might not be annoying, given that there's little content past 10 kHz or so. But what if I buy new IEMs later on, and their impedance varies in a region that's more problematic, like in the mids? I would _hate_ overemphasized mids.

Also, the 10Ω impedance is on the 1/4" jack, which would require the use of an adapter for no good reason. The 1/8" jack's impedance is 43Ω!


----------



## tdockweiler

Quote: 





skamp said:


> That's not speculation on my part, I've measured it, though with a lower output impedance (5.5Ω). The variation in frequency response that I will witness with my IEMs as output impedance grows, is a boost in the high frequencies.
> 
> Also, the 10Ω impedance is on the 1/4" jack, which would require the use of an adapter for no good reason. The 1/8" jack's impedance is 43Ω!


 
   
  Oh I know..I totally wouldn't use an IEM with it I think. It's just that i've yet to have anything not work well with the E9. I guess i'm lucky.
   
  I get super annoyed when people seem to think like the Q701 is TERRIBLE with the E9 without trying it, when it fact it's VERY good.
   
  The E9 is still a steal for $88..yeah the Magni (or O2) is technically better. If I had to pick between the Magni and E9 for just the Q701..I don't know what i'd pick. The E9 does sound a bit more colored and "musical". Ugh..am I calling the E9 musical?
   
  For some reason I find the 1/8" jack to sound a bit worse and not just due to the 43 ohm output. Probably hearing things. Seems like I get a reduced soundstage(!) and a warmer sound.
  Why is it that when a headphone gets warmer, my soundstage shrinks? 
	

	
	
		
		

		
		
	


	




 Stupid brain tricking me!
   
  BTW I tried my 36ohm KRKs with my 330 ohm output impedance receiver..now THAT was amusing. It sounded almost cave like. Totally ruined it. My DJ100, HD-650 and Q701 were fine though


----------



## adydula

The E9 with a 10 ohm output will degrade the sound with some headphones.
   
  Cans having a high impedace greater than 80 ohms are the best to use with it.....
   
  Other than that nwavguy has done a review of this amp and gave it a very good writeup....
   
  Wait...wasnt this an JDS O2 Black edition O2/ODAC discussion???
   
  Alex


----------



## tdockweiler

Quote: 





> Originally Posted by *adydula* /img/forum/go_quote.gif
> 
> Wait...wasnt this an JDS O2 Black edition O2/ODAC discussion???
> 
> Alex


 
   
  Nothing wrong with comparing the O2/ODAC to other amps..
   
  Maybe the O2 isn't the world's most transparent amp after all.
   
  It's the E9!!! 
	

	
	
		
		

		
		
	


	



   
  I still need to get the O2 to compare to the Magni. Maybe the Magni is really not as good as the O2 (to my ears).


----------



## miceblue

Quote: 





adydula said:


> The E9 with a 10 ohm output will degrade the sound with some headphones.
> 
> Cans having a high impedace greater than 80 ohms are the best to use with it.....
> 
> ...


 
  Isn't the general rule of thumb to have a load/headphone impedance at least 8 times that of the source's output impedance?
  If so, does that still apply to every-day earphones with a typical impedance rating of 16 ohms? And if yes, from what I recall, iPods tend to have a high output impedance (something like ~7 ohms), wouldn't the earphones be....not optimal-sounding (I don't know what happens when the output/source impedance ratio is less than 8)?


----------



## xnor

Quote: 





tdockweiler said:


> Nothing wrong with comparing the O2/ODAC to other amps..
> 
> Maybe the O2 isn't the world's most transparent amp after all.
> 
> ...


 
  NwAv also 'reviewed' the E9, but I guess you already knew that. It can output more power into low impedance headphones (I guess no or higher current limit), has a higher noise floor, and well the higher output impedance.
   
  You can always increase the output impedance by adding a resistor in series with each headphone driver. On the O2 you can also replace the output resistors (2x 1 ohm in parallel = 0.5 ohm output impedance) to pretty much any higher value you like.


----------



## xnor

Quote: 





miceblue said:


> Isn't the general rule of thumb to have a load/headphone impedance at least 8 times that of the source's output impedance?
> If so, does that still apply to every-day earphones with a typical impedance rating of 16 ohms? And if yes, from what I recall, iPods tend to have a high output impedance (something like ~7 ohms), wouldn't the earphones be....not optimal-sounding (I don't know what happens when the output/source impedance ratio is less than 8)?


 
  If it's a dynamic driver the bass will become a bit looser/boosted. If it's a multi-driver IEM with crossovers you have to look at the impedance curve to see what happens. Could be anything from bass to treble boosts. But we're talking small differences here.


----------



## Satellite_6

Wow the new version looks stunning, I just missed it unfortunately. :| I am very much enjoying my boring silver one tho. 
   
  Some additional stuff I wanted to say after reading the thread, not very organized: 
   
  It was in fact designed as a portable amp.
   
  The HD 650's sound great out of the O2. They are smooth an muscial and the O2 doesn't add anything to that obviously.
  No "synergy" is necessary to get the most out of them.
  Calling them inaccurate and veiled is ********. Do not claim everything is subjective and then say they are inaccurate crap. 
  For that you would have to break out frequency plots and a lot worse looking ones than the HD 650's exist for sure. 
  Not everyone likes their sound signature and that's fine. . . 
   
  The LCD-2's are not that hard to drive so the O2 can surely dive it "to its full potential in the bass department."
   
  You should not use the high gain mode with the ODAC, so 2.5X is probably a better idea than only 1X just in case. i.e. 1X would be marginal to get the HD 650's very loud.
   
  Oh god it's that cable guy. No comment.


----------



## tdockweiler

Quote: 





satellite_6 said:


> Oh god it's that cable guy. No comment.


 
   
  Are you referring to me? Please don't tell me I hurt your feelings because I actually have an opinion about cables that's different from yours.
   
   
  I must be really stupid for buying $5 Monoprice snake oil! What was I thinking...I knew I should have went to the dollar store danggit.
   
  If synergy wasn't important you could buy any crappy mis-matched amp and dac and be done with it. The HD-650 sounded awful with the wrong DAC IMO.
  Yes, transparent gear seems to be best for it. I haven't heard the veil yet on this HD-650. I've been through 3 amps just for the HD-650 and Q701. This was before the O2/Magni though.
   
  As much as I love the HD-650 I don't find it dead accurate. Fairly accurate but they make everything sound good. I won't say they dramatically change my music, but it's very obvious everything sounds a bit too good.
  This is with the Magni+ODAC. This is not news to anyone..


----------



## miceblue

This is probably going to end up sounding like a really dumb question, but does the DAC really make a difference in sound quality? I only have 1 dedicated DAC (ODAC) and it doesn't sound significantly better than my on-board computer DAC to me. The amp certainly makes a much larger difference to my ears. It's not what an audiophile would consider "good", but aren't most DAC's these days actually pretty decent in terms of audible differences, not measurements? My iPod Video has pretty good sound quality compared to the 2nd gen iPod Touch, but I don't know if that's due to the DAC (Wolfson vs Cirrus) or if it's due to the amp....I should really get one of those LOD's in the near future, shouldn't I?
   
  The whole Objective theme for Voldemort's projects is really intriguing to me. It boggles my mind how companies can charge so much for a product that doesn't even perform at its maximum potential (relating to Voldemort's process of getting the most out of the components). I mean, the most expensive part of the O2's circuit is the push switch (a whole whopping $1.60 per piece), it can't possibly take that much money to make a solid state amplifier. I was really surprised at how the O2 performed against other "bigger" and more expensive amplifiers at the last Head-Fi meet. If you can't tell by now, I think I'm pretty much set on my "journey" to find an amp. It was the quickest one yet!


----------



## tdockweiler

Quote: 





miceblue said:


> This is probably going to end up sounding like a really dumb question, but does the DAC really make a difference in sound quality? I only have 1 dedicated DAC (ODAC) and it doesn't sound significantly better than my on-board computer DAC to me. The amp certainly makes a much larger difference to my ears. It's not what an audiophile would consider "good", but aren't most DAC's these days actually pretty decent in terms of audible differences, not measurements? My iPod Video has pretty good sound quality compared to the 2nd gen iPod Touch, but I don't know if that's due to the DAC (Wolfson vs Cirrus) or if it's due to the amp....I should really get one of those LOD's in the near future, shouldn't I?


 
   
  The onboard sound you have is probably very flat and accurate. I know this sounds hard to believe, but my "crappy" Realtek HD sounds better than the Fiio E10 and a lot of other DACs. Mine is even labeled as having a headphone amplifier built in(!). This is on my MSI motherboard! Bizarre.
  Based on my experience, some of my headphones have benefited very little from DAC upgrades. It seems that my HD-650, DJ100 and Q701 have the most. My HD-598 doesn't seem to change a bit with anything. Not even my HD-600 does much as long as it's properly amped.
   
  To me the Ipod Video sounds a bit warmer than the Ipod Touch 2G. The Ipod Video 5.5 supposedly has slightly forward upper mids and rolled off low bass.
   
  The Ipod Touch 2G to my ears sounds very similar to my Magni+ODAC. Even brighter at times, which is weird.I think the Ipod Touch 2G is ruler flat, but sounds like it has sort of edgy treble.
  Despite bypassing the onboard amp, they still seem to have the same exact signature when using the LOD cable. What's interesting is that even the Ipod Docks have a DAC chip built inside of them. Not sure why..
   
  Sometimes I think this LOD cable = better sound is hogwash. I can't hear any distortion from using my Fuze's headphone out to amp. I'm sure it's there.
   
  One thing I noticed about the ODAC is that it's treble seems way smoother than 5-6 of my full sized CD players. Not sure why, but it's hard to believe all those are that much worse..
  It's not coming from my amp..my amp has no rolled off treble or anything. I highly doubt the ODAC has rolled off treble..


----------



## miceblue

Quote: 





tdockweiler said:


> Quote:
> 
> 
> 
> ...


 
  Woah, woah woah........wait a sec. The V-MODA Crossfade M-100 "sounds better" with the iPod Touch 2G versus the O2/ODAC? Colour me surprised, but the whole midrange is forward, not laid-back, on this setup. O_O
  I still like the O2/ODAC for being transparent though, no worries there because with that I actually know what the M-100's true sound is like.


----------



## skamp

miceblue said:


> iPods tend to have a high output impedance (something like ~7 ohms)




5.5Ω (iPod Classic) and less (the latest iPod Touch was measured at 0.75Ω).



miceblue said:


> I don't know what happens when the output/source impedance ratio is less than 8)?




Poor/inexistant damping, and possibly frequency response variations if the headphones' impedance varies with certain frequencies.

Sansa Clip+ (0.5Ω) with Ultimate Ears Triple-Fi 10:



iPod Classic (5.5Ω) with Ultimate Ears Triple-Fi 10:



Hifiman HM602 (11.4Ω) with Ultimate Ears Triple-Fi 10:


----------



## skamp

miceblue said:


> does the DAC really make a difference in sound quality? I only have 1 dedicated DAC (ODAC) and it doesn't sound significantly better than my on-board computer DAC to me. The amp certainly makes a much larger difference to my ears.




Indeed, onboard DACs are often able to deliver fine 16 bit performance these days. The main problem is the high output impedance of the headphone out (my laptop measures at 74Ω), which can be fixed with a decent headphone amplifier such as the O2.


----------



## ostewart

Quote: 





satellite_6 said:


> Wow the new version looks stunning, I just missed it unfortunately. :| I am very much enjoying my boring silver one tho.
> 
> Some additional stuff I wanted to say after reading the thread, not very organized:
> 
> ...


 
   
  Sorry to offend you, but i did say IMO i did not like the HD650, i dont like the sound signature of them, too warm for my taste.
   
  Also i know it was made to be portable, but because of the size, it is more transportable.
   
  And cables, yes i believe they make a difference, maybe not as big as some say, but with the Shure SE535 and my alclair reference monitors i do notice a difference between a cooper and a silver olated copper cable. Bass a little tighter but looses some body, mids gain more presence and deail, also highs are more extended. I also prefer the looks and build of my own silver cables, i use silver solder as its easier to work with too.
   
  Im not saying cables are the be all and end all, but for subtle differences, i like them. Also they dont have to be super expensive.


----------



## lorriman

ostewart said:


> Im not saying cables are the be all and end all, but for subtle differences, i like them. Also they dont have to be super expensive.




Supposedly in double blind testing no one can hear any difference. I haven't tried this myself so all I can contribute is an anecdote:

When I was a teen I tried to solder a new jack on to the end of my cheap headphones. Knowing what I know now about soldering, there's no question that I did a very bad job. The end result was appalling sound quality. I threw them away. Even the O2 designer has mentioned that poor quality banana plugs may affect sound quality. But this is a matter of defect rather than metals and solder used. Assuming there isn't an defect then except with long cable runs, there shouldn't be any difference in the audio.


----------



## lorriman

miceblue said:


> This is probably going to end up sounding like a really dumb question, but does the DAC really make a difference in sound quality? I only have 1 dedicated DAC (ODAC) and it doesn't sound significantly better than my on-board computer DAC to me. The amp certainly makes a much larger difference to my ears. It's not what an audiophile would consider "good", but aren't most DAC's these days actually pretty decent in terms of audible differences, not measurements? My iPod Video has pretty good sound quality compared to the 2nd gen iPod Touch, but I don't know if that's due to the DAC (Wolfson vs Cirrus) or if it's due to the amp....I should really get one of those LOD's in the near future, shouldn't I?




AFAIK a LOD doesn't make much difference in a good design. Perhaps a bit less crosstalk (better stereo). It should also give 2.1 V output which mean less need for high gain settings on amps, but some LODs don't. 

As for onboard DACs. I've compared (with level matching but not DBT) the ODAC/O2 against a 5 year old sigmatel implementation and also a recent Realtek using my etymotics (which are kind of reference grade phones themselves). Apart from a tiny bit of noise (and I mean really tiny), I can hear no difference. I also measured the sigmatel headphone jack and it has an output impedance of 0.5 . I was quite shocked. 

Now, perhaps there is in fact more distortion, but not such that I could consciously hear it but rather that would reduce the pleasure of the music. For that I would probably need to DBT to detect it. But my suspicion is that, as with modern speaker amplifiers, the DAC technology is mature and settled and hifi. So long as it's one of the cheap standard chipsets, you'll get as good as it gets. It's when manufacturers stray in to fancy stuff like Wolfson that I would expect issues; at the very least more noise. If the ODAC designer's reports are anything to go by, it's expensive to do a good implementation to realise the performance of a chipset. The Standard chipsets have already done that work.


----------



## ostewart

Another thing with cables, is that i make my own, i would not spend hundreds of dollars on one, when i can make myself one for less than half the price.
   
  I only use an LOD as i dont want to double amp, and also on the go i like to use an amp too.
   
  My portable rig is quite a nice size IMO, IPod classic + C421 = perfect size harmony.


----------



## antberg

Hey guys,i really need some help because i am shii-thing the pants out right now.i hope you technical guys can tell me some positive thoughts..
   
  I did received Friday my very first O2-Odac combo.I did ordered them on September ,but then my first package has been lost,then before to JDS send me another unit i had to wait for some complaining form to USPS and then another month to the new package to arrive here.well i did learn something more about patience ,hehe.
   
  So,when i received my combo i've gone to Capital city to find an adapter for the amp,but the first night i have been home with the combo i let the adapter on the 110V switch whereas my home town support 220V.Well for the first days i thought the batteries or the plug where not having a good connection because the O2 were able to work for a couple of minutes before stopping working.
   
  But then,i realize my stupidest misuse:The wrong switch on the voltage input.
  Now,i did call the manufacturer of the adapter and they told me that possibly the adapter would blew just after 30 minutes on the wrong switch input (well it has been all night plugged in ,and the amp turned on).
  My first worries were about the adapter but now i am afraid more about the amp,because they told me too that if the output voltage in my case is wrong the amp could receive more or less for about  28 volts,which i know is very high for the amp,so i hope i did not damaged my beloved and so long awaited amp.
  If this could help you,as i sad before,the amp just work for a few minutes before stopping working,due i suppose to the low charge of the batteries inside.
  I hope i have been clear as English is not my native language.
  Thank you very much guys


----------



## ostewart

Try opening and putting some normal 9v batteries in to see if its the batteries or the amp, if it works, then the amp is fine and the batteries have no charge, if it doesn't work, then maybe the amp has a problem. Before closing, put the rechargeable batteries back in, DO NOT TRY AND RECHARGE NORMAL BATTERIES, and get the right adapter.


----------



## snip3r77

The ODAC-O2 combo , anyone that is running 250ohms / 600ohms Beyer DT 880 or 990? I'm also looking at the HD700.
   
  Thanks


----------



## antberg

Thank you fella,thank you very much.I have been on the electric shop near my house and they could not help me because they had not an opened multimeter,so today on may way to work i am going to the main shop where i did brought the adapter so i can see if i can change the adapter ,and more important if i can find some normal battery to check on your advise.
  Tonight i let you know,going right now to Porto Alegre where work,before passing to the shop.I guess that's a very logical advise you told me.
  See you all later
  Antonio


----------



## ostewart

snip3r77 said:


> The ODAC-O2 combo , anyone that is running 250ohms / 600ohms Beyer DT 880 or 990? I'm also looking at the HD700.
> 
> Thanks



 
 O2 + HD700 works great, plenty of power and good sound.


----------



## snip3r77

Thanks for the prompt response. 

My odac O2 combo is set for 1x and 2.5x.

How does the gain correlates with impedance? Am I missing anything with 6.5x?

Thanks


----------



## skamp

You're missing the ability to properly amplify low power sources, such as DAPs.


----------



## ostewart

Using the ODAC too you won't be missing anything I don't think. The only problem would be if your using a weaker input like a DAP


----------



## skamp

With the ODAC, a high gain is interesting too when you're applying digital attenuation, like with Replaygain and a subtractive EQ, or simply when using digital volume control. You can easily "lose" 6-12 dB that way, which you might need with power hungry headphones.


----------



## HamilcarBarca

Quote: 





skamp said:


> With the ODAC, a high gain is interesting too when you're applying digital attenuation, like with Replaygain and a subtractive EQ, or simply when using digital volume control. You can easily "lose" 6-12 dB that way, which you might need with power hungry headphones.


 
   
  A poorly-implemented digital or analog volume control may distort the sound. This is completely independent of the ODAC.


----------



## skamp

How is this related to that? I don't know what you mean.


----------



## snip3r77

Anyone here tried it with the Beyer dt990 600ohm to specific?


----------



## antberg

Hey Random,i did purchase a pair of normal batteries and the amp is working with no problem,and i did change the adapter which now has a different plug size,and connected right away with the O2 and it's rechargeable batteries still working strong,Thank you for the responsive advise!!
  see ya all
  Antonio


----------



## miceblue

Quote: 





skamp said:


> Quote:
> 
> 
> 
> ...


 
  Oh yeah the output impedance could be a problem. Apparently my computer's output impedance is around 24 ohms.
   
   
  Quote: 





skamp said:


> Quote:
> 
> 
> 
> ...


 
  Woah jeeze that HiFiMAN output looks pretty scary with those IEMs. I'm guessing the Triple-Fi's multiple drivers and odd impedance response is partly responsible for that curve?
  I read from Voldemort's blog of the Clip+ vs iPod Touch 3G that the Clip+ has an output impedance of 1.02 ohms at 1 kHz, whereas the Touch was measured as 7 ohms.


----------



## ostewart

Quote: 





antberg said:


> Hey Random,i did purchase a pair of normal batteries and the amp is working with no problem,and i did change the adapter which now has a different plug size,and connected right away with the O2 and it's rechargeable batteries still working strong,Thank you for the responsive advise!!
> see ya all
> Antonio


 
   
  Glad it all works fine, come back with impressions when you can


----------



## skamp

miceblue said:


> I'm guessing the Triple-Fi's multiple drivers and odd impedance response is partly responsible for that curve?




