# Review: NwAvGuy's O2 DIY Amplifier



## Shike

Pics added!
   
*Sources:*
   
  FLAC > Foobar WASAPI > SPDIF > Cambridge DacMagic
  Ipod with 320CBR mp3's
   
*Headphones:*
   
  AKG K702, Grado SR60 (bowl pads), Audio-Technica ATH-AD700, HiFiMan RE262, Altec Lansing UHP336 (Rebadged Super.Fi 3 - will be referred to as Super.Fi 3 from now on)
   
*Past Amplifier Experiences:*
   
  Mini^3, Schiit Asgard, AV123 X-Head, Benchmark DAC (demoed), NuForce uDAC, Fiio E5 & E3, various Little Dot amps (demoed friends units), Audio-GD Sparrow
   
*Music (FLAC): *
   
  The National – Boxer, Spoon – Transference, Nine Inch Nails – With Teeth, White Stripes – White Blood Cells, Daft Punk – Alive 2007
   
  --All music is replaygained to ~89dB—
   
*Notes about the Amplifier:*
   
                  I expect this review is going to be a point of contention for a lot of people currently, considering this amp is designed by a banned member of Head-Fi.  Nonetheless, since I’m one of the first owners of this amp I’ve decided to make a review to help others that are currently considering it.
  This amplifier was made with a gain of two and six respectively to ensure safety against clipping from sources up to 3.4V while using AC while still offering a fair amount of gain from portable sources (2v when using headphone out from ipod with gain of two, 3v out when using an ipod LOD and gain of six).
  For more information, please read the DIY thread regarding this amp to understand the maximum input of this amp.  Considering my impressions, I believe this compromise was an excellent way of maximizing performance and compatibility of an excellent amplifier.
   
*Price:*
   
                  Approximately $100 DIY or $150 built by MySlim at DIY Audio/ABI (Anything But Ipod) forums for a fully finished unit.  For those in England keep your eyes on Epiphany Acoustics as they too will be offering it (currently in pre-order stage).
   
*The Impressions:*
   
                  I have to say that no holds barred I was impressed with this amplifier.  The authority bass was reproduced with was excellent; it provided the K702 with more than enough voltage and current to really shine.  Details were rendered impeccably, allowing the music to come through and not the sound of the amplifier.  Treble is definitely present, but not exaggerated or shrill in the least.  Everything sounded very straight forward and effortless with power to spare for what many at head-fi consider very power hungry headphones.  I wish I had my K601 to test with since they require a bit more power, but unfortunately they’re out for repair.  Nonetheless, with the headroom I got powering the K702 I have no doubt the O2 will power them just as well in all honesty – I may update this review once they’ve been returned to me from AKG.
   
                  When used with the various less demanding headphones, I still was continuously impressed.  The Grado’s had their bright house sound, but impactful lower end they’re known for when powered properly, the ATH-AD700’s had their nice full midrange with upper range “sparkle”, and the Super.Fi’s had their relative neutral sound about them.
   
                  In terms of hiss the amplifier was absolutely dead quiet; even with a gain of six, plugged in to AC, with a Super.Fi 3 at max volume (note – this is dangerous and I would *NOT* recommend you try it!).  Crosstalk is negligible really emphasizing the separation of left and right channels compared to the Mini^3, which when tested I found issues with potentially audible crosstalk (using RMAA and listening to test signals).  In fact, using RMAA I almost had identical test results to NwAvGuy.  The O2 scored -73dB on crosstalk. In comparison, the Mini^3 using the exact same load scored -39dB.  The volume control usually sat around 10 o’clock showing excellent potential for headroom (it can almost turn to 6 o’clock from past the 10).  I have yet to test a quietly mastered track (recommendations appreciated!), but I have no qualms saying this amp should be able to reproduce them loud and full with almost any dynamic headphone around.  This was also using an almost redbook standard DAC (2.1V RMS).  Those producing higher voltages (~3V) should benefit even more with a gain of 2.   
   
                  When used with batteries and an ipod I was able to drive the RE262’s with ease noting once again how balanced it sounded, more than likely due to the amount of available headroom.  I was curious and also tried the K702 off battery – to my surprise they were able to get more than loud enough with little to no distortion, but an obvious loss in the degree of headroom.  Obviously this won’t be common usage, but I found it quite impressive.
   
                   I only have a couple issues with this amplifier that I will address now.  First, there’s an on and off “click”.  It’s been noted this is a small on/off transient, and in line with what I heard powering on say the Mini^3 – not to the extent of a pre-relay Asgard that was potentially dangerous to many headphones (from the mouth of AKG).  Some may be a bit concerned upon hearing it, but it is very small in reality.  Even with the Super.Fi 3’s, while distinct, it surely doesn’t strike me as really bad.
                  The largest issue however is the pocketability of the amplifier.  It’s clear to me that this is a transportable amplifier more than a portable.  It will be great for stays at a hotel while traveling for example, but in terms of actually using it as a portable on one’s self I find it awkward at best.  I find the Mini^3, Cmoy, and O2 fit in this category of amplifiers I really wouldn’t want to carry on me.  If you’re serious about portable usage I recommend sticking with an E5 or a well performing slimmer amplifier.
   
   
   
*Aesthetics:*
   
                  The recommended case looks very basic yet handsome, but the biggest downfall is probably the fact all cables plug into the front including power.  Depending on the usage one can work out a different enclosure, but that may ruin the easiness of transporting the amp.  On the plus side though, the default enclosure is cheap and available in a wide range of colors to match whatever look you really want.  Personally I went with silver.
   
*Conclusion:*
   
                  Did this amplifier get across its point?  I think so.  I won’t say it’s the do everything amplifier that the designer intended, because I really don’t see it being used in someone’s pocket on the go.  If you’re the type to carry an amplifier in a bag and leave it in there while routing out your headphones then batteries may still be worth including.  As a transportable or even desktop amplifier it certainly is punching way above what the price would suggest, measurements show solid performance and my impressions though sighted are the same.  I would recommend it above any solid state amplifier I’ve had on hands experience with thus far, even if you have the funds available for some of the higher priced offerings.  I probably would not recommend it to tube user that is most likely used to a different sound thanks to tubes' higher output impedance, but if they want to see what their headphones sound like from a really accurate amplifier this would be the one I'd suggest.
   
  If you want a reference grade solid state amplifier on the cheap, this would be my go to recommendation right now.  When my AV123 dies I will probably get a second O2, or consider the future desktop version that’s currently in the works.
   
  PS:  If you plan on building this amp, there is currently a group buy for PCBs at DIY Audio.  The cut off is going to happen soon from my understanding, so if you’re on the fence I really suggest you go for it.
   

 Hopefully this was helpful, and I am open to recommendations of quietly mastered tracks with lots of dynamic range and other recommendations as to make this review as complete as possible.
   
*Pictures! :*
   
  Got the FPE panel installed, let's take a look shall we?
   

   
  Without flash.
   

   
  With Flash
   

   
  Size compare 1
   

   
  Size compare 2
   
*EDIT :*
   
  On batteries, it seems mine may have been lacking charge.  After letting them fully charge (at least they should be) I noticed no difference in average listening volume regardless of potentiometer position.  Apparently the battery section will not get as loud at the end of the pot travel, but it should be a max of ~3dB or so.
   
  As for quiet tracks, mentioned it later but there's plenty of power to bring quiet tracks up to a very high level.  Plenty of ability for tracks with large amounts of dynamic range IMO, but I don't have any seriously challenging headphones rated below 100dB (K702 and K601 are rated above, still need to try K601 when it arrives from repair this week presumably).
   
  Pics of amp in the enclosure to come sometime mid-next week.  May try doing something interesting to the box if I have some spare time . . . we'll see ^_-
   
*EDIT 2:*
   
  Pictures added, you can see it's a rather minimalist design, but looks quite good overall (do know that the left port is for the AC wire though - maybe taller feet can allow routing the wire.
   
  Experience with K601 same with K702- the get plenty loud with no distortion and plenty of "oomph" to say the least.  Even mildly efficient cans should be powered _very _well, and that on mine outputting a "measly" 4V with my standard setup (the 6V using the ipod sounds just as good).


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## arirug

Great review! I have allready ordered one from Mr. Slim. And later I will buy the desktop version.


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## khaos974

For tracks with a huge variation of volume, try:



BTW, artistically speaking, it's absolutely superb.


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## fabio-fi

Sounds really interesting, hopefully i can give it a try sometime.


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## i_djoel2000

great review, shike..
   
  looking forward to the comparison with other amps


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## TheGomdoRi

Great review, I've followed the amp for quite a while and although I never had the commitment to build one myself, I was always curious to see if designer's claims were true.
  When you get a chance, please post some pictures - I'd love to see the finished product and perhaps build one myself.
  BTW, are there any dealers from North America for the finished product?


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## upstateguy

Pics Please !!!!!
   
  Very  nice review.


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## mikeaj

Quote: 





khaos974 said:


> For tracks with a huge variation of volume, try:
> 
> [Holst, _The Planets_ (Dutoit)]
> 
> BTW, artistically speaking, it's absolutely superb.


 
   
  There are definitely albums with more dynamic range, but this is just a fine one all around.
   
  Thanks for the review Shike, and do make sure to get the K601 back soon for impressions since mine are waiting.  
	

	
	
		
		

		
		
	


	



   
  Regarding how portable you feel it is, it's because of the thickness, right?  The length seems to be in line with phones, portable players, and so on, but the height is a bit over an inch.  On second thought, the width is also not small.
   
   
  edit:  by the way, regarding the group buy on diyAudio, ending soon...price for a single unpopulated PCB is around $6.03 including shipping and including Paypal fees.  It may actually go down a bit too.  The organizer is in the UK, so shipping to other countries will vary a bit, but this is not much of an investment even if you decide not to build it later on.


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## Shike

Seems I made a mistake, the company doing pre-orders in England is Epiphany Acoustics, not audio.
   
  -Shike


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## Olli1324

Quote: 





mikeaj said:


> edit:  by the way, regarding the group buy on diyAudio, ending soon...price for a single unpopulated PCB is around $6.03 including shipping and including Paypal fees.  It may actually go down a bit too.  The organizer is in the UK, so shipping to other countries will vary a bit, but this is not much of an investment even if you decide not to build it later on.


 


  Just to keep everyone in the loop here - the GB will end on the 31st. The prices are indeed very low and we should be able to shave a dollar or two off the price for US/CAN orders owing to the fact that I am currently in talks with a US distributor.


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## Uncle Erik

Thank you for the review and I'm glad you measured it, too.

I am interested in the design, but am holding off for the forthcoming desktop version. Most of my listening is at home and I'd like a power supply that runs off the mains.

I also wonder if this might make a good preamp. If possible, I'll build it as both a headphone amp and a preamp. It'd be nice to avoid hot tubes when it's 116° F out.


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## Draygonn

Thanks for the review. I'll be ordering one from MrSlim once the desktop model becomes available.


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## keroro

interesting review! really do hope for a more portable one.


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## b0ck3n

How do you _hear _headroom?


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## Willakan

I assume he means that to achieve the same volume with batteries, he had to turn the volume knob up higher, leaving less additional headroom to turn it even higher than that on a quiet track vs AC power.


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## Shike

Quote: 





willakan said:


> I assume he means that to achieve the same volume with batteries, he had to turn the volume knob up higher, leaving less additional headroom to turn it even higher than that on a quiet track vs AC power.


 
   
  This is correct.  When I say headroom I mean available travel on the potentiometer to increase volume.  Obviously, running on batteries is going to decrease your voltage capability and decrease the ability to drive the headphones as loud.  Basically, headroom to me is how loud you can go before you either clip or max out the amplifiers ability to increase volume.
   
  I should be able to try a few quietly mastered tracks tonight with larger dynamic range, take a picture of the board since it's been requested, etc.


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## Shike

I tried to get decent pictures, but if I use a flash I get some . . . I'm not sure what it's called, flashback?  The board lights up like a Christmas tree making it hard to see anything.  Without it everything is fuzzy/blurry.  Sorry everyone, maybe the full amp pic will turn out better though.
   
  Listening to Holst The Planets as recommended I noticed it made a bit more use of the headroom available, but still got plenty loud in the areas that needed it.  I would say that some very insensitive headphones might not play as loud as some would like with it, but the K702 certainly doesn't mind with the amp.


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## Willakan

I think it's called flash burn (not to be confused with the medical definition). Don't suppose you have a tripod or anything like that to keep the camera still if you take a photo with flash forced off?


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## limpidglitch

Quote: 





shike said:


> I tried to get decent pictures, but if I use a flash I get some . . . I'm not sure what it's called, flashback?  The board lights up like a Christmas tree making it hard to see anything.  Without it everything is fuzzy/blurry.  Sorry everyone, maybe the full amp pic will turn out better though.
> 
> Listening to Holst The Planets as recommended I noticed it made a bit more use of the headroom available, but still got plenty loud in the areas that needed it.  I would say that some very insensitive headphones might not play as loud as some would like with it, but the K702 certainly doesn't mind with the amp.


 


  Turn the flash off, macro on, steady the camera on something reasonably steady (like a stack of books), and point any available light at the board.
  If if you have a nice powerful desk lamp on a flexible arm put it as close to the board, while being outside the frame of view of the camera.
   
  And shoot! 
   
  Oh, and when running from batteries and an iPod LOD you should be perfectly safe with a gain of at least 8X, unless I have missed something fundamental.
  With these settings you should be able to achieve 97dB with your K701s and source material peaking at -20dBFS. I'd say that's quite sufficient.


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## b0ck3n

willakan said:


> I assume he means that to achieve the same volume with batteries, he had to turn the volume knob up higher, leaving less additional headroom to turn it even higher than that on a quiet track vs AC power.




I know what headroom is. I think the wording of the original post may have changed, I read something along the lines of "when switching from AC to battery power I can instantly hear a decrease in headroom". I may have been mistaken.


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## Shike

Quote: 





limpidglitch said:


> Turn the flash off, macro on, steady the camera on something reasonably steady (like a stack of books), and point any available light at the board.
> If if you have a nice powerful desk lamp on a flexible arm put it as close to the board, while being outside the frame of view of the camera.
> 
> And shoot!
> ...


 

 @B0ck3n
   
  The volume substantially drops when kicking over to batteries due to less voltage, which is why headroom drops.  Messing with the volume control it's pretty easy to say it won't get as loud, but for most music it should still be sufficient - that's all I was getting at really.


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## b0ck3n

Fair enough, thanks for clarifying.


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## jellojoe

Now we know why the maker was badmouthing the other portable amps.


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## gelocks

So... how would this compare to another Cmoy like the JDSLabs one!?
  (just wondering cause I just bought that one! lol )


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## b0ck3n

Quote: 





jellojoe said:


> Now we know why the maker was badmouthing the other portable amps.


 

  You didn't really think that through, did you?


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## bada bing

Quote: 





shike said:


> @B0ck3n
> 
> The volume substantially drops when kicking over to batteries due to less voltage, which is why headroom drops.  Messing with the volume control it's pretty easy to say it won't get as loud, but for most music it should still be sufficient - that's all I was getting at really.


 


 I'm a bit curious. Why does the volume drop when the supply voltage changes ?
  The voltage gain remains the same and unless the amp clips, the volume should be unchanged ?


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## 129207

Can't wait to get my hands on the desktop model!


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## Shike

Quote: 





bada bing said:


> I'm a bit curious. Why does the volume drop when the supply voltage changes ?
> The voltage gain remains the same and unless the amp clips, the volume should be unchanged ?


 

  
  The batteries may not have had a full charge and may have caused it to clip some, now that they're fully charged it doesn't seem to be an issue.  I don't know how long they will take to deplete to the point where they cause clipping on 6v RMS.
   
  @Negakinu
   
  Honestly, I'd say it's good enough as is to qualify for desktop position.  Just pick the gains required to do so and go for it (2 & 3 for a desktop only model would be my recommendation allowing 6v from 2v and 3v sources).  Seriously, it's that good of an amp as is.


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## 129207

Shike, I already own the Arrow 12HE so another portable would be a bit overkill. I don't yet own a decent desktop amp though. I talk to NWavguy occasionaly and, considering his knowledge on the matter, let's say I think the desktop version will be something quite special.


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## deadlylover

Quote: 





negakinu said:


> Shike, I already own the Arrow 12HE. I talk to NWavguy occasionaly and, considering his knowledge on the matter, let's say I think the desktop version will be something quite special.


 
   
  Won't the desktop version be pretty much the same thing with a relay and a slight change to prevent input overload from hot sources?


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## b0ck3n

^Indeed.


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## milosolo

Very nice review! Sounds interesting. Any chance of a few photos including back panel?


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## Shike

Quote: 





milosolo said:


> Very nice review! Sounds interesting. Any chance of a few photos including back panel?


 


  The back panel has nothing on it, all connections are on the front panel which I need to send out to have someone else drill (don't have a drill press at my place).


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## rayuma

Looking forward to seeing the finished product!


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## rayuma

Shike, have you used the O2 with a mixamp? I'm planning on using it with my Q701s on the 360.


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## Draygonn

Thanks for the review Shike. I placed an order with MrSlim for the desktop version.


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## Shike

Quote: 





rayuma said:


> Shike, have you used the O2 with a mixamp? I'm planning on using it with my Q701s on the 360.


 


  I used it with the SU-DH1 with good results (another Dolby Headphone processor).  The combination should work very well.


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## LizardKing1

Very good review! Are you still going to publish photos?


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## Shike

Quote: 





lizardking1 said:


> Very good review! Are you still going to publish photos?


 
   
  Yes, unfortunately the front panel I tried drilling got pooched.  As such I have an order at Front Panel Express that should show up approximately next Wednesday.


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## upstateguy

Quote: 





> Originally Posted by *Shike* /img/forum/go_quote.gif
> Quote: Originally Posted by *limpidglitch*
> 
> 
> ...


 
   
  We want to see your build.
   
  Just take a tall glass from your kitchen and rest the camera on it.  Use the macro setting and you're good to go.  All you need for lighting is regular room light, or put the board on your laptop keyboard and use the light from the screen.  Set the camera for florescent lighting, macro setting, rest on tall glass if you need it, but I found that the laptop light was enough to take very sharp pics hand held...
   
   
  Here's one I took for knife-Fi with the light from my laptop screen (click to enlarge)


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## i_djoel2000

concluding your review, are you saying that o2 is better sounding than Schiit Asgard and Audio-GD Sparrow, shike? if it is, that's pretty interesting..


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## Willakan

Both the Asgard and AudioGd products are cases of "Buzzword Design", IMO. Suffice to say that being fully discrete or single-ended has precious little to do with audio quality, so I wouldn't be surprised if they were actually audibly inferior. The only comprehensive measurements I've ever seen for AudioGd products (their discrete opamps) were abominable.


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## rroseperry

Willakan, could you explain what you mean by that? Thanks,


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## Willakan

/*mild rant alert*
  What I mean is that when I head on over to the Schitt/AudioGd sites and read the descriptions/FAQs for their products, I become incredibly sceptical of their offerings - mainly where they follow design practises which seem hugely counter-intuitive and justify them incredibly flimsily. For example, to quote the page for the AudioGd Sparrow:
   
  "The Sparrow uses ACSS (Audio-gd Current Signal System, which is a current signal transmission system). ACSS is a non-feedback technology make by Discrete amp. Most people had know the global feedback can offer better specs for the meters, non-feedback can't please the meters but can offer better sound for human's ears . Here is a conflict of the class circuits. But the ACSS arrive a new field, it can offer least coloration sound which is more neutral with very low distortion and high linear . So it can recur the dynamic, detail and neutral sound but not bright or harsh."
   
  This is pandering to audiophile mythology, not solid design practises. Sure, it's _possible _to get acceptable results whilst avoiding global feedback, but why would a designer begin their design process by handicapping themselves? Perhaps they're referring to feedback used incorrectly in some way? But no, they admit it will bugger up their measurements.
   
  It gets worse - they go on to paint the absence of a voltage switch as some ludicrous crusade to prevent audio degradation and to ensure that their users can hear the effects of upgrading their power cables. At this stage I'm feeling more than a little cynical regarding their marketing literature. Regrettably, they're not done - it's "fully discrete."
  Now, fully discrete is all very well in power amps, but in headphone amps it doesn't make any sense. Firstly, it is monstrously expensive to do well, both in R&D and in sheer parts cost. Even then, you're going to have a phenomenally hard time equalling the performance of a cheap little IC opamp. Trying to paint this as "not using cost cutting measures" is utter crap. The only examples of AudioGd's attempts at discrete opamps I've seen measured terribly - doesn't fill me with confidence regarding their designer/s.
  This is finally exacerbated by how they describe their products. The one thing that puts me off a company's product range is when they assure me the sound isn't "digital."
   
  Call me paranoid, but I get the feeling that these design decisions are not justified by some incredible crusade for pure audio. This is, as I put it earlier, "designing by buzzwords." Audiophiles have various irrational dislikes of things such as IC opamps and get all excited when somebody shouts "Fully Discrete!" at them. Thus, people don't design for low distortion, or maximum neutrality, or anything like that. They design to pander to audiophile mythology and do so at such a price point and so utterly that you become incredibly wary as to the quality of their products.
   
  Let's move on to Schiit. In some ways (such as basic literacy - I know AudioGd are Chinese, but other small companies pull off rather better translations) they are superior, but they still ultimately annoy me in much the same way. The very first line on the Asgard's web page reels out its fully discrete credentials and follows up with the line "No opamps, no shortcuts" - This is, again, pandering to audiophile mythology, so people on Head-Fi can go "Ooh, fully discrete at such a low price!"
  I was recently further annoyed by the publicity spiel for their new DAC:
   
  "The ugly truth about most DACs in this price range is that they sacrifice every single one of your original music samples to get their magic "192kHz" spec"
  This is scaremongering crap, playing to audiophile paranoia. The Benchmark DAC1, for example, resamples to 110khz and I'll wager it beats the crap out the Bifrost delivering - god forbid - what's on the recording! With minimal variance! 
  Compared to the "Fully Discrete" BS however, it's small fries.
   
  And don't get me started on Burson. Their "The Naked Truth About Opamps" article single-handedly dissuades me from ever touching any of their products with a barge pole - I could make up something better myself. Seriously, raving on about "The size of opamps compared to discrete circuits causes forms of quantum degradation which are only clearly apparent in listening tests." would have been more plausible.
   