Yes, it's the combination of a high output impedance and a non-flat impedance curve on the IEMs.


----------



## antberg

Well,i guess i can now share some fun (i hope) thoughts within this thread,now that everything ,or almost,is working.
   
  Like i sad before,i have been waiting something to drive properly my HD650 since September,i were more prone to listen some Rock'nRoll from my Clip Zip via HF5 rather then plug my Sennheiser directly to my old Samsung laptop..
  It has been a little bit an endurance of waiting because i wanted as much as soon to have some good sounding listening session for myself,deserved,and i have never been a person with the virtue of patience,sadly for me,more the contrary,a hyperactive and nervous cook who like to listen from Metal to Bossa Nova,from Jazz to Symphonies.
   
  A chronological marathon in trying to achieve my health trough the gym,going every sacred morning Monday to Saturday ,unwilling to put more weight to lift up.Then go back home to a quotidian dish made of unsalted and un-fatted chicken and sweet potato.It is a miracle i have now been on this routine since October,and honestly sometime i feel i start to grow feathers and clucking.
  But i can't deny i feel the positive results ,paradoxically even that i am taking this seriously i can work better and with more stamina everynight.
  A Sunday off work with some great traditional barbecue accompanied with a German Weiss bier is more than welcome,more then ever,haha!!
   

   
  Not that surprising i did had more time to listen to music on my oldye and very noisy hometown buses going and returning from work then on my computer;i have never been a long number poster on Head-Fi,and now even less.
   
  And right now i am taking advantage of my own coincidental short free time,because of what has been happening in the last few days:

 Well to start today i have been to the hospital having a liver biopsy operation routine due to my chronic pancreatic pathology (Which now is completely regular- lousy dried sponge between my stomach and spinal cord..would say Homer), so i knew i would have a day off from work because i knew,even if this is the first time,the doctor told me i could not make any physical effort -Bye work and gym,mhuahah..-and consequently some extra time to listen to AC\CD,Nile,and well,even some Jazz At The Pawnshop.Some affordable strippers maybe next week...
   
  But yesterday ,when cleaning the grill at work some dust split off right on my left eye,and quickly i realized i had suffered an injury because i was seeing quite unfocused ,even with my glasses on.So today early before the biopsy i have been on my town public opthamologist to some advise ,so i did spent from 8.30 to 12.30 to having the relieved news that i just need some optical pomade for about 10 days and my left eye vision would restore to normal (I hope,at least).Then i have been from 13.00 to 18.00 for the biopsy and one more hour to come back home feeling like shiit with a bandage on the eye and another on the right back side.So another misfortune:
   
  I had to hurt myself on the eye right now that i received my long projected collection of professional and casuals cookbook!
   

   

  I guess you can never had it all in just one time,eh?At least my palate still enough sensible...
   
  So right now what just left me is a few hours to listen to some tracks and testing my new rig capabilities.That's some awful photo to you to see how asparagus rubber feet can put firmly together  an amplifier,a DAC and their much confused cable very bad managed.
   
   

   
   

   
   
  So ,now that i have been listening to Vader-Welcome To The Morbid Reich,AC\DC-Highway To Hell,and Daft Punk-Human After All,i can see,even in those little physical conditions ,and considering i have some kind of Lead Ears ,that differences between with and without additional related audio devices are (Very ,sometimes) noticeable ,but i guess i have to gain some more hours of experiences with this technological mass produced devices to affirm for sure i can define where quantity and the quality of those achievement sound wise.
   
  One thing for sure i know,after some day-to-day adventures and coincidental obstacles ,stress testing situation and running fast time living,my ears now are happier then ever ,Angus Young
  is a demon ,always get my hearing possessed through Rock'N'Roll.
   
  Sorry guys to derail the thread enormously ,especially to the thread started!!
	

	
	
		
		

		
			





 and Happy O2-Odac to everyone.
  Best
  One-eyed Antonio


----------



## ostewart

That's one hell of a story, enjoy your listening time while you can, and get better soon mate  as melhoras


----------



## ostewart

That's one hell of a story, enjoy your listening time while you can, and get better soon mate  as melhoras


----------



## ostewart

That's one hell of a story, enjoy your listening time while you can, and get better soon mate  as melhoras


----------



## lorriman

Randomkid is in fact a vinyl record...with some groove.


----------



## antberg

hahaha  lol.


----------



## ostewart

Quote originally Posted by *lorriman* /img/forum/go_quote.gif 





> Randomkid is in fact a vinyl record...with some groove.


 
   
  Dodgy internet connection, although the groove may be real


----------



## adydula

Antonio!!
   
  German Weiss bier!!!
   
  Now were talking!!!
   
  Ayinger as well!!
   
  Alex


----------



## antberg

hahaha,beeeer...
   

   
  Anyway,i was surfing uselessly on the net when i found out some news for us head-fiers,when:
   
   

   
  so,somebody dare to guess?


----------



## antberg




----------



## antberg

....


----------



## antberg

well,i won't start a new thread cause i won't be able to follow constantly,so i will give to you a clue to ,well,we know how,around here,we use to already create Expectation-Anticipation-Pre-Appreciation threads for every products months before the supposed new device is ready to be released...
   
Fotos da Linha do tempo | Facebook
   
  enjoy it!


----------



## miceblue

Quote: 





antberg said:


> well,i won't start a new thread cause i won't be able to follow constantly,so i will give to you a clue to ,well,we know how,around here,we use to already create Expectation-Anticipation-Pre-Appreciation threads for every products months before the supposed new device is ready to be released...
> 
> Fotos da Linha do tempo | Facebook
> 
> enjoy it!


 
  asdfasdfasdf <- me being speechless
  So stoked for it. Is this a portable O2? JDS Labs said it's a "tremendous upgrade to the C421" and reviews of the C421 vs O2 say they sound similar, but not quite the same.
   
   
   
  On a more related note, is there a reason why some of the amplifiers don't have a feedback system? I'm taking a systems engineering course and so far it seems to be a universal agreement that negative feedback is really good in a system since it "improves fidelity of the output signal" and "resists internal and external changes via a buffering mechanism (in this case it's the op-amp I think)". Op-amps usually amplify the difference between the inputs, so if there's no negative feedback, wouldn't small errors be larger than if there was a feedback system?
   
  ^or maybe I should post this in the sound science forums


----------



## adydula

How about a C5 from JDS?
   
  Alex


----------



## adydula

You know that this wll immediately be compared to the O2....so lets make sure we are talking apples to apples etc....
   
  Alex


----------



## lorriman

miceblue said:


> asdfasdfasdf <- me being speechless
> So stoked for it. Is this a portable O2? JDS Labs said it's a "tremendous upgrade to the C421" and reviews of the C421 vs O2 say they sound similar, but not quite the same.




As I remember (and I don't remember so well these days), the C421 was designed before the O2. He mentions that the C5 'measures well'; so I would suspect that this isn't the O2 since its designer had very strict conditions for re-implementation that I suspect the C5's small case make impossible, but has been designed in the spirit of the O2 with a proper audio measurement device. That being true, then the C5 could be a serious portable amp. 

But we need a lot more details.


----------



## xnor

Quote: 





miceblue said:


> On a more related note, is there a reason why some of the amplifiers don't have a feedback system?


 
  Because of irrational fear or failure to use it correctly. If done wrong it can lead to instability.
   
  Feedback = good, unless you start with a bad circuit to begin with.


----------



## antberg

adydula said:


> How about a C5 from JDS?
> 
> Alex


 
  Well you got it!
   Quote:
   


lorriman said:


> As I remember (and I don't remember so well these days), the C421 was designed before the O2. He mentions that the C5 'measures well'; so I would suspect that this isn't the O2 since its designer had very strict conditions for re-implementation that I suspect the C5's small case make impossible, but has been designed in the spirit of the O2 with a proper audio measurement device. That being true, then the C5 could be a serious portable amp.
> 
> But we need a lot more details.


 
  You got that right,their origin and purposes are clearly different,but i guess both devices have in common the will to be as much as transparent as any amp should be,as they are as a matter of fact especially when measured with proper testing devices.
  I am in the process of saving money to buy a C421,but right now i am gonna wait to see how the C5 plot will develop.
  Quote: 





miceblue said:


> asdfasdfasdf <- me being speechless
> So stoked for it. Is this a portable O2? JDS Labs said it's a "tremendous upgrade to the C421" and reviews of the C421 vs O2 say they sound similar, but not quite the same.
> 
> 
> ...


 
  To my personal very little experience in electric language,you are speaking prehistoric mandarin ,
	

	
	
		
		

		
		
	


	




.
  Anyway ,if it would depending on me,you could still talking about sound science right here ,i always end up learning something new.


----------



## HamilcarBarca

Quote: 





> Originally Posted by *miceblue* /img/forum/go_quote.gif
> 
> On a more related note, is there a reason why some of the amplifiers don't have a feedback system? I'm taking a systems engineering course [...]


 
   
  It's a marketing gimmick. Science and engineering are irrelevant.


----------



## mikeaj

It's become some kind of mark of quality to not "cheat" like that.  Though mostly we're talking about global feedback.  You generally can't run these components completely open loop with zero local feedback of any kind and get a usable product; gains would be too high, for starters.
   
  In a related manner, there is some kind of ambivalence, particularly among the old guard, about prepackaged ICs that do all sorts of jobs very well nowadays.  "Kids these days can't design these things from scratch" and so on.  It's maybe more interesting or rewarding to do things the hard way or alternate way sometimes, and this is feasible when selling audio products with higher than razor-thin penny-pinching margins.  Their hands aren't really forced with regards to design decisions to be competitive, outside of maybe the lower-margin stuff like some receivers and some pro audio gear.


----------



## HeatFan12

Linking the OPs thread to another one of his..lol
   
http://www.head-fi.org/t/647838/new-jds-labs-c5-portable-amplifier
   
   
  I'm enjoying my O2 in the meantime.  Received my WAU16-1000 so all is well.


----------



## miceblue

Quote: 





hamilcarbarca said:


> Quote:
> 
> 
> 
> ...


 
  Eh...okay? 
	

	
	
		
		

		
		
	


	



   
  Many biological systems use negative feedback to regulate/maintain processes...
   
   
   
   
  Quote: 





mikeaj said:


> It's become some kind of mark of quality to not "cheat" like that.  Though mostly we're talking about global feedback.  You generally can't run these components completely open loop with zero local feedback of any kind and get a usable product; gains would be too high, for starters.
> 
> In a related manner, there is some kind of ambivalence, particularly among the old guard, about prepackaged ICs that do all sorts of jobs very well nowadays.  "Kids these days can't design these things from scratch" and so on.  It's maybe more interesting or rewarding to do things the hard way or alternate way sometimes, and this is feasible when selling audio products with higher than razor-thin penny-pinching margins.  Their hands aren't really forced with regards to design decisions to be competitive, outside of maybe the lower-margin stuff like some receivers and some pro audio gear.


 
  So zero feedback amplifiers are more prestigious/of higher quality?


----------



## ostewart

I should be getting the C5 to review, I heard about the C5 a few weeks ago from John, but was sworn to secrecy. It looks really good so far, and may replace my faithful C421 as my portable amp. It will be interesting to compare the C5 vs C421 with maybe a little comparison to O2 if worthy, as O2 is more desktop, C5 looks really portable and small. Volume control looks good though. Can't wait for it to come out, and wait for my review on it


----------



## adydula

John did reply to my email query but I wont post what he said....it looks like this will be a really nice amp...always room for another toy!!
   
  I just got a new Internet Ready AVR....and am listening to Pandora via its headphone jack and the LCD2's really nice...and it plays USB 1.5 TB drive ...flacs!!
   
  Technology never sleeps..
   
  Alex


----------



## wolfetan44

Quote: 





ostewart said:


> I should be getting the C5 to review, I heard about the C5 a few weeks ago from John, but was sworn to secrecy. It looks really good so far, and may replace my faithful C421 as my portable amp. It will be interesting to compare the C5 vs C421 with maybe a little comparison to O2 if worthy, as O2 is more desktop, C5 looks really portable and small. Volume control looks good though. Can't wait for it to come out, and wait for my review on it


 
  How much money will they be?


----------



## miceblue

Quote: 





wolfetan44 said:


> Quote:
> 
> 
> 
> ...


 
  It's probably top-secret information/not to be leaked to the general public until it gets posted on JDS Lab's website.


----------



## HeatFan12

Alex, where ya at?  Some pics sir.  How about some O2 & LCD love....?
   
  If I post another pic in this thread I think randomkid will kick me out...lol...On the other hand, this hobby is supposed to be fun...We gotta enjoy it to give us a break from everything else....
	

	
	
		
		

		
			




   
  Last pic...
	

	
	
		
		

		
		
	


	




..........Setting her up now.....Since I received the WAU16-1000, the O2 can finally rest in its spot with her siblings.
   
  Good times!!!


----------



## wolfetan44

Quote: 





heatfan12 said:


> Alex, where ya at?  Some pics sir.  How about some O2 & LCD love....?
> 
> If I post another pic in this thread I think randomkid will kick me out...lol...On the other hand, this hobby is supposed to be fun...We gotta enjoy it to give us a break from everything else....
> 
> ...


 
  What headphones ya using with your O2?


----------



## HeatFan12

Quote: 





wolfetan44 said:


> What headphones ya using with your O2?


 
   
   
   
  Hey wolfetan44,
   
  I have given it some love so far with some Ultrasones (PRO750, HFI-2200), Denon D5000s and briefly with Grados RS-2.  Now that I set her up in her final destination, some more head time indeed with others.
   
  Cheers!!!


----------



## wolfetan44

heatfan12 said:


> wolfetan44 said:
> 
> 
> > What headphones ya using with your O2?
> ...


Nice cans!


----------



## adydula

heatfan12...
   
  Hello.....
   
  I am in Raleigh , NC.
   
  Cold and Icy here today!!
   
  Pix!!! Ok I will work on that I have posted quite a few pix of the O2 DIY I did and the ODAC in my homebrew case....somewhere on this site!! LOL.
   
  Need to get the camera out...stay tuned!
   
  Alex


----------



## adydula

Found this one..


----------



## adydula

Another...this has my 2 o2's one with an internal odac and the other using an external ODAC.
  The grey box it my HRT MSii+ Asynchronous USB DAC. LCDs on the right, Grados on the left..
  Lime green AKS Q701's didnt make the pix!!


----------



## ostewart

Heatfan nice setup and cans, Alex cool pics, keep em coming folks


----------



## HeatFan12

Quote: 





wolfetan44 said:


> Nice cans!


 
   
  Quote: 





ostewart said:


> Heatfan nice setup and cans, Alex cool pics, keep em coming folks


 
   
  Quote: 





adydula said:


> Another...this has my 2 o2's one with an internal odac and the other using an external ODAC.
> The grey box it my HRT MSii+ Asynchronous USB DAC. LCDs on the right, Grados on the left..
> Lime green AKS Q701's didnt make the pix!!


 
   
   
  Thanks guys!  
	

	
	
		
		

		
		
	


	



   
   
  Now Alex, that's what I'm talking about...Pics always speak for themselves and give members different outlooks, possibilities and ideas for future or present audio chains.  Awesome pics and gear...Outstanding.....Cheers!!
   
   
  Raleigh, NC....Lived there a couple years in the mid '90s...Off Millbrook and close to Six Forks, IIRC...Almost purchased a home out in Knightdale...Never got used to the ice..lol...but a beautiful and great place to live...


----------



## mikeaj

If pictures are the name of the game now, these are not from JDSLabs, but seems appropriate.
   
  Some combination of the way the lighting is set up in the room normally (most of it behind computer monitors), my lack of camera skills, cell phone camera, and black color make the quality lower than it could be, so my apologies...
   
   

   
   

   
   
  Amp is on, just with the LED taped up so the light doesn't get out.  I use relatively thick rubber stick-on feet meant for desktop computer cases, which does a reasonable job for stopping sliding and also elevating the controls so they are more convenient to reach.


----------



## JakeJack_2008

Congrats RandomKid,
   
  for a very nice review and pics. 
   
  How is [size=x-small]*Cristiano Ronaldo* ​[/size] doing in Real Madrid?
   
  Now offtopic:
  Can  JDS Labs install a 1/4" headphone jack (instead of the 1/8" jack)?
   
   
  I am going to order the O2 and ODAC as two separates within a few days.
  I want to use them with my brand new Toshiba Satellite laptop and the DT 880 (250 Ohm, 2005 edition).
  Has anyone tried the DT 880 with the O2 (and ODAC)?


----------



## atomix

Quote: 





jakejack_2008 said:


> Congrats RandomKid,
> 
> for a very nice review and pics.
> 
> ...


 
   
  Used the O2 to power my DT880 600 Ohms for a few months.  This seems to be a bit of an uncommon combination, but the O2 did a great job.  The DT880's strengths really shone through with the O2 -- great control, detail, and soundstage.  But the O2 also shows the DT880s slightly recessed midrange, which had me try a Bottlehead Crack -- which I will probably stick with.  If you're interested in it...it's JDS stuffed with a 1/4" output and RCA ins let me know, I won't troll it anymore here.


----------



## antberg

Quote: 





jakejack_2008 said:


> How is [size=x-small]*Cristiano Ronaldo* ​[/size] doing in Real Madrid?


 
  Playing as some of the best soccer player at the moment....
  But living under the shadow of the Messi era.hehe


----------



## chewynuts

Does anyone know of a builder (either a member here on head-fi or commercial company) other than JDS Lab that will build a O2+ODac Amp to my specifications?
  Specifically I want RCA inputs and AC input to be behind, a 1/4" headphone jack to be in front, a higher quality volume control, and a souped up PSU.


----------



## MannerPylon

Audio Poutine in Markham, Ontario, Canada does custom desktop O2's though I'm not sure if he does exactly all of those particular customizations. You can reach him through the Audio Poutine facebook page.
   
  In terms of head-fi builders, you could ask MisterX if he's up for it. He does really good work.


----------



## ostewart

Not a fan of football, so I wouldn't know anything about Ronaldo.

Also I think JDS only offer it with 1/8 jack


----------



## ostewart

Not a fan of football, so I wouldn't know anything about Ronaldo.

Also I think JDS only offer it with 1/8 jack


----------



## shinex64

jakejack_2008 said:


> Congrats RandomKid,
> 
> for a very nice review and pics.
> 
> ...


 
   
  He sucks camel d_cks, FCB all the way!
   
   - Sorry for the OT


----------



## RustA

Quote: 





chewynuts said:


> Does anyone know of a builder (either a member here on head-fi or commercial company) other than JDS Lab that will build a O2+ODac Amp to my specifications?
> Specifically I want RCA inputs and AC input to be behind, a 1/4" headphone jack to be in front, a higher quality volume control, and a souped up PSU.


 
   
  Mayflower electronics... I have two different O2+ODAC combos, both built specifically to my needs. However, do not expect that he can do EVERYTHING, like optional positioning of inputs/outputs or so since this is limited by the original design as well.


----------



## JakeJack_2008

I want a 1/4" headphone jack  for my DT 880 cans, badly.
  Besides the 1/4" headphone jack is much more sturdier than the other one.
  I'll ask the JDS Labs about it.
  (I'd rather go with _well known _manufacturers because there's so much dishonesty on the Internet.)


----------



## adydula

I use these:
   
http://www.amazon.com/Hosa-MHE100-5-Headphone-Adapter-Extension/dp/B000068O6B/ref=sr_1_1?ie=UTF8&qid=1359747532&sr=8-1&keywords=1%2F4+to+3.5mm+extension
   
  JDS Labs is a good place to get an O2 and ODAC from.....great customer service.
   
  Alex


----------



## adamlr

Quote: 





adydula said:


> I use these:
> 
> http://www.amazon.com/Hosa-MHE100-5-Headphone-Adapter-Extension/dp/B000068O6B/ref=sr_1_1?ie=UTF8&qid=1359747532&sr=8-1&keywords=1%2F4+to+3.5mm+extension
> 
> ...


 

 seconded. iv sent them several emails and john was very helpful, informative and patient each time =]


----------



## ostewart

Well be getting ODAC soon 

I see the C5 is getting a lot of attention, portable O2 pretty much, will be comparing C5 to C421 and O2


----------



## MrMateoHead

Quote: 





ostewart said:


> Well be getting ODAC soon
> 
> I see the C5 is getting a lot of attention, portable O2 pretty much, will be comparing C5 to C421 and O2


 

 Look forward to the review! From what I can tell, the C5 has some nice features, but it less powerful and more expensive than the O2. Not that I have needed so much power . . . yet!


----------



## jeffphus

Just got the O2 two days ago.  Have it paired with VModa M80s.  Sourcing from iPhone with LOD Cable Jive.  
  This is easily the best sound I have obtained since I started with this sound path last year. 
   
  As soon as I can figure out how to post a profile I will post more details.


----------



## disastermouse

Quote: 





thekillerpiglet said:


> Source from laptop is HRT MS II, FLAC, JRiver WSAPI Event, no DSP.
> 
> KP


 
  How is this not sucking?  I have an HRT MSii+ and everyone's been telling me it's a major source of my problems with the O2.  How are you avoiding getting a totally anemic sound and clipping on high gain?  Even the E9 blows away the O2 with my similar setup.


----------



## xnor

Why would you need high gain with those headphones and such a hot source? ... just don't set the gain above x3.


----------



## disastermouse

xnor said:


> Why would you need high gain with those headphones and such a hot source? ... just don't set the gain above x3.



To power HE-500, low gain is not loud enough. The anemic sound does alright by my HD650 (since they're warm anyway) but my 'Schiity' Magni works better with both.

I'm just having a really hard time reconciling my terrible experience with this amp with all the high praise it's getting in this thread. I will try the higher power wall wart, but the Magni is several levels of magnitude better in pretty much every aspect.

Maybe some folks just LIKE a thin sound?


----------



## disastermouse

xnor said:


> Why would you need high gain with those headphones and such a hot source? ... just don't set the gain above x3.



To power HE-500, low gain is not loud enough. The anemic sound does alright by my HD650 (since they're warm anyway) but my 'Schiity' Magni works better with both.

I'm just having a really hard time reconciling my terrible experience with this amp with all the high praise it's getting in this thread. I will try the higher power wall wart, but the Magni is several levels of magnitude better in pretty much every aspect.

Maybe some folks just LIKE a thin sound?


----------



## xnor

What's your low gain, 2.5x? Maybe you should reconsider your listening level, which seems to be quite high. The sensitivity difference between HD650 and HE-500 is less than 4 dB.
   
  You also seem to be confusing thin sound with accurate sound. And no, the magni is far from being better in every aspect. EMI, noise, fixed (imo too high) gain ...


----------



## disastermouse

Quote: 





xnor said:


> What's your low gain, 2.5x? Maybe you should reconsider your listening level, which seems to be quite high. The sensitivity difference between HD650 and HE-500 is less than 4 dB.
> 
> You also seem to be confusing thin sound with accurate sound. And no, the magni is far from being better in every aspect. EMI, noise, fixed (imo too high) gain ...


 
  Accurate in what way?  Acoustic music sounds more like I'm 'there' with the Magni than the O2 - at least on the HE-500.  Are we saying accurate to transducer or accurate to the music or both or neither?  I have my Magni right near my computer (it's just the most convenient place to put it with my set-up) and the noise floor sounds totally black to me.  
   
  Also, I know I seem like a pest, but I really _want_ to get the O2 to work.  I hate being so underwhelmed by a product (although I shut up the ZO2 in a drawer to avoid looking at it and have given up on it with any headphone or IEM I own)!


----------



## miceblue

Quote: 





disastermouse said:


> Quote:
> 
> 
> 
> ...


 
  Probably accuracy of the signal coming out of the amp. If you add something to signal, the sound you hear is less accurate from its original source despite it sounding subjectively better. This can be called synergy in some cases as some coloured amps might "sound good" with a headphone.


----------



## Shazb0t

Disastermouse you are the worst. If you refuse to get a standard input voltage dac or a different wall wart then sell your o2 and stop posting about it.


----------



## disastermouse

shazb0t said:


> Disastermouse you are the worst. If you refuse to get a standard input voltage dac or a different wall wart then sell your o2 and stop posting about it.



I don't think I'll do that. I do have an E7. Should I try that with the O2 or is it a non-standard voltage DAC?

Even if I can get it to sound good with the HD650s, I'd consider it a victory.


----------



## xnor

Again, just use a gain less than or equal to 3x (with a 2.25 V source) or 3.5x (with a 2 V source) and turn up the volume control.
  You should be able to turn up the volume to about 2 o'clock. Oh and btw, lowest possible gain that does the job is usually best.


----------



## Shazb0t

The E7 is an amp/dac..


----------



## disastermouse

shazb0t said:


> The E7 is an amp/dac..



Right. I spaced that because shortly after I got it I used it with the E9 solely as a DAC.


----------



## Shazb0t

You obviously like Schiit. Get the Modi for your Schiit stack and try it with the o2.


----------



## miceblue

Quote: 





shazb0t said:


> You obviously like Schiit. Get the Modi for your Schiit stack and try it with the o2.


 
  Hey hey now, no need to get into a flame war.


----------



## disastermouse

shazb0t said:


> You obviously like Schiit. Get the Modi for your Schiit stack and try it with the o2.



I have thought about that but aside from a nonstandard power output I don't know if the Modi is better than the MSii+ or not.

Magni is the only Schiit product I have and as much as I like it I can't speak to anything else the company makes.


----------



## Shazb0t

disastermouse:
   
  http://www.mouser.com/ProductDetail/Triad-Magnetics/WAU16-400/?qs=IW9Tsl75qsVPD8fyORcCjg==
   
  DO IT!


----------



## ostewart

Well that escalated quickly.

My bet is the MSII is your problem, to high an output into the O2, get the ODAC, or you need to lower the source volume.


----------



## disastermouse

ostewart said:


> Well that escalated quickly.
> 
> My bet is the MSII is your problem, to high an output into the O2, get the ODAC, or you need to lower the source volume.




I did lower the source volume but I think I need the wall wart improvement. It's thin sound combined with clipping that was problematic. If the wall wart takes care of the clipping and I run it with the HD650 -which demands less power and has been demonstrated to work with the O2 - I should get better results, shouldn't I? Even with a hot source.


----------



## disastermouse

ostewart said:


> Well that escalated quickly.
> 
> My bet is the MSII is your problem, to high an output into the O2, get the ODAC, or you need to lower the source volume.




I did lower the source volume but I think I need the wall wart improvement. It's thin sound combined with clipping that was problematic. If the wall wart takes care of the clipping and I run it with the HD650 -which demands less power and has been demonstrated to work with the O2 - I should get better results, shouldn't I? Even with a hot source.


----------



## ostewart

Yes power supply could be the problem, not getting enough power, I used the O2 with HE-6 fine but from a iPod line out


----------



## disastermouse

Quote: 





ostewart said:


> Yes power supply could be the problem, not getting enough power, I used the O2 with HE-6 fine but from a iPod line out


 
  Powering an HE-6 with an O2 strains credibility seeing as these are legendarily demanding headphones.  I guess I'd have to hear your set-up.  I guess stranger things have happened.  I read you using the HE-6 with the O2 earlier in the thread and figured you must have mis-typed.


----------



## xnor

Quote: 





disastermouse said:


> Powering an HE-6 with an O2 strains credibility seeing as these are legendarily demanding headphones.


 
  Why? Planar magnetics are almost purely resistive. The only difference with the HE-6 is the low sensitivity / inefficiency.
  You won't be able to blow your brains out with an O2..


----------



## adydula

The O2 will power the 500's aplumb.
   
  From: http://www.techpowerup.com/reviews/JDSLabs/O2_ODAC/3.html
   
  The test unit JDSLabs so kindly sent to us was setup with the stock gain of 2.5x and 6.5x, which should fit both low and [size=100%]high efficiency[/size] headphones. If you plan on using it solely with in-ears, you might want to set the gain set to 1x and 2.5x. To put it into perspective: this little amp has more than enough power to get the HiFiMAN HE-500s singing at 2.5x gain, and even the notoriously hard to drive HE-6s had plenty of volume available on the 2.5x gain setting.
   
  There are tons of posts from people using the 500's and the O2 and working very well.
   
  I use (2) Odacs and a MSii+....I cant tell the difference between the 2 except for the 2.25 volts out of the MSii+....both awesome dacs and work well.
   
  Remember this is a "low cost DIY" amp  that was designed to prove a point....that great performance and neutrality does not have to come at great cost....
   
  If you honestly dont like it fine....then move on to other amps  and dacs to your "objective" liking...
   
  all the best
  Alex


----------



## Dark Helmet

I just got my O2.  Absolutely killer!  I also have a C&C BH and as good as that amp sounds it just can't squeeze the sound out of my DT770 Pro's.  It will drive them fine, but the O2 just gives it that special sound.  Before getting the O2 I was going to get rid of the 770's.  Not now!


----------



## adydula

Isnt it nice to have a totally transparent neutral device that can finally allow you to hear what your cans really "sound" like.
   
  Alex


----------



## ostewart

I enjoy reading about more happy owners of the O2, it's still my reference amp, and nothing's beaten it yet!


----------



## adydula

random...
   
  "ditto'..
   
  Alex


----------



## leadbythemelody

Gonna get these soon! Gonna pair em' with my Sennheiser HD650's, hell yea!


----------



## wolfetan44

Quote: 





leadbythemelody said:


> Gonna get these soon! Gonna pair em' with my Sennheiser HD650's, hell yea!


 
  Just like me


----------



## leadbythemelody

How is it?


----------



## wolfetan44

Quote: 





leadbythemelody said:


> How is it?


 
Amazing.


----------



## ostewart

Nice pics!


----------



## wolfetan44

Quote: 





ostewart said:


> Nice pics!


 
  Thanks!


----------



## leadbythemelody

Nicee...


----------



## wolfetan44

Quote: 





leadbythemelody said:


> Nicee...


 
  ? Would you like a better description?


----------



## leadbythemelody

Sure!


----------



## wolfetan44

Quote: 





leadbythemelody said:


> Sure!


 
  So what was the rolling of the eyes for? 
   
  Anyways, the O2 drives them at 25%, so power is very, very good. The O2 is very powerful for how small it is. The O2 with the HD650 is great, wish it were a bit warmer though, as I feel it would make the HD650 more romantic, which is what I love about the HD650. The O2 is a bit cold, but is still an amazing, cheap amp. At all costs, if you can get a tube amp, get one.


----------



## xnor

Just make a simple adapter to raise the output impedance. Total cost around 5 bucks and should add warmth, or just use an EQ for more flexibility.


----------



## leadbythemelody

I wasn't rolling my eyes but looking up and daydreaming 
	

	
	
		
		

		
		
	


	




 haha. My O2 and Sennheiser HD650's are gonna arrive around next week, can't wait! But what do you mean by the O2 sounding cold? Does the HD650's sound cold as a result of pairing it to the 02 amp?


----------



## leadbythemelody

Will using a Copper LOD also add warmth to the sound?


----------



## xnor

No.
   
  The HD650 is 'warm' to begin with so you should be fine. Otherwise try #307.


----------



## leadbythemelody

Okay appreciate the advice!


----------



## wolfetan44

Quote: 





xnor said:


> Just make a simple adapter to raise the output impedance. Total cost around 5 bucks and should add warmth, or just use an EQ for more flexibility.


 
  Not sure I'm so qualified..


----------



## JakeJack_2008

Quote: 





ostewart said:


> I enjoy reading about more happy owners of the O2, it's still my reference amp, and nothing's beaten it yet!


 
  Yes, count me in. I am super 
	

	
	
		
		

		
		
	


	




 happy with my *silver *





 JDS Labs  O2 and ODAC as two separates & the DT 880 (250 Ohm).
   
  By the way, is it worth to upgrade the stock FiiO line-out/line-in cable which connects the ODAC and  O2?
  I'd be willing to pay under $30 *if *I can hear a noticeable improvement in sound.


----------



## skamp

jakejack_2008 said:


> By the way, is it worth to upgrade the stock FiiO line-out/line-in cable which connects the ODAC and  O2?




Not even a little bit (as far as sound quality is concerned).


----------



## JakeJack_2008

Quote: 





skamp said:


> Not even a little bit (as far as sound quality is concerned).


 
  Thanx.
   
   
  Apropos the USB cable _with a bead  _which JDS Labs supplied with the ODAC.
   
   
  I've read on this site that the quality of USB cables matters and here's why.
  The *timing *when sending those digital files (0s and 1s) is _critical _and _matters._
  Then another expert said: a DAC working in an asynchronous mode using _buffers_, etc.
  ensures perfect _timing _and cheap stock USB cables are enough.
  Then yet another expert said: those buffers are _not _perfect, etc.  ..
  ... And then I've stopped reading because I was very confused.
   
  Now, the ODAC is _not _an asynchronous DAC.
  So, to ensure a perfect *timing *while sending those 0s and 1s _perhaps _the ODAC might _benefit _





 from
_better _and _more expensive _





USB cables?


----------



## skamp

No. Nein. Nej. Niet. Non.


----------



## xnor

Adaptive DACs also have a buffer, just smaller. Instead of using their own clock they _derive _the clock based on _multiple _received frames. Plus you're probably just streaming 2 channel audio which doesn't need much bandwidth. Cheap cables can easily handle 30 times higher bandwidth. Don't waste your money.


----------



## leadbythemelody

Hey guys, any suggestions for warm sounding amps that are below $200?


----------



## DemonFox

leadbythemelody said:


> Hey guys, any suggestions for warm sounding amps that are below $200?




I'm sure there are others but from personal experience the Hifiman EF2A is very warm and stupid powerful! It also has a built in DAC but I wouldn't really use it because its not very good. The Amp on the other hand is pretty good for the money. You could also find a used Headstage Arrow 3G for around $200.


Thanks,


D


----------



## TheGame21x

Quote: 





leadbythemelody said:


> Hey guys, any suggestions for warm sounding amps that are below $200?


 

 I believe the Aune T1 is a warm sounding amp with a built in DAC that's supposed to be pretty good for under $200 on eBay.


----------



## leadbythemelody

Thank you for the recommendations! The Aune T1 looks very interesting 
	

	
	
		
		

		
			





, what are the output impedances for the T1 or the Headstage Arrow 3g?


----------



## adydula

You dont need another cable........save you $$$$$....
   
  Alex


----------



## JakeJack_2008

Thanx to all of you.
  - No need for an  _expensive _USB cable (to ensure a perfect _timing _and other blah-blah-blah's) for the *ODAC*.
  - No need for an _expensive _line-out\line-in  cable (to connect  the *ODAC *with the *O2*) either.
   
  The money I'm saving I'll use to buy a very good pair of headphones under $300.
   
   
  JJ


----------



## Ultimate Mango

Is there such a thing as an O2/ODAC that has a line out in addition to the headphone out?


----------



## leadbythemelody

Can anybody tell me what the second button does on the O2's? Just got them right now. Is it the gain switch? If so is "pressed down" low gain and "unpressed" high gain or vice versa?


----------



## HamilcarBarca

Quote: 





leadbythemelody said:


> Can anybody tell me what the second button does on the O2's? Just got them right now. Is it the gain switch? If so is "pressed down" low gain and "unpressed" high gain or vice versa?


 
   
  Yes, it's the gain switch. Pressed down is high gain on my JDS model.


----------



## xnor

The gain switch? It switches from low amplification to higher amplification, which is useful if you want to use a portable player or other weak sources (~1 V) instead of a dedicated source with ~2 V output.


----------



## leadbythemelody

Thank you so much! I was afraid to use it because I didn't know what it was..so is high gain or low gain appropriate for a 300 ohm headphone? Moreover, is high or low gain appropriate for a 32 ohm headphone?


----------



## HamilcarBarca

Quote: 





leadbythemelody said:


> Thank you so much! I was afraid to use it because I didn't know what it was..so is high gain or low gain appropriate for a 300 ohm headphone? Moreover, is high or low gain appropriate for a 32 ohm headphone?


 
   
  If the sound using the low-gain setting  is loud enough for you and you don't have to crank the O2 to full volume, use the low-gain setting. Otherwise, the high-gain setting is more appropriate. The impedance of the headphones isn't the appropriate criterion for choosing gain.
   
  Even at low gain, the O2 will go far too loud for me with 32-Ohm headphones (Grado SR325i), 250-Ohm headphones (Beyerdynamic T70), and 300-Ohm headphones (Sennheiser HD-650) -- and the 650's impedance increases to nearly 500 Ohms at some frequencies.


----------



## wolfetan44

Quote: 





hamilcarbarca said:


> Quote:
> 
> 
> 
> ...


 
  I have it low gain on my Beyer DT880-600. And its at about 35% volume


----------



## leadbythemelody

Oh okay. But wouldn't the sound of a 300 ohm headphone be different when using different gains high/low even though a low gain can produce enough volume? (sorry don't have much experience with amps).


----------



## wolfetan44

Quote: 





leadbythemelody said:


> Oh okay. But wouldn't the sound of a 300 ohm headphone be different when using different gains high/low even though a low gain can produce enough volume? (sorry don't have much experience with amps).


 
  It produces more bass right now as I'm testing it. I don't like that.


----------



## leadbythemelody

Plus, what are the proper reasons for using which gain other than impedance which is not a proper criterion?


----------



## HamilcarBarca

Quote: 





leadbythemelody said:


> Plus, what are the proper reasons for using which gain other than impedance which is not a proper criterion?


 
   
  What I wrote wasn't especially meaningful. The O2 can drive most headphones (other than the most demanding.) Most amplifiers (Class A amps being a notable exception) tend to have a higher level of distortion with (a) higher gain; or (b) their lowest and maybe highest volume settings.
   
  The most important criterion is efficiency (the ratio of "sound output" for a given "power input".) Less efficient headphones, such as 600-Ohm Beyers, the Q701 and its cousins, and isodynamic headphones, need more power. To get very loud, the HiFiMan HE-500 probably requires the high-gain setting. All of my headphones would work fine with a gain lower the the lowest default setting, 2x, to suit my taste.
   
  All this is more or less theoretical. I find the theory interesting. But there are probably other considerations which I've missed.
   
  The "bottom line" is not to worry about it. Use the low-gain or high-gain setting. Use low or high volume levels. Choose the ones which suit you. The audible difference, if there is any, should be extremely small. If you like the sound, listen to it.


----------



## leadbythemelody

Okay thank you for clearing that up for me, I think I understand now


----------



## leadbythemelody

I was considering buying an ODAC but I'm not sure...did using an ODAC paired with the O2 amp give any huge improvement to sound quality when using 128-320kpbs mp3's?


----------



## leadbythemelody

Or maybe even minute improvements?


----------



## HamilcarBarca

Quote: 





leadbythemelody said:


> I was considering buying an ODAC but I'm not sure...did using an ODAC paired with the O2 amp give any huge improvement to sound quality when using 128-320kpbs mp3's?


 
   
  DAC's and amps can't exactly improve anything. A neutral DAC and amp will produce audio signals which are exactly as good or bad as the original material. (Plus, good 320kbps MP3 files are almost always indistinguishable from the original material.)
   