  I realise this is reading like an incredibly ill-natured rant against some of the most popular products on Head-Fi. But when a company sells its products to irrational audiophile criteria...on the one hand, I can't blame them. Nobody wants to hear about how little distortion your amplifier has when you can rave on about how it uses no evil "short-cut" opamps - even if thanks to that 0.1% THD is the best you can manage on your own specs - that's not Hi-Fi by the standards of a SS power amp in the 1980s, let alone a modern headphone amp. When I read the list of reasons why I should purchase such company's products, I don't expect them to reel off the number of ways they handicapped their designs.
   
  I understand that it is entirely possible to make an OK product despite such self-imposed stumbling blocks - but when half their publicity literature is about claiming that they are all plus points... Meanwhile, I can't really begrudge companies playing a little to their audience. But likely screwing over their product so the marketing department has something to say? People will say "Oh, but this distortion is inaudible," - but how can all these audiophiles claim to care about the supposedly subtle and unmeasurable when they don't seem to care about the basic, measurable aspects of a product that determines that it is competent?
  Good grief, this is getting more rant-y by the second. The really infuriating part is that if you were ever to post something like this in its own thread, I can predict the first 5 responses:
   
  1: OMG, not another measurement wh***, bugger off.
  2: I can hear how opamps corrupt the music - you must be deaf.
  3. I think designer "X" knows a little more than you do (delivered condescendingly)
  4. Fully discrete is always better because opamps are cheap.
  5. Well I like how they sound! Some people, always stirring things up...
   
  So the best I can say is that companies who design primarily to buzzwords will never, ever get any of my money. It's a pity, because designing in this way is so common you have to pay hugely over the odds simply to ensure that the designer didn't decide he knew more about opamp design than the entire R&D department of Texas Instruments.


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## fubar3

I think Willakan has a sensible point about discrete vs opamp.  The more components in a design, the more variance that can occur between assemblies of the same design.  With discrete there are collections of transistors, caps, resistors, etc from different vendors. Of course, they are spec'd within a tolerance but there is variance.  So it is probable that each amp rolling off the assembly line has a unique signature. On the other hand, opamps are manufactured from monolithic blocks, as far as I know, so I expect they will be self-consistent.
   
  Opamps and buffers from National and others claim incredible low distortion. They provide reference boards (too expensive for DIY) which others vendors can test for quality.
   
  IMO, discrete designs without blocking capacitors are too difficult and risky for DIY. One mistake, and poof goes the expensive headphones.  Stick with opamps.


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## CEE TEE

*@OP:*  Late morning or late afternoon, you might...
   

 take the amp outside (in the shade but where it is _bright enough to shoot well)_
 place on ground (not on dirt of course, concrete is better)
 use exposure compensation of about +1 stop (_or don't if you are unfamiliar with this control_)
 stand over amp and photograph downward (adjust zoom depending upon lens)
 try to shoot in-focus (zoom-in to max on your camera's display to see if you are sharp)
 don't worry about color balance (bluish-tinge look)
 sharpen
 adjust exposure globally (should be pretty evenly lit, probably "brighten")
 *OR:* if pics are looking a bit "off" in any way- *send pics to me in PM to correct and return.*
   
*Just an offer...so we may SEE the amp too!*


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## Willakan

Quote: 





fubar3 said:


> I think Willakan has a sensible point about discrete vs opamp.  The more components in a design, the more variance that can occur between assemblies of the same design.  With discrete there are collections of transistors, caps, resistors, etc from different vendors. Of course, they are spec'd within a tolerance but there is variance.  So it is probable that each amp rolling off the assembly line has a unique signature. On the other hand, opamps are manufactured from monolithic blocks, as far as I know, so I expect they will be self-consistent.
> 
> Opamps and buffers from National and others claim incredible low distortion. They provide reference boards (too expensive for DIY) which others vendors can test for quality.
> 
> IMO, discrete designs without blocking capacitors are too difficult and risky for DIY. One mistake, and poof goes the expensive headphones.  Stick with opamps.


 
  It's not just being fully discrete. Avoiding negative feedback like the plague and going single ended are certainly not done for "sound quality." Either the designer believes they do in fact boost sound quality, or he knows exactly what affects sound quality and is more interested in meeting various arbitrary "audiophile" criteria. Neither makes me want to hand over my CC.
   
  Anyways, back on topic: pics?


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## Shike

This seems to be about the best PCB pic I can get.  Not sure how helpful it will be, but might give people an idea of the attention to layout of the design.  It's going to go back in the enclosure and stay there now, I don't want to risk any ESD.
   
  @Willakan
   
  I actually believe opamps can perform well even in speaker amplifiers.  See the gaincard and various clones for example - as long as nothing nasty is popping up on the measurements and it's providing sufficient power all is good IMO.  Discrete should only really be considered in very high power designs IMO - we're talking greater than 100W into 4 ohms territory though.


----------



## Deep Funk

Interested...


----------



## Willakan

By all means, opamps can perform well in power amps, it's just not as clear cut as I understand it vs headphone amps or other low power applications (DAC internals). It's rather harder to say definitively to the designer "There is no audio-related reason for doing that."
   
  PCB looks like a nice job.


----------



## everlong

Looking forward to test this all-for-one amp
   
  But i can't see anywhere what kind of inputs this got? And has there been any mention on a recommended dac?
  And any status on the desktop edition with AC-adpter power?


----------



## LizardKing1

Guys I by no means want to start a flamewar. Understand that this is a question since I am not sure about these things. But I read a quite convincing argument about how all good DACs would/should sound exactly the same. I mean, obviously an amp can have minute differences, since that deals with an analogic sound signal. But a DAC deals with 1s and 0s, with digital content. Basically the point I read was that even though a DAC could be flawed and transmit the music badly, the differences wouldn't be "slightly veiled mids" or "a bad extension on the treble", it would be more like "choppy music" and audible artifacts. Jitter would be a problem, but it would result in a certain part of the music playing or not, not in playing with a slightly worse quality. Not so much bad perception of music, but more like a corrupted file. So, if two DACs are well-designed and don't have these artifacts audibly, the music they play is exactly the same right?


----------



## castlevania32

"If two DACS sounds different, it means *at least one of them* is a flawed design"


----------



## Willakan

@everlong:
  Inputs: Either board mounted 3.5mm jack or case-mounted RCA jacks.
  Recommended DAC: NwAvGuy is evaluating various cheap DACs at some point, but any competently designed DAC will be fine. I'm pairing mine with a Cambridge Audio DACmagic; it is considerable overkill from an objective perspective but the input switching and digital passthrough made it just about justify a not insignificant cost.
  Desktop Version: The current version has a jack to plug in a recommended AC adapter. NwAvGuy's summary article on his blog details the particular advantages a desktop version might hold - mainly dealing with weird, high voltage sources and the ability to boardmount everything.


----------



## upstateguy

Quote: 





castlevania32 said:


> "If two DACS sounds different, it means *at least one of them* is a flawed design"


 

 I was under the impression that although digital 1s and 0s go into one end of a DAC, good old fashioned analog music comes out of the other.   It is in the analog sections that the differences in sound occur.


----------



## mikeaj

Quote: 





upstateguy said:


> I was under the impression that although digital 1s and 0s go into one end of a DAC, good old fashioned analog music comes out of the other.   It is in the analog sections that the differences in sound occur.


 

 Yes, but the DAC itself is one of the analog sections you're referring to, since the output of the DAC is an analog waveform after all.  It's something like copying bits of a music file off of the hard drive or optical drive to the USB interface that is pretty much irrelevant, so long as the bits all get there.  There are plenty of ways for DACs to muck up the signal such that you don't get what was intended (but getting it "right" or good enough for music playback, really shouldn't be too hard or require exotic implementations and super-duper expensive-o components).


----------



## upstateguy

Quote: 





mikeaj said:


> Yes, but the DAC itself is one of the analog sections you're referring to, since the output of the DAC is an analog waveform after all.  *It's something like copying bits of a music file off of the hard drive or optical drive to the USB interface that is pretty much irrelevant, so long as the bits all get there*.  There are plenty of ways for DACs to muck up the signal such that you don't get what was intended (but getting it "right" or good enough for music playback, really shouldn't be too hard or require exotic implementations and super-duper expensive-o components).


 


  I wish it was so simple.  I have 2 USB transports, (Blue Circle Thingee/ HiFace) that don't sound the same......  and if you really want to make yourself crazy, the BCT uses the same PMC2707 chip that is built into my Stello DA100 DAC, and the two of those don't sound the same.


----------



## judmarc

Quote:


lizardking1 said:


> Guys I by no means want to start a flamewar. Understand that this is a question since I am not sure about these things. But I read a quite convincing argument about how all good DACs would/should sound exactly the same. I mean, obviously an amp can have minute differences, since that deals with an analogic sound signal. But a DAC deals with 1s and 0s, with digital content. Basically the point I read was that even though a DAC could be flawed and transmit the music badly, the differences wouldn't be "slightly veiled mids" or "a bad extension on the treble", it would be more like "choppy music" and audible artifacts. Jitter would be a problem, but it would result in a certain part of the music playing or not, not in playing with a slightly worse quality. Not so much bad perception of music, but more like a corrupted file. So, if two DACs are well-designed and don't have these artifacts audibly, the music they play is exactly the same right?


 

 Read some online academic papers or other available information written by audio engineers regarding jitter.  The result is not just dropouts, which are vanishingly rare in the absence of something badly wrong.  It also, in well-known non-voodoo ways, causes at least the following two problems: (1) raising the noise floor, resulting in less dynamic range; and (2) high frequency intermodulation distortion.


----------



## Willakan

True, but you need obscene amounts of jitter to be audible. Ironically, the gear with the most jitter is likely some dodgy, half-baked "audiophile" design. Stereophile have measured some insanely pricey equipment with very high jitter levels. For example, when used as a USB DAC the HifiMan HM601 had so much jitter that it was difficult to reliably measure it.


----------



## judmarc

Quote: 





willakan said:


> True, but you need obscene amounts of jitter to be audible. Ironically, the gear with the most jitter is likely some dodgy, half-baked "audiophile" design. Stereophile have measured some insanely pricey equipment with very high jitter levels. For example, when used as a USB DAC the HifiMan HM601 had so much jitter that it was difficult to reliably measure it.


 

 I'm sure there's gear of which that's true.  The audiophile gear I'm familiar with does a lot better on these sorts of things - e.g., the Wavelength stuff, whose Cosecant was measured by Stereophile as having the best jitter numbers they'd ever seen in a USB DAC; or the Theta I've got, 20 years old but designed by folks who knew jitter was bad and how to minimize it.
   
  Regarding how much jitter is audible, I've seen statements all over the lot.  There are some extremely well respected people in the industry (Keith O. Johnson of Spectral is one who comes to mind) who claim differences in the tens of picoseconds are audible.  I don't know about that, but then there's a hell of a lot I don't know about audio compared to Keith O. Johnson.


----------



## limpidglitch

Quote: 





judmarc said:


> I'm sure there's gear of which that's true.  The audiophile gear I'm familiar with does a lot better on these sorts of things - e.g., the Wavelength stuff, whose Cosecant was measured by Stereophile as having the best jitter numbers they'd ever seen in a USB DAC; or the Theta I've got, 20 years old but designed by folks who knew jitter was bad and how to minimize it.
> 
> Regarding how much jitter is audible, I've seen statements all over the lot.  There are some extremely well respected people in the industry (Keith O. Johnson of Spectral is one who comes to mind) who claim differences in the tens of picoseconds are audible.  I don't know about that, but then there's a hell of a lot I don't know about audio compared to Keith O. Johnson.


 


  Have you ever considered the possibility that Johnson and other people in the business may have some interests to protect?
   
  Any serious independent study that has been made on the subject show that you need several orders of magnitude more jitter than what Keith O. Johnson 'think' you do, for it to be audible.
  A good example is the 1998 AES paper by Benjamin and Gannon showing that under the most optimal conditions jitter under 10 nanoseconds cannot be detected. For music, where you get all sorts of masking effects, none of the subjects could detect it under 20ns.


----------



## Willakan

Based on all the stuff I've seen on jitter, claiming 10ps differences are audible seems like pure fantasy to me - like claiming you can distinguish 0.0005 and 0.0001% THD.
  Audible jitter is in about the 10s of nanoseconds IMHO (as above post) which is three orders of magnitude worse. (3!)


----------



## skeptic

Quote: 





judmarc said:


> I'm sure there's gear of which that's true.  The audiophile gear I'm familiar with does a lot better on these sorts of things - e.g., the Wavelength stuff, whose Cosecant was measured by Stereophile as having the best jitter numbers they'd ever seen in a USB DAC; or the Theta I've got, 20 years old but designed by folks who knew jitter was bad and how to minimize it.
> 
> Regarding how much jitter is audible, I've seen statements all over the lot.  There are some extremely well respected people in the industry (Keith O. Johnson of Spectral is one who comes to mind) who claim differences in the tens of picoseconds are audible.  I don't know about that, but then there's a hell of a lot I don't know about audio compared to Keith O. Johnson.


 
   
  Not sure which version of the Coescant you're thinking of, but stereophile's measurements of the v3 actually revealed some serious flaws.  See http://www.stereophile.com/content/wavelength-cosecant-v3-usb-digitalanalog-converter-measurements and http://www.head-fi.org/t/560122/all-dac-s-sound-the-same/225#post_7574387


----------



## i_djoel2000

ok, maybe this is a stupid question but someone has to ask it anyway 
	

	
	
		
		

		
			




   
  shike, have you tried b22 before? how do you compare this o2 to the amb b22 (2, 3, 4 , 5 channels, whatever)?


----------



## Shike

Quote: 





i_djoel2000 said:


> ok, maybe this is a stupid question but someone has to ask it anyway
> 
> 
> 
> ...


 


  Haven't tried a b22 before, sorry!


----------



## Shike

See EDIT 2: pictures and comments on usage with K601 added.  Still VERY impressed to say the least ^_-


----------



## khaos974

I know why you have problems with the flash, the sensor on your camera has a limited dynamic range, even the best DSLR are limited to less than 14 bit of real dynamic range, point and shoot camera (or phone cameras) have sometimes less than 8 bit of dynamic range. 

The very high contrast of the scene (black background vs silver amp) tricks the exposure meter and makes the flash brighter than necessary and the sensor simply can't handle this amount of light, creating burned areas in the brightest spots.


----------



## Shike

Quote: 





khaos974 said:


> I know why you have problems with the flash, the sensor on your camera has a limited dynamic range, even the best DSLR are limited to less than 14 bit of real dynamic range, point and shoot camera (or phone cameras) have sometimes less than 8 bit of dynamic range.
> 
> The very high contrast of the scene (black background vs silver amp) tricks the exposure meter and makes the flash brighter than necessary and the sensor simply can't handle this amount of light, creating burned areas in the brightest spots.


 


 Yeah, it's a Panasonic LS70 which was at best "okay" at the time I got it . . . now it's ancient.  The second it dies I hope to buy a newer and hopefully better "true" compact camera (the bulk on this thing is the second largest drawback for me)


----------



## estreeter

(disclaimer: I dont have a dog in this fight - no AMB products, no CMOY, and no axe to grind with Jude or anyone here)
   
  My thoughts after reading nwavguy's incredibly detailed blog entries on this amp:
   
  - whatever you think of nwavguy, he makes some good points - when the hell are amp manufacturers going to included detailed specs with every new blurb on their latest 'must have' amp ? Forget expensive measuring gear - I understand they dont all have access to that - some RSA amps dont have even the most basic of specs on the product page for some of their amps ....
   
  http://www.raysamuelsaudio.com/products/sr-71b
   
  - nwavguy has antagonised a lot of people here, and there is no denying that he can be a thorny character, but offering $500 to anyone who can independently verify their amp tests better in a DBT is, AFAIK, the first time anyone has been willing to do this. I guess some will write it off as a 'stunt', but I dont know of too many charities that wouldnt want $500. Time for someone to put up or shut up.
   
  - he has put his design where his mouth is, which is a long way from most of the keyboard warriors in Sound Science. Anyone who wants to measure/DBT/whatever his design and tear it to shreds (or not) is now free to do so - its no longer people arguing over the theoretical benefits of balanced ground or whatever. Even if this doesnt alter the audio landscape irrevocably, kudos to nwavguy for doing it
   
  Now to play Devils Advocate. nwavguy has gathered a host of acolytes who lap up everything he says, accept his measurements without question and pretty much bag every other sub-$1000 amp on the planet. I dont have the technical understanding to challenge any of his measurements, or even his design principles, but I struggle with the concept that a single amp (roughly the footprint of the QA350) costing $150 assembled will drive everything from 16-ohm IEMs to planar magnetics flawlessly. Go back and re-read the early posts where he debated the merits of a gain switch, finally conceding that he needed to make it happen : I think that was a good move.
   
  The final point I want to make is that he has put himself in an enviable position, assuming the amp lives up to its promise of 'wire with gain' : in any blind test where you tell me I couldnt tell the difference between a $150 amp and one costing $450, which one do you think I will buy ? Even if the aesthetics arent as good, is the additional 'sig cred' of the $450 amp worth it ? He mentions that many will favour the 'name brand' amp in a sighted test, and I'm sure thats true, but anyone paying for an amp with their own money will struggle to follow that with their wallet IF the subjective differences are negligible - at least that would be my attitude.
   
  I dont accept everything nwavguy tells us at face value, and I'm far less concerned with graphs than subjective performance, but for $150 assembled, what competition does this amp have ? nwavguy may have taken some paint off my beloved E9 (output impedance too high), but for that kind of money, I may just have to put my ZO V2 plans on hold.


----------



## maverickronin

It not impossible that he faked all those measurements but if he did it would have to be some of the world's most elaborate trolling because otherwise its just going to ruin his reputation for no other gain because just about no one (including me) is going to pay attention to anything he says anymore if such a thing turns out to be true.
   
  Given all the emphasis he's put on measurements someone is probably going to check it out sooner or later (even if all his talk about finding someone else to verify the measurements is just a smokescreen) and if both sets of data don't match fairly closely there are precious few excuses as to why that might be.
   
  Also, that fact that he uses a handle doesn't matter to the fact that no one will pay attention to him anymore.  Its not like he could start another blog under another name testing with the exact same kilobucks worth of testing gear and expect no one to notice it wasn't the same person.


----------



## mikeaj

I agree; a good amount of skepticism here is healthy, but as pointed out above, the whole thing is rather believable. Personally I have a degree in EE and am working on another, but analog electronics is definitely out of my area of specialty.

The questions come down to
1) Are the measurements valid and as advertised? (edit: to be clear, I think it's borderline preposterous to think that they were faked, though 3rd party testing is always welcomed)

Shike tested the crosstalk at least, and it seems to match up. Some other independent validation would be nice though. If you have an O2 and no expensive test gear, it should be still fairly easy with a reasonable sound card to do a line out -> O2 (loaded with resistor or even headphones) -> line in loopback test. Run say the 1 kHz test tone THD test, guesstimate the output level (or measure it with a multimeter) and compare the result with the matching part on one of his graphs. Either you can see if the measurement is similar to his, or you can note that line out -> O2 (loaded) -> line in produces the same THD score as line out -> line in, meaning that the O2 (loaded) added less distortion than your sound card can measure. If it's better while driving headphones than your sound card can measure, that would be a noteworthy data point in of itself.

2) Supposing the measurements are valid, do you believe that a device with that kind of performance will sound good and drive everything as advertised, or do all those extensive industry-standard benchmarks not capture the capability (or sound quality) of the device? Does a device that does really well at reproducing combinations of test tones at a good range of output levels and into different loads, somehow fall flat with real music?

Seems really unlikely but possible. Also, why would those be accepted industry benchmarks and metrics if they were not valuable in some sense? One possible test that could be done would be to play and record some real music (again, line out -> O2 loaded -> line in) and then do a comparison between the original music file and he recorded file. Comparison could be a listening test between the two files or doing looking at the difference in the files sample by sample (and/or do some spectral analysis) to see if some uglies showed up, if anything was clipped, if somehow the treble got peaky, if somehow the bass changed in character and became less authoritative, and so on. Again, any differences could be caused by your D/A and A/D rather than the amp though.


All this in addition to just listening to it normally of course.


----------



## LFF

Quote: 





mikeaj said:


> Does a device that does really well at reproducing combinations of test tones at a good range of output levels and into different loads, somehow fall flat with real music?
> 
> 
> All this in addition to just listening to it normally of course.


 

 Music is a series of tones and silences.....
   
  If something does well at reproducing test tones, it will do well with music....


----------



## Maxvla

"Sig cred" is overrated. Once one gets past this, you finally begin to gain from your experience at Head-fi. Many people get caught up in the who's who of Head-fi with gear lists and gold lined signatures, but you have to get past that and get back to the real passion, the music. The only reason I post gear in my signature is for a point of reference for readers of my posts.

If I find the O2 to be the best amp for me, it will find it's spot below my posts just as other gear does. Recreating the music in as transparent a way possible while not spending a lot should be the goal of any person on this site. Not spending a lot is relative to ones budget, but you should never buy anything just because it's the next new expensive shiny toy everyone has crowned champion. This is one of the reasons I highly recommend going to meets. There's no replacement for experience.


----------



## LFF

Quote: 





maxvla said:


> This is one of the reasons I highly recommend going to meets. There's no replacement for experience.


 

 So true.....
   
  That is my first recommendation to any newb that PM's me...


----------



## LizardKing1

Quote: 





maverickronin said:


> It not impossible that he faked all those measurements but if he did it would have to be some of the world's most elaborate trolling because otherwise its just going to ruin his reputation for no other gain because just about no one (including me) is going to pay attention to anything he says anymore if such a thing turns out to be true.
> 
> Given all the emphasis he's put on measurements someone is probably going to check it out sooner or later (even if all his talk about finding someone else to verify the measurements is just a smokescreen) and if both sets of data don't match fairly closely there are precious few excuses as to why that might be.
> 
> Also, that fact that he uses a handle doesn't matter to the fact that no one will pay attention to him anymore.  Its not like he could start another blog under another name testing with the exact same kilobucks worth of testing gear and expect no one to notice it wasn't the same person.


 

 Like you said, why would he do that? Besides the reputation of being the inventor of one of the best DIY amps, what would he gain from faking those measurements? The fact that he doesn't make any money out of the O2, added with the fact that he's still got the 500$ amp-DBT running would make that possibility very slim.


----------



## maverickronin

Quote: 





lizardking1 said:


> Like you said, why would he do that?


 

 Maybe he's a deep cover subjectivist out to discredit science and evidence in this hobby...somehow or other...


----------



## Willakan

It's unfair to assume that an amp design that does not supply comprehensive measurements is automatically crap - unless of course the publicity literature places emphasis on the number of ways they compromised the design (surprisingly common) to meet some strange "audiophile" rules.
  So when someone provides full and entirely reasonable looking measurements, has no real motive to fake them and appears to have invested huge amounts of time into the design, it appears strange that he is met with more skepticism that usual.