  Some listeners prefer a certain sound signature. They perceive electronics which color their output as improving the sound quality. If they like it, it's an improvement. Some listeners, such as myself, aren't interested in this kind of equipment. If we don't like it, it's not an improvement.


----------



## adamlr

to the guy asking about using an O2 with 32 ohm headphones:
   
sorry, but i forgot to quote so i used big letters to attract your attention...
   
anyway, im currently using the O2 with a pair of m-100s, who have an impedance of 32 ohm and sensitivity of 103 dB @ 1kHz 1mW. using an amp for these is just overkill. my laptops sound gear is terrible, so i use an odac+o2, but let me tell you - its WAY too powerful for them, even when using unity gain. 
what you can do is lower digital volume, or get an impedance adapter like this one, which i got as an experiment and am happy to report that it works just fine, with no major alterations to the sound that my untrained ears can detect.


----------



## xnor

It depends on your headphone but these adapters with resistors will effectively raise the output impedance and can certainly change the sound signature. The ER4P to S adapter probably adds about 70 ohm (since it will turn a ~30 ohm P into a 100 ohm S model).


----------



## leadbythemelody

Hmm... that is interesting. Thank you for educating me haha.


----------



## xnor

Ime, output impedance is the main reason for people hearing differences between amps. With less than 1/8th or 1/10th, or to be on the safe side close to zero ohms, the frequency response will remain "unchanged".
  With increasing output impedance there will be peaks in the FR similar to what you see in the impedance plot of the headphone.
   
  A 30 ohm headphone with a 60 ohm impedance peak at 100 Hz would result in a +2.5 dB peak with a 30 ohm output impedance. With 60 ohm output you'll get about +3.5 dB. Basically it works like a peak filter in a parametric EQ. Increase the output impedance and you'll increase the boost.
  Some IEMs have a very weird impedance curve due to multiple crossovers, drivers .. so you could get a peak in the treble or even mids.
   
  Everyone using a headphone amp should know that but sadly many don't (from what I can tell anyway).
   
  ---
   
  As you wrote you could use digital attenuation if 1x gain is still too much. But you can also use an attenuator _between your source and amp_.


----------



## adamlr

Quote: 





xnor said:


> It depends on your headphone but these adapters with resistors will effectively raise the output impedance and can certainly change the sound signature. The ER4P to S adapter probably adds about 70 ohm (since it will turn a ~30 ohm P into a 100 ohm S model).


 
   
  Quote: 





xnor said:


> Ime, output impedance is the main reason for people hearing differences between amps. With less than 1/8th or 1/10th, or to be on the safe side close to zero ohms, the frequency response will remain "unchanged".
> With increasing output impedance there will be peaks in the FR similar to what you see in the impedance plot of the headphone.
> 
> A 30 ohm headphone with a 60 ohm impedance peak at 100 Hz would result in a +2.5 dB peak with a 30 ohm output impedance. With 60 ohm output you'll get about +3.5 dB. Basically it works like a peak filter in a parametric EQ. Increase the output impedance and you'll increase the boost.
> ...


 

 i actually got a 200 ohm one. i was under the impression that it "adds" to the headphones impedance, making my 32 ohm cans into 232 ohm cans, i guess i was wrong? i must say i really dont notice a very big difference, but the way i test for changes is i listen to something new for a while until i feel used to it, then i go back to what i had before. i find differences are more apparent to me this way than plugging something new in and seeing whats up. in a week or so ill try again without the adapter. 
   
  are you saying that bad impedance matching causes the peaks and nulls in the frequency response to become more extreme?
   
  and how would one position an attenuator between source and amp? put the same plug on the cable going from odac into o2? or is it a different kind of plug?
   
  again, this was only an experiment, im very comfortable using digital volume, i just wanted to see what would happen...


----------



## xnor

Yeah, the resistance of the adapter adds to the load impedance so for the amp it's an easier load, after all it has to provide less current. Of course the headphone will only receive a fraction of the voltage that the amp outputs and that's the crux. 1 V will split at 0.5 V if the resistor and the impedance of the headphone are 30 ohm each. But if the headphone impedance rises at 100 Hz, which it usually does with dynamic headphones, let's say to 60 ohm the 1 V will now split at 0.333 V. The headphone now gets 0.666 V instead of 0.5 V causing the peak in the FR mentioned above.
   
  From the drivers' point of view: If the diaphragm moves the driver generates voltage. If you short the driver (by having a close to zero output impedance) you will stop the diaphragm from vibrating more quickly. For the headphone it doesn't matter if the output impedance comes from resistance inside the amp, the cable, or resistors in adapters.
   
  Yes, impedance _matching _is usually a bad idea with headphones and speakers though there are exceptions. Normally you want the output impedance to be a lot smaller than the load impedance.
   
  I guess the attenuator would ideally be 1/8" to 1/8". I'm not sure such in-line attenuators are available, it would be a nice beginner DIY project though.


----------



## adamlr

Quote: 





xnor said:


> Yeah, the resistance of the adapter adds to the load impedance so for the amp it's an easier load, after all it has to provide less current. Of course the headphone will only receive a fraction of the voltage that the amp outputs and that's the crux. 1 V will split at 0.5 V if the resistor and the impedance of the headphone are 30 ohm each. But if the headphone impedance rises at 100 Hz, which it usually does with dynamic headphones, let's say to 60 ohm the 1 V will now split at 0.333 V. The headphone now gets 0.666 V instead of 0.5 V causing the peak in the FR mentioned above.
> 
> From the drivers' point of view: If the diaphragm moves the driver generates voltage. If you short the driver (by having a close to zero output impedance) you will stop the diaphragm from vibrating more quickly. For the headphone it doesn't matter if the output impedance comes from resistance inside the amp, the cable, or resistors in adapters.
> 
> ...


 

 that was a bit over my head im afraid = \
   
  what was the bottom line? load impedance = headphone impedance (in this case ofcourse) right? when using the adapter like this:
   

  do my 32 ohm headphones "become" 232 ohm headphones (assuming were measuring the same sine wave at the same set voltage and all that), or is my O2's output impedance of ~0.5 ohm "becoming" 200.5 ohm? or does it make no difference and the end result the same? i really dont notice alot of difference to the sound at all btw. again, im still getting used to it as it were, its only been a few days, and my ears arent exactly trained, but you say its usually noticeable at ~ 100 hz? if theres one thing id notice changing - its the bass. i gave a few tries with and without the adapter while listening to some bass heavy tracks and detected nothing. ok, no volume matching, but still. then again, perhaps there werent any frequencies of ~100hz recorded... meh...
   
  and is this what you meant about attenuating the input stage? would this work? im afraid to try in case i kill something electronical 
	

	
	
		
		

		
			





 (i recall reading the input jack has quite a high impedance anyway, but im still afraid of trying without consulting someone about it first.....)
   

   
  thanks for all the explanations. this is like the #20 time you have explained things to me since i signed up to head-fi, much appreciated =]


----------



## mikeaj

Load impedance = headphone impedance, yes. In this system, the load is the headphone.
   
  The system is the amp (voltage source) connected to the resistor (in the adapter) and headphones, as well as the amp's own output impedance, in series—all that for a single channel. It looks identical on the other channel.
   
  As a result, the total load from the amp's perspective is the sum of its own output impedance, any impedance from cables or adapters or whatever else, and the impedance of the headphones. So 232 ohms, around. From the headphone's point of view, it's being driven by an amp with ~200 ohms output impedance (everything else connected in series that's not the headphones itself). The voltage the headphones get is proportional to its impedance compared to the total amount: so 32 / 232 = 13.8% of whatever comes out of the amp.
   
  Yes, you could attenuate the input in the way the picture shows, but 200 ohms wouldn't be enough for that. As you said, input impedance is ~10,000 ohms, so to reduce the level in half you'd need 10,000 ohms there. And really, you'd want to reduce it by significantly more than half. There are other configurations you could do too.


----------



## adamlr

Quote: 





mikeaj said:


> Load impedance = headphone impedance, yes. In this system, the load is the headphone.
> 
> The system is the amp (voltage source) connected to the resistor (in the adapter) and headphones, as well as the amp's own output impedance, in series—all that for a single channel. It looks identical on the other channel.
> 
> ...


 

 thank you very much, your also one of the members who frequently answer my questions, and i do appreciate it very much.
   
  you know? this business has got me thinking perhaps aspiring to have the lowest output impedance from an amp is also not as calved in stone as most people make it out to be, but i wont make my final judgment for atleast another week or two. i am starting to see the irony of using an O2 together with this adapter though XD


----------



## xnor

Well you can always _increase_ the output impedance with adapters, but _not decrease_ it without significantly reducing the output level.
  So having a low output impedance amp like the O2 is a better starting point. And maybe you'll get a different headphone in the future that you prefer without the adapter.


----------



## JakeJack_2008

From my Toshiba Satellite's manual:
   
    


> *Using external speakers or headphones*
> 
> To play back sound files through external speakers or headphones:
> 
> ...


 
   
  Any comments_ in the context of _





 the Toshiba Satellite laptop?
  I think that they _assume_ that one would use a very low _impedance _IEMs or headphones or external speakers?
   
  Before I bought the ODAC and O2 from JDS Labs I was using the Sennheiser HD 595 (50 Ohm) and the sound was pretty good.
  (Obviously my Beyerdynamic DT 880 (250 Ohm) sounded very anemic and not good.)
   
  The O2 (along with the ODAC) improved the sound of both the HD 595's and _above all _the DT 880's.


----------



## xnor

My guess is that the minimal load should be 16 ohms.


----------



## adamlr

Quote: 





xnor said:


> Well you can always _increase_ the output impedance with adapters, but _not decrease_ it without significantly reducing the output level.
> So having a low output impedance amp like the O2 is a better starting point. And maybe you'll get a different headphone in the future that you prefer without the adapter.


 

 like using salt in your cooking, mum always said:"you can always add more, but you cant take it out once youve added it!" =]


----------



## xnor

Exactly.


----------



## lukEM22

random kid, 

how is this amp with the HP100's?


----------



## ostewart

I didn't have them together, but I bet they pair really well, I used a C421 with the HP100


----------



## Poetic

Im using the DX100 lineout to the O2 with the HE-500. I know ur suppose to max out the volume on the source first. Then Adjust the volume with the amp. Im trying to figure out the sweet spot for the O2 on the HE-500 I assume putting it on High Gain and setting it past 12:00?
   
   
  EDIT: I didn't make any changes to the amp section when I purchased the O2 So assume it's 2.5x when press the button in..
  Anyways the HE-500 sound cleaner on low gain and way too messed up on high gain...


----------



## mikeaj

Quote: 





poetic said:


> Im using the DX100 lineout to the O2 with the HE-500. I know ur suppose to max out the volume on the source first. Then Adjust the volume with the amp. Im trying to figure out the sweet spot for the O2 on the HE-500 I assume putting it on High Gain and setting it past 12:00?
> 
> 
> EDIT: I didn't make any changes to the amp section when I purchased the O2 So assume it's 2.5x when press the button in..
> Anyways the HE-500 sound cleaner on low gain and way too messed up on high gain...


 
   
  What's the source?
   
  The defaults (from the docs of the designer, and also how most builders including JDSLabs set it up) are 2.5x out / 6.5x pushed in.
   
  On AC power, if source RMS output level is higher than 2.8 V with the 2.5x gain, the amp will clip (no matter what the volume is set to).
  On AC power, if source RMS output level is higher than 1.08 V with the 6.5x gain, the amp will clip (no matter what the volume is set to).
   
  If it clips, expect to hear some distortion on a lot of music: any time the level gets close to 0 dBFS (max). If you have a standard Redbook ~2 V output source, that means you want to use no higher than 3.5x gain. Many audiophile sources output higher than 2 V, so you really don't want to use the 6.5x. That was set in some fantasy land where a lot of users are using their phones or other portable sources (which often have weaker, quieter outputs) to feed the amp.
   
  You'd generally be losing a usually insignificant amount of resolution by turning down the source volume a tad. Just turn it down, reconfigure the amp, or ignore the high gain.


----------



## Poetic

Quote: 





mikeaj said:


> What's the source?
> 
> The defaults (from the docs of the designer, and also how most builders including JDSLabs set it up) are 2.5x out / 6.5x pushed in.
> 
> ...


 
  Im using the IBasso DX100 Digital Audio Player, im also using the Lineout of my music player to allow the O2 act as the amp for me. I turned the O2 back on Low gain and maxed out the volume of my source. Also i wasn't maxing out the volume on my music player when i was using the lineout, but i noticed the big improvement in resolution when maxing out the source volume.
   
  EDIT But now im just trying to find out the Sweet spot on the O2 for my He-500


----------



## JakeJack_2008

Quote: 





mikeaj said:


> What's the source?
> 
> The defaults (from the docs of the designer, and also how most builders including JDSLabs set it up) are 2.5x out / 6.5x pushed in.
> 
> ...


 
   
  I am a bit confused.
  I am using the JDS Labs ODAC and O2 (which has standard 2.5x &  6.5 X gain) as two _seperates_.
  I always use the 2.5x gain with my Beyerdynamics *DT 880 (250 Ohm).*
  (I never use the 6.5x gain because the sound is muddy and somewhat distorted.)
  Well, the ODAC has about 2 V RMS output (and is connected via the USB cable to my laptop).
  So the O2  will clip but not  
	

	
	
		
		

		
		
	


	




  too much?  There was a whole discussion about _clipping _in the ODAC/O2 thread.
  It was suggested that to reduce _clipping _one should reduce the computer's  volume level to, say, 50%.  ...
  ...or to _clip _some resistors or capacitators or something else in the O2 amplifier. -
  I am not a DIY'er or an engineer, so I don't know that at all.
   
  On the other hand the instructions from the JDS Labs say that one should max 
	

	
	
		
		

		
		
	


	




 the volume on the computer to 100%...
  but max volume causes _clipping._


----------



## nothing4me

The one thing I don't like about the O2/ODAC is that the power plug is in the front. I think it would be much tidier in the back.
   
  That said, the laser engraving is only for the black edition, correct? Thank you!


----------



## jseaber

Quote: 





nothing4me said:


> The one thing I don't like about the O2/ODAC is that the power plug is in the front. I think it would be much tidier in the back.
> 
> That said, the laser engraving is only for the black edition, correct? Thank you!


 
   
  Laser engraving is free for any aluminum surface (black or clear/silver).


----------



## adamlr

Quote: 





jakejack_2008 said:


> I am a bit confused.
> I am using the JDS Labs ODAC and O2 (which has standard 2.5x &  6.5 X gain) as two _seperates_.
> I always use the 2.5x gain with my Beyerdynamics *DT 880 (250 Ohm).*
> (I never use the 6.5x gain because the sound is muddy and somewhat distorted.)
> ...


 

 your confusing two things:
  1. "clipping" resistors: in order to change the gain settings of the (standard) O2, you need to open it up and cut out one of the resistors. depending on which you cut out, your gain settings will be changed to either x1 and x2.5, or x1 and x6. ive done it myself.
  2."clipping" is also a term for when an amp reaches its limits:
   
  Quote: 





nothing4me said:


> Clipping is a form of waveform distortion that occurs when an amplifier is overdriven and attempts to deliver an output voltage or current beyond its maximum capability. Driving an amplifier into clipping may cause it to output power in excess of its published ratings.


 
  btw, i own dt770s, also 250 ohm. and on x2.5 gain i do believe youll deafen yourself before you reach into clipping... its more likely to occur as a result of improper eqing i think. but i may be wrong there.


----------



## adydula

Hello,
   
  I always have my windows player at 100%.
   
  I use the lowest gain setting and adjust the volume control to the levels I want to listen to.
   
  If the lowest gain allows you to play at sane levels there is no need to use any higher gain setting with your setup.
   
  If not then you would try the higher gain setting again using the volume control to get to levels that are sane and wont cause hearing damage.
   
  The amp was designed to be used with a wide variety of devices.
   
  I have one O2 amp set to unity gain (clipping the resistor for the 6.5 gain setting)...and to 2.5 gain.
   
  I mostly use unity gain with most of my cans and very rarelt use the 2.5 gain setting.....
   
  If your using very sensitie cans or in ear devices, you most likely will never need the higher gain settings....you arent loosing anything.
   
  Enjoy
  A.


----------



## orangecr

I have the JDS black edition, and I want to remove the resistors to have 1X and 2,5X gain settings. 
   
  Is it as easy as it looks? Just cut and remove?
   
  What's the worst case scenario?
   
  I don't think it's necesary to say I know nothing about electronics 
	

	
	
		
		

		
		
	


	




 Thanks!


----------



## mikeaj

orangecr said:


> I have the JDS black edition, and I want to remove the resistors to have 1X and 2,5X gain settings.
> 
> Is it as easy as it looks? Just cut and remove?
> 
> ...




Right, you want to electrically remove them from the circuit, which is achieved by physically severing the metal leads (and removing the things).

Worst-case scenario is... you cut the wrong parts, making the amp not work anymore?

It's R19 and R23 for the switch-in setting. They're right next to the volume control potentiometer. Those are the ones you'd remove.


----------



## jseaber

Quote: 





mikeaj said:


> Right, you want to electrically remove them from the circuit, which is achieved by physically severing the metal leads (and removing the things).
> 
> Worst-case scenario is... you cut the wrong parts, making the amp not work anymore?
> 
> It's R19 and R23 for the switch-in setting. They're right next to the volume control potentiometer. Those are the ones you'd remove.


 
   
  It's easy as long as you have diagonal cutters. Here's a PDF guide with an actual photo:
http://www.jdslabs.com/pdf/O2_LowGain.pdf


----------



## orangecr

Thanks. Will definitely try it that.
   
  BTW, I just found this picture in the JDS Labs site: http://www.jdslabs.com/pdf/O2_LowGain.pdf


----------



## adamlr

Quote: 





orangecr said:


> Thanks. Will definitely try it that.
> 
> BTW, I just found this picture in the JDS Labs site: http://www.jdslabs.com/pdf/O2_LowGain.pdf


 

 i have no idea either, and i did it with the scissors on my pen knife. easy peasy =]
   
  the hardest part was removing the face plates, which jds labs glue on


----------



## iguanajm

If I'm not using LOD, would that affect volume level?  
   
  i'm pairing the O2 with Beyer DT880 250Ω cans.  this is hooked directly to my iphone 5.  yes, i'm double amp'ing.  i'm on battery power and to get to something loud (not ear splitting), i can take it to 3/4 volume level.  obviously i dont need it this high for everyday use, but was just curious.  i figured you could get this to something unbearably loud and was surpised to see that it was at a level i'd still tolerate.


----------



## miceblue

iguanajm said:


> If I'm not using LOD, would that affect volume level?
> 
> i'm pairing the O2 with Beyer DT880 250Ω cans.  this is hooked directly to my iphone 5.  yes, i'm double amp'ing.  i'm on battery power and to get to something loud (not ear splitting), i can take it to 3/4 volume level.  obviously i dont need it this high for everyday use, but was just curious.  i figured you could get this to something unbearably loud and was surpised to see that it was at a level i'd still tolerate.




Technically the LOD makes your iPhone at the maximum volume. If you set the iPhone volume at maximum without any volume limits, you get the same volume as what the LOD does.


----------



## iguanajm

I thought LOD, was bypassing the amp/dac??  Maybe I'm getting my terms mixed up.  But basically the signal is still in digital form.  Line Out D......(device??)
   
  And so if you want the purest form of audio, you would want to get a dac and an amp, or a dual amp/dac unit.  The O2 is amp only.  So I'd need a fiio or similar and use the dac portion.  Next i'd take my lightning connector and stick that in the USB of the dac.  take the line out of the dac, stick that in the amp, and then amp to my cans.  That would be purest audio possible.
   
  What I'm doing is using my iphone's amp and dac, sticking that to the line in on the O2 (effectively double amp'ing my source) and then to my cans.  I also know there aren't any cheap solutions for the lightning connector.  I did read about mixed results using the 30pin connector....
   
  Please correct me if I misspoke, I'm still learning


----------



## miceblue

Yeah the Line Out Dock connector bypasses the internal amp only, but it outputs the same volume as maximum volume on the iPhone.

E.g. Set your O2's potentiometer at 9 o'clock, plug in the LOD to your iPhone, connect the LOD to the O2, and play some music. Your music's volume level will be the same as if you had set the iPhone volume level to maximum and double amped with the O2 with the potentiometer still in the 9 o'clock position.

You can bypass both the DAC and amp with a digital out connector with a USB-terminated end to connect the iPhone to a special "Apple certified" DAC. A Line Out Dock connector just has a 3.5 mm-terminated end.


----------



## iguanajm

Gotcha.  Thanks for the explanation.  So, going LOD, is cheap and doable, BUT bypassing the DAC is what gets expensive (with lightning connectors at least)?  Obviously with time things will get cheap, but last I checked there were only a couple DAC's made specifically for lightning all were over $500 I believe....
  Thanks again!


----------



## xnor

The question is rather why bypass an excellent DAC and even great amp in the first place.


----------



## miceblue

xnor said:


> The question is rather why bypass an excellent DAC and even great amp in the first place.




Because this is Head-Fi, where people need to spend $500+ USD on a portable rig to be considered an audiophile. Forget logic and common sense. XD


----------



## ostewart

miceblue said:


> Because this is Head-Fi, where people need to spend $500+ USD on a portable rig to be considered an audiophile. Forget logic and common sense. XD




You sir are a genius, you summed it up perfectly.
I try and keep it simple, iPod > LOD > amp > headphones, sometimes just iPod > headphones

DACs are too expensive for I devices, and the sound quality increase just doesn't justify the price for me anyway.


----------



## iguanajm

miceblue said:


> Because this is Head-Fi, where people need to spend $500+ USD on a portable rig to be considered an audiophile. Forget logic and common sense. XD







xnor said:


> The question is rather why bypass an excellent DAC and even great amp in the first place.




Very funny!! I thoroughly enjoy my $60 creative live aurvana cans. Not nearly as comfy as an expensive set, but I still consider them a great value for performance. 

I was driving a set of 250ohm cans and had to max the volume on my iDevice. I have since bought an amp, but still in a double amp setup since I haven't gone LOD yet.


----------



## JakeJack_2008

Quote: 





miceblue said:


> Yeah the Line Out Dock connector bypasses the internal amp only, but it outputs the same volume as maximum volume on the iPhone.
> 
> E.g. Set your O2's potentiometer at 9 o'clock, plug in the LOD to your iPhone, connect the LOD to the O2, and play some music. Your music's volume level will be the same as if you had set the iPhone volume level to maximum and double amped with the O2 with the potentiometer still in the 9 o'clock position.
> 
> You can bypass both the DAC and amp with a digital out connector with a USB-terminated end to connect the iPhone to a special "Apple certified" DAC. A Line Out Dock connector just has a 3.5 mm-terminated end.


 
  Well, i am puzzled by this:
   
   
  Quote: 





> You can bypass both the DAC and amp with a *digital out connector *with a *USB-terminated end *to connect
> the iPhone to a _special _"Apple certified" *DAC*. A Line Out Dock connector just has a 3.5 mm-terminated end.


 
   
  I don't understand. The signal coming out from any LINE-OUT port on any device, (including the iPhone?)  is an an *analog signal*.
  By design, the   LINE-OUT port outputs _only _*






 analog signal*.
  So, how a '*digital out connector *with a *USB-terminated end*' can _still _retrieve the *digital signal*?
   
  Perhaps the LINE-OUT port on the iPhone doubles as  
	

	
	
		
		

		
		
	


	




 a *digital-out  *port as well???
  If this is the case, such a port should be called: LINE-OUT / DIGITAL-OUT.
  I don't have any Apple product and that's why I am very confused.


----------



## skamp

Yes, iPods and iPhones have both analog and digital outputs (different pins on the 30-pin connector). Recent ones with the lightning connector only have digital out.


----------



## iguanajm

I'm a newb, but I'll take a stab at this....
   
  They are different connectors......
   
  The digital out connector would be a lightning/30 pin connector at one end and a usb connector at the other end.  this would be a digital signal and you'd input this into a DAC device, then to an amp or DAC/amp combo.  
   
  The analog out (LOD) would be a specialized module that has a lightning/30pin on one end and a 3.5mm jack at the other.  So after writing this and thinking about it, if these LOD modules DO NOT have a dac chip in them, then the idevice MUST output both A and D signals.  right?
   
  Another stab - with lightning devices, the reason why going all digital is so expensive is because Apple is requiring licensing of their tech.  I don't think anyone has stated exactly how much it costs, but everything seems to be absurdly expensive, and most blame this requirement as the reason for cost.


----------



## iguanajm

Quote: 





skamp said:


> Yes, iPods and iPhones have both analog and digital outputs (different pins on the 30-pin connector). Recent ones with the lightning connector only have digital out.


 
   
  I've seen mixed results when using the 30p to lightning adapters, so wouldnt this mean that lightning is also dual A&D out?


----------



## miceblue

Quote: 





iguanajm said:


> I'm a newb, but I'll take a stab at this....
> 
> They are different connectors......
> 
> ...


 
   
  Quote: 





jakejack_2008 said:


> Quote:
> 
> 
> 
> ...


 
  Sorry if my post was confusing. >_<
   
  If you use a Line Out Dock connector (e.g. FiiO L3 or L9, and is terminated with a 3.5 mm minjack), then you get an analog signal out from the iDevice and the signal gets amplified from your own external amp. The audio signal still goes through the iDevice DAC.
   
  If you use a digital out connector (i.e. the ones that come with "Apple certified" DACs, and is terminated with a USB end to plug into the DAC), then you get a digital signal coming out of the iDevice and the signal gets converted to analog and amplified through your own DAC and amp respectively. The audio signal doesn't get processed by the iDevice at all.
   
   
  I don't know much about the new Lightning dock connector since I don't have any products that use it, but it sounds like the Lightning dock to 30-pin dock adaptor extracts a digital out from the iDevice and there's actually a DAC built in the adaptor such that you get analog out from the 30-pin adaptor. I'm not 100% sure about this though. Or special Lightning dock connectors such as the one from VentureCraft don't have a built-in DAC which allows you to utilise the digital out of the iDevice to connect to your own DAC and amp.
   
   
  In any case, to connect the O2 to the iDevice, you can either double amp it by just plugging in a 3.5 mm to 3.5 mm minijack into the O2 and iDevice's headphone port, or you can use a Line Out Dock connector to bypass the iDevices' internal amplifier and the O2 amplifies the analog signal coming out of the iDevice.


----------



## JakeJack_2008

Quote: 





miceblue said:


> Sorry if my post was confusing. >_<
> 
> If you use a Line Out Dock connector (e.g. FiiO L3 or L9, and is terminated with a 3.5 mm minjack), then you get an analog signal out from the iDevice and the signal gets amplified from your own external amp. The audio signal still goes through the iDevice DAC.
> 
> ...


 
   
  Yes, I've known this:
   
   
  Quote: 





> In any case, to connect the O2 to the iDevice, you can either double amp it by just plugging in a 3.5 mm to 3.5 mm minijack into the O2 and iDevice's *headphone port*, or you can use a *Line Out Dock *connector *to bypass *the iDevices' *internal amplifier *and the O2 amplifies the analog signal coming out of the iDevice.


 
   
  (By the way, by iDevice you mean _any _iPod, iPhone, i*Pad*, iMac, ...?)
  But I'm still _puzzled _





 by the *mysterious*  
	

	
	
		
		

		
		
	


	




 _dual _'digital/analog' port of iPhones, iPads,  ....


----------



## miceblue

Quote: 





jakejack_2008 said:


> Quote:
> 
> 
> 
> ...


 
  Yeah, iDevice = iPod, iPad, iPod Touch, iPhone, iMac.
   
  And yeah iDevices are weird like that. If you have a digital out option, the device needs to be "Apple certified" since the digital signal is signed(?) and verified by Apple? I don't know the specifics of that. I do know you can't jailbreak an iDevice and use an external DAC because the signal becomes unverified(?) or something weird like that. The Camera Connection Kit is an exception for the iPad though so it makes it even more confusing. -_-
   
  I'm trying to avoid external DACs with iDevices due to their insanely high price tag for a small increase in sound quality.


----------



## skamp

iguanajm said:


> I've seen mixed results when using the 30p to lightning adapters, so wouldnt this mean that lightning is also dual A&D out?




What? I don't understand that sentence. I just said that iDevices with the Lightning connector only have a digital out. That is an absolute certainty.



miceblue said:


> it sounds like the Lightning dock to 30-pin dock adaptor extracts a digital out from the iDevice and there's actually a DAC built in the adaptor such that you get analog out from the 30-pin adaptor.




That is absolutely correct.


----------



## orangecr

Do you guys think the ODAC will be a significant upgrade over the E07k (_just for the DAC section of the Fiio_).
   
  I am using the Fiio E07K to feed the O2, and as a portable amp, but I can not help wondering if I am missing something. I can tell for sure that the Fiio + O2 is a noticeable upgrade over the laptops sound card + O2.
   
  Here is my home set up; please ignore the headphone stand:


----------



## cheuh

Quote: 





orangecr said:


> Do you guys think the ODAC will be a significant upgrade over the E07k (_just for the DAC section of the Fiio_).
> 
> I am using the Fiio E07K to feed the O2, and as a portable amp, but I can not help wondering if I am missing something. I can tell for sure that the Fiio + O2 is a noticeable upgrade over the laptops sound card + O2.


 
   
  Bump because I'm interested in finding out this as well.


----------



## Ashade

Pretty late but... Yes, it is an update. This is what I´m hearing right now:
  
 - Slightly more neutral (less warmer).
 - More detailed. (It does much better in the base and treble department).
 - Slightly smoother sounding.
 - Larger soundstage.
 - Much louder!!


----------



## ostewart

NICE!


----------



## senorx12562

I'm pretty new to digital audio, so after reading this entire thread, my head is kind of spinning. I have a Fiio E07k that I use just for the amplification, since none of my non-laptop sources (Zune HD, Sansa Clip+, Creative Zen Touch) are capable of putting out a digital signal for conversion to analog by an outboard device (as far as I know), and my laptop won't even recognize my E07k when plugged in via USB. I mostly use IEMs, (although I have a pair of Sony MDR-V900HDs, but I think these are pretty low-impedance, high sensitivity cans, and in fact their impedance is stated as 24ohms, vs. 56 Ohms for my UM3xs, with sensitivity of 107 db spl/watt) and though my iems all will get way more than loud enough without amping, using the E07K amp with any portable source results in significantly better sound, especially when it comes to the sense of space and location (soundstage?). Would there be anything to gain at this point soundwise from either an O2 for use at home, and/or either an ODAC or other DAC for use with my laptop (or trying to figure out how to use the DAC of my E07k)?


----------



## Ashade

Ok, I'm gonna try to explain it as I understand it, anybody correct me if I'm wrong...
  
 DAC: Digital-Analog Converter. Is the responsible of transforming your digital signal to analog signal and this way allowing you to listen to it through your headphones. The quality of the transformation may be good or bad, depending on the implementation of the DAC itself. Each DAC has its own technical characteristics and resolutions. The DAC is gonna be the first bottleneck between your files and the final sound, therefore if you have a very high quality file but your DAC is not capable enough, you will never get the quality of the original file on your headphones.
  
 Amplifier: Initially it only serves two purposes: 1. Amplify the signal to make it louder. 2. Properly feed the later load (your headphones). There are difficult and easy to drive headphones, and it's something that depends of the frequency you are reproducing. Let's say that the prebuilt amplifier of your phone might be able to drive properly between 3k and 7kHz but it's not able to drive properly in the sub 400Hz region, therefore your music is gonna sound weird and muddy. The better the amplifier the better the sound usually.
  
 Initially both the amplifier and the DAC should be completely transparent, that means that they should not boost any frequency nor modify their responses (that is what an objective DAC, amp does). In the reality the world is far from being perfect, which means that you are gonna be altering the signal by passing it through several steps. That's why everybody talks about warm or bright DAC's / amps, and even more, some people try to find some sinergy between their headphones and gears (this is something that depends on you, and on what you give the highest emphasis in your equipment).
  
 All of this being said, you might not experience an improvement by buying a better amp if your IEMs are already properly driven (amp section). Regarding the DAC section it will depend of your current source. Let's say that the amp should only increase the volume or the way your IEMs are driven, but if your DAC is providing a ****ty sound, your amp is not going to improve that.
  
 Hope this helps.


----------



## xnor

ashade said:


> Ok, I'm gonna try to explain it as I understand it, anybody correct me if I'm wrong...


 
 Okay, less of a correction but more like a few additions and adjustments.
  


> DAC: Digital-Analog Converter. Is the responsible of transforming your digital signal to analog signal and this way allowing you to listen to it through your headphones. The quality of the transformation may be good or bad, depending on the implementation of the DAC itself. Each DAC has its own technical characteristics and resolutions. The DAC is gonna be the first bottleneck between your files and the final sound, therefore if you have a very high quality file but your DAC is not capable enough, you will never get the quality of the original file on your headphones.


 
 Most better DACs support 24 bit samples and reach about 20 bits of performance, so can reproduce even the recorded noise on a CD (which you usually do not hear because instruments play a lot louder). A Xonar DX should be pretty close to that and only costs € 65 here.
  
 So a good enough DAC is usually the smallest problem in a hi-fi chain.
  


> Amplifier: Initially it only serves two purposes: 1. Amplify the signal to make it louder. 2. Properly feed the later load (your headphones). There are difficult and easy to drive headphones, and it's something that depends of the frequency you are reproducing. Let's say that the prebuilt amplifier of your phone might be able to drive properly between 3k and 7kHz but it's not able to drive properly in the sub 400Hz region, therefore your music is gonna sound weird and muddy. The better the amplifier the better the sound usually.


 
 1. is voltage gain, 2. is current gain
 Depending on the source and sensitivity of your headphones you may not even need voltage gain. In-ears for example will blow up if you feed them 1-2 Volts, many DACs output 2 Volts however.. not to mention what would happen to your hearing.
  
 The better the amplifier, the less it will change the signal (less noise, lower distortion, flatter frequency response etc.). A DAC is actually trying to achieve the same - convert the digital signal into an analog signal that is as close as possible to the theoretically reconstructed signal. This works for most DACs, again, pretty well, up to some point (20+ kHz for CDs for example).
  


> Initially both the amplifier and the DAC should be completely transparent, that means that they should not boost any frequency nor modify their responses (that is what an objective DAC, amp does). In the reality the world is far from being perfect, which means that you are gonna be altering the signal by passing it through several steps. That's why everybody talks about warm or bright DAC's / amps, and even more, some people try to find some sinergy between their headphones and gears (this is something that depends on you, and on what you give the highest emphasis in your equipment).


 
 The idea of synergy is highly problematic. Imho, it's more of satisfying an urge to buy new audio stuff than going at it from an angle that _really _focuses on an improvement in sound quality.
  
 Lots of what you read in reviews about some electronics being bright/dark/warm/cold etc. is wrong. For example, a reviewer used to an amp with high output impedance (like a receiver's headphone jack) will say a more accurate amp with 0 ohm output will sound bright. It doesn't, it's flat. If anything, you could say it has less bass boost and "sounds" more accurate with a dynamic headphone.


----------



## Ashade

Every addition is welcome! The problem with audio is that you can be talking for hours! 

I agree with everything you said as well.


----------



## senorx12562

I guess my question was not very clear. If the only effect an amplifier can have on recorded music is to play it back at a higher volume, then the effect on the sound of my music that I noted when using my E07K is imaginary, because I'm still listening to music at the same volume, I just thought I heard more of a sense of "space" between the components of the music, along with more "directionality" with respect to the various instruments /voices than without the amp. I definitely am not in the subjectivist camp of the ongoing debate in audio between measurement and just listening, so I have no interest in spending any money on a perceived but not real improvement in sq. I don't need more volume, unless that also brings better sq because of the additional "headroom." Probably heresy around here, but so be it. So, is my sq maxed out? I'd be more than happy to keep what I've got and spend my $ on bourbon.


----------



## xnor

E07k seems like a very good little device especially for IEMs. Just wondering why your laptop doesn't recognize it.


----------



## stv014

senorx12562 said:


> If the only effect an amplifier can have on recorded music is to play it back at a higher volume


 
  
 That is not necessarily true, especially if you are using IEMs from a computer onboard audio output, which is likely to have a high output impedance, a relatively high noise floor (low dynamic range at a volume that is bearable with sensitive IEMs), and possibly undersized output capacitors. Factors like these can affect the sound regardless of the available maximum power, and, contrary to popular belief, they can affect _low_ impedance headphones.
  


senorx12562 said:


> then the effect on the sound of my music that I noted when using my E07K is imaginary, because I'm still listening to music at the same volume


 
  
 It is not easy to judge absolute loudness by ear, especially if the switching time between the devices is not very short (I mean less than a second). To really compare amplifiers at matched levels, you need to measure the output voltage with the load (headphones) connected.


----------



## senorx12562

Ironically, my full size cans sound worse than my iems directly from my laptop. They just won't get loud enough. The iems sound ok, but as I said, its not a lack of volume. I don't have ready access to the specs for my laptop now so I don't know any particulars, although it was a "media/entertainment" laptop when I bought it (Sony VAIO) so it might be a little better than average in the audio realm, but then again, maybe not. Most of my files are 320kbps MP3 files. So far, reripping them at 320 instead of 128 has done the most for the sound of my music.


----------



## stv014

If low impedance and reasonably efficient full size headphones are not loud enough from the laptop, then it quite likely has a high output impedance (something like 75 Ω), which reduces the output voltage when driving a low impedance load. It also explains bad frequency response with IEMs like the Westone UM1 or UM3X that have significant impedance variations depending on the frequency.


----------



## Ashade

​


senorx12562 said:


> I guess my question was not very clear. If the only effect an amplifier can have on recorded music is to play it back at a higher volume, then the effect on the sound of my music that I noted when using my E07K is imaginary, because I'm still listening to music at the same volume, I just thought I heard more of a sense of "space" between the components of the music, along with more "directionality" with respect to the various instruments /voices than without the amp. I definitely am not in the subjectivist camp of the ongoing debate in audio between measurement and just listening, so I have no interest in spending any money on a perceived but not real improvement in sq. I don't need more volume, unless that also brings better sq because of the additional "headroom." Probably heresy around here, but so be it. So, is my sq maxed out? I'd be more than happy to keep what I've got and spend my $ on bourbon.




Let's put it this way: The amp is not going to make your crappy recordings sound better, but if the internal amp of your laptop is not powerful enough to drive your headphones/IEMs properly it will make the music sound better by driving them better. The result may be better instrument separation, larger sound stage and basically everything you described above.

Now, if you get the internal DAC of the E07K to be recognized by your laptop, the sound quality will improve even more.

All of thia is gonna depend of course on the limitations of your headphones / IEMs as well. By the way, the difficulty of the headphones to be driven properly not always relates with the impedance. For example Q701 and FA003 have pretty similar impedance and while the second one is really easy to drive the first one requires something like the O2 to be properly driven.


----------



## senorx12562

None of my headphones are hard to drive, especially not my iems of course, and I don't listen to my computer directly that often, other than via a bluetooth soundbar/sub combo. When I listen to music via 'phones its usually from one of my portable devices, even at home. Maybe that's because the sound quality on the laptop isn't as good as the devices, although it still isn't as bad as what people here always say about their computers' sq. I was hoping that the O2 would give me a desktop that would provide better sound with my portable devices when I was at home, especially with headphones, and also improve the sound out of my laptop. It's all good, I just have a thing about audio gear.