----------



## Modo

Quote: 





willakan said:


> So when someone provides full and entirely reasonable looking measurements, has no real motive to fake them and appears to have invested huge amounts of time into the design, it appears strange that he is met with more skepticism that usual.


 

 It's called successfull propaganda.


----------



## mikeaj

lff said:


> Music is a series of tones and silences.....
> 
> If something does well at reproducing test tones, it will do well with music....




That would pretty much be my position too. But there's always the question of "sure, THD was really low, but what about with multiple tones together?" And even if one IMD test reveals nothing wrong, another with different tones may produce a different result. You can't test every combination of everything.

But with a large body of measurements across many situations, seems unlikely that these tests--which are designed to show the extent of nonlinearities--would somehow overlook something important. i.e. performance with a large set of benches is good, but in some real-world scenario, not so good


----------



## rroseperry

Whoa, where's the suggestion that the measurements could be faked coming from? Did I miss something? 

That just makes no sense.


----------



## mikeaj

rroseperry said:


> Whoa, where's the suggestion that the measurements could be faked coming from? Did I miss something?
> 
> That just makes no sense.




I think that's a hypothetical more than anything. Too many objectivists playing devil's advocate to try to appease the holdouts.

Actually there was one guy who thought the noise measurements were faked because of the kind of weird noise in dB referenced to 400 mV signal level. Noise is -115 dBV A-weighted, which is of course a better number than if you reference it to 400 mV.


----------



## purrin

Quote: 





mikeaj said:


> That would pretty much be my position too. But there's always the question of "sure, THD was really low, but what about with multiple tones together?" And even if one IMD test reveals nothing wrong, another with different tones may produce a different result. You can't test every combination of everything.
> 
> But with a large body of measurements across many situations, seems unlikely that these tests--which are designed to show the extent of nonlinearities--would somehow overlook something important. i.e. performance with a large set of benches is good, but in some real-world scenario, not so good


 
   
  Hehe. I believe LFF was being sarcastic.
   
  When we examine non-linear distortion tests that display the entire spectrum, the multi-tone (three to five) approach tends to create a lot more "garbage" than single tone tests. Two tone tests start to create IMD which is more audible than THD. Here's a visual example. 
   
  As far as measurements for the O2, the best approach is to develop a comprehensive suite of tests, have someone independent perform them on the O2, and then perform the exact same tests on other amps. The comparison aspect is crucial.


----------



## upstateguy

Quote: 





purrin said:


> <snip>
> As far as measurements for the O2, *the best approach is to develop a comprehensive suite of tests, have someone independent perform them on the O2, and then perform the exact same tests on other amps.* The comparison aspect is crucial.


 

 Good idea.  Too bad no one does that for anything.


----------



## purrin

Quote: 





upstateguy said:


> Good idea.  Too bad no one does that for anything.


 

 That's really the sad part. I'm going through Stereophile amp reviews, and when they do provide measurements, they don't provide meaningful information. 
   
  For example, they have nice graphs on THD and IMD. But examining a graph and noting that there 0.5% THD at 100Hz really does not tell me anything. Is that distortion mostly 2nd harmonic, 3rd harmonic, a series of nasty odd harmonics, etc. Full spectrum graphs of non-linear distortion at 100Hz?" Those typically look the same. Industry standard" IMD full spectrum measuring at 19kHz and 20kHz? C'mon! When does music ever contain 19kHz + 20kHz tones at 0db?
   
  Let's run a comprehensive series of 3-5 tone tests (throughout the audio band) at reasonably loud listen levels into realistic loads to show us how messed up the entire spectrum really looks like. These tests aren't perfect, but they are better than the typical stuff we see now.
   
  I'd also like to see tests that measure dynamic compression and ability to accurately reproduce low level signals during loud passages. I don't think anyone's invented these types of tests yet. These are two major aspects which I subjectively feel separate the good amps from the bad.


----------



## maverickronin

Quote: 





rroseperry said:


> Whoa, where's the suggestion that the measurements could be faked coming from? Did I miss something?
> 
> That just makes no sense.


 
   
  I don't think its been seriously proposed in this thread specifically, but some other people have been suggesting conspiracy theories elsewhere.  I think they're silly but there's no end to the sort of silly stuff that needs to be argued against.
  
  Quote: 





purrin said:


> Industry standard" IMD full spectrum measuring at 19kHz and 20kHz? C'mon! When does music ever contain 19kHz + 20kHz tones at 0db?


 

 From what I understand, the point of that test is that those high frequencies are where negative feedback is least effective so its sort of a worst case scenario kind of thing.


----------



## estreeter

Quote: 





purrin said:


> That's really the sad part. I'm going through Stereophile amp reviews, and when they do provide measurements, they don't provide meaningful information.


 
   
  Stereophile's measurements are debated up hill and down dale each and every time that John Atkinson or one of the other staff members dares to question the performance of a highly-regarded piece of kit, particularly when there is a big sticker on said gear. While I admit to being a subjectivist (I'll drink the tube amp Kool-Aid no matter how much distortion nwavguy tells me they produce), surely there's room for both listener emotion and objective measurement in audio ?
   
  As I said before, love him or loathe him, he had the guts to put this out there for dissection. Not _broad theory_ to be endlessly debated in Weird, er, Sound Science, not some half-baked ideas for an amp - a flesh-and-blood product that most of us can afford to buy. If nwavguy took his bat and ball and went home tomorrow, I *believe* he has left enough detail in the public domain for someone else to produce the amp (happy to hear otherwise) or, even better, to refine and improve his design.
   
  I know there are plenty here who have built impressive DiY projects, and I'm sure that some have design ideas of their own, but how many can take something to the point where its a reality for others to build their amp ? I look back on various fiascos (Mikael, you out there ? Stanley, come back - all is forgiven) in the world of headphone amps, and its clear that tying your $500 deposit to a lone gunslinger can be a minefield - to his credit, nwavguy has distanced himself from that side of the Objective2.
   
  To his more_ vocal _opposition, can you swallow your pride long enough to buy one and post your impressions ?


----------



## khaos974

estreeter said:


> Stereophile's measurements are debated up hill and down dale each and every time that John Atkinson or one of the other staff members dares to question the performance of a highly-regarded piece of kit, particularly when there is a big sticker on said gear. While I admit to being a subjectivist (I'll drink the tube amp Kool-Aid no matter how much distortion nwavguy tells me they produce), surely there's room for both listener emotion and objective measurement in audio ?
> 
> As I said before, love him or loathe him, he had the guts to put this out there for dissection. Not _broad theory_ to be endlessly debated in Weird, er, Sound Science, not some half-baked ideas for an amp - a flesh-and-blood product that most of us can afford to buy. If nwavguy took his bat and ball and went home tomorrow, I *believe* he has left enough detail in the public domain for someone else to produce the amp (happy to hear otherwise) or, even better, to refine and improve his design.
> 
> ...




Plenty?

The Dynalo, dynahi, the Cavalli designs, the Pete Millett designs, the AMB designs, the Pimeta, the Cmoy, the Bottlehead, the Wire ... plenty of of in the sea. Not all of them are as thorough measured as the O2, but the schematics are out there. 

And I have not doubt at least one of the performs better than the O2. What's cool with the O2 is that it's cheap and a through hole design.


----------



## estreeter

Which board member can take credit for designing the CMOY ?


----------



## khaos974

estreeter said:


> Which board member can take credit for designing the CMOY ?




Sorry for the CMoy and probably one or to of the others, but assuredly, Kevin Gilmore and AMB are members of HF, I'm sure I could find a few other designs where whose authors are also members of HF.


----------



## purrin

There are maybe one or two more who are no longer active on HF. There were other contributors on HeadWize too (which I knew about before HF.) Besides, last time I checked, nwavguy was technically not a member of HF.


----------



## mikeaj

In general, one of the big benefits of 3rd party testing, in addition to independent verification, is that the 3rd party may have a different idea of what parameters are important, which tests to run, and so on. If hypothetically some product were designed to meet design specs A, B, and C, the designer may primarily test A, B, and C, find good results for those, and declare success. But maybe metric D sucks?



estreeter said:


> S While I admit to being a subjectivist (I'll drink the tube amp Kool-Aid no matter how much distortion nwavguy tells me they produce), surely there's room for both listener emotion and objective measurement in audio ?



Well yeah of course. You don't have to be a subjectivist to like the sound of different tube amps, anyhow. Whatever sound you prefer is a personal preference.


----------



## LeonardS

This looks interesting.  My mini3 really couldn't drive my AKG701's, not that I travel with them.  But if this thing compares favorably with the amp section of the DAC1, as the creator indicates, then woo-hoo, I'm in!!
   
  Now I just have to figure out how to order it, or the pcb, or...?


----------



## estreeter

Quote: 





mikeaj said:


> Well yeah of course. You don't have to be a subjectivist to like the sound of different tube amps, anyhow. Whatever sound you prefer is a personal preference.


 

 I'm not going to quote from nwavguy's blog, for obvious reasons, but he has some strong views on the distortion introduced by tubes. I'm sure there are ways around it, but I expect that they add to the cost of the finished product - I'll leave it to the tube gurus to discuss at their leisure - all I'm saying is that I can live with the possibility that what one hears from a tube amp may not be 100% 'accurate' - the Objective2 was designed to be accurate above all else, at least based on my reading of his manifesto


----------



## googleborg

*Really *looking forward to getting this amp from EA http://www.epiphany-acoustics.co.uk/7.html (British/European supplier?).


----------



## Zynec

Interesting thread.  I do find the lack of numbers for amps suspicious... and annoying!  Are there actually any manufactures of integrateds (for example) that do actually provide detailed specs?


----------



## estreeter

Quote: 





zynec said:


> Interesting thread.  I do find the lack of numbers for amps suspicious... and annoying!  Are there actually any manufactures of integrateds (for example) that do actually provide detailed specs?


 

 I'm not aware of any that provide the kind of measurements nwavguy has with the Objective2 (happy to hear otherwise), but something along the lines of the spec Justin provides for his portable amps would suffice for me:
   
_Specification_
_Maximum Continuous Power output:_
_60 mWrms/channel into 32 ohm @ nominal (3.6V) battery voltage;_
_10 mWrms/channel into 300 ohm load @ nominal battery voltage;_
_16 mWrms/channel into 300 ohm load @ fully charged (4.2V) battery voltage;_
_28 mWrms/channel into 300 ohm load with 5.2V USB power supply;_
_Distortion (THD): <0.005% @ 1KHz (-20dBu to 5dBu output level)[1];_
_Dynamic range (dBA): >100dB_
_Bandwidth (-1dB): 10Hz-40kHz_
_Output impedance: < 1 ohm [2]_
_Output current limit: ~= +/-80mA per channel_
_Maximum Gain (REV A): 12dB;_
_Maximum Gain (REV B): 10dB/6dB (based on jumper setting);_
_Battery recharge time (max): 2.5 hour fast charge; 6 hour normal charge;_
_Dimensions (approx): height=23mm; width=52mm; length=85mm_
_Weight = 125g +/-1g_
   
_http://www.justaudio.co.uk/uha-120.html _
   
  The key figure for me is Output Impedance, but it doesnt tell the entire story with this amp. Early versions with the Vishay P11 pot had too much gain for many IEMs, but Justin was very graceful about it and I think many of those folk were accommodated, either via a mod or the second revision of the amp. That sort of attention to customer needs is what separates the good from the mediocre in audio, IMO.


----------



## Head Injury

Quote: 





estreeter said:


> I'm not aware of any that provide the kind of measurements nwavguy has with the Objective2 (happy to hear otherwise), but something along the lines of the spec Justin provides for his portable amps would suffice for me:


 

 I agree. Output into various loads, output impedance, frequency response (preferably with low variation), and THD should be the bare minimum.
   
  So many amps lack measured output impedance, and especially with portable amps it is very important.


----------



## Zombie_X

You guys,
   
  I must say that was a good read indeed and I am now curious. I tried to find this MySlim guy on ABI and on DIY Audio but could not locate him. Could anyone tell me where I could order this from within the USA? I want to compare it to my other amps.


----------



## Head Injury

Quote: 





zombie_x said:


> You guys,
> 
> I must say that was a good read indeed and I am now curious. I tried to find this MySlim guy on ABI and on DIY Audio but could not locate him. Could anyone tell me where I could order this from within the USA? I want to compare it to my other amps.


 
   
It's MrSlim.
   
  He's not offering the service anymore, because the group buy is over. He might offer it again in the future.


----------



## Maverickmonk

Any word on a potential next-group buy?


----------



## Zynec

Quote: 





head injury said:


> I agree. Output into various loads, output impedance, frequency response (preferably with low variation), and THD should be the bare minimum.
> 
> So many amps lack measured output impedance, and especially with portable amps it is very important.


 


  Also slew rate?


----------



## Head Injury

Quote: 





zynec said:


> Also slew rate?


 

 Sure, why not? Are there really any amps with bad enough slew rates to impact performance, but otherwise have good specs? The impression I got from NwAvGuy's posts about the O2 is that modern opamps themselves don't have a problem with slew rates, but no doubt it depends on the design of the amp.


----------



## Zombie_X

Too bad then. Know of any place else in the USA the makes these or sells the kits for them?
  
  Quote: 





head injury said:


> It's MrSlim.
> 
> He's not offering the service anymore, because the group buy is over. He might offer it again in the future.


----------



## khaos974

zombie_x said:


> Too bad then. Know of any place else in the USA the makes these or sells the kits for them?




Maybe Ollie1324 has some spare boards.

http://www.diyaudio.com/forums/group-buys/194708-o2-headphone-amplifier-gb-85.html


----------



## Zynec

Quote: 





head injury said:


> Sure, why not? Are there really any amps with bad enough slew rates to impact performance, but otherwise have good specs? The impression I got from NwAvGuy's posts about the O2 is that modern opamps themselves don't have a problem with slew rates, but no doubt it depends on the design of the amp.


 


  I have no idea... .but yeah I guess that is the point


----------



## estreeter

Again, I have to play Devil's Advocate - we run the risk of going from people who work off 'Wow - that sounds good !' to the worst kind of gear queer - obsessed with every conceivable measurement, lying awake at night wondering if the slightest fluctuation in a frequency curve could ruin our entire experience ...... its a tightrope : the trick is to avoid turning it into a noose, IMO.


----------



## limpidglitch

Quote: 





estreeter said:


> Again, I have to play Devil's Advocate - we run the risk of going from people who work off 'Wow - that sounds good !' to the worst kind of gear queer - obsessed with every conceivable measurement, lying awake at night wondering if the slightest fluctuation in a frequency curve could ruin our entire experience ...... its a tightrope : the trick is to avoid turning it into a noose, IMO.


 


  You could be right, but that would have nothing to do with objectivity.
  If you pull objectivity to the extreme you only get more pragmatic. Audible thresholds can be measured and used objectively.
  So your DAC's got 1ns of jitter and is 1dB down at 20k? Obviously this isn't state of the art equipment, but at the same time, who's going to notice?
   
  What you are envisaging is just another kind of subjectivism: an unreasonable obsession with the insignificant.


----------



## estreeter

Quote:  





> What you are envisaging is just another kind of subjectivism: an unreasonable obsession with the insignificant.


 

 True - fortunately, _we don't have any of that on Head-Fi !_


----------



## limpidglitch




----------



## Head Injury

Quote: 





estreeter said:


> True - fortunately, _we don't have any of that on Head-Fi !_


 

 Thank god!
   
  Hold on, I think I have my EQ set 0.2dB too high at 16kHz and it's causing phase shift. BRB.


----------



## estreeter

Quote: 





head injury said:


> Thank god!
> 
> Hold on, I think I have my EQ set 0.2dB too high at 16kHz and it's causing phase shift. BRB.


 
   
  You should see someone in Sound Science immediately ! Most of those guys are seeing a doctor and they'll be able to prescribe something.  :evil:


----------



## treal512

Subbing for later


----------



## normalwrong

cant find MySlim on those forum


----------



## Head Injury

It's MrSlim, with an R.


----------



## estreeter

Sadly, I think MrSlim filled his quota and I *think* _that's all she wrote_ - anyone ?


----------



## normalwrong

Ya.. I found his post and his order is cut off..
  does anyone in Headfi will make it..?


----------



## estreeter

I think there are several (thats anywhere from 3 to 300 worldwide ..) people waiting to see if MrSlim or another DiYer offers to build more amps for sale. FWIR, its *not* the case that anyone with a soldering iron and the ability to read a circuit diagram can put this amp together - it will be interesting to see how many of the DiYers actually end up with a running amp. As always, very happy to be proved wrong.


----------



## deadlylover

Quote: 





estreeter said:


> I think there are several (thats anywhere from 3 to 300 worldwide ..) people waiting to see if MrSlim or another DiYer offers to build more amps for sale. FWIR, its *not* the case that anyone with a soldering iron and the ability to read a circuit diagram can put this amp together - it will be interesting to see how many of the DiYers actually end up with a running amp. As always, very happy to be proved wrong.


 

 You don't even have to be able to read a circuit diagram to put this amp together. Match the component and designation from the BOM, and place it where the silkscreen says. There is nothing to adjust/configure, so as long as the parts aren't junk, and everything is in the right spot, the amp will work.
   
  I haven't been keeping up with the project at all, but have there been people having trouble putting this thing together? I would be very surprised if that's the case, considering the overwhelming support for this project from the designer and his followers.


----------



## brown5629

For those of you who missed out on O2 amps from MrSlim, my friend is selling several on DiyAudio. (He already has most boards soldered... now waiting on enclosures)
  If there's more interest, he might make some more.
   
http://www.diyaudio.com/forums/swap-meet/198536-fs-o2-headphone-amp-assembled-boards.html
   
   
  As far as my own review - 
   
  I'm currently using HD580s (with HD600 grills). My source is a modified Zero DAC.
  I love this little amp so far. Such a tiny package can pack a huge punch.
  The clarity seems limitless , with great dynamic range. Works great at any listening level.
   
  I mostly use the wall adapter for power, as my setup is located on my desktop.
  My Zero amp has too high of an output (2V RMS) and may cause clipping with the O2 on battery power.
  Those of you who intend to have a desktop setup may want to be aware of this possible issue.


----------



## Head Injury

Quote: 





brown5629 said:


> I mostly use the wall adapter for power, as my setup is located on my desktop.
> My Zero amp has too high of an output (2V RMS) and may cause clipping with the O2 on battery power.
> Those of you who intend to have a desktop setup may want to be aware of this possible issue.


 

 2Vrms is standard. The O2 isn't normally meant to be used with a standard DAC on battery, but can be with the right gain settings. What gain settings are you using?


----------



## normalwrong

Does it comes with power supply?
  So I need to get a chargeable 9V battery?
  Is it possible to put a RCA input?


----------



## brown5629

Quote: 





head injury said:


> 2Vrms is standard. The O2 isn't normally meant to be used with a standard DAC on battery, but can be with the right gain settings. What gain settings are you using?


 

  
  For now I'm using the stock gain settings. I may change the gain resistors for a lower value gain if I have time.


----------



## brown5629

I think my friend's selling them with power supplies, so if you are going portable you may need to buy batteries.
  I'm not sure about the RCA input, as the enclosure doesn't have the necessary drilled holes. You would need some sort of custom back panel.
  For now, I 'm using an RCA to 3.5mm adapter cable and have had no problems.
  
  Quote: 





normalwrong said:


> Does it comes with power supply?
> So I need to get a chargeable 9V battery?
> Is it possible to put a RCA input?


----------



## estreeter

Quote: 





deadlylover said:


> You don't even have to be able to read a circuit diagram to put this amp together. Match the component and designation from the BOM, and place it where the silkscreen says. There is nothing to adjust/configure, so as long as the parts aren't junk, and everything is in the right spot, the amp will work.
> 
> I haven't been keeping up with the project at all, but have there been people having trouble putting this thing together? I would be very surprised if that's the case, considering the overwhelming support for this project from the designer and his followers.


 

 Thanks for the clarification - I was working off some of the comments nwavguy made earlier in the project, but clearly I was off-beam. Look forward to hearing more impressions.


----------



## Willakan

As someone who has put one together that is awaiting testing, it really isn't hard - if board polarity markings aren't enough NwAvGuy has advice on everything from the type of solder to use, the kind of soldering iron and how to drill the front panel - there's a reason the article is so long. Only real problem is the MOSFETS, which are liable to die if you touch the pins.


----------



## Hi-fi Wigwammer

Since i live in the UK i have preordered an O2 from Epiphany Acoustics. They took my deposit earlier this week. Should take a few weeks for it to arrive.


----------



## estreeter

Quote: 





hi-fi wigwammer said:


> Since i live in the UK i have preordered an O2 from Epiphany Acoustics. They took my deposit earlier this week. Should take a few weeks for it to arrive.


 

 Thanks for that, wiggy - I'm hoping mine will be here before Xmas Day. Short of Fiio and some of the CMOYs, I dont know too many commercial amp makers who can deliver a portable amp for under 200 AUD.


----------



## normalwrong

can it drive lcd2?


----------



## deadlylover

Quote: 





normalwrong said:


> can it drive lcd2?


 
   
  Yes, I've tried it myself.


----------



## everlong

Is this amp sold as a kit, so you have to solder and put it together yourself?


----------



## LizardKing1

No, you have to buy the parts, the enclosure and the board.


----------



## estreeter

Quote: 





lizardking1 said:


> No, you have to buy the parts, the enclosure and the board.


 

 Please confirm that there is _absolutely no soldering required _- that doesnt gel with my initial understanding of what was required.


----------



## micmacmo

There is most definitely soldering involved.
  Quote: 





estreeter said:


> Please confirm that there is _absolutely no soldering required _- that doesnt gel with my initial understanding of what was required.


----------



## Willakan

There is a guy on DIYAudio flogging fully populated boards if you don't feel up to it. Then all you need is a front panel, case and a screwdriver!


----------



## Hi-fi Wigwammer

Epiphany Acoustics in the UK are taking preorders for their first batch of O2 amps now. £100 plus shipping, fully built with a properly finished/labelled casing.


----------



## estreeter

Quote: 





hi-fi wigwammer said:


> Epiphany Acoustics in the UK are taking preorders for their first batch of O2 amps now. £100 plus shipping, fully built with a properly finished/labelled casing.


 

 Wiggy, did they give you any details about opamps, (individual) measurements etc for your amp ? I appreciate that its not a custom order amp, but something beyond 'thanks for your deposit' would be nice.