----------



## Sonic Atrocity

Hey everyone, Mr. Fidelity here.  I'm a freak about fidelity (neutral frequency response (or in other words, "flat"), very high transparency, accurate instrument positioning, accurate sound staging, etc. 
  
 Anyhow, I haven't read the whole thread, as it is 26 pages long, but every post I've read thus far says the _amp _portion of this product is transparent. Okay, great! That's awesome. Hence I'm interested!  However, I am curious, is the _DAC _portion of this product transparent/neutral as well? If not, then I was thinking I would purchase the amp portion on it's own, and a different DAC to go with it.


----------



## stv014

> However, I am curious, is the _DAC _portion of this product transparent/neutral as well?


 
  
 I do not have one, but it is claimed to be transparent. However, DACs can be transparent or very close to transparent (save for a small number of "golden eared" listeners) at a fairly low price now, so it is not an outstanding feature for a $150 USB DAC without any additional features to be neutral and transparent, it just has measurements made with professional equipment published, which is often not the case for other products.


----------



## adydula

The ODAC is extremely transparent.
 A.


----------



## miceblue

I think this DAC is more transparent. 

 http://hobbyaudios.blogspot.com/2013/08/transparent-box-for-dac-akm4396.html
  
 On a more serious note, what defines transparency in audio? The O2 was shown to be transparent against the DAC1PRE, but that's it. That does not necessarily mean it's transparent. For all we know, the DAC1PRE could be really coloured, which is analogous to saying the O2 is really coloured.
  
 Likewise for the ODAC. What makes it transparent? From what I recall, they didn't do any [insert sound science only term] tests with the ODAC.


----------



## Sonic Atrocity

Hahahahhaa, I'm sitting in class, listening to a lecture on Kantian ethics, and I almost laughed out loud at the photo you posted, hahaha. Indeed, he who shall not be mentioned has not tested this product, and therefore you pose a good question. 
  
 In my personal opinion, neutrality/transparency/fidelity is a concept that should be verified within a product on it's own, independent of the status of fidelity in other products.


----------



## adydula

This one is more transparent than your plexiglass one....your plexiglass isnt totally clear on all the edge contact points.....
 This has got to affect the transparecy dont you think?
 Not to mention all the AC floating around next to the circuitry....yuck!


----------



## tdockweiler

LOL my definition of transparency is if I can use it for 2+ years and it doesn't audibly change the sound of any of my headphones.
 If the amp is only good with specific types of headphone then it's somewhat of a fail for ME. To me a headphone amp should be equally good with those that are bright/warm/v-shaped etc.
  
 I'm sure others have a different idea of what "sounds" transparent to them.
  
 For me the most transparent amp i've "heard" is the Micro Amp with Astrodyne unit. Usually when people criticize it I think it's their source. O2 sounds pretty similar..as close as i've come. I'd probably fail a blind A/B test perhaps. There's some small differences though.
  
 BTW I read somewhere that the O2 can sound a tiny bit more trebly than normal with a weaker AC adapter using the Q701. Doubt this is true but it's worth a try.
  
 ODAC mostly definitely sounded transparent. Didn't sound bright/warm etc. No change to any of my headphones. Same with the Modi.


----------



## adydula

You know the main reason I like the O2.ODAC combination so much is it lets me forget about the amplification and listen to what the music sounds like with a set of cans....
  
 Its a standard to me that doesnt change.
  
 It just works and works so well.
  
 Very transparent..
  
 Listening to Kenny Rankin right now and it SUPERB, absolutely SUPERB on my new Beyer T90's.
  
 Absolutely luscious....
  
 Over and Out...
  
 Alex


----------



## Ashade

I didn't want to post anything but...

The definition of transparent is pretty clear: The signal coming out should be the same than the one coming in. If it's an amp it has just to be amplified. If it's a DAC the analog signal must be equivalent to the digital signal. THAT'S transparent by definition from an electronic perspective.

The objective 2 DID demonstrate to be pretty transparent for a broad range of frequencies ( 10 Hz to 50kHz if I recall properly). It doesn't have anything to do with sinergies. I don't remember what kind of test where performed with the ODAC but free was searching to get an objective DAC.

If you don't like how your headphones sound out of a transparent amp then you don't like your headphones, that's it, pretty simple. If you prefer it with another amp then you don't like transparency, again, that simple.


----------



## Sonic Atrocity

ashade said:


> I didn't want to post anything but...
> 
> The definition of transparent is pretty clear: The signal coming out should be the same than the one coming in. If it's an amp it has just to be amplified. If it's a DAC the analog signal must be equivalent to the digital signal. THAT'S transparent by definition from an electronic perspective.
> 
> ...


 
  
 ^^^ This. Completely agree. That is what I seek.
  
 However, I still appreciate Tdock's post. I understand what he's getting at. If I had V-curved cans I might want to apply the same reasoning.


----------



## miceblue

So you guys are saying the O2 is the end-of-all-amps for transparency then?


----------



## tdockweiler

sonic atrocity said:


> ^^^ This. Completely agree. That is what I seek.
> 
> However, I still appreciate Tdock's post. I understand what he's getting at. If I had V-curved cans I might want to apply the same reasoning.


 
  
 That's basically what I said 
	

	
	
		
		

		
			




 It should not alter anything. If the DAC is colored then the amp itself will sound colored (duh). Same goes with the headphone.
 If I don't like how the headphone sounds then I should get a new headphone and not a new amp.
  
 I like how with my current amp for the last 2-3 years I could plug in any new headphone (or one I've had before) and it doesn't change.
  
 The only time my amp has changed it's sound is when I got a new DAC. That's it.
  
 A good sign of transparency is when you blame your amp for faults when it's actually the DAC. I've done that once! For awhile I always complained that my amp was too warm, had a small soundstage etc and it was 100% the DAC. Doh! Luckily i've found two DACs that are transparent enough to me (Modi and ODAC).
  
 So with a good amp/dac there is no such thing as "synergy". Synergy is stupid!
  
 What's amusing to do is connect really crappy sources up to your amp and see if they sound the same/any different. On the O2/Micro for me there is really no change just some minor improvements (not in sound signature). I hate it when a desktop amp seems to add it's own signature to the sound.


----------



## tdockweiler

miceblue said:


> So you guys are saying the O2 is the end-of-all-amps for transparency then?


 
  
 Not for me, but close enough for me to not care much.
  
 I haven't heard anything past $500 though.
  
 I've heard some say the UHA-6s "sounds" more transparent than the O2, but no idea myself.
  
  
 ODAC/Modi for sure. But i've only had those and the E7, HRT MSII and E17.
 If the MSII is considered transparent than I'm retiring from all this nonsense! Sounded quite colored, but some nice coloration


----------



## Sonic Atrocity

Yeah, I heard the HRT was pretty coloured. I will be sure to check out the modi. It is likely I will get the o2 + odac though.


----------



## stv014

miceblue said:


> So you guys are saying the O2 is the end-of-all-amps for transparency then?


 
  
 Well, not in some "extreme" cases, for example:
 - with headphones that are unusually hard to drive (e.g. the HE-6 with very dynamic classical music at high SPL the power output might simply not be enough)
 - some IEMs can have audible (barely, a few tenths of a dB) FR variations even with the low output impedance of the O2
 - channel imbalance at low volume with very sensitive headphones/IEMs - this is perhaps the most common problem
 - clipping in the gain stage can be an issue sometimes, depending on the source output voltage and the available gain settings; this can, however, be worked around by reducing the volume at the source


----------



## adydula

Yup I am.....unless someone can demo one for me and show me the error of my 'ears" and bias.
 But let me add.....(post after thought)..tha there are others that are just as transparent...
 Alex


----------



## Sonic Atrocity

adydula said:


> Yup I am.....unless someone can demo one for me and show me the error of my 'ears" and bias.
> But let me add.....(post after thought)..tha there are others that are just as transparent...
> Alex




Which amps would you say are transparent?


----------



## adydula

One that comes to mind is the Violectric V100  ( and the V200).
 Another would be the Benchmark HP2A.
  
 A.


----------



## Ashade

The objective 2 is definitely transparent which doesn't mean is perfect nor the ultimate amp as stv014 already mentioned. It's just a super cheap, super transparent amp.

You might not like its transparency or you might search for other features such as eq, bass boost, etc. Or it might just not work in your application, but it's a very good reference.

DAC's are another story, because there are many factors in a digital analog conversion processes, and every chip converts under different criterias, but still I think ODAC is a very nice option.


----------



## adydula

Ashade,
  
 Whats not perfect about it?
  
 A.


----------



## stv014

ashade said:


> DAC's are another story, because there are many factors in a digital analog conversion processes, and every chip converts under different criterias


 
 DACs can be just as transparent (except maybe for the rare golden eared person hearing a - very minor - difference between reconstruction filters for Red Book audio, which, however, can be changed with software upsampling), but there is a lot of misinformation leading many to the belief that there are huge audible problems unless you spend a lot on a "high end" DAC.


----------



## Sonic Atrocity

I think what I'm most concerned about, now that it has been verified that the O2 is pretty much neutral (this claim has been reaffirmed by many sources, including you-know-who), is that I have an equally neutral DAC, and I am hoping the ODAC is equally neutral. If it isn't then I will get the O2 but with a different DAC. 
  
 Is the ODAC neutral? Or where should I look?


----------



## tdockweiler

sonic atrocity said:


> I think what I'm most concerned about, now that it has been verified that the O2 is pretty much neutral (this claim has been reaffirmed by many sources, including you-know-who), is that I have an equally neutral DAC, and I am hoping the ODAC is equally neutral. If it isn't then I will get the O2 but with a different DAC.
> 
> Is the ODAC neutral? Or where should I look?


 
  
 Yes definitely! No audible colorations to any of my headphones at all.
 It's comparable to the Schiit Modi.
  
 ODAC doesn't sound bright/warm/cold etc. Well for that it depends only on the recording but it's not coming from the DAC.


----------



## Ashade

adydula said:


> Ashade,
> 
> Whats not perfect about it?
> 
> A.




Usually not a problem but as already mentioned:



stv014 said:


> Well, not in some "extreme" cases, for example:
> - with headphones that are unusually hard to drive (e.g. the HE-6 with very dynamic classical music at high SPL the power output might simply not be enough)
> - some IEMs can have audible (barely, a few tenths of a dB) FR variations even with the low output impedance of the O2
> - channel imbalance at low volume with very sensitive headphones/IEMs - this is perhaps the most common problem
> - clipping in the gain stage can be an issue sometimes, depending on the source output voltage and the available gain settings; this can, however, be worked around by reducing the volume at the source


----------



## Ashade

That was probably what "this guy" was trying to demonstrate with the ODAC, that a good implementation is not necessarily expensive.



stv014 said:


> DACs can be just as transparent (except maybe for the rare golden eared person hearing a - very minor - difference between reconstruction filters for Red Book audio, which, however, can be changed with software upsampling), but there is a lot of misinformation leading many to the belief that there are huge audible problems unless you spend a lot on a "high end" DAC.






tdockweiler said:


> Yes definitely! No audible colorations to any of my headphones at all.
> It's comparable to the Schiit Modi.
> 
> ODAC doesn't sound bright/warm/cold etc. Well for that it depends only on the recording but it's not coming from the DAC.




^ +1


----------



## Sonic Atrocity

tdockweiler said:


> Yes definitely! No audible colorations to any of my headphones at all.
> It's comparable to the Schiit Modi.
> 
> ODAC doesn't sound bright/warm/cold etc. Well for that it depends only on the recording but it's not coming from the DAC.


 
  
 Yeah, I checked out the Modi on behalf of your suggestion.  I think I still want to go with the ODAC, and I am taking into account your claim that it's a neutral DAC. I will be further researching this.


----------



## adydula

Agree there.....no real need to spend mega-bucks there.....
  
 as an aside I noticed JDS is selling a O2 kit!!!
  
 A.


----------



## jseaber

adydula said:


> Agree there.....no real need to spend mega-bucks there.....
> 
> as an aside I noticed JDS is selling a O2 kit!!!
> 
> A.


 
  
 O2 kits have been up for a while. We recently updated the photo:


----------



## Ashade

Yeap! And there you have my kit assembled!


----------



## adydula

With the cans I use there is never a clipping issue at the levels I listen to....I dont want to loose any of my hearing capabilities!!
  
 IEM's arent in my world...so no worry there...
  
 HE6 not going there as well....so for me
  
 the O2 is "perfect"......
  
 A.


----------



## Ashade

For my application is kind of perfect as well. Pretty happy with the combo.


----------



## eltonkawei

it sounds slightly warm in comparison. C421 wasn't made to drive the T1 really.thank you


----------



## ostewart

Kit version is awesome! May have to get one one day


----------



## puskuruk

Do you have any idea o2 with lipo batteries in higher voltages from the normal batteries? Or what do you think the best battery for o2?


----------



## jseaber

puskuruk said:


> Do you have any idea o2 with lipo batteries in higher voltages from the normal batteries? Or what do you think the best battery for o2?


 
  
 Voltage in O2 is internally limited to +/-12VDC. It's only safe to use NiMH types, and NwAvGuy's recommendation to use a Low Self-Discharge NiMH remains best. Tenergy is the most popular brand.


----------



## puskuruk

Thank you for your reply. I will buy this: 

http://www.all-battery.com/COMBO4Cardsof2pcs9VLSDNiMHBatteries-90372.aspx

Do you have any other suggest?


----------



## jseaber

O2's case is held together by screws and is intended for infrequent battery access.
  
 So, a single set of batteries should last for years. No need to order four sets.


----------



## RandomNumber

Hi, I puchased an ODAC + O2, is there anyway I can extract the standalone ODAC from the package? Would be good to keep it simple as I am not an expert audophile...


----------



## Ashade

randomnumber said:


> Hi, I puchased an ODAC + O2, is there anyway I can extract the standalone ODAC from the package? Would be good to keep it simple as I am not an expert audophile...




It is possible but... what for? It would require desoldering...


----------



## RandomNumber

ashade said:


> It is possible but... what for? It would require desoldering...


 
  
 Hey dude, thanks for the reply! I intend to use only the stand alone ODAC and use the new ifi ican as my new amp. 
  
 I regretted buying ODAC + o2 as a single unit but it's too late for it now!


----------



## adydula

its easy to do, but your going to have to put in into a case or use is bare bones, it has a micro usb input but no audio out jack.
  
 you will have to hard wire or add a output jack for that....again not hard but a minor pain.
  
 you should call JDS labs and they can sell you the jack and external case and endplates..
  
 good luck..
  
 A.


----------



## Ashade

adydula said:


> its easy to do, but your going to have to put in into a case or use is bare bones, it has a micro usb input but no audio out jack.
> 
> you will have to hard wire or add a output jack for that....again not hard but a minor pain.
> 
> ...




+1 ^. It's not difficult. There is a lot of information to do it.

You can buy the case from JDS Labs, no need to call, just order online.


----------



## mcandmar

I believe these are the parts you will need, and a soldering iron to attach the 3.5mm socket to the board.
  
http://www.jdslabs.com/item.php?fetchitem=80
http://www.jdslabs.com/item.php?fetchitem=50
http://www.jdslabs.com/item.php?fetchitem=45
  
 With a little bit of creativity you could also fit one into an O2 enclosure so they are both the same size.


----------



## acetylmine

Will the Akg k702s sound great in response to the o2 odac?


----------



## adydula

Yes....I had both AKG 702 and Q701's...works well...
  
 Alex


----------



## tdockweiler

Getting another O2! I sold mine 4 months ago for something that was more expensive but much worse. Big mistake.
 I still think it's the 2nd best amp i've heard. The other one costs almost 3x as much new.
 I like how when I connect many different sources to the O2 I can totally expect to HEAR what's connected (unless it's transparent) without much change coming from the O2.
  
 Despite how some say the HD-650 sounds "lifeless and boring" with the O2, I actually love it. I don't want to add a single thing to the HD-650's sound.
  
 O2 was one hyped up amp that is actually as good as they say to my ears.


----------



## ostewart

I'm hopefully getting an O2 kit to build as I will add RCA inputs, power jack on the back and also 6.3mm output


----------



## adydula

Ha!!
  
 Amazing....absolutley amazing....
  
 Yes I have done the same thing.....all the other amps here are gone only the O2 remain are are working very, very
 well!!
  
 Alex


----------



## ostewart

I must say the iFi iCan can hold its own against the O2, but costs more. It does however have some interesting sound tweaks you can alter.
I will keep the O2 though as its good for reference purposes and I really enjoy listening to it.


----------



## tdockweiler

ostewart said:


> I must say the iFi iCan can hold its own against the O2, but costs more. It does however have some interesting sound tweaks you can alter.
> I will keep the O2 though as its good for reference purposes and I really enjoy listening to it.


 
  
 Well, if it sounds similar to the O2 I'd like to check it out sometime. I've always been looking for amps similar to an O2.
 Right now the closest match i've found to the O2's sound is the Headroom Micro Amp, but only with the Astrodyne power supply (I won't go there..it's cheap).
 It costs way more and is discontinued, but maybe i'd fail a blind A/B test between the two.
 Some brighter headphones might be like 2% better on the Micro, but that's nit-picking.
  
 I've owned many a couple dozen headphones since owning it and they all sound good with it and without any extra coloration. I bet i'd get similar results with the O2.
 This makes sense considering the Micro is made by a company that sells headphones 
	

	
	
		
		

		
			




  
 Like the O2, the amps sound can change depending on what's connected as a source (unless it's transparent).
  
 BTW often when I used the O2 I'd keep forgetting it's battery powered and transportable!


----------



## ostewart

The iCan can definitely compete plus it has RCA in, 6.3mm out and bass boost + 3D sound options.

Check out clieOS's review on it. He says its the only other amp he's had that was on par with the O2


----------



## MrMateoHead

ostewart said:


> The iCan can definitely compete plus it has RCA in, 6.3mm out and bass boost + 3D sound options.
> 
> Check out clieOS's review on it. He says its the only other amp he's had that was on par with the O2


 

 I am having trouble getting pricing information and specs on the iFi products. From their website, it would seem that it has some nice features, but is not as powerful as the O2. I don't really plan to make any new audio purchases for a very long while, but when I do, they will probably be planar's again.


----------



## ostewart

It doesn't quite output as much mW per ohm but has variable gain so don't worry about power as it can drive the HE-500 and LCD2 easily.

Price in gbp is £225 I think. Not sure in $


----------



## MrMateoHead

Can you explain how gain substitutes for Power? Haven't heard that one before.


----------



## ostewart

it doesn't substitute for power, but amplifies the signal more (i know it can introduce distortion), so less power + more gain should equal same volume....
  
 Also if it can drive the HE-500 and LCD2 then it obviously doesn't lack power.


----------



## ostewart

iCan: 400mW of output power (@32 Ohms)
O2: 613mW of output power (@33Ohms)
  
so the O2 puts out more power, i already know that. But power isn't everything.
  
Not my review:
http://noblehifi.blogspot.co.uk/2013/05/ifi-ican-review.html
  
 But mine is the new version with adjustable gain.


----------



## xnor

Put simply, power is the result of applying voltage to a load. You control the output voltage with your volume control. If you set the volume control low, the headphones will for example receive 10 mW max even if the amp *could* provide more power.
  
 The max output voltage is the input voltage (from your source, 2V in case of ODAC) multiplied by the gain.


----------



## ostewart

Thank you. I'm not as knowledgeable as you when it comes to electronics.
I just know how it sounds and if I like it or not...