----------



## Hi-fi Wigwammer

Quote: 





estreeter said:


> Wiggy, did they give you any details about opamps, (individual) measurements etc for your amp ? I appreciate that its not a custom order amp, but something beyond 'thanks for your deposit' would be nice.


 


 Just had a reply from Oliver at Epiphany Acoustics:
   
   
  The Opamps are the NJM2068D and the NJM4556AD. The gain settings 3.1x low gain and 6.5x high gain.
   
*Measurements etc.*

 THD @ 1kHz: 0.0017%
 Noise level (ref 400mV): -105dB
 IMD: 0.001%
 Power output @ 33Ω : 641mW
 Crosstalk: 65dB
 Channel balance 0.6dB
 Battery life: 8 hours
   
   
   
  I hope thats helps a bit?


----------



## limpidglitch

Do you know if other gain settings can be requested, or if the gain resistors are socketed?
  3.1X is rather a lot when using IEMs and a 2V source.


----------



## Hi-fi Wigwammer

Sorry, but I really don't know. You can e-mail Oliver at oliver@epiphany-acoustics.co.uk for more info.


----------



## micmacmo

Quote:


limpidglitch said:


> Do you know if other gain settings can be requested, or if the gain resistors are socketed?
> 3.1X is rather a lot when using IEMs and a 2V source.


 

 According to the O2 site, "*Gain Switch* – The out position is Low Gain (2.5X or 8 dB) and the in position is High Gain (6.5X or 16 dB)." Interesting that Oliver went with a slightly higher low-gain setting.
   
  The BOM includes an optional socket for the resistors, so it's certainly possible to get a socketed version. It could be just a matter of asking.


----------



## estreeter

Thanks for the feedback Wiggy - I'm hoping that your good self or one of the other 'early adopters' of the EPH-02 will start a separate impressions thread when you receive your amp - I ordered mine at least a week after you. Sure, its a 'stock' Objective2 implementation, but I think others may be interested as (afaik) its the only commercial offering of the amp atm - not sure if MrSlim has started on another batch.
   
  As far as the gain goes, I mainly use fullsize cans with my amps so I'm not particularly concerned about those settings. I admit that I have some misgivings about a design that is intended to be 'all things to all people' up to 600 ohms - my experience with Rev 1 of the uHA-120 was that it wasn't a good fit for IEMs, and Justin subsequently revisited his gain settings and recommended the stock pot over the optional Vishay for IEM users.


----------



## estreeter

I hope my photos turn out as well as this HK DiYers did:


----------



## limpidglitch

Looking good, but I hope he's not planning to recharge those batteries like that.


----------



## estreeter

I think its a work-in-progress, but it goes a long way to explaining why the footprint of the amp is more 'transportable' than 'portable' -  for my purposes, this IS the 'desktop version' !


----------



## limpidglitch

I was thinking more that if he were to plug in the AC, those batteries would explode.


----------



## estreeter

All part of the reason why I'm having a professional assemble mine. At least he became a professional the day he start accepting deposits to build the Objective2 !


----------



## shadow419

Quote: 





limpidglitch said:


> I was thinking more that if he were to plug in the AC, those batteries would explode.


 


  Actually, the design charges NiMH batteries when it's connected to AC.  A nice feature in my book.
   
  err. ninja edit:  just noticed those are li d'oh


----------



## mikeaj

Quote: 





limpidglitch said:


> Do you know if other gain settings can be requested, or if the gain resistors are socketed?
> 3.1X is rather a lot when using IEMs and a 2V source.


 

 Good question.  I know MrSlim was building them with socketed resistors.  Or at least he said so earlier.  Fortunately, if you want 1x gain, all you need to do is remove the resistor for each channel (snip snip).  I think I'll be leaving out those resistors to have 1X gain be the low setting.
   
   
  Quote: 





micmacmo said:


> Quote:
> 
> According to the O2 site, "*Gain Switch* – The out position is Low Gain (2.5X or 8 dB) and the in position is High Gain (6.5X or 16 dB)." Interesting that Oliver went with a slightly higher low-gain setting.
> 
> ...


 


 As I recall, originally the low gain was 3.1X.  Later revision changed the default to 2.5X.  Maybe Oliver didn't catch that?  If so, there are a few other changes since the original revision, that reduce turn on/turn off transients (I think) and reduce hum while charging batteries.  Maybe Oliver made a mistake in saying what it was, since I don't think he would have missed all the later revisions.  After all, he ordered the PCBs based on the latest O2 revision.
   
  Actually, changing the default low gain was in response to input clipping concerns, though personally I think 2.5X or even 2X is a more appropriate choice in general for low gain because of IEMs and other more sensitive headphones.  With 3.1X gain and some really hot source with no volume control and full scale output above 2.25V (rms), the amp will clip the input (regardless of the amp's volume control setting), even on AC power.  Then again, this wouldn't be the only amp to clip with really high input levels.


----------



## normalwrong

Are these the best opamp??
Should i get them from ebay..? Is it likely to be fake?



hi-fi wigwammer said:


> Just had a reply from Oliver at Epiphany Acoustics:
> 
> 
> The Opamps are the NJM2068D and the NJM4556AD. The gain settings 3.1x low gain and 6.5x high gain.
> ...


----------



## estreeter

Quote: 





mikeaj said:


> As I recall, originally the low gain was 3.1X.  Later revision changed the default to 2.5X.  Maybe Oliver didn't catch that?  If


 

  Oliver is building mine with gain set at 2x and 5x - that should be fine for my undemanding can collection. Thanks for the info though - nwavguy has written so much on his blog that it can be hard to keep on top of it all.


----------



## turokrocks

Quote: 





estreeter said:


> Oliver is building mine with gain set at 2x and 5x - that should be fine for my undemanding can collection. Thanks for the info though - nwavguy has written so much on his blog that it can be hard to keep on top of it all.


 


  Please update us as you receive your O2 as i ordered  one a week ago.


----------



## Willakan

To put the gain settings into perspective, I find my O2 unbearably loud much past 9 o'clock on the volume control. However, rather than IEMs, I am listening with AKG K702s. I built mine with 3.1X gain - I would seriously consider unity gain for IEMs, at least as one of the settings. Source voltage is 2.1V RMS.
   
  I do listen quite quietly, but even so...


----------



## Head Injury

Something like 1x and 3x gain would work if you're planning to use this with IEMs. 1x would be enough for most of them with a 2 V desktop DAC, and 3x would be good for DAPs (which are like 0.5-1 V or something right?) 3x would also work with any full-sized headphones in the future and avoids clipping with normal 2ish V sources.


----------



## bada bing

Quote: 





willakan said:


> To put the gain settings into perspective, I find my O2 unbearably loud much past 9 o'clock on the volume control. However, rather than IEMs, I am listening with AKG K702s. I built mine with 3.1X gain - I would seriously consider unity gain for IEMs, at least as one of the settings. Source voltage is 2.1V RMS.
> 
> I do listen quite quietly, but even so...


 


 I just built my second O2 board. The first was built with the default gain, my second with 1X and 3x. I listen just about exclusively to HD650 and HD800 at my desk and use a couple ~2v desktop sources. 1x has all the volume I need for the HD650 & HD800, I listen with the knob about 10:00 at 1x gain with HD650. I would consider anything above 3x gain to be usable only for some very difficult & unusual headphones or for use as a pre-amp. Later this week I will break out my K1000's and see if they can make the O2 choke.


----------



## LizardKing1

I'm sorry, but I must ask this: the gain multiple (3X, 4X,...) refers to how much the source's voltage will be amplified, right? So not all DACs output the same? I'm just trying to know so I can tell if my E7's DAC output will be enough coupled with the O2, as soon as I can find out how much the output is which is hard, since almost no one uses it as a DAC only.


----------



## Willakan

I *think* the Fiio's output voltage is about 1.3V RMS, but don't quote me on that. The most any USB power-only DAC is going to pump out is about 1.4V RMS.
   
  @bada bing:
   
  I think the O2 choking on headphones designed to be driven from a speaker power amp is a foregone conclusion.


----------



## khaos974

Quote: 





lizardking1 said:


> I'm sorry, but I must ask this: the gain multiple (3X, 4X,...) refers to how much the source's voltage will be amplified, right? So not all DACs output the same? I'm just trying to know so I can tell if my E7's DAC output will be enough coupled with the O2, as soon as I can find out how much the output is which is hard, since almost no one uses it as a DAC only.


 

 DACs voltage outputs vary wildly, the output of a CD player is supposed to be 2 Vrms, but a lot of sources ohave outputs that vary between 1V and 3V especially some more exotic audiophile sources. Portable sources usually don't exceed 1V.


----------



## katzer1

I got my O2 from another diyaudio builder called aerohoff.
  He lives close to me so I got to meet him in person. He is a very nice fellow who does an excellent job yet maintains zero attitude about it.
   
  I like this amp a lot: it drives my HD580, ER4P/S and DT880 (600ohm) wonderfully.
  It just takes the signal from my DAC (rega dac) and adds a volume knob on top.
  The soundstage feels very wide, the separation is excellent and it is neutral, it just amplifies the source signal without any fusses. Good recordings sound good, poor recordings sound poor.


----------



## turokrocks

Quote: 





katzer1 said:


> I got my O2 from another diyaudio builder called aerohoff.
> He lives close to me so I got to meet him in person. He is a very nice fellow who does an excellent job yet maintains zero attitude about it.
> 
> I like this amp a lot: it drives my HD580, ER4P/S and DT880 (600ohm) wonderfully.
> ...


 
  Thanks for the update, can you be more elaborate ?


----------



## estreeter

sobbingwallet does a pretty good job of summing it up in the other thread - if your O2 is working properly, you will be hearing your source/the recording and any coloration introduced by your phones. Theoretically, the amp should be invisible - mine hasn't arrived yet, but I believe that is the ideal for a neutral amp.


----------



## everlong

Was thinking of building this, but it need to end up in a nice enclosure, and I would like to build a DIY DAC(USB) too, that ends up in the same enclosure type(not the same box). So both the amp and dac will look like it comes of the same brand.
   
  Any ideas on that? And what DIY DAC would be a good match for the amp?


----------



## upstateguy

Quote: 





estreeter said:


> sobbingwallet does a pretty good job of summing it up in the* other thread* - if your O2 is working properly, you will be hearing your source/the recording and any coloration introduced by your phones. Theoretically, the amp should be invisible - mine hasn't arrived yet, but I believe that is the ideal for a neutral amp.


 


  Hi estreeter
   
  Do you have a link for the other thread?


----------



## shadow419

Quote: 





upstateguy said:


> Hi estreeter
> 
> Do you have a link for the other thread?


 


http://www.head-fi.org/t/577535/o2-build-complete-let-the-objective-subjective-listening-tests-commence/165
   
  Post #176


----------



## estreeter

Thanks, shadow419 - I have to be careful what I link to given the sensitivity of the subject matter here - there were rules somewhere, but I just err on the side of caution cowardice.


----------



## Yoga Flame

Quote: 





everlong said:


> Was thinking of building this, but it need to end up in a nice enclosure, and I would like to build a DIY DAC(USB) too, that ends up in the same enclosure type(not the same box). So both the amp and dac will look like it comes of the same brand.
> 
> Any ideas on that? And what DIY DAC would be a good match for the amp?


 

 The O2's enclosure is the same type as the recommended one for the AMB gamma1 (config F). The gamma2 also.


----------



## francisdemarte

Quote: 





yoga flame said:


> The O2's enclosure is the same type as the recommended one for the AMB gamma1 (config F). The gamma2 also.


 

 That how I was going to use mine. Stack it on top of the AMB Gamma2 for a nice transportable unit. I wonder if you can squeeze a GrubDac or BantamDac into the case too?
   
  Check out http://www.diyforums.org/ for really small DIY DAC's


----------



## JamesMcProgger

Say if you put your cellphone on top of the unit while using the amp.
  does the O2 caught cellphone interferences? with the original case open at the sides or the full enclosed one?


----------



## maverickronin

Quote: 





jamesmcprogger said:


> Say if you put your cellphone on top of the unit while using the amp.
> does the O2 caught cellphone interferences? with the original case open at the sides or the full enclosed one


 
   
  There's almost none with my O2 and GSM cell phone.  You can hear a bit if they're right on top of each other but its not bothersome even with sensitive headphones.


----------



## 4nradio

I finished the first of two O2 amps today. All of the initial tests went well and when I was finally able to plug in some "non-throwaway" headphones and listen to some FLAC files I came away impressed. I find the O2's sound to be very transparent and easy to listen to. I've tried some IEMs and Beyer DT-770 80 ohms headphones, but haven't yet plugged in my LCD-2 Rev. 2 headphones (need to get an 1/8" to 1/4" adapter).

 BTW, the front panel from FPE is a perfect fit and alignment of all the machined holes is very accurate. They do great work...I look forward to seeing their facility in January at a Seattle Head-Fi enthusiasts meet.

 An image of my first O2 amp is here:


----------



## turokrocks

Quote: 





4nradio said:


> I finished the first of two O2 amps today. All of the initial tests went well and when I was finally able to plug in some "non-throwaway" headphones and listen to some FLAC files I came away impressed. I find the O2's sound to be very transparent and easy to listen to. I've tried some IEMs and Beyer DT-770 80 ohms headphones, but haven't yet plugged in my LCD-2 Rev. 2 headphones (need to get an 1/8" to 1/4" adapter).
> 
> BTW, the front panel from FPE is a perfect fit and alignment of all the machined holes is very accurate. They do great work...I look forward to seeing their facility in January at a Seattle Head-Fi enthusiasts meet.
> 
> An image of my first O2 amp is here:


 
  Looks clean and nice, I ordered mine from 


  Epiphany Acoustics


  Hope it will be to my expectation, your (initial) review makes me impatient to get mine!!!
  Please update us.


----------



## shadow419

I've been rocking my o2 for about two weeks.  Still waiting on my front panel from a group buy, but it sounds and performs like it should.  I'm using a a pair of HD 25-1 II.  I'd heard that they were a bit sibilant before from a lot of reviews, but I never heard it until I started using the o2 to power my cans.  I still love my HD 25's, but I can definitely hear them as they really are now.


----------



## hans030390

What would be a good DAC for this? If I get one of these amps, I'll be using my PC as my source. I'm currently using an Auzentech Bravura sound card. Would that be sufficient as a DAC? I would not be opposed to getting something different if it would work better. If the Bravura would be fine, are there any particular settings/configurations that work best with the amp (16-bits vs 24-bits, sampling rate, etc.)?


----------



## Willakan

Quote:


hans030390 said:


> What would be a good DAC for this? If I get one of these amps, I'll be using my PC as my source. I'm currently using an Auzentech Bravura sound card. Would that be sufficient as a DAC? I would not be opposed to getting something different if it would work better. If the Bravura would be fine, are there any particular settings/configurations that work best with the amp (16-bits vs 24-bits, sampling rate, etc.)?


   
  I can't speak for the Auzentech, but sample rate and the like should simply be set to automatically match the source material.


----------



## hans030390

Quote:


willakan said:


> I can't speak for the Auzentech, but sample rate and the like should simply be set to automatically match the source material.


 

 OK. It's just that I was reading something about the usage of (certain?) USB DACs (not sure if it applies to sound cards) set to 16-bit that would drop bits depending on the volume. I'm not very knowledgeable on some of these more technical aspects, so I don't remember exactly what I read.


----------



## mikeaj

Quote: 





hans030390 said:


> OK. It's just that I was reading something about the usage of (certain?) USB DACs (not sure if it applies to sound cards) set to 16-bit that would drop bits depending on the volume. I'm not very knowledgeable on some of these more technical aspects, so I don't remember exactly what I read.


 

 It's not just USB DACs.  If you have software volume control lowering the volume below 100%, that's done by (more or less) dividing all the amplitude values by a certain amount.  Thus what the DAC gets is not the original, but a scaled-down version.  Because of the way the data is represented, when you scale things down, you effectively are rounding data out and losing it.  e.g. 186 -> 18.6 gets rounded to 19, so some info is lost (but it's not in base 10 of course)
   
  If you have 16 bit output and using software volume control set fairly low, the data that is lost was potentially audible.
   
   
  So set 24 bits (even if your music is 16 bits) since the hardware supports that, and then set the sample rate to the sample rate of the music.  That's 44.1 kHz for CD Audio, 48 kHz for DVD audio, and so on.


----------



## Willakan

You do get lower resolution using the software volume control - so don't use it. Best practise is to keep everything at full volume (no processing) in the digital domain and then use the analog volume control on your amplifier to adjust the volume level.


----------



## mikeaj

I did a quick assessment of the amp using RMAA (for what little that's worth) and my cheapo USB X-Fi Surround 5.1 sound card.  Measurements are limited by the line in on the sound card in many cases.  This is with default Windows drivers, so 24-bit modes don't work; I tested 16-bit 48 kHz only.  For some reason, the line in level is not calibrated right using default Windows drivers somehow, so the noise floor is a bit high I think. 
   
  First test was sound card loopback (no load).  Then I tested with three different headphones in turn:  AKG K601 (120 ohms nominal), Beyerdynamic DT770 Pro (80 ohms nominal), Beyerdynamic DT 235 (32 ohms nominal).  After that, I tested with the sound card into the O2 (no load), and then into the O2 with those same three headphones.
   
  My O2 has gains of 1x and 5.1x.  Below tests are for 1x gain, on AC power.  I started to test the 5.1x gain setting, but the results were all the same, so I got bored and didn't finish that.  I also spot checked with battery power only, but that looked the same too.  THD = total harmonic distortion; IMD = intermodulation distortion (SMPTE test).  Though really, these are looking at THD + noise, and IMD + noise.
   
  All tests were at the max line out voltage of 1.1V rms, measured with a multimeter.  Actually, the sound card's output impedance is nontrivial, so the headphones were getting a little less than that on some tests, but not with the O2.  Click on graphs for large versions as usual.
   
*Sound card (**no O2) THD:*

  0.0027%, 0.018%, 0.025%, 0.046% (top to bottom, meaning unloaded, K601, DT770 Pro, DT235).
   
*Sound card (no O2) IMD:*

  0.0098%, 0.025%, 0.096%, 0.050% (top to bottom).
   
   
*Sound card -> O2* *THD:*

  0.0028%, 0.0026%, 0.0025%, 0.0025% (top to bottom).
   
*Sound card -> O2 IMD:*

  0.010%, 0.010%, 0.010%, 0.010% (top to bottom).
   
   
*Again, note that results are limited by the sound card**.  *Also this is just RMAA.  Don't take too seriously.


----------



## hans030390

Quote:


mikeaj said:


> It's not just USB DACs.  If you have software volume control lowering the volume below 100%, that's done by (more or less) dividing all the amplitude values by a certain amount.  Thus what the DAC gets is not the original, but a scaled-down version.  Because of the way the data is represented, when you scale things down, you effectively are rounding data out and losing it.  e.g. 186 -> 18.6 gets rounded to 19, so some info is lost (but it's not in base 10 of course)
> 
> If you have 16 bit output and using software volume control set fairly low, the data that is lost was potentially audible.
> 
> ...


 
   
  Gotcha, thanks! I'm assuming I'll be using the same line-out that I use to connect the sound card to my stereo receiver, then? Oh, and to clarify, does software volume control only refer to the volume control in software such as Foobar, iTunes, etc., or does it include the volume control in Windows as well?
   
  I'm mostly concerned about my sound card (Auzentech Bravura) being a limiting factor to the amp...would that be the case, or should it be a good DAC for the amp?


----------



## mikeaj

Quote: 





hans030390 said:


> Gotcha, thanks! I'm assuming I'll be using the same line-out that I use to connect the sound card to my stereo receiver, then? Oh, and to clarify, does software volume control only refer to the volume control in software such as Foobar, iTunes, etc., or does it include the volume control in Windows as well?
> 
> I'm mostly concerned about my sound card (Auzentech Bravura) being a limiting factor to the amp...would that be the case, or should it be a good DAC for the amp?


 

 Software volume control meaning the OS (Windows) master volume as well as those of any program.  This includes ReplayGain, any volume altering say for an EQ setting, and so on.
   
  Auzentech Bravura might be a limiting factor to the amp in some sense, but I don't think it will be bad.  I think it's more likely that your music's recording/mastering, your headphones, or your ears will be the limiting factor first though, but that's just a guess.


----------



## hans030390

Quote:


mikeaj said:


> Software volume control meaning the OS (Windows) master volume as well as those of any program.  This includes ReplayGain, any volume altering say for an EQ setting, and so on.
> 
> Auzentech Bravura might be a limiting factor to the amp in some sense, but I don't think it will be bad.  I think it's more likely that your music's recording/mastering, your headphones, or your ears will be the limiting factor first though, but that's just a guess.


 

 Well, would I be able to find a better DAC under, say, $100-150?


----------



## turokrocks

Its now available @ JDLABS, the makers of cmoy, nice!!!!


----------



## F900EX

^^^ Indeed and sold  ... I'm in for one.
   
  I am more interested in the amp itself then the enclosure and I see that the group buy for the front panel is closed.
   
  To protect the amp, does anyone have a link or source as to where I can find an enclosure to protect it.
   
  Thanks ...


----------



## kingoftown1

Quote: 





turokrocks said:


> Its now available @ JDLABS, the makers of cmoy, nice!!!!


 
  Mine shipped out this past Friday--hoping it'll arrive tomorrow.  John was also nice enough to swap in a wallwart instead of shipping it with batteries, much to my delight.  Saves me a $15 mouser order.


----------



## LFF

FWIW, I plan on putting an Audiotrak Optoplay inside my O2 so I can have a portable amp/dac combo.


----------



## estreeter

Quote: 





kingoftown1 said:


> Mine shipped out this past Friday--hoping it'll arrive tomorrow.  John was also nice enough to swap in a wallwart instead of shipping it with batteries, much to my delight.  Saves me a $15 mouser order.


 


  Can I ask how long ago you ordered it, kingoftown1 ? Its one thing to sign up for a 6-week lead time on an amp build, but it starts to drag.


----------



## kingoftown1

I actually put in my preorder on November 11th.  Not too bad of a wait.  I'm pretty sure he has a number in stock now and ready to ship.


----------



## Questhate

Since we're posting pics:
   

   
  I have this built with the stock gains at 2.5x and 6x but I'm going to lower it to something like 1x and 3.5x because the stock configuration is way more than I need. With Grados, I barely turn the volume knob on low gain and get plenty of volume. With an LCD-2, I listen somewhere between 10 and 11 o'clock on low-gain.


----------



## estreeter

Clear plexiglass, eh ? I prefer the earlier black faceplate, but for all I know Oliver has painted mine bright pink with purple polka-dots. Luck of the draw, I guess.