----------



## MrMateoHead

xnor said:


> Put simply, power is the result of applying voltage to a load. You control the output voltage with your volume control. If you set the volume control low, the headphones will for example receive 10 mW max even if the amp *could* provide more power.
> 
> The max output voltage is the input voltage (from your source, 2V in case of ODAC) multiplied by the gain.


 

 I see. But any amp would therefore be limited, no matter the gain, but the amount of voltage it could provide. So, for example, the Ifi Can would tap out at 9 volts while the O2 (on adapter), can swing 12 volts. Right? A lot of amps seem capable of providing a lot of power at low impedance, but high impedance loads can be a very different story. I think the fact that high impedance phones can also be very efficient fools people into believing that Amp A is "just as good" as Amp B, even when it in fact provides less power.


----------



## xnor

mrmateohead said:


> I see. But any amp would therefore be limited, no matter the gain, but the amount of voltage it could provide.


 
 Well yeah. Primary limit would be the gain itself, after that the internal power supply will limit the voltage swing. If you overdo the gain (iCAN 20 dB setting = 10x) with a hot source (e.g. 2 V ODAC) you will get nasty clipping. High gain doesn't mean high or clean power.
  
 On the other hand, difficult low-impedance loads (where current requirements are more problematic than voltage) will also cause the output power to be limited.
  


> So, for example, the Ifi Can would tap out at 9 volts while the O2 (on adapter), can swing 12 volts. Right?


 
 I like to always use RMS numbers: The iCAN seems to be able to output 5 V, the O2 can output about 7 V with the right gain. Thats 40 / 80 mW into 600 ohms respectively.
  
 At 32 ohm the iCAN can output about 400 mW (= 3.5 V), while the O2 outputs over 600 mW (= 4.5 V). There are no 32 ohm headphones afaik that need nearly that amount of power, but you can see the limiting.
  


> A lot of amps seem capable of providing a lot of power at low impedance, but high impedance loads can be a very different story. I think the fact that high impedance phones can also be very efficient fools people into believing that Amp A is "just as good" as Amp B, even when it in fact provides less power.


 
 Yeah, voltage swing can be a problem with high-impedance headphones (thinking of portable devices with 1 V output ...). But all it takes is the right gain setting and an amp that can handle it.


----------



## tdockweiler

You know one thing I love about the O2 on my setup?
 I can go from a recording with the HD-650 and it sounds really warm and full sounding and the next track is ultra thin, metallic and too trebly (sounding like an AD700 due to recording). Like there is no bass and this is the HD-650! Other tracks give you bloated bass, but again it's IN the recording and not due to my HD-650 (confirmed this many times).
  
 I got similar results on the T90 and on my modded Q701. You really feel like you're hearing what exactly is on the recording. Same deal on my Micro Amp.
  
 Well..I guess i'm listening to a 128kbps Jpop recording..how'd that get in there. On some DACs you can't even hear Itunes samples as being bad.
  
 Some amps will not give you this kind of result...I'm guessing it's a combination of my DAC and Amp. Actually, probably more like the DAC without the AMP screwing with things.
  
 Right now I don't have an ODAC but am using the Headroom Micro DAC (CS4398). It's very revealing to my ears and even more so than the Modi.
   
It's amazing how with this setup now there is such a massive variation in how each recording sounds..and this is on the HD-650!!

  
  
 BTW someone mentioned the iFi iCAN earlier. I'm getting to try one tomorrow! Can't wait.


----------



## ostewart

You'll enjoy the iCan I think. I'll be reviewing it soon. Just listening to it a lot now


----------



## shyamelge

Is swapping opamps in O2 a good idea? No harm in doing so?
  
 Has anyone tried it previously? 
  
 Any feedback on swapping opamps such as 2132, 49720HA, 2017, 4562 is welcome. I shall be using it through power supply.


----------



## xnor

The op-amps in the O2 have been chosen carefully and the whole thing is optimized for input bias, gains, load impedance, quiescent current, speed, bandwidth, compensation (to ensure stability!), power supply voltage ....

If you have a favorite op-amp that you like to stick into anything that's pin compatible ... don't. As he-who-must-not-be-named said:


> “when you have only a hammer everything looks like a nail”. But that just doesn’t work for op amps.





Swapping op-amps should always be considered as a risk, unless you have the equipment to measure stability etc.


----------



## shyamelge

Thank you for your advise and the quote.


----------



## mcandmar

I have to agree, i built an eBay dac kit and replaced the 5532 with a 4562 and it transformed it, but with the O2 its best to leave well alone. The designer wrote an entie article on the subject where he tested various different opamps and picked the best ones for the job. If your going to do anything replace the chips with the DD versions are they are slightly quiter, but i doubt but you will ever hear the difference.
  
 On the other hand look up agdr's posts on diyaudio, he is continuing to develop the amp and has some interesting upgrades in the works..


----------



## adydula

If you want to muck around with the O2 there is only one real person that I know of that has had success in this area....take a look at
 agdr posts here: http://www.head-fi.org/t/693300/o2-headamp-output-booster-modification-pcb#post_10037386
  
 Also take a look at the DIY Audio site under headphone amps and there is a quite in depth discussion about this amp, its design, and lots of stuff.
  
 Alex


----------



## Koukol

ostewart said:


> iCan: 400mW of output power (@32 Ohms)
> O2: 613mW of output power (@33Ohms)
> 
> so the O2 puts out more power, i already know that. But power isn't everything.
> ...


 

 Ostewart,
  
 I'm considering this Amp but I'm a bit concerned as I'd be using it for an already neutral headphone (Shure SHR 840) so it has me wondering if I should find a similar priced TUBE amp to warm things up and bring out the bass?
  
 I'm looking for something to connect to my Oppo 95


----------



## ostewart

The SRH840 are a little on the warm side so the O2 would sound great with them. If you want a budget tube amp, the Bravo Ocean would fit the bill.


----------



## Koukol

Thanks Ostewart.
  
 Yes, I bought the 840's because they seemed to have the best balance of clarity and warmth so I can use them for mixing AND listening.(In my price range)
  
 Which would be the better choice to bring out the bass making the cans fuller and warmer for movie and CD listening?


----------



## ostewart

The Bravo Ocean would be better.


----------



## adydula

The Ocean has an output impedance spec of 20-100 ohms...wow that's going to affect the bass dept.
  
 If you want good controlled tight bass this is not the amp to look at.
  
 Its cute, small and inexpensive...it runs HOT!..
  
 I would get the O2 amp and if you really want to warm up things just EQ via your player software...
  
 All the best and good luck..
  
 A.


----------



## Koukol

OK,
  
 I'll get the O2
  
 thanks guys.


----------



## adamlr

adydula said:


> I would get the O2 amp and if you really want to warm up things just EQ via your player software...
> 
> All the best and good luck..
> 
> A.


 

 +1


----------



## Mmet

I see that jds labs o2 have socketed op amp ...is those rollable ?? So I can change the op amps ?


----------



## Sonic Atrocity

Hey guys, would this unit be powered sufficiently by 2.0 USB ports? Or will I need to supplement it with an externally powered USB hub? 
  
 Also, I'm wondering if I will have any issues (distortion, clipping, funny noises, problems with operation, or any problem possible) plugging this thing into my power bar? Or should I just plug it into the wall socket? And if I plug it into the wall socket can something else be plugged into it as well? 
  
 Like, ya know how there are two sockets, one above the other, would using BOTH sockets (one for my odac+o2 and one for my power bar that runs my computer and stuff) be a problem? 
  
 I'm just being super extra double sure with all these questions before I drop 300 bucks  
  
  
 Also, this thing is neutral, and transparent right? 'Cause, that's why I'm interested in it. 
  
 Edit: Does it matter if I get the headphone jack to be the 3.5 or the 6.5? Is there any difference in performance? I was also thinking I'd get the gain options at 1X & 2.5x. The 1x would be for my KRK KNS 8400 and the 2.5x would be for when I get the HD600. Thing is, I heard that if you don't raise the volume past 10'oclock on this thing there is a channel imbalance. So, a 2.5x would be too strong for my not-so-hungry KRKs. But it'd suit the HD600 nicely. Correct me if I'm wrong!


----------



## miceblue

mmet said:


> I see that jds labs o2 have socketed op amp ...is those rollable ?? So I can change the op amps ?



Yup, op-amp rolling is possible.




sonic atrocity said:


> Hey guys, would this unit be powered sufficiently by 2.0 USB ports? Or will I need to supplement it with an externally powered USB hub?
> 
> Also, I'm wondering if I will have any issues (distortion, clipping, funny noises, problems with operation, or any problem possible) plugging this thing into my power bar? Or should I just plug it into the wall socket? And if I plug it into the wall socket can something else be plugged into it as well?
> 
> ...



Yes, the ODAC is meant to be powered via USB 2.0. Unless your USB ports don't supply enough power (one of my ports on my old MacBook has this issue), then a powered USB hub may be necessary then (or you can just try another USB port).

Power bar and/or wall socket should be fine I believe. I would be worried if multiple-socket plugs weren't able to handle more than 1 device. With the O2 at 6.3x gain, you might hear clipping/distortion, but that's not because of the power, it's because of the amp design itself.

Yes, the ODAC and O2 were built to be transparent when compared/blind tested to a DAC-1 Pre.

No it doesn't matter which socket you use. Channel imbalance only occurs at low volume levels of the potentiometer (9 o'clock or lower-ish) because that's inherently a problem with pretty much all analogue volume potentiometers.


----------



## Sonic Atrocity

miceblue said:


> Yup, op-amp rolling is possible.
> Yes, the ODAC is meant to be powered via USB 2.0. Unless your USB ports don't supply enough power (one of my ports on my old MacBook has this issue), then a powered USB hub may be necessary then (or you can just try another USB port).
> 
> Power bar and/or wall socket should be fine I believe. I would be worried if multiple-socket plugs weren't able to handle more than 1 device. With the O2 at 6.3x gain, you might hear clipping/distortion, but that's not because of the power, it's because of the amp design itself.
> ...


 
 Cool, thanks for the response! So, by transparent, you mean neutral as well? 
  
 Also, would you suggest I stick with the 1x and 2.5x gain then? 
  
 I desperately want this unit. I am really, really excited to move beyond my clip zip. I've heard the improvement is very noticeable.


----------



## miceblue

sonic atrocity said:


> miceblue said:
> 
> 
> > Yup, op-amp rolling is possible.
> ...



Er, I should have said neutral instead of transparent. In terms of audio, transparent means the audio system sounds realistic (as if the sound is coming from a live performance rather than a speaker or headphone) whereas neutral just means not coloured. A system can be neutral but not transparent and vice versa. I almost never use neutral since I don't think it's possible to have uncoloured audio unless you were the original mastering engineer and you know exactly what the music is supposed to sound like.

I have the O2 at 1.0x and 2.5x gain, so yup!


----------



## MrMateoHead

sonic atrocity said:


> Cool, thanks for the response! So, by transparent, you mean neutral as well?
> 
> *Also, would you suggest I stick with the 1x and 2.5x gain then? *
> 
> I desperately want this unit. I am really, really excited to move beyond my clip zip. I've heard the improvement is very noticeable.


 
 I advocate keeping the 6.5X gain - it comes in handy when using 1V (or less) sources and HDR recordings (Live music, Movies, some Video Games). Particularly if you are using the O2 with headphones in the 90 dB efficiency range. If you think that will NEVER be the case, unity and 2.5x will probably be great.
  
 Remember that if you wanted, you can use the windows volume control (for example), you get your levels where you want them with whatever phones you are using. Also, you can take the O2 from 2.5X to 6.5X to 1X, 2.5X if you want, but you can't "add" gain later!


----------



## adydula

Sure you can, but it means opening the amp up and doing some soldering and some resistors!
  
 lol
  
 Alex


----------



## Sonic Atrocity

mrmateohead said:


> I advocate keeping the 6.5X gain - it comes in handy when using 1V (or less) sources and HDR recordings (Live music, Movies, some Video Games). Particularly if you are using the O2 with headphones in the 90 dB efficiency range. If you think that will NEVER be the case, unity and 2.5x will probably be great.
> 
> Remember that if you wanted, you can use the windows volume control (for example), you get your levels where you want them with whatever phones you are using. Also, you can take the O2 from 2.5X to 6.5X to 1X, 2.5X if you want, but you can't "add" gain later!


 
 Hmm, I am getting the ODAC+O2 combo so my source will always be the same. Either that or I'm misunderstanding you.


----------



## r010159

miceblue said:


> Yup, op-amp rolling is possible.
> 
> [deleted]
> 
> .




What compatible op amp chips do you recommend? What audible difference would it make?


----------



## adamlr

r010159 said:


> What compatible op amp chips do you recommend? What audible difference would it make?


 

 im not sure how advantageous opamp rolling would be... the whole circuit was built around these specific ones, and the measured performance has been proved and tested to many times... just my 2 cents...


----------



## Mmet

adamlr said:


> im not sure how advantageous opamp rolling would be... the whole circuit was built around these specific ones, and the measured performance has been proved and tested to many times... just my 2 cents..


 
 agree with you in some points ..... but may be you want to alter the sound signature .... would want more bass presence ... warmer sound ,,, or more intimate sound ....opamps offers that kind of tweaking ... it is not something like a day and night difference but it is noticeable .... and even the same opamp sound different from implementation to another


----------



## r010159

adamlr said:


> im not sure how advantageous opamp rolling would be... the whole circuit was built around these specific ones, and the measured performance has been proved and tested to many times... just my 2 cents...




I agree. But this may give me something to do.  I first have to make sure my relatively new O2 is fully functional before attempting any modifications. But then again, the O2 sounds great the way it is now.


----------



## adydula

Swapping op amps in an O2....hmmmm
  
 oh well....enjoy..
  
 Alex


----------



## adamlr

mmet said:


> agree with you in some points ..... but may be you want to alter the sound signature .... would want more bass presence ... warmer sound ,,, or more intimate sound ....opamps offers that kind of tweaking ... it is not something like a day and night difference but it is noticeable .... and even the same opamp sound different from implementation to another


 
  
  


r010159 said:


> I agree. But this may give me something to do.
> 
> 
> 
> ...


 

 rolling opamps, or tubes for that matter, or whatever other hardware modifications, will ofcourse effect the sound and may well be part of a hobby, granted, no argument. if thats what you wanna do - go for it. im just saying, that of all the amps to mess around with, i find the choice of the O2 to be strange. its built to be a high performance, cheap alternative to otherwise way more expensive gear. the whole argument around it is whether or not it could actually achieve "perfect linearity", or "perfect neutrality" if you will. many people will tell you that it does, and as you can see, im not the only one raising my eyebrows, its just a little strange is all... after all the fuss and argument, its become somewhat of a "cult" product, and most of its buyers want that "neutral" response its so famous for...
  
 all that being said - do whatever you want mate, i was just throwing in an opinion


----------



## r010159

I have considered your post. I agree. I decided not to roll my opamps. This would be to what advantage? This would be questionable at best.


----------



## tdockweiler

If you love how the stock O2 sounds, then there is no real reason to swap op-amps.
 I actually only did it because I don't love how it sounds with the Q701 and some brighter headphones.In this case I don't care about having the best measurements. I only care about what my ears tell me. Some minor coloration is OK.
 I also found myself almost never using the O2 and op-amps (in most cases) are dirt cheap!
  
 Swapping op-amps on the O2 is easy and all it requires is a few minutes. You don't even need to buy a chip puller. You can use a toothpick(!) or some pliers (not suggested).
  
 So far i've tried the OPA2227 and LM4562. OPA2227 is nice, but seems better for the Q701 than HD-650. It seems to be a little warmer than the stock op-amps.
 The LM4562 is a no go with the stock Q701, but I love it with the modded Q701 (which is warmer/bassier). Most say it's a brighter op-amp.
  
 The differences are minor really. For something like a DT-990 or grado SR-325i swapping to the OPA2227 or OPA1234 might be a good idea.
  
 I think you'll probably void your warranty though.
  
 BTW I think the stock O2 is great with warmer headphones like my HD-650 and DJ100. With my O2, the HD-650 sounds exactly how it should without much change at all.
  
  
 Haha, if you're nuts you could try getting the OPA627 to work with the O2. I don't think it's possible. I think that must be one of the most expensive op-amp there is. It's only single channel and you'd probably need one of those adapters. I don't even know if those fit on the O2. $34 for a single channel op-amp chip!!
  
 The OPA2134s are just $4.50 each.
  
 One i'd like to try is the AD8397. Not sure if it'd work and it'd require soldering onto an adapter.
  
 I'm new to op-amp swapping and it's kind of a cheap & fun experiment.


----------



## adydula

I agree...changing ops amps in an O2 to me is kind of defeating what its design is all about, but its easy to do....
  
 The O2 is about having a linear transparent amp, straight wire with gain.....
  
 Enjoy..
  
 A.


----------



## adydula

Note if your wanting something different, the new ODA has been completed over at DIY Audio.....agdr has redesigned the amp into something that might have
 been what a desktop version of the O2 might have been....
  
 I just got all my parts and am starting on it this weekend..
  
 ~~The current version uses 3 NJM4556AL chips per channel in parallel (6 op amps total per channel), no longer uses an OPA627 at all, uses LME49990 chips for the gain stage, and many other changes.
  
 http://www.diyaudio.com/forums/headphone-systems/229934-version-o2-desktop-amp-oda.html
  
 A.


----------



## 329161

Does anyone know if the 02/ODAC works with IOS sources (eg Ipod Touch) using a CCK?


----------



## jseaber

@dcfac73 - Yes, you'll also need a small hub to redirect ODAC's power consumption. See here for pictures and through explanation:
  
 http://blog.jdslabs.com/?p=838


----------



## WhiskeyJacks

ostewart said:


> Thanks for the comment, yes it takes a while to get used to if your used to a warmer source.
> 
> Look out in February for more from me on JDS labs products, including the ODAC


 
 Do you feel like brighter headphones at the top like the HP100s and the DT 990 pros(250ohms) would sound unkind with this pairing of the ODAC and the O2, and, have you ever tried the CDAC+(ODAC better isolation and power supply)


----------



## ostewart

I doubt there will be anything wrong with the pairing
 The O2 if very neutral so if you like the headphones all the O2 will add is gain.

Not tried the CDAC. ODAC is great but I prefer the iDAC from iFi.


----------



## WhiskeyJacks

ostewart said:


> I doubt there will be anything wrong with the pairing
> The O2 if very neutral so if you like the headphones all the O2 will add is gain.
> 
> Not tried the CDAC. ODAC is great but I prefer the iDAC from iFi.


 
 yeah I like the sound, of the DT 990s it is more fun but I actually enjoy things like London Philharmonic Orchestra from it, along with De-loused in the Comatorium  by Mars Volta sounds fantastic as well, I was just checking because of what people tend to say about them being slightly bright with the odac and I was not sure if that was true. Anyways thanks for the replies like usual.


----------



## ostewart

No problem


----------



## Fungus

Ok guys, I just bought a new 02 and noticed that the power port is located on the back, not front.
  
 Also there no light indicator when the power cord it's plugged in.
 The charger plug in adaptor doesn't no go the way in and can easily slide out. 
  
 Is this normal?


----------



## Connectz

I'm getting ready o order the O2 on monday.  I was reading the first page of this thread.  I LOVE the HD 650's sound signature; even right out of my laptop.  I just want them to be LOUDER, which is why i'm ordering the O2.  I prefer a flatter sound, which is why I have my HD650s in the house, some Focal KRX 2s in my car (DEH PRS80 driving them), and some Yamaha HS80Ms monitors for listening in the house.  All I want is an amp to make my laptop's signal louder, thats all.  If the O2 with the dac makes it sound cleaner, then thats a bonus.


----------



## Solrighal

I don't know what your built-in souncard is like but the JDS Labs models will likely improve things no end.


----------



## eargasmo22

Will the sound improve if I use IFI iusb with the 02 and Odac?


----------



## eargasmo22

I inevitably experience the popping sound when the 02 gets low battery. Will this damage my headphones? It doesn't take more than 5 seconds but you know it kinda scared the hell out of me when I hear that popping aound because it's sound is like something that can damage a headphone.


----------



## jseaber

eargasmo22 said:


> I inevitably experience the popping sound when the 02 gets low battery. Will this damage my headphones? It doesn't take more than 5 seconds but you know it kinda scared the hell out of me when I hear that popping aound because it's sound is like something that can damage a headphone.


 
  
 As long as the amp is powered down quickly, headphones will incur no damage.
  
 Allowing the cyclic, low battery operation to continue for extended durations may overheat some drivers.  Note that *heat* damages drivers. Brief transients from O2 are safe, just as playing excessively loud and/or clipped music for a short time is also safe (extended clipped playback produces heat --> heat kills drivers).


----------



## eargasmo22

jseaber said:


> As long as the amp is powered down quickly, headphones will incur no damage.
> 
> Allowing the cyclic, low battery operation to continue for extended durations may overheat some drivers.  Note that *heat* damages drivers. Brief transients from O2 are safe, just as playing excessively loud and/or clipped music for a short time is also safe (extended clipped playback produces heat --> heat kills drivers).




Do you mean that it is not good to invariably use my headphones with the 02 in low battery?


----------



## jseaber

eargasmo22 said:


> Do you mean that it is not good to invariably use my headphones with the 02 in low battery?


 
  
 Not good? It's safe, just not recommended for long durations. There is no chance of damage unless you allow the amp to cycle on/off long enough to simulate clipped music playback. This would take quite a long time--several minutes or even hours. I'm not sure why you'd want to do that. Consider this behavior O2's way of providing low-battery-indication.
  
 We test thousands of O2's per year, and thousands of customers make longer use of the amp. It's completely safe to operate O2. Simply turn the amp off or connect its AC adapter when its batteries are too low for normal playback.
  
 You'll find a suggestion in O2's instructions guide to turn the amp off when batteries are too low for playback. This statement exists because 1 in the past 10,000 customers fell asleep while his new O2 was running on battery power. After more than an hour of on/off transients, his headphones had overheated. JDS Labs replaced this guy's AKG's, and added a cautionary statement to the instructions guide. Solution: Keep O2 plugged into AC when you step away, or turn it off to avoid neglect.


----------



## dauhak

Will this Amp sound good with jvc sz1000 ? I want to hear sub bass, and i hate mid bass, is there a solution to eq down the mid bass.


----------



## MrMateoHead

dauhak said:


> Will this Amp sound good with jvc sz1000 ? I want to hear sub bass, and i hate mid bass, is there a solution to eq down the mid bass.


 
 Depends more on how the JVC's sound than the amp. I haven't found a headphone that doesn't work with the O2 yet and I see no reason why yours wouldn't.
 To EQ down the mid-bass, use an EQ! But I think you knew that. If you still can't get the sound you want, time to try some different headphones.


----------



## dauhak

mrmateohead said:


> Depends more on how the JVC's sound than the amp. I haven't found a headphone that doesn't work with the O2 yet and I see no reason why yours wouldn't.
> To EQ down the mid-bass, use an EQ! But I think you knew that. If you still can't get the sound you want, time to try some different headphones.




The JvC sz1000 is a weird headphone, it says 16 ohm impedence, but the sub bass doesn't work until I give a good amp to drive, I heard this headphone is power hungry.
I have fiio x3, sounds lil veiled, I want to hear the full potential of this headphone.

Used my phone lg g2, it sounds like crap.


----------



## MrMateoHead

dauhak said:


> The JvC sz1000 is a weird headphone, it says 16 ohm impedence, but the sub bass doesn't work until I give a good amp to drive, I heard this headphone is power hungry.
> I have fiio x3, sounds lil veiled, I want to hear the full potential of this headphone.
> 
> Used my phone lg g2, it sounds like crap.


 

 The specs claim power handling up to 1.5 watt, so it would seem they don't mind power! On the other hand, the 107dB efficiency @1 mW suggests they do not need a TON of power to crank.
  
 The main problem could be output impedance - that is, with a low 16 Ohm rating, it is very important that the amps you strap them to have very low output impedance. Sadly, most amp makers don't reveal that spec and it can definitely have an impact on your listening experience. Your fiio should be up to the task based on the specs alone, but you hear a "veiled" sound. Are you sure that isn't just the headphone itself? Lots of my sennheiser phones sound good but always a little "veiled".


----------



## eargasmo22

Can someonw make a comparison between the 02 and cyphee labs duet? It would be very helpful. Thanks!


----------



## JakeJack_2008

jseaber said:


> As long as the amp is powered down quickly, headphones will incur no damage.
> 
> Allowing the cyclic, low battery operation to continue for extended durations may overheat some drivers.  Note that *heat* damages drivers. Brief transients from O2 are safe, just as playing excessively loud and/or clipped music for a short time is also safe (extended clipped playback produces heat --> heat kills drivers).


 
  
 Hi,
  
  
 I am not experiencing any  _popping sound_ when the 02 gets low battery.
 Simply, at a certain point the batteries are 'dead' and the O2 is* absolutely quiet*. - No _popping _sound, hiss, buzz etc. et all. 
 Is this normal? 
	

	
	
		
		

		
			





   Ha, ha, ...
  
 This is exactly as if I turned the O2 off.
  
 P.S.
 I am extremely happy with the JDS Labs ODAC and O2 (as two separate units).


----------



## jseaber

jakejack_2008 said:


> Hi,
> 
> 
> I am not experiencing any  _popping sound_ when the 02 gets low battery.
> ...


 
  
 Also normal! The power management circuit in O2 is impacted by battery type/age, and capacitor tolerances. So, the circuit either shuts down the amp completely or slowly toggles power on and off.


----------



## Mkilci

Anyone has the Bravo Audion Ocean and O2 to compare?


----------



## Sam21

Sorry folks, I have a question:
  
 How do I make the JDS Labs O2 work without batteries and only with the AC adapter ? I took the batteries out some time ago but the unit wouldn't turn on without the batteries !


----------



## adamlr

sam21 said:


> Sorry folks, I have a question:
> 
> How do I make the JDS Labs O2 work without batteries and only with the AC adapter ? I took the batteries out some time ago but the unit wouldn't turn on without the batteries !


 
 i imagine youd need to solder the batter thingy out, and solder a cable or something to "connect the dots" as it were. im sure youll find all you need on the jds labs website. and if you email them theyll help you out for sure - they were very nice when i emailed them a while back..


----------



## Sam21

I took out the batteries, it still doesn't work, jseaber said in another thread that it must work if you just take out the batteries...maybe it is a power supply problem ? that is what jseaber said.


----------



## adamlr

sam21 said:


> I took out the batteries, it still doesn't work, jseaber said in another thread that it must work if you just take out the batteries...maybe it is a power supply problem ? that is what jseaber said.


 
 well he kinda knows what hes talking about doesnt he ;p only one way of finding out...


----------



## Sam21

seriously ? it doesn't power up with batteries removed ? I tried it and it didnt power up ...something wrong with my AC adapter ?


----------



## adamlr

if thats what john seaber says, then yea, id go get another adapter... hes the guy that makes these things after all.. be sure to take the old one with you so you get the same size plug. any ac-ac adapter outputting 14-20V will do (as written on the chassis). mine is 1A but if memory serves 500mA will do also... check out the site for exact requirements. 
  
 just to get this straight, you emailed jds labs, and the response was that the adapter was bad and needed replacing?
 if i were you, id put the batteries back in, and leave the amp on for a while, so as to empty the batteries, then plug in the adapter and see if they charge. if they dont - you need another adapter. if they do charge up, and you take the batteries out, plug the adapter in - and the amp doesnt work (like you were told it should), well, i find that alittle strange, but i am by no means an authority, i know next to nothing about electronics.


----------



## Sam21

thanks, I will use a multi-meter to see if the adapter is working or not.


----------



## Ritwik

Hi, I justed ordered O2+ODAC Combo! and I am a novice in amplifier section. I will run my Grado SR325e using this. I know Grado is easy to drive, but still I bought it to get better performance!
  
 Now please tell whether my following assumptions are correct or not:
 1. I need to run my Grado in low gain(i.e. NOT pressing the right pushbutton)  [Mine is not custom O2+ODAC]
 2. If I increase volume, the gain will start to increase.
     So,
           Lowest gain = Low gain mode + volume at the lowest level
           Highest gain = High gain mode + volume at the highest level
  
 3. It runs on AC Power. Then why the heck people are talking about batteries?  Sorry for being so novice! 
    Is it the case that in the box, the ac power charges batteries and they do have a lifetime. After that they need to be changed.
  
  
 WHY ARE DEVICES NOT AS SIMPLE AS IPHONES ?


----------



## canDigger

ritwik said:


> Hi, I justed ordered O2+ODAC Combo! and I am a novice in amplifier section. I will run my Grado SR325e using this. I know Grado is easy to drive, but still I bought it to get better performance!
> 
> Now please tell whether my following assumptions are correct or not:
> 1. I need to run my Grado in low gain(i.e. NOT pressing the right pushbutton)  [Mine is not custom O2+ODAC]
> ...



http://nwavguy.blogspot.in/2011/09/all-about-gain.html?m=1
Please read the blog and self educate yourself.


----------



## henkie196

Try your Grados on both gains and listen which sounds best to you. High gain will give you a louder sound than the low gain at the same volume setting. Low gain should typically have less noise, so would be more suitable for sensitive in-ears and/or headphones. I typically have everything on low gain, but I tend to listen at low volumes only, so YMMV.
See above, with low gain you'll be able to get a softer lowest and highest volume, with high gain you'll be able to get a louder lowest and highest volume.
It has an adapter that turns AC power into DC power (and a lower voltage). Internally it will be running on DC (hence the batteries). Your phone does the same (and when you are charging your phone, it charges on 5V DC power, regardless what you plug it in to).


----------



## Ritwik

Thanks man!
  
 I want to know the probable cases where, the chances are that my Grado can be damaged.
  
 Apart from that, it's an AC/AC adapter. So who is actually converting from AC to DC?


----------



## henkie196

Hmm, you're right, it is an AC/AC adapter. You can read some more details here (probably more than you'd ever need to know). There must be some AC/DC converter somewhere in the O2. The output to the headphones should definitely be DC.
  
 It mentions on the JDS labs site that their O2 + ODAC combo is without batteries, but the O2 alone does come with 2x 9V batteries.
  
 /edit
 I'm guessing from the designs on nwavguy's website, that in the JDS O2+ODAC combo, the ODAC PCB takes the place of the batteries, as they appear to use the same case for both the O2 and the O2+ODAC.


----------



## adamlr

sorry for the weird text layout - my computer is being weird...
  
 headphones, and all drivers of any kind "receive" ac, alternating current - which is what music is. a dc signal
  will kill most any driver. the inner workings of the 02 are powered by dc voltage (the only kind a battery 
 knows how to supply. but "the signal sent to the headphones" will definitely be ac.
 the 02 runs on ac power. 14-20 Volt. that why you need the adapter - to turn 110/220V ( depending on where
  you live) into 20V (for example).
 i imagine theres a componenet that converts the ac into dc in order to charge the batteries...
 gain settings are there to be played with. i have mine on unity gain - always. i rarely use the x2.5 option.
 if yours in completely "regular" from the site, x2.5 will be the low gain, and x6 (i think) is the high gain - which will]
  definitely be too much for your grados.
 if you feel that x2.5 is too much aswell, you can easily make unity gain an option with some super easy diy - why not cross that bridge
  when you get there?
 i say listen first and see. if on the low gain setting you cant listen at a comfortable level with the pot at (atleast)
  9 oclock, then maybe you should think of a little diy - the further you twist your volume pot right, the less imbalance
  between the channels you see.
 but if you can twist your pot to 9 oclock or more and the volume if good to your ears, i imagine youll be fine.


----------



## Sam21

*headphones, and all drivers of any kind "receive" ac*
  
 Wrong, Headphones receive a varying DC current. it is like a sinusoidal wave with varying wavelength and amplitude over time.


----------



## adamlr

sam21 said:


> *headphones, and all drivers of any kind "receive" ac*
> 
> Wrong, Headphones receive a varying DC current. it is like a sinusoidal wave with varying wavelength and amplitude over time.


 
 the driver works by pushing air. it moves forward, and backward. an ac current, say a sine wave at 1 KHz will make the driver move backwards AND forwards 1000 times per second. a dc current doesnt alternate - direct current. feeding a driver dc current will make the driver move backwards only, or forwards only - which is a sure way to kill the driver. that why distortion (the unintentional type) is so damaging to the pa systems. "clipping" creates small amounts of dc current at the "clipped" peaks, and if the technicians arent carefull - drivers may blow.
  
 music and sound are composed of frequencies. i,e how often the signal alternates. if a 100 Hz tone is played, the driver will alternate 100 times.
  
 theres no such thing as "varying dc current". by definition, direct current DOES NOT ALTERNATE.


----------



## adamlr

from wikipedia: 
 "*Direct current* (*DC*) is the unidirectional flow of electric charge. Direct current is produced by sources such as batteries,thermocouples, solar cells, and commutator-type electric machines of the dynamo type... ... *The electric current flows in a constant direction, distinguishing it from **alternating current (AC)."*


----------



## Sam21

yes but a DAC chip outputs different values of DC voltages at any given time...it is DC current but varies at any given time..in mathematical terms it is like a sinusoidal wave that is smooth.


----------



## adamlr

mate. a "sinusoidal" wave is another way of saying "sine wave". a sine wave alternates between positive and negative polarity at a given frequency. i guess you could say that a sine wave "alternating" at 0 Hz is like a direct current - but thats just a backwards way of seeing it.
 a smooth sinewave isnt really a sinewave is it? 
 direct current doesnt change its polarity... it remains positive (if im correct). if it doesnt change - you simply cannot hear it...
  
 from wiki:

 note the difference between the green line and the red line...
  
 im sorry, but will have to continue this at some other time, im done for the night...


----------



## adamlr

one more thing actually....
  
 you mentioned dacs. im assuming your talking about the 2Vrms standard output?
 rms means in laymens terms "average". the 2V will also fluctuate depending on the music...
  
 understand. the dac takes data and translates it into an analogue signal - which is electricity. 
 said signal passes on to be amplified and eventually to move the membrane. in order to create movement, the polarity has to change, or the membrane will only move in one direction.


----------



## Ritwik

I have received my Grado SR325e and O2+ODAC Combo a week back. So as you can all understand, I was busy last week experimenting.There are some noticeable attributes what I have found so far. I am listing them down.


 


My set:


Source: Apple Music(256 kbps AAC)


Player: iTunes in laptop/ Apple Music in iPhone 5s


DAC/AMP: JDS Labs O2+ODAC Combo (I only use low-gain)


Headphone: Grado SR325e Prestige series


 


My findings:


------------------


1. O2+ODAC is treble heavy(NwAvGuy said multiple times that it is neutral). The hi-pitch growls and shrills are crystal clear. I listen to post-hardcore bands like UnderOATH, Papa Roach and the output is tremendous.But sometimes the treble gets too sharp and it feels more of a bullet and less of a song.  


2. Whenever I listen to Adele(e.g. Don't you remember), I find the output to be not full. It lacks bass and sometimes the treble gets way sharper making the overall experience one-sided. Whenever I listen to the same song from my iPhone 5s without any amping, the overall performance seems better. With amp, the vocal is crystal clear but the overall output lacks fullness. It feels a bit cold sometimes.


3. People say Grado is only for metal. But I find Diana Krall or Adele sound supreme with these cans. Problem is if I use amp, I am not getting that out of the world feeling. 


4. SO I did the easiest thing possible. I changed the default EQ in iTunes.And now the output is far better with amp. But still I'd expect more.  


5. Out of context but still: _/\_ DAC in iPhone 5s _/\_


 


Can anyone please tell me how to get a better overall experience? I know Grado is not famous for bass. But if I am more than happy with the performance without amp, I should be happier with the performance with amp  . But for some sound signature, i am not.


 


Thanks in advance!


----------



## Mmet

ritwik said:


> I have received my Grado SR325e and O2+ODAC Combo a week back. So as you can all understand, I was busy last week experimenting.There are some noticeable attributes what I have found so far. I am listing them down.
> 
> My set:
> Source: Apple Music(256 kbps AAC)
> ...


 
 a bright headphone with a neutral to bright amp is not balanced compo i think ... so you can try to change either the amp or the headphone ....


----------



## MrMateoHead

ritwik said:


> I have received my Grado SR325e and O2+ODAC Combo a week back. So as you can all understand, I was busy last week experimenting.There are some noticeable attributes what I have found so far. I am listing them down.
> 
> My set:
> Source: Apple Music(256 kbps AAC)
> ...


 
  
 The problem is that you are listening to Grados which you don't seem to like . . . in the long-run, far easier, and far cheaper, to change your speakers than attempt to change your sound by looking for amps with the right "distortion" profile. Just sayin'


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## Ritwik

That's not at all true. I am loving my Grado from day 1. It's the performance of the amplifier that is making me puzzled.


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## MrMateoHead

ritwik said:


> That's not at all true. I am loving my Grado from day 1. It's the performance of the amplifier that is making me puzzled.


 

 Other than issues with recordings, like clipping from excess dynamic compression, the speakers are typically 99% of the problem. The O2 should be no more "treble heavy" than the recording + speakers. Sorry.


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## henkie196

It's all relative. The O2 is supposed to be neutral, i.e. no colouration of the sound. However, if you are used to listening to an DAC+amp that colours the sound to be a bit warmer, the O2 will sound bright or cold in comparison. If this is combined with headphones that are already somewhat on the brighter side of things, the treble might become too much.
  
 If the DAC and amp are indeed neutral, the brighter sound is actually what your headphones sound like. Technically, one could say that you should look for a more pleasant sound signature from the headphones themselves, as there is nothing wrong with the DAC/amp itself. On the other hand, if you like the sound of your Grados straight out of your iPhone, you could also ask yourself why you'd even bother with an external amp and possible uncomfortable sound signatures combinations. Or you could look for a DAC/amp with your prefered sound signature, or synergy as they like to call it here. Beware that this can be a rather lengthy and expensive pursuit.


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## Ritwik

I bought the DAC+AMP because it's written in almost all reviews that within 300$, it's the best you can get. And I have as a friend an international death metal band member in FB who suggested me this amp. So I didn't think much. I wanted to get the best sound in 600$ setup .
  
 This is my first DAC+AMP combo. I like it with no doubt. But I am more amused with the prowess of iPhone DAC. Anybody who will listen to Adele's "Don't you remember" by using both iPhone and this DAC+AMP from Apple Music, will find that out.


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## ostewart

Lets revive this thread, just finished building my HeadNHifi desktop O2 amp, it has RCA inputs and outputs, 6.3mm jack on the front and power jack on the back. My new reference stack is the O2 paired with the OL DAC.

Built with 1x and 4x gain

http://www.headnhifi.com/objective2


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## ostewart

Just posted my review of the desktop O2 by Head "n" Hifi: http://www.soundperfectionreviews.com/2017/09/review-and-build-head-n-hifi-objective.html

I'll copy it on to the review section soon


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## ostewart

Posted up on Head-Fi now: https://www.head-fi.org/showcase/head-n-hifi-objective2-desktop-version.22677/reviews#review-19254


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## Jimster480

ostewart said:


> Posted up on Head-Fi now: https://www.head-fi.org/showcase/head-n-hifi-objective2-desktop-version.22677/reviews#review-19254


Great review man, I feel the same myself.
I have a custom JDS Labs o2 with the same configuration as you and it performs just as you said and is useful for sensitive IEMs, etc.


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