----------



## kingoftown1

Turns out my O2 got here today, but the mailman was just incredibly late.  I've listened for about 5 minutes with the T50RP and so far so good.


----------



## turokrocks

Quote: 





estreeter said:


> Can I ask how long ago you ordered it, kingoftown1 ? Its one thing to sign up for a 6-week lead time on an amp build, but it starts to drag.


 


  Take care it is a PCB build with an option for enclosure only for now, John confirmed in 4-8 weeks he will have the front panels ready for a complete O2, but also   there is the price difference (Jdlabs wins on EPH), and in reference to my cmoy, I like their build quality. But we already ordered it and I think it will be shipping next week (with my own calculation, not confirmed yet), any update about when yours will be shipping?


----------



## turokrocks

Quote: 





kingoftown1 said:


> Turns out my O2 got here today, but the mailman was just incredibly late.  I've listened for about 5 minutes with the T50RP and so far so good.


 

  
  Any update, I know you are enjoying it ,for sure you got it without the front panel, any  pics????


----------



## kingoftown1

I've only got a terrible cellphone camera that just looks terrible in low light--I'll try to remember to take pics and update this post tomorrow during the day.


----------



## Willakan

Heh, I need to get the camera out for my build. It looks...interesting, especially since I went with a desktop build (RCA and 1/4 inch jacks) and still kept everything on the front panel.


----------



## everlong

Wouldn't it be better to have the DC output back? And could it be an idea to have headphone output both on the front- and the backpanel?


----------



## Willakan

I wanted to save by only getting/making one front panel, so everything went on the front! I'm using the larger case, so it all just about fits.


----------



## turokrocks

Quote: 





willakan said:


> I wanted to save by only getting/making one front panel, so everything went on the front! I'm using the larger case, so it all just about fits.


 


  Folks, dedicated digital cameras are becoming cheaper and cheaper these days, I find it strange that you don't have some descent camera, I never leave home without my canon ixus. but for real shooting I have a Pentax and a Nikon DSLR with Limited Lenses.
   I am not showing off,  we just need to see your setups. make us jealous!


----------



## Willakan

I posted a photo of my build on the thread in the DIY forum: http://www.head-fi.org/t/577535/o2-build-complete-let-the-objective-subjective-listening-tests-commence/270#post_7910250


----------



## estreeter

Quote: 





turokrocks said:


> Take care it is a PCB build with an option for enclosure only for now, John confirmed in 4-8 weeks he will have the front panels ready for a complete O2, but also   there is the price difference (Jdlabs wins on EPH), and in reference to my cmoy, I like their build quality. But we already ordered it and I think it will be shipping next week (with my own calculation, not confirmed yet), any update about when yours will be shipping?


 

 Last estimate from Oliver puts mine in a box roughly two weeks from today.


----------



## turokrocks

Quote: 





estreeter said:


> Last estimate from Oliver puts mine in a box roughly two weeks from today.


 

  
  Not including shipping time, well *"[size=medium]Good things come to those who wait[/size]"*


----------



## turokrocks

A warm up picture for the *EHP-O2*,
   the screws used will be little black hex button bolts rather than the place holders in the photo.
  Will be waiting for more pics, It just looks nice.


----------



## estreeter

Dont tease me - I just want the blinking amp. Now.


----------



## calico88




----------



## limpidglitch

OOOH, that's pretty!


----------



## francisdemarte

How did everyone get that plastic cap from the BOM to stay on the attenuator?


----------



## fishski13

Quote: 





francisdemarte said:


> How did everyone get that plastic cap from the BOM to stay on the attenuator?


 

 are you talking about the volume knob?  it's a tight fit and should stay on the pot shaft without issue.  if not, try a skinny piece of Scotch tape on the flat side of the shaft.


----------



## wje

I'm joining the O2 family.  For now, I'm looking to use my Walkman (with a LOD) as the input / source.  I'll be driving woody Grados with the Magnum drivers.  The O2 amp should be on its way to me soon.  I was wondering if someone could put me in touch with a U.S. source that has the front panels available now?
   

 I'm aware of some panels being released at the end of December from one vendor.
 I'm also aware of Front Panels Express and am in communication with them.  However, they consider the templates that people have designed to be proprietary to the designer, so I'd need the permission or template file to proceed.
 Any other ideas?
   
  The amp I'm getting was built by a member here who just drilled the necessary holes into the front aluminum panel to get things all tidy and sealed up, but there are no logos or lettering.  Also, I do have the capability to work with wood - as I have all of the necessary tools.  I guess if it came down to it, I could make the skeleton out of some lightweigh luan and then pick a nice veneer to finish off the case.
   
  Thanks,  
	

	
	
		
		

		
		
	


	



   
*Edit: A friend came through for me.  It looks like I'm connected to a panel.  Happy, happy, joy, joy.*


----------



## LizardKing1

Maybe you're looking for this: http://www.jdslabs.com/item.php?fetchitem=O2FP
  Sorry if I misundertsood, as I assume this as been mentioned quite a few times by now.


----------



## Willakan

I'm not sure anyone is selling the front panels separately - there was a front panel GB, but that's closed now.
  Perhaps a mahogany front panel?
	

	
	
		
		

		
		
	


	



   
  EDIT: I stand corrected, didn't know JDS Labs were selling front panels separately.


----------



## wje

Quote: 





lizardking1 said:


> Maybe you're looking for this: http://www.jdslabs.com/item.php?fetchitem=O2FP
> Sorry if I misundertsood, as I assume this as been mentioned quite a few times by now.


 
  Yeah I caught that earlier in some of my readings.  My impatience sort of got in the way of waiting until the end of the month.  There's that other place that will make panels on the fly when you submit the template to them.  Front Panel Express will do the work.  I did get a response back to my inquiry earlier.  They do have some templates on hand from the O2 panels that they've made for users already.  However, they respect the proprietary nature of the design and will only cut a new panel based on another's design if that creator has given approval for them to do so.  Seems fair enough.  However, then again, if a member has created a nice design for a plate and they don't mind sharing the design, they should post a link to their template to allow others to use it.


----------



## Twinster

Welcome in the family Wayne 
	

	
	
		
		

		
		
	


	



  Quote: 





wje said:


> I'm joining the O2 family.  For now, I'm looking to use my Walkman (with a LOD) as the input / source.  I'll be driving woody Grados with the Magnum drivers.  The O2 amp should be on its way to me soon.  I was wondering if someone could put me in touch with a U.S. source that has the front panels available now?
> 
> 
> I'm aware of some panels being released at the end of December from one vendor.
> ...


----------



## wje

I've been communicating a bit in the "group buy" thread over at DIYAudio with FlyinHawaiian.  He's the guy who arranged the group buy for the face plates.  Essentially, the stock screws that come with the basic anodized case leave a bit to be desired.  He talked of finding some nice flat-head bolts that were 6-32 in size.  He then partially drilled the holes on the face plate, which allowed the screws to slightly recess and give the front plate a more professional appearance.
   
  I was out to a local hardware store at noon today.  I found some hex bolts that you use an allen wrench to tighten.  The bolts were 6-32 in size, too.  They're black in color.  I also picked up a thread tapping bit so I can cut new threads in the case, so the mouning screws / bolts will appropriately thread into place.  I also located some small black rubber washers that I'll place under the screws so when the screws reach the metal plate, they won't scratch off the black facing as I tighten them down.
   
  I wanted to give it a slight upgraded appearance.


----------



## Twinster

Pictures please 
	

	
	
		
		

		
			




  Quote: 





wje said:


> I've been communicating a bit in the "group buy" thread over at DIYAudio with FlyinHawaiian.  He's the guy who arranged the group buy for the face plates.  Essentially, the stock screws that come with the basic anodized case leave a bit to be desired.  He talked of finding some nice flat-head bolts that were 6-32 in size.  He then partially drilled the holes on the face plate, which allowed the screws to slightly recess and give the front plate a more professional appearance.
> 
> I was out to a local hardware store at noon today.  I found some hex bolts that you use an allen wrench to tighten.  The bolts were 6-32 in size, too.  They're black in color.  I also picked up a thread tapping bit so I can cut new threads in the case, so the mouning screws / bolts will appropriately thread into place.  I also located some small black rubber washers that I'll place under the screws so when the screws reach the metal plate, they won't scratch off the black facing as I tighten them down.
> 
> I wanted to give it a slight upgraded appearance.


----------



## wje

Quote: 





twinster said:


> Pictures please


 
   
  Coming soon.  Actually, this weekend, I'll have time to properly mount my face plate after tapping the new bolt holes.  It should be relatively painless.  Also, my replacement Magnum drivers arrived yesterday, so I can also start the assembly of the Mahogany cups from Marty.  Time to put another great pair of Magnums into use.
   
  The last 2.5 months have been crazy.  Work demands, the passing of my father-in-law, my wife handling the estate, etc.  Finally, it feels as though I'm getting somewhat caught up.  I also have my leather sewing machine ... just sitting there.  Hopefully, winter will mean plenty of hobby time.  But, who knows, I could have never predicted the last 3 months of my life either - as it really changed from what I would have envisioned it as.


----------



## wje

Quote: 





twinster said:


> Pictures please


 

  Ask, and ye shall receive.  First, I must admit that I hate taking pictures inside.  The case for my O2 is the anodized silver and the face plate is the satin black from the DIYAudio group buy.  However, the picture from inside the house actually makes the colors blend too much as opposed to showing the contrast.  But, in the picture,  you can get an idea on how I "revised" the method for attaching the front face plate by switching over from the phillips self-tapping silver screws to black 6-32 bolts that use a hex wrench to install.  The thread holes on the case itself were re-bored using a 6-32 tool for that purpose.  The washers behind the fasteners are actually rubber washers, so you can't torque down on them too hard or it will kind of twist them up and make them behave funny.  I'm not sure if I'll keep the rubber washers in place for the long haul - as I'd hate to see the fasteners start to back out of the threads from not being tightened down enough.
   
  Here goes ... comments and complaints alike, are both welcome.


----------



## shadow419

Ha!  Great minds think alike...


----------



## wje

Quote: 





shadow419 said:


> Ha!  Great minds think alike...


 

  
  Yes.  You know it.  I'm really loving the amp. 
   
*Edit*: I had previously made a comment regarding an "odd" issue.  The problem was traced back to the LOD cable for my Sansa.  It looks like I need to get a replacement.


----------



## Project22a

Any opinions on this vs. the Matrix M-Stage?


----------



## Willakan

Bleh, yours are all much prettier than my yellow-acrylic-front-panel'd abomination.


----------



## shadow419

Quote: 





willakan said:


> Bleh, yours are all much prettier than my yellow-acrylic-front-panel'd abomination.


 


  Meh, I used it without a case or front panel for weeks.  If it works, it's fine by me.  Some of the more exotic diy enclosures are where the real pretty is at.


----------



## Twinster

Like this one:
   

  
  Quote: 





shadow419 said:


> Meh, I used it without a case or front panel for weeks.  If it works, it's fine by me.  Some of the more exotic diy enclosures are where the real pretty is at.


----------



## Twinster

or this one:


----------



## drexman

what is BOM?


----------



## shadow419

Quote: 





drexman said:


> what is BOM?


 


  Bill Of Materials
   
  Basically everything you need to populate the pcb and get the amp to work.


----------



## drexman

pcb is the amp without the enclosure? if i order all the pcb parts they will come seperately and i will have to build the pcb myself? i have no idea how to. i looked at NwAvGuy's blog and i didn't see any instructions...


----------



## mikeaj

Quote: 





drexman said:


> pcb is the amp without the enclosure? if i order all the pcb parts they will come seperately and i will have to build the pcb myself? i have no idea how to. i looked at NwAvGuy's blog and i didn't see any instructions...


 

 The PCB is the board into which some ~80 components go into.  If you get a PCB, it has all the holes drilled in already and all the points wired together as needed.  To have a working amp, you need (1) PCB, (2) components soldered into that PCB, and (3) power source.  Power can come from two 9V batteries or from certain suitable AC/AC wall transformers.  If you use rechargeable batteries and the transformer, the circuit will charge the batteries.  It can charge batteries and operate at the same time.
   
  There is a complete parts list (bill of materials) you can find, and it's possible to just copy + paste the list from mouser and order them, at least in the US.  They also stock suitable AC/AC transformers.  Parts can also be gotten elsewhere.
   
   
  To assemble it, you need to obtain all ~80 components and the PCB, and solder the correct component into the correct holes marked for it.  There's no particular order--though as usual, starting from the smaller components first makes more sense--thus, no real instructions needed.  Solder them all in and it's done.  There are some extensive tips and troubleshooting advice on the blog, though.
   
  Cost of ~80 components + AC/AC adapter is just under $30 before shipping.  PCB is about $10 before shipping.  Rechargeable batteries cost about $10.  If you'd rather not solder it yourself, JDS Labs offers the PCB + all components (all soldered in, so assembled), for $95 plus shipping.  You still need to get the AC/AC adapter if you buy the completed board from JDS Labs, but they do supply the batteries.
   
   
  If you want an enclosure and front panel, those need to be gotten separately.


----------



## drexman

what is a suitable AC/AC adapter for europe 220V? specs, brands..?


----------



## mikeaj

Quote: 





drexman said:


> what is a suitable AC/AC adapter for europe 220V? specs, brands..?


 
   
  It should output between 13.5V to 20V with no load.  200 mA or higher is okay.  400 mA and maybe like 14V or higher output is preferred if you're driving insensitive lower-impedance headphones like some of the planar magnetics models.


----------



## symphonic

I have a couple of laptop power supplies that are around 15 V, I think - these should do the job, right?


----------



## wje

Quote: 





symphonic said:


> I have a couple of laptop power supplies that are around 15 V, I think - these should do the job, right?


 


  Are they *AC* (alternating current) adapters?  Keep in mind, the DC adapters won't work.


----------



## mikeaj

It's almost undoubtedly DC...and yes, AC/AC adapters are more difficult to find.  The point is that the board itself contains most of the power supply, which does the AC/DC conversion to generate the positive and negative rails.


----------



## wje

Quote: 





mikeaj said:


> It's almost undoubtedly DC...and yes, AC/AC adapters are more difficult to find.  The point is that the board itself contains most of the power supply, which does the AC/DC conversion to generate the positive and negative rails.


 

 OK, I'm not a pro when it comes to the Objective 2... just a happy owner.  However, I did come across a thread on DIYAudio, I believe where a user wanted to use a DC adapter.  In order to do so, it meant that some internal modifications to the amp itself had to be applied.  While the AC power supplies / adapters are harder to locate, it still seems like less of an issue as opposed to messing with the original design of the amp itself.  Just my .02


----------



## Willakan

Yup, using a DC adaptor is considerably more trouble than it's worth IMHO.


----------



## ChickWhite

If you really wanted to use a DC adapter, you would need to find one with +/- 12V outputs which would then require a different power connector on the O2.
   
  If you wanted to use a single supply DC adapter, then you would need to do some major work on the O2, adding some sort of switcher to provide the negative supply. It will put noise on the O2. Unless you really know what you are doing, don't do it. If you do do it, I would be willing to bet that you have seriously compromised the noise floor of the O2.
   
  The regulators on board are linear regulators. They do not generate any high frequency hash of their own.  It is far cheaper  to just order an AC to AC adapter from Mouser.  If you really can't find one, go to your local electronics part store/e-tailer and buy a stepdown transformer that will provide anywhere from 12Vrms to 20Vrms at 200 mA. Put it in a box with AC cord and AC out plug to match the AC in on the O2.With the specified 12V regulators 14Vrms out will handily do the job. The higher the voltage, the more heat you are going to generate. I actually have a 12V 400mA rated transformer. It's output under load from the O2 (charging batteries and playing fairly loudly with Sennheiser HD600's) is 13.8V RMS. Just enough to keep the regulators from dropping out of regulation. Under those conditions, the regulators barely feel warm to the touch.


----------



## symphonic

AC/AC it is then - I didn't realise that it was doing the conversion on board. I'll save the other DC supplies for T-amps. Thanks for the info guys.
  
  Quote: 





chickwhite said:


> If you really wanted to use a DC adapter, you would need to find one with +/- 12V outputs which would then require a different power connector on the O2.
> 
> If you wanted to use a single supply DC adapter, then you would need to do some major work on the O2, adding some sort of switcher to provide the negative supply. It will put noise on the O2. Unless you really know what you are doing, don't do it. If you do do it, I would be willing to bet that you have seriously compromised the noise floor of the O2.
> 
> The regulators on board are linear regulators. They do not generate any high frequency hash of their own.  It is far cheaper  to just order an AC to AC adapter from Mouser.  If you really can't find one, go to your local electronics part store/e-tailer and buy a stepdown transformer that will provide anywhere from 12Vrms to 20Vrms at 200 mA. Put it in a box with AC cord and AC out plug to match the AC in on the O2.With the specified 12V regulators 14Vrms out will handily do the job. The higher the voltage, the more heat you are going to generate. I actually have a 12V 400mA rated transformer. It's output under load from the O2 (charging batteries and playing fairly loudly with Sennheiser HD600's) is 13.8V RMS. Just enough to keep the regulators from dropping out of regulation. Under those conditions, the regulators barely feel warm to the touch.


----------



## glenda

Quote: 





shadow419 said:


> I've been rocking my o2 for about two weeks.  Still waiting on my front panel from a group buy, but it sounds and performs like it should.  I'm using a a pair of HD 25-1 II.  I'd heard that they were a bit sibilant before from a lot of reviews, but I never heard it until I started using the o2 to power my cans.  I still love my HD 25's, but I can definitely hear them as they really are now.


 


 Found this thread as I was looking for an FPE template to finish up this O2 build,  man this post doesn't inspire a lot of confidence. " My headphones weren't sibilant before but now with the O2 they are?"
	

	
	
		
		

		
			





   Kinda makes you think maybe _just maybe headphones in general aren't design for an instrumentation type amplifier _like this.  Oh well I'll finish it up and be able to hear for myself soon enough.


----------



## Br777

Quote: 





mikeaj said:


> The PCB is the board into which some ~80 components go into.  If you get a PCB, it has all the holes drilled in already and all the points wired together as needed.  To have a working amp, you need (1) PCB, (2) components soldered into that PCB, and (3) power source.  Power can come from two 9V batteries or from certain suitable AC/AC wall transformers.  If you use rechargeable batteries and the transformer, the circuit will charge the batteries.  It can charge batteries and operate at the same time.
> 
> There is a complete parts list (bill of materials) you can find, and it's possible to just copy + paste the list from mouser and order them, at least in the US.  They also stock suitable AC/AC transformers.  Parts can also be gotten elsewhere.
> 
> ...


 


   
  JDS sells fully assembled, and cased O2 amps - http://www.jdslabs.com/item.php?fetchitem=O2Full
  as does epiphany acoustics for ya'll UK types - www.epiphany-acoustics.co.uk.
  As does (at least i think he still does) "MRSLIM" via the diy audio forum -  http://www.diyaudio.com/


----------



## shadow419

Quote: 





glenda said:


> Found this thread as I was looking for an FPE template to finish up this O2 build,  man this post doesn't inspire a lot of confidence. " My headphones weren't sibilant before but now with the O2 they are?"
> 
> 
> 
> ...


 

 Don't be scared of a little sibilance.  I actually like the sizzle in the highs better this way.  My motherboard onboard sound card, while pretty quiet, has very little power and rolled off the highs a bit. The EDM and rock I listen to definitely sounds better now.
   
  And there's a difference between not being sibilant, and not being able to hear the sibilance.  The HD 25-1 II's have been called slightly sibilant in nearly every review I read before I bought them.


----------



## LizardKing1

The sibilance sounding good is just like tube distortion! It doesn't matter if you like it, it's still not part of the intended music. An amp shouldn't be creating it. If an amp creates te most gorgeous eargasming sibilance ever, then no matter how much better your music sounds this way, the amp is flawed.


----------



## shadow419

Quote: 





lizardking1 said:


> The sibilance sounding good is just like tube distortion! It doesn't matter if you like it, it's still not part of the intended music. An amp shouldn't be creating it. If an amp creates te most gorgeous eargasming sibilance ever, then no matter how much better your music sounds this way, the amp is flawed.


 


  Well it's a good thing the amp doesn't make the headphone sibilant, as it's not imparting it on any of my other headphones.  The HD 25-1's are sibilant.


----------



## Willakan

Headphones make amplifiers sound sibilant, not the other way around!
   
  (Unless you have a really crap amp, I suppose)


----------



## estreeter

Willakan, it could be anything in the chain, including the recording. Freddie Mercury was notorious for his sibilant vocals.


----------



## Willakan

Forgot about the recording! I'm clearly spending too much time on audiophile sites...


----------



## Br777

my JDS labs O2 shipped today -yipee!


----------



## Draygonn

br777 said:


> my JDS labs O2 shipped today -yipee!




That's great news. MrSlim finished my build and will ship it out soon.


----------



## glenda

Listening breifly to my O2 trying to get my head around its popularity.   It is very transperant,  one can distiguish between my cheap DAC vs my expensive one very easily.  But I can't get beyond the sibilance mentioned earlier,  maybe its something else causing it but it isn't there with my other amps.  The amp has amazing clarity but is sharp as a knife.  I guess it deserves more time.


----------



## turokrocks

While waiting for my Dacport LX to arrive, my PlayStation 1 is so clear, good soundstage and very good instrument separation with the O2, it brought the prat factor to my songs (as clear but there is sibilance), most importantly I am enjoying it .


----------



## shadow419

Quote: 





glenda said:


> Listening breifly to my O2 trying to get my head around its popularity.   It is very transperant,  one can distiguish between my cheap DAC vs my expensive one very easily.  But I can't get beyond the sibilance mentioned earlier,  maybe its something else causing it but it isn't there with my other amps.  The amp has amazing clarity but is sharp as a knife.  I guess it deserves more time.


 


  Really?  I don't get any sibilance with my Sennheiser 558.  Are you using a headphone that is naturally pretty bright?  I don't use the 558's much because i find it a little boring for the music I like, but definitely not getting any sibilance with them.


----------



## shotgunshane

I may have missed it but has anyone suggested a good inexpensive usb dac to use with the O2 on a computer?  I was considering picking up the Headphonia usb dac cable for $69.


----------



## Br777

voldemort often recommends the dacport or the hrt streamer line
  he also liked that $30 behringer model that measured REALLY well but i cant remembe if its usb
   
  as we all knoow if he recommends stuff its b/c it measures well


----------



## pancakeplease

Quote: 





br777 said:


> voldemort often recommends the dacport or the hrt streamer line
> he also liked that $30 behringer model that measured REALLY well but i cant remembe if its usb
> 
> as we all knoow if he recommends stuff its b/c it measures well


 


  This is the one he recommends. At least for the cheap price. http://www.amazon.com/Behringer-Control-UCA202-Audio-Interface/dp/B000J0IIEQ
   
  Outmeasured the expensive uDAC-2.


----------



## Br777

^ yes, thats the one, thanks.


----------



## CherryBomb

I purchased on O2 from a builder in England, and it stopped working after only a few hours use.   I assume I cannot mention the builder by name since they are a sponsor here at HF.  The builder is not returning my emails.


----------



## LizardKing1

Uhm I think you can mention whoever you want. We're talking about epiphany acoustics? They have a representative here at Head-Fi I suggest you contact him.


----------



## Br777

just remember, its new years/holiday season.. i wouldnt expect a response for at least a day or two.


----------



## Br777

Quote: 





cherrybomb said:


> I purchased on O2 from a builder in England, and it stopped working after only a few hours use.   I assume I cannot mention the builder by name since they are a sponsor here at HF.  The builder is not returning my emails.


 


   
  silly question but have to ask.. maybe the batteries just need charging?


----------



## Draygonn

br777 said:


> silly question but have to ask.. maybe the batteries just need charging?


----------



## turokrocks

Quote: 





br777 said:


> silly question but have to ask.. maybe the batteries just need charging?


----------



## Willakan

We're not actually joking: When the batteries in the O2 are low enough to potentially cause problems, it drops into a "stand-by" mode, where the power LED still illuminates but no sound is heard (if memory serves, mine is a AC wallwart-only build), which if you didn't know would seem exactly like a broken amp!


----------



## pinkfloydfan

Quote: 





cherrybomb said:


> I purchased on O2 from a builder in England, and it stopped working after only a few hours use.   I assume I cannot mention the builder by name since they are a sponsor here at HF.  The builder is not returning my emails.


 

 I was wondering if I was the only one with problems until I saw your post, mine had an intermittent channel which happened after it had been on for a few hours, I never got a reply either from Epiphany Acoustics & since I got this for a trip coming up shortly I couldnt wait any longer, it took enough time to get one in the first place & now this! (YIKES) 
	

	
	
		
		

		
		
	


	




, I made a pimeta amp a year ago & so luckily I can solder (just about) 
	

	
	
		
		

		
		
	


	




so I opened up my O2 & had a look around to see if there was a wire off or something easy that I could fix save sending it all back with more waiting, but nothing, then I noticed a few poor looking solder joints on the board so redone those & to my suprise DADA!!! its working again 
	

	
	
		
		

		
		
	


	




, I should have probably bought the board only & made it myself but I was lazy & assumed that somebody else might do a better job 
	

	
	
		
		

		
		
	


	




, phew at least its fixed now, crysis over, now that I have had a proper listen I just have to decide which of my portables is best for my headphones, the verdict is still out on that one but my Pimeta is proving hard to improve upon but it does have better parts, followed closely by my Neco V2 which is a cracker with my O2 in third at the moment but it is too early to tell for sure yet.


----------



## pinkfloydfan

Quote: 





br777 said:


> silly question but have to ask.. maybe the batteries just need charging?


 


   
  An obvious simple one but often overlooked so good advice


----------



## CherryBomb

Yes, I checked the battery.  It is definately a defective build.


----------



## jseaber

There was a steep learning curve to achieving 99.5%+ yields with the O2. NwAvGuy uses several thin traces throughout the O2 PCB, which are prone to breaking when trimmed by certain lead clippers. That, and he's not joking about the extreme ESD sensitivity of the MOSFETS. You need ESD jackets, wristbands, work surfaces, proper tools, and a well devised cleaning process.
   
  O2 is a tedious build, to say the least.
   
  Quote: 





cherrybomb said:


> Yes, I checked the battery.  It is definately a defective build.


----------



## shotgunshane

I just placed my order with John and requested modified gain of 1.5x and 3x.


----------



## PelPix

Wouldn't you know it?  My O2 is getting here in less than 12 hours and my cat batted my wall wart straight onto the tile!


----------



## Br777

Quote: 





pelpix said:


> Wouldn't you know it?  My O2 is getting here in less than 12 hours and my cat batted my wall wart straight onto the tile!


 


   
  nothin a little scotch tape cant fix


----------



## PelPix

It fell 5 feet directly onto the plug and dislodged the mount on the plug, bent it at a 90 degree angle, and arguably damaged the internals.
  I got the 16V 1A model, so it's like 5 pounds.  Guess I have to wait for a new one to ship!


----------



## Willakan

Quote: 





jseaber said:


> There was a steep learning curve to achieving 99.5%+ yields with the O2. NwAvGuy uses several thin traces throughout the O2 PCB, which are prone to breaking when trimmed by certain lead clippers. That, and he's not joking about the extreme ESD sensitivity of the MOSFETS. You need ESD jackets, wristbands, work surfaces, proper tools, and a well devised cleaning process.
> 
> O2 is a tedious build, to say the least.


 


  Which traces in particular are you talking about? I saw someone on DIYAudio talk about a pretty nasty failure condition whereby DC goes to both the DAC and the headphones if some of the traces for the PSU caps are damaged - but the good thing is that should be obvious in initial testing and is very unlikely to develop as a fault later.
  As for the MOSFETS, I just never touched any part of them that wasn't plastic - probably for the best!


----------



## Br777

So far so Great!


----------



## liamstrain

Quote: 





pelpix said:


> Wouldn't you know it?  My O2 is getting here in less than 12 hours and my cat batted my wall wart straight onto the tile!


 


  Can you opamp roll that cat into a dog?


----------



## maverickronin

Quote: 





br777 said:


> So far so Great!


 

 Is that a custom cable on your LCD-2s or did your ES5s come in?


----------



## pancakeplease

Lucky. When'd yours ship out? 
  I think mine will be here around Thursday.. can't wait.
  Quote: 





br777 said:


> So far so Great!


----------



## mikeaj

Quote: 





willakan said:


> Which traces in particular are you talking about? I saw someone on DIYAudio talk about a pretty nasty failure condition whereby DC goes to both the DAC and the headphones if some of the traces for the PSU caps are damaged - but the good thing is that should be obvious in initial testing and is very unlikely to develop as a fault later.
> As for the MOSFETS, I just never touched any part of them that wasn't plastic - probably for the best!


 

 Interesting.  Do you recall any more details about PCB traces?  When I originally built my O2, it worked fine, but at one point it had issues.  I thought it was the regulators, the diodes, or whatever else, but it turned out to be a PCB trace issue I think...at the power supply caps.  Eventually I fixed it by using my own wire to connect the negative power supply caps to the 7912 regulator.  For me the problem developed probably after handling it when touching up some solder joints, and not with it lying around.  I doubt something like that would happen without mishandling.  I should note that I didn't have any trimmers on hand, so I "trimmed" leads by bending them back and forth until they could be snapped.  Yes, that's _really_ asking for trouble, I know.
   
  IIRC there was some non-trivial DC to the headphones, but they're relatively insensitive AKG K601, which were promptly disconnected and ended up none worse for the wear.  I never checked the input for DC though, so I wonder if I also got some there as well.  Fortunately, I was using a cheap source with a DC blocking cap on the output, so I'm pretty sure it wouldn't have been damaged anyway.  On the other hand, it would have been a good excuse to replace it.


----------



## Draygonn

br777 said:


> So far so Great!



Nice faceplate. Mine is very basic. It'll ship out in the next few days,


----------



## PelPix

Just got mine.  It's leagues ahead of my modded M-Stage.  My source is too powerful, though.  High gain clips, but low gain is plenty loud.


----------



## Br777

Quote: 





pelpix said:


> Just got mine.  It's leagues ahead of my modded M-Stage.  My source is too powerful, though.  High gain clips, but low gain is plenty loud.


 


   
  ^ whats your source?
   
  as for my O2 and some impressions after maybe 10 minutes listening:
   
  low gain is plenty loud for me with my lcd-2's -  you can see where i'm keeping the volume in my photo.. i will rarely be going any louder. 
   
  build quality, looks and feel seem excellent.. everything feels really solid.  The amp is smaller than i anticipated, which is just fine by me.
   
  sound is just excellent.  It is going to be very interesting listening to my stacker II when it arrives. 
   
  Im happy to report that no matter what i plug or unplug there is no pops or noises.  only when i turn the amp off do i hear a very slight "woof" which was expected, but its hardly bothersome.
   
  the cable you are seeing in my photo is the brown one in the back which i made and has a 1/4" neutrik on the end, which is connected to a three inch long 1/4 to 1/8 "tail" that goes into the amp.  .. the curly thing is a phone cord that snuck into the photo
   
  I dont have my es5's yet.. holidays really slowed that process down.


----------



## SanjiWatsuki

Just got my O2 amp. It's lovely with my modded T20RP. Significant improvement in the bass compared to driving it out of my X-Fi Go! straight, and I feel like the bass is better compared to my integrated audio jack as well.


----------



## Br777

Quote: 





pancakeplease said:


> Lucky. When'd yours ship out?
> I think mine will be here around Thursday.. can't wait.


 
   
  ordered 21st (pre-order actually as they were not complete yet) shipped on the 30th.. of course new years slowed it down a bit.


----------



## pancakeplease

Quote: 





br777 said:


> ordered 21st (pre-order actually as they were not complete yet) shipped on the 30th.. of course new years slowed it down a bit.


 

 I'm assuming you bought it preassembled? I bought the front panel and a completed PCB and bought the enclosure somewhere else so I dont have to wait until the preorder is up. I got the enclosure today and can't get the screws on... ****


----------



## Br777

Yes, fully preassembled.


----------



## estreeter

Quote: 





cherrybomb said:


> Yes, I checked the battery.  It is definately a defective build.


 

 CherryBomb:
   
  1. What gave you the impression that you cant mention the name of the builder because he is a Head-Fi sponsor ? Thats BS - go back through the old threads on amps from Ray Samuels, Justin Wilson and others - there are numerous posts from frustrated people who were advised to ring Ray (as an example) because he wasnt on top of his email backlog.
   
  2. If your EPH-02 is defective, Oliver has all the details on the Epiphany Acoustics website for you to have it fixed under warranty. They guy is just starting out on this endeavour - if he has dropped the ball due to his workload or whatever, you really need to make him aware of that.
   
  http://www.head-fi.org/t/584202/epiphany-acoustics-join-head-fi-with-the-ehp-o2-portable-headphone-amp
   
  If you still havent received any response via email by the end of the week, you should take it further with your Consumer Affairs people, but dont just write the builder or his amp off because you have a problem and didnt get an immediate response. I dont have any personal relationship with Oliver, but my view is that competition is good : Ray, Justin and others didnt build their businesses overnight, so lets give Oliver a fighting chance. AFAIK, this isnt Mikael from Singlepower (at least, I *hope* it isnt Mikael ...)


----------



## ClieOS

Order my JDS O2 last week and it should ship this week. Can't wait to listen to it and find out what all the fuzz is about!


----------



## Br777

Quote: 





clieos said:


> Order my JDS O2 last week and it should ship this week. Can't wait to listen to it and find out what all the fuzz is about!


 


   
  Dare I ask - do you have a "main" or "favorite" rig?   If so what is it?
   
  Browsing your amp collection in your profile, i would not be surprised if the O2 trumps them all, at least as far as sound quality goes.
   
  on a side note-
  It's interesting to watch as NwAvGuys knowlege begins to permiate head-fi.   I am seeing a lot of people reference his work, or ask questions about measurements in more and more threads these days.
  Glad to know that being banned is not stopping him from turning this hobby on its head... ok maybe thats an overstatement.. maybe not...


----------



## khaos974

Quote: 





br777 said:


> on a side note-
> It's interesting to watch as NwAvGuys knowlege begins to permiate head-fi.   I am seeing a lot of people reference his work, or ask questions about measurements in more and more threads these days.
> Glad to know that being banned is not stopping him from turning this hobby on its head... ok maybe thats an overstatement.. maybe not...


 







 It's not Lord Voldemort's knowledge, just basic design concepts that have been known forever and have been forgotten and put in a corner for some time when idiophilia took over audiophilia.


----------



## Br777

Quote: 





khaos974 said:


> It's not Lord Voldemort's knowledge, just basic design concepts that have been known forever and forgotten for some time when idiophilia took over audiophilia.


 


   
  fair enough.  None the less, he's bringing it back to life with a vengance and he seems *very *thorough in his knowlege.  I havent seen anyone even touch him as far as opposing or arguing his ideas/practices.    I mean when it comes down to it i'd wager that the info on his blog alone more or less destroys about 90% of the current dac/amp market.  But i dont really know what i'm talking about


----------



## maverickronin

Quote: 





khaos974 said:


> It's not Lord Voldemort's knowledge, just basic design concepts that have been known forever and forgotten for some time when idiophilia took over audiophilia.


 

 That fact that on Head-Fi we have to pass around tidbits of his writings in secret and how his blog is treated like the Necronomicon or something contributes to that sort impression.
   
  Sure its been around a long time by now but since few people with the technical expertise and the test equipment to speak definitively about this sort of stuff have spend the time to tell others, answer questions, be helpful, and offer criticism so many people don't know much about it.
   
  OTOH, I eagerly await Lord Voldermort's final and complete grimoire of occult audio knowledge.


----------



## SanjiWatsuki

The drop in the noise floor has been very apparent. I used to notice this odd humming sound during the quiet parts of some of my music that was repeatable between me running my headphones through the X-Fi Go! DAC into a 50 ohm load, my laptop's headphone out, and my computer's output but the combination of the O2 amp and X-Fi Go! has really cleaned up little details like that. With that little bit of noise gone, the music sounds overall more detailed. Although I didn't analyze this aspect of the music when I was using a Pro-Ject Head Box MK II, it was noticeable compared to the subtle improvements I got out of that headphone amp.
   
  I also get the gut feeling that both the X-Fi Go! and my computer's normal output both rolled off the lowest bass registers by several dB, because I did notice a noticable improvement in lower bass impact without equalization. 
   
  Definitely worth the $170 I put into it. This is a very good entry level source and amp as far as I'm concerned.


----------



## ClieOS

Quote: 





br777 said:


> Dare I ask - do you have a "main" or "favorite" rig?   If so what is it?
> 
> Browsing your amp collection in your profile, i would not be surprised if the O2 trumps them all, at least as far as sound quality goes.
> 
> ...


 

 I don't consider myself a desktop guy so I don't really have a desktop rig. But as far as portable rig is concerned, I don't usually stick to any particular combo. For review purpose, I use the following the most: Fuze - diyLOD - 3MOVE. I am very familiar to its sound so it is my 'stable' choice, but not the best sounding choice.
   
  As for NwAvGuys - I don't necessary agree on his take of audiophilia that everything must be measured perfect to sound good, but I do agree science has its role. Just that perfect measurement has no important for me if my ears don't agree. If my ears do approve, all the better.


----------



## Br777

Quote: 





clieos said:


> As for NwAvGuys - I don't necessary agree on his take of audiophilia that everything must be measured perfect to sound good, but I do agree science has its role. Just that perfect measurement has no important for me if my ears don't agree. If my ears do approve, all the better.


 


   
  I've read a LOT of his blog and from what I gather, he does not say gear "must" measure well to sound good, only that he personally prefers gear that measures well over other charecteristics, and that there is definitely a scientific connection to measuring well and sounding good or at least sounding "pure"
   
  I do not think that he claims that absolute measurement based gear will always be the preferred sound for everyone.  He acknowleges that many people prefer tube sound, or colored sound and so on...  He mainly just says that clean measureing gear will be the least colored, and cleanest signal/ sound so to speak.


----------



## ClieOS

Quote: 





br777 said:


> I've read a LOT of his blog and from what I gather, he does not say gear "must" measure well to sound good, only that he personally prefers gear that measures well over other charecteristics, and that there is definitely a scientific connection to measuring well and sounding good or at least sounding "pure"
> 
> I do not think that he claims that absolute measurement based gear will always be the preferred sound for everyone.  He acknowleges that many people prefer tube sound, or colored sound and so on...  He mainly just says that clean measureing gear will be the least colored, and cleanest signal/ sound so to speak.


 

 I do read his blog from time to time, and not always get the same feeling as you. I guess that's just how each of us interpret other's wording.


----------



## pancakeplease

Quote: 





br777 said:


> Yes, fully preassembled.


 


  I figured it out. It came with 2 sets of screws. I'm good. 
   
   
   
   
  On another note, I can't wait to see what his full desktop+usb dac version looks like. This current O2 is said to be better than the new E17 and the M-stage and for $150, it's a pretty good deal, so can't wait to see what the new one brings.


----------



## Br777

well after a thorough evening of listening with the O2, I am continuing to be very impressed.  I wont really know if I'm just delusional until i have something comperable to compare it to, but my oh my is this amp impressing me.  Everything I throw at it sounds so smoothe and musical.    I was concerned that this amp might be boring, sterile, clinical, etc.. probably a common concern with a by the book measurement amp, but definitely not the case. 
   
  so either the stacker II is going to be on another stratosphere and maybe its just been too long since i have had a proper amp paired with my lcd-2's, or.... the stacker is gonna get trounced or equaled by an amp nearly 1/10th its price.
   
  Oh i cant wait to find out!


----------



## Willakan

Quote: 





br777 said:


> I was concerned that this amp might be boring, sterile, clinical, etc.. probably a common concern with a by the book measurement amp, but definitely not the case.


 


  If you do find the O2 does sound strange in comparison to the more expensive amp, a few resistors to change its output impedance could save you a lot of money!


----------



## Anaxilus

Quote: 





clieos said:


> I do read his blog from time to time, and not always get the same feeling as you.


 

 Ain't that the truth.


----------



## glenda

Quote: 





willakan said:


> If you do find the O2 does sound strange in comparison to the more expensive amp, a few resistors to change its output impedance could save you a lot of money!


 

 FYI:  The stacker has a lower output impedance than the O2.


----------



## LizardKing1

Quote: 





br777 said:


> I've read a LOT of his blog and from what I gather, he does not say gear "must" measure well to sound good, only that he personally prefers gear that measures well over other characteristics, and that there is definitely a scientific connection to measuring well and sounding good or at least sounding "pure"
> 
> I do not think that he claims that absolute measurement based gear will always be the preferred sound for everyone.  He acknowleges that many people prefer tube sound, or colored sound and so on...  He mainly just says that clean measureing gear will be the least colored, and cleanest signal/ sound so to speak.


 

 You know when 2 groups of people with opposite ideas are confronted, they usually have taken the other group's idea and distorted it to make it sound bad? Like a Republican might say that since Democrats agree with abortion they are baby killers, and Democrats might say that because Republicans don't want social support they are a bunch of rich snobs who hate the poor? The same kind of happens between subjectivists and objectivists. I will say it again: there is no need to belong exclusively to any of these categories, but instead believe in an agreement of both.
   
  Anyway, amongst the subjectivists there's this idea that an objectivist's wet dream is a dry, sterile, boring rig. That's wrong. An objectivist agrees with a scientific approach to draw conclusions, so if someone swears they hear a difference between 2 amps that measure exactly the same, they are either hearing things, they are biased (likely) or the sort of test to measure the difference has not been thought of (unlikely). It also means, from what I've been told by a few objectivists, that only the last link should be colored. There's this stupid thing around called synergy that tells you to pair a K701 with a tube amp, since that smooth distortion makes the analytical K701 more neutral and less edgy. This assumes you'll only use that amp with the K701. If you have that same amp with an HD650 which is already smooth and tube-y, it might sound a veiled. I believe your source player, your DAC and your amp should be as neutral as possible, and then you can color the hell out of your headphones (warning: do NOT stick crayons inside the drivers), because if you color anything in between it will color everything from that point on.


----------



## Willakan

Quote: 





glenda said:


> FYI:  The stacker has a lower output impedance than the O2.


 

 Well, I suppose that increases the chance they will sound similar then!
  As for the objectivist approach, it is simply the denial of magical unmeasurable stuff which inevitably only comes when the user has either inconvenienced a huge amount of their time, money or both. The reason objectivists are prone to look down on gear that distorts or somehow colours the sound as part of its design, whether unintentionally or intentionally, is because there are far easier ways of achieving colouration in the digital domain, which can cost nothing and be turned on and off at will.
   
  Imagine you have bought a very expensive projector, but you find the colour balance slightly cold for your liking (say you prefer skin tones to look warmer or something). Do you:
  1) Purchase tinted screens to project onto to alter the colour balance: you go through several before finding something that looks reasonable - only to find it makes other colours look off - but you may not notice this?
  2) Buy a different projector?
  3) Change the projector's settings to alter hue/saturation and the like, with perfect precision, on a per colour basis?
   
  Which option would you pick?


----------



## Br777

Quote: 





glenda said:


> FYI:  The stacker has a lower output impedance than the O2.


 

  
  I thought the O2 was close to zero. Like less than 1ohm, but i cant remember off hand.  How much lower can it be?
   
  By the way if u could pm me any info on the stacker i'd appreciate it.  I know practically nothing about it from a technical/specs standpoint
   
  Thanks.


----------



## fishski13

Quote: 





br777 said:


> fair enough.  None the less, he's bringing it back to life with a vengance and he seems *very *thorough in his knowlege.  I havent seen anyone even touch him as far as opposing or arguing his ideas/practices.    I mean when it comes down to it i'd wager that the info on his blog alone more or less destroys about 90% of the current dac/amp market.  But i dont really know what i'm talking about


 

 when your only criteria for the evaluation for music reproduction is measurements, there's not much to argue about.  

  
  Quote: 





lizardking1 said:


> Anyway, amongst the subjectivists there's this idea that an objectivist's wet dream is a dry, sterile, boring rig. That's wrong. An objectivist agrees with a scientific approach to draw conclusions, so if someone swears they hear a difference between 2 amps that measure exactly the same, they are either hearing things, they are biased (likely) or the sort of test to measure the difference has not been thought of (unlikely). It also means, from what I've been told by a few objectivists, that only the last link should be colored. There's this stupid thing around called synergy that tells you to pair a K701 with a tube amp, since that smooth distortion makes the analytical K701 more neutral and less edgy. This assumes you'll only use that amp with the K701. If you have that same amp with an HD650 which is already smooth and tube-y, it might sound a veiled. I believe your source player, your DAC and your amp should be as neutral as possible, and then you can color the hell out of your headphones (warning: do NOT stick crayons inside the drivers), because if you color anything in between it will color everything from that point on.


 

 i'm not sure i understand why it's o.k. to have a HP that may sound more colored (or subjectively worse) because of an amplifier mismatch, despite the amplifier measuring "accurate".    
   
  i have 3 different opamp output HP amps here, including the O2 (now gone).  volume matched to 0.2mV, i couldn't tell a difference.  however, when i played around with the volume without matching, 2 of the amps were identical, and the O2 slightly different.  if i EQed a couple spikes from 5K-8K with my K702, i could get the O2 to sound "identical" without volume matching.


----------



## maverickronin

Quote: 





br777 said:


> I thought the O2 was close to zero. Like less than 1ohm, but i cant remember off hand.  How much lower can it be?
> 
> By the way if u could pm me any info on the stacker i'd appreciate it.  I know practically nothing about it from a technical/specs standpoint


 

 The O2's output impedance is .54 ohms.  Its not hard to get lower but it doesn't matter a whole lot since half an ohm should be low enough to not cause audible issues with anything currently on the market.  The O2's Z out would have been about .04 ohms if it just had a single NJM4556 for its output stage but adding another one and parralleling them for more power required adding a little bit of extra resistance to keep it working properly and added .5 ohms to the Z out in exchange for more power.
   
  I'd assume the the Stacker uses a discrete output stage with plenty of feed back to get a lower Z out but I don't know much about it either.
   
  It _might _possibly affect something like the AKG K3003 or the Sony XBA4 IEMs which are rated at 8 ohms nominal but could conceivably have even wilder impedance swings than normal for IEMs.


----------



## francisdemarte

I agree between the O2 and the Lovely Cube (like the M-Stage this is a Lehmann Black Cube Linear clone) with the same opamp in it and volume matched. I was hard pressed to hear much difference between them.
   
  Your headphones will be more colored than most well designed amps.


----------



## LizardKing1

Quote: 





fishski13 said:


> i'm not sure i understand why it's o.k. to have a HP that may sound more colored (or subjectively worse) because of an amplifier mismatch, despite the amplifier measuring "accurate".
> 
> i have 3 different opamp output HP amps here, including the O2 (now gone).  volume matched to 0.2mV, i couldn't tell a difference.  however, when i played around with the volume without matching, 2 of the amps were identical, and the O2 slightly different.  if i EQed a couple spikes from 5K-8K with my K702, i could get the O2 to sound "identical" without volume matching.


 

 I think you're referring to the 2 hypothetically equal amps scenario I used as example. I was talking about 2 equally-measuring amps, they don't necessarily have to measure well. In any case, if all measurements point out none or insignificant differences (hundredths of 1% THD, for example), and yet someone hears a difference, an objectivist will see no logical reason for this in the amp, so the answer must be in the subject, who is biased.


----------



## atothex

We can't measure everything. Even objectivists know that. If someone thinks they can measure everything, then they're just dumb.


----------



## maverickronin

Quote: 





fishski13 said:


> i'm not sure i understand why it's o.k. to have a HP that may sound more colored (or subjectively worse) because of an amplifier mismatch, despite the amplifier measuring "accurate".


 

 I don't think anyone says that its wrong to use "colored" DACs or amps instead of a "colored" headphone.  I'm a big fan of Voldermort but I also agree that the music and my enjoyment of it is what's important as opposed to trying to perfectly reproduce the recording of that music at my eardrums.  The recording, and the rest of the equipment for that matter, is only a means to an end.  I personally just think its impractical and more expensive to look for "synergy" between equipment to get me to that enjoyment.
   
  I find it easier and cheaper to remove as many variables from the chain as I can.  Insofar as human hearing can discern it is possible to make perfect amps and DACs but even before accounting for taste there isn't such a thing as a perfect headphone or recording and because I would prefer to remove as many potential sources of coloration as I can I'll opt for for the transparent amp and DAC.  After that you can chose some headphones you like and mod those to taste if you're up for a little DIY.  Further corrections can be made with EQ and DSPs.  Not everyone uses a computer for playback but from what I've seen most of the people on here who prefer spinning discs of either poly-carbonate or vinyl spend enough on fancy amps that they could get something powerful and transparent to use along with a very high quality hardware EQ/DSP box for the same or less money and get increased variety and versatility as well.
   
  Of course that's just what I'd do myself.  Everyone has different hobbies, preferences, and budgets.  Plenty of the stuff I enjoy looks weird from the outside.  Pretty much any hobby which isn't mainstream enough to give the general public some degree of desensitizing exposure is like that.  I'm not going to, nor do I want to, tell anyone that they shouldn't do it they enjoy it and have the budget or that they're wrong for liking whatever they happen to like.
   
  What really bothers me and what I think bothers many of the so-called "objectivists" (Which we're not.  Seriously, has no one around here heard of Ayn Rand?) is when people are told things which are either untrue or unsupported by evidence and that diving into very expensive and usually (but not always) "colored" amps and DACs is the only way to get "good sound".  I get angry when I see complete newbies waste money on thing they don't need or get talked into upgrades that waste their money and don't add to their enjoyment because the sort of changes that we consider huge around here are insignificant to the general public.  I don't like it when someone's opinion is derided as invalid or useless because their associated equipment isn't expensive enough to meet someone's snobbish standards despite its lack of measurable flaws.
   
  I'm not accusing you or anyone else in this thread of that sort of thing.  Its been polite in here so far.  I'm just pointing out the sort of thing we usually argue against.  We're not trying to "take over" Head-Fi in the name of the O2, The Wire, or something similar.  I just want to point out that there are different paths to follow in pursuit of enjoying music and that people should make an informed decision before spending their money.


----------



## mikeaj

Quote: 





lizardking1 said:


> I think you're referring to the 2 hypothetically equal amps scenario I used as example. I was talking about 2 equally-measuring amps, they don't necessarily have to measure well. In any case, if all measurements point out none or insignificant differences (hundredths of 1% THD, for example), and yet someone hears a difference, an objectivist will see no logical reason for this in the amp, so the answer must be in the subject, who is biased.


 


  There's a distinction here to be made.  If two amps have almost exactly the same THD into the same load at the same output level using the same test tone, there's no guaranteeing that they will still be similar at different output levels, different frequencies, different loads, and so on.  Even more importantly, if the THD is almost all 2nd order harmonics, that's quite different than if there's significant power in anything else.  There's no reason to think they should necessarily sound the same.  However, we should note the result of the Carver challenge, in which a solid-state amplifier was tuned to match the distortion of an expensive tube amp--which shows that despite some complications in this scenario, you can still readily get something very close, to (well-trained) human ears.
   
  If two amps measure with extremely low THD, IMD, noise, etc., into any practical headphone at any audible frequency, are stable, and have a very flat frequency response into the frequency range we care about, and so on, then we can fairly confidently say that these are indicators of very high linearity into the loads we care about.  Thus the input/output relationship is closer to ideal in a linear systems theory sense, and you would expect very similar results from both amplifiers no matter what the input signal is, as long as it only consists of those frequencies in the frequency range in which they are well matched.  Sure, you don't have infinite time and can't measure every possible input into both systems, but in this case it may not be necessary anyway.  If SMPTE and CCIF both show very low residual distortion, I would guess that real music consisting of whichever frequencies you want, would also show very low distortion.  There are audio differencing techniques to use if real-world music playback is what you're interested in, anyhow.


----------



## fishski13

Quote: 





maverickronin said:


> I don't think anyone says that its wrong to use "colored" DACs or amps instead of a "colored" headphone.  I'm a big fan of Voldermort but I also agree that the music and my enjoyment of it is what's important as opposed to trying to perfectly reproduce the recording of that music at my eardrums.  The recording, and the rest of the equipment for that matter, is only a means to an end.  I personally just think its impractical and more expensive to look for "synergy" between equipment to get me to that enjoyment.
> 
> I find it easier and cheaper to remove as many variables from the chain as I can.  Insofar as human hearing can discern it is possible to make perfect amps and DACs but even before accounting for taste there isn't such a thing as a perfect headphone or recording and because I would prefer to remove as many potential sources of coloration as I can I'll opt for for the transparent amp and DAC.  After that you can chose some headphones you like and mod those to taste if you're up for a little DIY.  Further corrections can be made with EQ and DSPs.  Not everyone uses a computer for playback but from what I've seen most of the people on here who prefer spinning discs of either poly-carbonate or vinyl spend enough on fancy amps that they could get something powerful and transparent to use along with a very high quality hardware EQ/DSP box for the same or less money and get increased variety and versatility as well.
> 
> ...


 

 i had $10K invested in a speaker rig, built up over a period of a couple of years, with $4K of that tied up in a vinyl spinner.  in the end, i didn't care for the sound.  i felt like an audiophool.  when i needed a special RCA cable with a DIN connector to fit the DIN only British amplifiers i was using at the time, i was charged over double the $100 i was quoted.  that was the last straw.  i bought a BM DAC1...and was floored.  the turntable was sold in short time and the amps and speakers were replaced with Adcom, Krell, and ATC SCM12 monitors.  then came DIY.
   
  if you're unfamiliar with ATC loudspeakers, do a search.  while i like to play around with full-range speakers for a different flavor, in my experience, if there is such a thing as neutrality, the ATC are the closest.  they are my "reference" and they sound pretty special.  in HP-dom, the closest i've come to them are the K702 or my modified D2000, but not when driven by an opamp - they sound dry and sterile.  it's a personal preference and i'm not claiming to have golden ears or that my preferences are "absolute neutrality" - no such things exist.  i have no issues with judicious EQing and use it from time to time as well with HPs.  
   
  other than the Naim Headline2 and tubed Cayin i once owned, or my Bijou, none of my SS amps, DIY or the BM DAC1, sound "colored".  they all have output impedances less than 1ohm, with global NFB ranging from none, moderate, and high in the DAC1.  they individually have different strengths and weaknesses, most notably in how they _portray_ the music.  this is highly subjective though and where the friction between the 2 camps occur - what is measurable, what is audible, and listener bias considerations.


----------



## estreeter

Putting the objectivist rhetoric to one side, *would it really hurt* boutique audio manufacturers to publish meaningful measurements with each of their products ? I'm not talking in-depth measurements _ala_ Voldemort, but how about output impedance and power under varying loads ? Even if such figures were determined using RMAA from a soundcard, it has to be better than the void that currently sits next to the pretty pics on more than one product page. If you are going to spend 12+ months doing the development work on a new product, surely an afternoon compiling measurements wouldnt be a huge investment ?


----------



## jseaber

Quote: 





willakan said:


> Which traces in particular are you talking about? I saw someone on DIYAudio talk about a pretty nasty failure condition whereby DC goes to both the DAC and the headphones if some of the traces for the PSU caps are damaged - but the good thing is that should be obvious in initial testing and is very unlikely to develop as a fault later.
> As for the MOSFETS, I just never touched any part of them that wasn't plastic - probably for the best!


 

 Any of the 10-12mil traces are fragile (most of the board...). Be extra cautious with traces running to/from D7 and R6. Cold solder joints are also harder to avoid on O2 due to the small component pads, especially at C2/3/4/5. Insert components, then trim, then solder. And solder thoroughly, with a eutectic blend. Water soluble is best for the majority of the board, since it makes for easy cleaning. Clean the board before installing the MOSFETS, then switch to a no-clean eutectic&nbsp;blend to solder Q1 and Q2. Using two solder blends minimizes cold joints, and this method protects ESD sensitive MOSFETS from potential handling damage during the cleaning process. This is nothing new, but it's particularly important when building O2.
   
  Quote: 





clieos said:


> Order my JDS O2 last week and it should ship this week. Can't wait to listen to it and find out what all the fuzz is about!


 

 Just an FYI: FedEx wiped out two days this week for us with PCB delivery. Nick and I will be working extra this weekend to catch up.


----------



## fishski13

Quote: 





estreeter said:


> Putting the objectivist rhetoric to one side, *would it really hurt* boutique audio manufacturers to publish meaningful measurements with each of their products ? I'm not talking in-depth measurements _ala_ Voldemort, but how about output impedance and power under varying loads ? Even if such figures were determined using RMAA from a soundcard, it has to be better than the void that currently sits next to the pretty pics on more than one product page. If you are going to spend 12+ months doing the development work on a new product, surely an afternoon compiling measurements wouldnt be a huge investment ?


 

 i agree.  something like the FirstWatt F5 manual (first paragraph and scroll near the bottom) would be enough - http://www.firstwatt.com/pdf/prod_f5_man.pdf


----------



## Br777

certainly makes one wonder just how many designers are just trusting their knowlegebase, and going by ear, and if they measure their gear at all.
   
  one really never knows unless the builders make themselves clear


----------



## liamstrain

Quote: 





atothex said:


> We can't measure everything. Even objectivists know that. If someone thinks they can measure everything, then they're just dumb.


 


  Agreed. However, if it can be considered an audible change, I would be _*extremely*_ surprised to find that it did not reflect somewhere in a measurement. By the same token, if there are no significant differences in measurements, I would be _*extremely*_ surprised if it could be detected as an audible change in a well conducted double blind test.


----------



## Br777

Quote: 





liamstrain said:


> Agreed. However, if it can be considered an audible change, I would be _*extremely*_ surprised to find that it did not reflect somewhere in a measurement. By the same token, if there are no significant differences in measurements, I would be _*extremely*_ surprised if it could be detected as an audible change in a well conducted double blind test.


 


  that - exactly


----------



## mikeaj

Quote: 





estreeter said:


> Putting the objectivist rhetoric to one side, *would it really hurt* boutique audio manufacturers to publish meaningful measurements with each of their products ? I'm not talking in-depth measurements _ala_ Voldemort, but how about output impedance and power under varying loads ? Even if such figures were determined using RMAA from a soundcard, it has to be better than the void that currently sits next to the pretty pics on more than one product page. If you are going to spend 12+ months doing the development work on a new product, surely an afternoon compiling measurements wouldnt be a huge investment ?


 

 I think it really might, overall.  People might take a second look and wonder why they want an amp that prides itself on being able to put 4W into 32 ohms, if they've got Grados, Audio-Technicas, Ultrasones, that need under 50 mW to be really loud.  Then again, I don't think many audio gear purchasers think like that.
   
  By the way, your computer sound card and especially RMAA are not going to be able to tell you the output voltage levels.  Most sound cards would just clip the inputs at 12V or whatever output voltage many of these amps can do.  But even with a bare minimum of equipment, it would take little effort to rig up a voltage divider, feed the smaller voltage into the sound card to check for 1% THD or so, and use a multimeter to check the total voltage levels.  They're not exactly excused.
   
   
  On a side note, nothing beats all those headphone manufacturers specifying frequency range on the spec sheets.


----------



## maverickronin

Quote: 





mikeaj said:


> On a side note, nothing beats all those headphone manufacturers specifying frequency range on the spec sheets.


 

Marketing
   
   
  Quote: 





> Frequency Response : 6Hz -100,000Hz


 
   
Reality.
   
  Th cold harsh light of reality...


----------



## LizardKing1

Quote: 





maverickronin said:


> I don't think anyone says that its wrong to use "colored" DACs or amps instead of a "colored" headphone.  I'm a big fan of Voldermort but I also agree that the music and my enjoyment of it is what's important as opposed to trying to perfectly reproduce the recording of that music at my eardrums.  The recording, and the rest of the equipment for that matter, is only a means to an end.  *I personally just think its impractical and more expensive to look for "synergy" between equipment to get me to that enjoyment.*
> 
> I find it easier and cheaper to remove as many variables from the chain as I can.  Insofar as human hearing can discern it is possible to make perfect amps and DACs but even before accounting for taste there isn't such a thing as a perfect headphone or recording and because I would prefer to remove as many potential sources of coloration as I can *I'll opt for for the transparent amp and DAC.  After that you can chose some headphones you like and mod those to taste if you're up for a little DIY.*  Further corrections can be made with EQ and DSPs.  Not everyone uses a computer for playback but from what I've seen most of the people on here who prefer spinning discs of either poly-carbonate or vinyl spend enough on fancy amps that they could get something powerful and transparent to use along with a very high quality hardware EQ/DSP box for the same or less money and get increased variety and versatility as well.


 
   
  Thank you, I was hoping someone with better speech abilities than me could put into words why a neutral approach makes more sense.


----------



## Hi-fi Wigwammer

Blantant plug I know, but I have an O2 amp for sale in the Classifieds!


----------



## ClieOS

Quote: 





jseaber said:


> Just an FYI: FedEx wiped out two days this week for us with PCB delivery. Nick and I will be working extra this weekend to catch up.


 
  No problem, I can wait. I have seen worst thing done by Fedex myself as they have recently knocked my FiiO E17 sample out of commission (partially anyway) during the shipping. 
	

	
	
		
		

		
			




   
  p/s: Might order the C421 next month or so if I actually have some money left. 
	

	
	
		
		

		
		
	


	




 Hope the final case will be ready by then.


----------



## caracara08

Listening to my new O2 and it sounds pretty good.  im very happy for the money i spent on it.  i have it on AC power but have the option of throwing batteries in. i do not plan to. I never planned to use it as a portable. 
   
  my dac is the Muse TDA1543x4 dac coupled with this amp, it makes a very good sounding super budget setup (spent approx 140$ on the pair). tried it with my FX700 and FXT90 last night and liked it with the FXT90 more.  today been listening to it with my T1 and it sounds very very good. kudos to V.


----------



## jseaber

Quote: 





clieos said:


> No problem, I can wait. I have seen worst thing done by Fedex myself as they have recently knocked my FiiO E17 sample out of commission (partially anyway) during the shipping.
> 
> 
> 
> ...


 

 Good news: FedEx decided to deliver only 1 day late, so we're almost back on schedule 
	

	
	
		
		

		
		
	


	



   
  About those c421 enclosures--worst manufacturing I've ever managed. They will finally ship February, and they will look nice!
   
  Three O2 customers e-mailed this afternoon describing clicking noises after charging. Twenty minutes on the phone with one kind fellow from CA solved the problem. Please, please note that AC-to-DC adapters are commonly abbreviated "AC Adapters", but they are not AC adapters in an electrical sense! The O2 requires a 14V AC adapter, which is an entirely different beast. You cannot use a laptop power adapter, or the adapter from your Cypher Labs AS! The plug may fit, but those electrons move around quite differently...


----------



## turokrocks

Quote: 





jseaber said:


> Good news: FedEx decided to deliver only 1 day late, so we're almost back on schedule
> 
> 
> 
> ...


 


   
  Please supply the adapter, at least give the option, it took me 6 days to look for an AC-AC adapter but could not find one, I had to order it on-line  and wait for  6 days to receive it, you should consider this as this is a big let down!!!!!!!!!!!!!!  I got mine from another DIY.............


----------



## khaos974

Quote: 





turokrocks said:


> Quote:
> 
> 
> 
> ...


 

 Isn't that what the option "add North America AC Adapter" is for?


----------



## pancakeplease

Quote: 





turokrocks said:


> Please supply the adapter, at least give the option, it took me 6 days to look for an AC-AC adapter but could not find one, I had to order it on-line  and wait for  6 days to receive it, you should consider this as this is a big let down!!!!!!!!!!!!!!  I got mine from another DIY.............


 


  Where are you located? I ordered my charger off Mouser for $20 shipped and got the good charger. It took them 2 days to get it over here. 
  The O2 blog details page has the exact models of the chargers you can use so its really not too hard to just look them up. Plus the charger would drive up prices substantially. $20 shipped and JDSlabs to make any kind of profit including their own shipping is going to cost like $30 minimum with a low profit margin.


----------



## turokrocks

Quote: 





khaos974 said:


> Isn't that what the option "add North America AC Adapter" is for?


 


   


  Quote: 





pancakeplease said:


> Where are you located? I ordered my charger off Mouser for $20 shipped and got the good charger. It took them 2 days to get it over here.
> The O2 blog details page has the exact models of the chargers you can use so its really not too hard to just look them up. Plus the charger would drive up prices substantially. $20 shipped and JDSlabs to make any kind of profit including their own shipping is going to cost like $30 minimum with a low profit margin.


 

 I had to get 220/230AC so...


----------



## glenda

This O2 I built is pretty much blowing me away with my Magnums,  amazing detail.
   
  For Grados instead of clipping the gain resistor has anyone thought about bypassing the first stage completely,  I mean if we have the gain set at 1 why do we need U1 and all those ceramic caps in the signal path ?


----------



## zzffnn

I love the O2 with my Lcd-2s. Having the O2 amp in hand, I do not miss my previous AMB M3 or Cavalli CTH that much. The O2 sounds like a M3 with AD843 IIRC, and it can fit into my pocket while M3 can not.
   
  I also tried my custom IEMs (Westone ES3Xs) with the O2. Again very very good sound. No hiss, even at high listening volume.
   
  If I have to nitpick, I would say:
   
  1) the O2 may not match very well with bright / cold / aggressive headphones, because O2 seems to be very honest and does not "warm up" the sound like tube amps. I guess it is expected in view of its "objective" nature.
   
  2) Make sure you charge the battery fully, before using it with high impedance headphones such as Beyer DT880s/600 ohm. Without fully charged batteries you will hear distortion at peaks. Not an issue with fully charged batteries. The O2 drives my DT880s/600ohm very well.
   
  Edit: I would like to add that I love how the O2 runs on battery and fits into my pocket. Its size is about the same as Hifiman HM-801.


----------



## Br777

i clipped the gain and am enjoying it with both my LCD-2's and Westone ES5 Customs
   
  a true world beater amp if you ask me.


----------



## shotgunshane

What did you change the gain too?  Mine should be here tomorrow.


----------



## zzffnn

I am using the default low gain (2.5X, IIRC) with all my IEMs (Westone ES3Xs) and headphones (DT880/600, Lcd-2s). Perfect for ~80-82db music listening. Good range of volume control.


----------



## Br777

it now defaults at 1.  cant remember.. the instructions are HERE


----------



## Reticuli2

Is there any advantage to using it at the higher gain settings if you can get enough volume on the pot at 1X on low impedance or high impedance headphones?
   
  Is there an advantage to using the AC adapter as far as speed of bass transients or anything?  It's just so low distortion and clean on batteries I haven't even bothered with plugging the adapter in yet.


----------



## LizardKing1

Quote: 





reticuli2 said:


> Is there any advantage to using it at the higher gain settings if you can get enough volume on the pot at 1X on low impedance or high impedance headphones?
> 
> Is there an advantage to using the AC adapter as far as speed of bass transients or anything?  It's just so low distortion and clean on batteries I haven't even bothered with plugging the adapter in yet.


 

 I've been meaning to ask question 1 as well.


----------



## maverickronin

Quote: 





reticuli2 said:


> Is there any advantage to using it at the higher gain settings if you can get enough volume on the pot at 1X on low impedance or high impedance headphones?
> 
> Is there an advantage to using the AC adapter as far as speed of bass transients or anything?  It's just so low distortion and clean on batteries I haven't even bothered with plugging the adapter in yet.


 

 Voldermort has the gain and battery or AC specified on most (if not all) of his measurements so you can decide for yourself.
   
  The short answer is that the AC pretty much just gives you more power and raising the gain increases the noise and distortion a tiny bit.  You'd have to use an amazingly high gain before it became audible though.


----------



## Br777

he says on his blog that using lowest gain possible is always best on any amp.  sorry i cant remember the details, but as usual he makes a good case for it.


----------



## estreeter

I find the negative impacts of higher gain clearly audible, and in general I far prefer amps with sufficient grunt on low gain to allow me to avoid 'cranking it'. The EHp-O2 is the first amp, portable or otherwise, that I have owned which made high gain desirable.
   
  To be fair, I think nwavguy specified the original gain settings at 2.5 and 6.5 (see below), and I was fine with that until some bozo posted that they felt that 'low gain' would still be too much for sensitive IEMs. I had Oliver change my settings to '2x and 5x', respectively, and I now believe it was a mistake.
   
  From Voldemort's blog:
   
_The standard gains are 2.5X and 6.5X but can be internally changed to anything from 1X to 12X._
   
  With my 150-ohm RE262 IEMs, low gain just doesnt have enough juice unless I crank the volume around to 3pm and beyond (!) : unthinkable on any of my other amps as it really would blow my head off. The situation is a little better with my 32-ohm cans, but its disappointing that such a 'large' amp seems to have less power than most of my portables. Even with high gain, I dont find it to be a particularly powerful amp - I guess I should have left well enough alone and ignored the comment from our bat-eared friend with the thousand-dollar IEMs.  :banghead:


----------



## khaos974

I don't think that the gain structure of the O2 allows the potentiometer to clip the signal, I actually see no reason why the it shouldn't be used at 3 o'clock or even fully turned.


----------



## Br777

with my es5's and my gain clipped to 1, i can turn the knob about a centimeter at most before its too loud.  With my LCD-2's, the loudest i can go is 9pm
   
  estreeter what is your source? i ask because if i use a source like my clip+, even with the volume all the way up on the Clip, i find i have to turn the volume up WAY more on the same headphones.. maybe this issue.. whatever it is..maybe voltage output?, has something to do with it.
   
  try another source and see if you have the same issue.
   
  by the way, its not my bat ears 
  its that my iem's are very low impedance and high sensitivity, they are expected to behave the way they do.  Yours are probably the oppisite.. best to check ahead of time.
   
  and FYI my average listening level is measured at around 73-80db, which is considered average.


----------



## maverickronin

Quote: 





khaos974 said:


> I don't think that the gain structure of the O2 allows the potentiometer to clip the signal, I actually see no reason why the it shouldn't be used at 3 o'clock or even fully turned.


 
   
  Can't the 4556s can run out of current and clip into loads less than 50 or so ohms?
   
  Also even from a source with a volume control, I wouldn't run _any _amp this strong at max volume like that unless you only ever have really inefficient headphones hooked up to it.  One click or pop from your source could ruin some pretty expensive headphones and give you a very unpleasant ringing in your ears.


----------



## limpidglitch

Quote: 





estreeter said:


> I find the negative impacts of higher gain clearly audible, and in general I far prefer amps with sufficient grunt on low gain to allow me to avoid 'cranking it'. The EHp-O2 is the first amp, portable or otherwise, that I have owned which made high gain desirable.
> 
> To be fair, I think nwavguy specified the original gain settings at 2.5 and 6.5 (see below), and I was fine with that until some bozo posted that they felt that 'low gain' would still be too much for sensitive IEMs. I had Oliver change my settings to '2x and 5x', respectively, and I now believe it was a mistake.
> 
> ...


 


  I believe that bozo was me, but to be fair I did preface the statement with 'for sensitive IEMs'.
  Mine are 124dB/mW and 46Ω. To get 115dB from a .5V source (say my Clip+) I need a gain of .2x , or 1/5th.
  If your IEMs happen to need more than what you specified from Oliver, you only have your own lazyness to blame.


----------



## Br777

Quote: 





limpidglitch said:


> I believe that bozo was me, but to be fair I did preface the statement with 'for sensitive IEMs'.
> Mine are 124dB/mW and 46Ω. To get 115dB from a .5V source (say my Clip+) I need a gain of .2x , or 1/5th.
> If your IEMs happen to need more than what you specified from Oliver, you only have your own lazyness to blame.


 


   
  funny, we both thought he was talking about us, and we both gave the same answer


----------



## limpidglitch

Quote: 





br777 said:


> funny, we both thought he was talking about us, and we both gave the same answer


 


  Hah!
  Apparantly the world is full of bozos like us


----------



## khaos974

Quote: 





maverickronin said:


> Quote:
> 
> 
> 
> ...


 

 Sorry, I was rather imprecise, I meant clipping  hitting the voltage rails, yes, running out of current is quite possible, but not with any normal IEMs,
   
  @estreeter, I just checked the RE262 specs, 150 ohms and what I assume is 95 dB/mW (since the other HifiMan are rated in dB/mW), WOW! That's 103 dB/V compared to 105 dB/V for the K701.
  The Re262 need a higher voltage swing than the K701.


----------



## maverickronin

Quote: 





limpidglitch said:


> Mine are 124dB/mW and 46Ω. To get 115dB from a .5V source (say my Clip+) I need a gain of .2x , or 1/5th.


 

Wow.  These IEMs are _seriously _getting out of hand...
   
  At this rate induction is going to let you detect oscillating magnetic fields with IEMs just by walking around with them.


----------



## estreeter

Guys, I did omit some important info from my earlier post.
   
  1. Yes, using the line-out from my T51 or the RCA-to-mini from my HRT MSII *does* improve things, but its more pronounced with my other portables.
   
  2. I agree that specifying my gain settings improperly did come down to my own laziness, but I had just been bitten by the ZO2V1, where the default gain was ridiculously high and I couldnt use the line-out from *anything*
   
  If I can be more specific, using the same source/phones, I can get the same overall volume at about 10am on the uHA-120, and taking it past 'midday' would be a bad idea for my longterm hearing. When I had the P4, I rarely had to take it beyond 9am. 
   
  I will also add that the EHP-02 has channel imbalance at low volumes, but its at lower volumes than I would ever listen to music. I have been assured that this is merely imbalance in the 'gang pot', whatever that is, and I only need to cut a single connection to remove the 'low gain' multiplier and the problem will disappear. Given that I dont like '2x', I'm unlikely to go with '1x' .......


----------



## khaos974

FWIW, the optimal zone of a pot is usually beyond 11 am and the UHA-120 has a gain of 4X.


----------



## zzffnn

II would like to add that my O2 amp has also served me very well as a pre-amplifier. Transparent, enough gain (even from iPhone 3GS' HO) and volume control. Zero noise.


----------



## Willakan

Just to confuse the matter further, I am driving the K702s and find they get plenty loud with unity gain. At 3.5X gain my listening level is sitting firmly in the realm of channel imbalance. I do have a slightly hot source though (2.1V) and I tend to listen in quiet places, quietly. Took my Grados in a car once: had to boost the volume of my player by about 10db just to hear the music quietly over the engine noise.


----------



## PelPix

You think that's fun, my source poops out an awful _5.65VP-p (+-2.825V)_!  That's +8dBu!
   
  Anything above 2.5X gain clips.  Good thing 2.5X gain is more than loud enough for my 880/600's.


----------



## maverickronin

Quote: 





willakan said:


> Just to confuse the matter further, I am driving the K702s and find they get plenty loud with unity gain. At 3.5X gain my listening level is sitting firmly in the realm of channel imbalance. I do have a slightly hot source though (2.1V) and I tend to listen in quiet places, quietly. Took my Grados in a car once: had to boost the volume of my player by about 10db just to hear the music quietly over the engine noise.


 

 A lot of people really overestimate the power they need to drive their headphones.  There are some situations where you really may need "moar power" like for the HE-6 and K1000 or if you eat up headroom by using ReplayGain with a lot EQ with mildly inefficient 'phones as I usually do.
   
  Even my Cowon D2+ drives many full size 'phones I've owned quite well if you didn't want to pile on the EQ or listen at live levels.  My former HD650s (103dB/V, 300 ohm) and new K601s (101dB/V, 120 ohm) are quite good from just the D2+.  My modded T50RPs are a bit more efficient than the K601s but seem to do a little worse from the D2+ as compared to a "proper" amp due to their lower impedance and extra current draw.  The reason I use a portable amp with my D2+ is for the crossfeed, not more power.
   
  One hypothesis I have is that some people think they need a high power rating because they've used an amp with distortion that steadily climbs as output increases instead of something like the O2 which stays super clean right up until clips.  That would give the impression that you need an amp with a much high maximum output than you will ever actually use with your 'phones because it would keep the distortion under audible levels at listening volumes.  I don't have a whole lot to back that up at the moment though.  Its just a thought.


----------



## Br777

i really wish i could understand all this better...   O2 owner here...
   
  so its the voltage output of a source that determines how loud it will be going through an amp?
   
  as an example, an ipod with LOD is not as loud as the signal coming from my dac, both going through the same O2 amp.


----------



## shotgunshane

Holy sweet baby Jesus it sounds good with my RE262's.


----------



## maverickronin

Quote: 





br777 said:


> so its the voltage output of a source that determines how loud it will be going through an amp?


 
   
  In general:
   
  Source Voltage X Gain Factor = Max Output Voltage


----------



## shotgunshane

I am rediscovering my all my IEM's. The dynamics and clarity are superb.  I was not expecting to be this excited about an amp.  I asked john to configure my gain settings at 1.5x and 3x and couldn't be happier with that decision.


----------



## Maxvla

Mmmmm... sooo many glowing reviews. Need desktop version asap!


----------



## stv014

Quote:  





> One hypothesis I have is that some people think they need a high power rating because they've used an amp with distortion that steadily climbs as output increases instead of something like the O2 which stays super clean right up until clips.  That would give the impression that you need an amp with a much high maximum output than you will ever actually use with your 'phones because it would keep the distortion under audible levels at listening volumes.  I don't have a whole lot to back that up at the moment though.  Its just a thought.


 

 Like many other audiophile myths (such as solid state/integrated circuits/negative feedback/op-amps/digital audio/whatever else are bad, etc.), this is probably based on old and/or poorly designed amplifiers that did indeed start to distort significantly, especially in the high frequency range, well before reaching the clipping level. Add to that the inability to quantify exactly how much power and headroom are actually needed in practice, the lack of knowledge and/or understanding of the detailed specifications of the amplifiers, the lack of objective testing, sighted subjective tests affected by the placebo effect, and it is not surprising at all that a myth like this is so widely spread on internet forums.


----------



## scootermafia

Here's my review.
   
  I use mostly HD800 and LCD3, and I'm a picky person.  My home setup is a balanced B22 etc etc as you can see below.  I'm pretty unimpressed by practically everything I hear, even my home setup at times, so if a rare moment arises where a piece of gear doesn't piss me off, this is worth paying attention to.  
   
*The O2 is a ridiculously good amp at any price, and every other amp manufacturer out there needs to be very, very afraid.*  It does not sound like a portable amp, it's well within the desktop class.  It embarrasses my topkit iBasso Pelican.  It can fiercely compete with any amp under $1000 and give really good listening pleasure to people that can't afford something more expensive...but now people don't have to feel bad that they don't have some cool kid overpriced amp with an inferior circuit, because this thing is putting out 75% of the listening pleasure of my full home setup (when paired with my Boomslang2 balanced portable DAC and laptop) which is a setup worth 30x as much.  It gets very loud without distorting and I get the sense that it's "right" which I've only ever gotten from my Beta22, the feeling that I'm listening to my big home setup that I'm so used to.  
   
  It's a good match with the LCD3.  They sound very alive and not deprived of anything in the O2 + Boomslang2 setup.  The HD800s sound a bit thin with it, of course they sound thin with everything, but they need the brute Neanderthal power of my Beta22 to sound acceptable.  
   
  Words to describe it - transparent; punchy tight bass; non fatiguing; crisp fresh treble; fun.


----------



## Willakan

Someone really needs to measure the Beta22 properly one of these days, seeing as it seems to be the de facto high-end amp to to compare things with.
  You do realise the fashionable thing to do when met with an amplifier containing cheap opamps is to declare it bright and shrill, then make up something about negative feedback
	

	
	
		
		

		
			





?


----------



## PelPix

I'd just like to say that I have synesthesia (which recent studies suggest may actually be the brain's process of organizing information made tangible to those who suffer from it), and the O2 is the only amp I have ever listened to that does not smell, taste, or feel like any colors.
  It inspires no cross-reference in the circuitry of my brain.  I can finally listen in peace!


----------



## scootermafia

Hard not to be biased when I've got expensive gear all around that I'd love to proudly declare as better than the O2...but for the most part it's not better.  Cheap opamps aside, the designer is just a very gifted person and we're lucky to have this amp in existence.


----------



## shotgunshane

Quote: 





scootermafia said:


> Words to describe it - transparent; punchy tight bass; non fatiguing; crisp fresh treble; fun.


 


  x2.  This sums it up for me.


----------



## zzffnn

I have listened to LCD-2 rev1 on my Beta22 and O2, although I did not do head-to-head critical comparison. Based on my memory, O2 is not lacking much. O2 seems to be a little more upfront in terms of presentation, with slightly less soundstage in other words. But hey, O2 is transportable and so much cheaper! Having heard Beta22, I would not feel too bad to sell it and keep O2, if I am broke.


----------



## Br777

Quote: 





scootermafia said:


> Here's my review.
> 
> I use mostly HD800 and LCD3, and I'm a picky person.  My home setup is a balanced B22 etc etc as you can see below.  I'm pretty unimpressed by practically everything I hear, even my home setup at times, so if a rare moment arises where a piece of gear doesn't piss me off, this is worth paying attention to.
> 
> ...


 


   
  I knew it would only be a matter of time before reviews like this started coming.  I of course agree.  WORLD BEATER!
  now if only NwAvGuy was also a headphone designer!!!


----------



## limpidglitch

Quote: 





br777 said:


> I knew it would only be a matter of time before reviews like this started coming.  I of course agree.  WORLD BEATER!
> now if only NwAvGuy was also a headphone designer!!!


 


  Headphone design is a whole other ball game, I'm afraid, but if what I hear about the new Philips headphones is correct, we have some frugal world beaters right there.


----------



## cifani090

Quote: 





scootermafia said:


> Words to describe it - transparent; punchy tight bass; non fatiguing; crisp fresh treble; fun.


 

 SOLD! To the man names cifani090.


----------



## Draygonn

My O2 arrived. I listened all last night to my modded T40RPs with a big smile.


----------



## rogan

Quote: 





draygonn said:


> My O2 arrived. I listened all last night to my modded T40RPs with a big smile.


 


  wheres this one from? lovely casing


----------



## Anaxilus

Quote: 





rogan said:


> wheres this one from? lovely casing


 

 John Dempsey.


----------



## Maxvla

That's a step in the direction I want for my O2. Looks much better than most of the boxes I've seen, and it's close to what I want in front and back panel. Does yours even have batteries in it or is that step skipped? (or is that even possible)


----------



## Anaxilus

Quote: 





maxvla said:


> That's a step in the direction I want for my O2. Looks much better than most of the boxes I've seen, and it's close to what I want in front and back panel. Does yours even have batteries in it or is that step skipped? (or is that even possible)


 

 Dempsey's O2's have batteries, LFF skipped on the batteries for his build so you can just run it off the wall.  Still waiting on my O2 to compare to LFF's to verify even though the layout and build is identical.  Took pics for comparison when it arrives.  I still prefer my Leckerton UHA6S over LFF's O2 though.  Both are in the top 3-4 portable transportable amps I've heard so far.  Need to get mine to be sure.


----------



## evanft

All this thread does is wake me more jiggly in anticipation for the desktop version.


----------



## estreeter

*World beater *? Guys, isnt this *exactly* the kind of hype machine that Voldemort set out to destroy ? I'm sure similar phrases have been bandied around for almost every _cheaper-than-it-has-a-right-to-be_ amp, but seriously ...
   
  I came to this thread intent on detailing my newfound appreciation for the things that the EHP-02 gets right - super black background, zero turn-on thump, great separation (particularly around the drumkit/percussion) and good bass response - but I'm leaving before I find myself on the hype train. Voldemort can take a bow for designing a very good 'first amp', but I think I'd hold off on the 'world beater' stuff until we see what he does with the desktop version. As a 'portable' device, the sheer heft of the Objective2 makes it a very poor choice for newbie Head-Fiers, and those outside the loop would find it hilarious that this could be considered a 'portable' amp by anyone : there's a splash of ice-cold reality for those basking in the warm glow of their purchases. I've stopped listening for similarities/differences with my other amps, and can now simply enjoy my music - I'd suggest that's as much as any amp maker can hope for.


----------



## scootermafia

I'm not saying it beats 100% of amps, just that it provides a large measure of the personality and listening enjoyment of the B22, which I consider to be quite neutral and the standard of listening in my home.  It is vastly better than amps of the same form factor and I'm sure plenty of larger ones, and it sounds much nicer than my Pelican which previously I thought was one of the best portable amps.  The only hype is that for $150 delivered it is going to give the best value for the money than anything else I know of, not that it's the best amp ever made.  It could be one of the smartest designs ever.  The only thing that will prevent it from taking off even more on headfi is that some people have to spend a ton in order to feel good about themselves.  In the past you did have to spend a fair bit to get really good sound, but this amp has changed the game a lot...and the fact that it's a DIY design being sold for fairly low profit makes it very high value too.  
   
  I will get the desktop version when it comes out.  Really wish it was balanced so I didn't have to make new cables, eh well.  Not like it needs to be...


----------



## Br777

ok, dont call it a world beater, call it a $1000+ amp competitor if that makes you feel better, but when a $150 amp can compete with or surpass amps nearly ten times its price, i believe a little hype is in order 
   
  honestly I'm just having some fun here.  It's an exciting time in headphone audio and what can it say, its fun to get a bit excited now and then.  Part of the fun of throwing around terms like "world beater, or Night and day" is in making fun of just how rediculous those terms have come to sound in these forums.  It all becomes tongue in cheek after awhile around here.
   
  The other thing to consider is that everyone's definition of portable is different.. Just because its called portable doesnt mean it has to fit in your jeans pocket.  Ok so maybe we're blurring the line between portable and transportable, but none the less, I think a lot of people, myself included are considering this amp as something they can "take with them easily" and not necessarily something to jog with.
   
  also, Voldemort has made it pretty clear that the amp section of the desktop will not be an improvement in sound, but simply a more desktop oriented amp configuration.. of course the dac that will be built in is another story.


----------



## maverickronin

Quote: 





estreeter said:


> *World beater *? Guys, isnt this *exactly* the kind of hype machine that Voldemort set out to destroy ? I'm sure similar phrases have been bandied around for almost every _cheaper-than-it-has-a-right-to-be_ amp, but seriously ...


 

 Well since its not looking likely that anyone will step up ABX it from another amp which measures similarly or better per Voldermort's challenge its probably tied for first place with a lot of other amps.


----------



## Br777

I would really love to do some ABX-ing but as we all know it's not so simple, first of all you need the gear, then you need a helper, and the time.. not to mention you need to know at least some of the measurements of the other gear...


----------



## estreeter

There are significant practical considerations in meeting either of Voldemort's challenges, and I doubt that any of the professional builders are going to take time from *earning a living* to engage in the inevitable to-and-fro that would follow any such attempts. I also feel that there is considerable resistance to anything resembling DBT/ABX testing from a large segment of the audio industry, extending well beyond our little corner. Hi-Fi Choice has done a reasonable job of getting 3 non-industry folk in each month to do blind testing of various kit, but its a long way from being the kind of 'scientifically valid' testing that many would insist on for Voldemort's challenge.
   
  As far as the measurements challenge goes, I don't think anyone further down the ladder than Benchmark would have a dScope at their disposal - happy to hear otherwise - and Voldemort is openly cynical about anything generated using a sound-card and RMAA. Either of his challenges would consume more time and money than I suspect most of us realise, and to what end ? Anything declared the 'winner' would be the subject of ongoing debate in the same way that various Stereophile measurements continue to be challenged by folk who have nothing beyond their golden ears as a basis for comparison.
   
  Its a good amp, no question - I just dont have any $1000 amps to compare it with, and that causes me more angst than wondering if the Objective2 is the 'best under 1K' .....


----------



## tedkalaw

I will definitely be building one of these soon. I'm pretty excited.
   
  Is this a suitable first DIY project? I was thinking of building a CMOY but I am positive that I will probably never use it.


----------



## rogan

Quote: 





anaxilus said:


> John Dempsey.


 


  where does one get in contact with said john ;D?


----------



## Twinster

Well there is no way I'm going to build one of this O2 amplifier. Not one but two 
	

	
	
		
		

		
			





. I finally place the orders for the parts. I got the board and the front plates for couple of weeks now and never got around to import the BOM in Mouser's site. It's done now and after reading this thread today I'm very excited on this project. One is the regular portable model and the other would be the larger case with RCA connectors and full size headphone jack.


----------



## frenchbat

I'm pretty sure Benchmark isn't the only company out there using decent instrument. I'd take the measurements of the DACMini from Centrance by MillerAudio (http://www.milleraudioresearch.com/avtech/index.html) as a sign of this. The DACMini actually measures better than the DAC1, and from what I gather around here, it's also pretty good sonically.
  
  Oh and look at the measurements from the Antelope if you want to have a good laugh 
	

	
	
		
		

		
		
	


	



  Quote: 





estreeter said:


> As far as the measurements challenge goes, I don't think anyone further down the ladder than Benchmark would have a dScope at their disposal - happy to hear otherwise - and Voldemort is openly cynical about anything generated using a sound-card and RMAA. Either of his challenges would consume more time and money than I suspect most of us realise, and to what end ?


----------



## maverickronin

Quote: 





estreeter said:


> There are significant practical considerations in meeting either of Voldemort's challenges, and I doubt that any of the professional builders are going to take time from *earning a living* to engage in the inevitable to-and-fro that would follow any such attempts. I also feel that there is considerable resistance to anything resembling DBT/ABX testing from a large segment of the audio industry, extending well beyond our little corner. Hi-Fi Choice has done a reasonable job of getting 3 non-industry folk in each month to do blind testing of various kit, but its a long way from being the kind of 'scientifically valid' testing that many would insist on for Voldemort's challenge.


 
   
  The manufacturer doesn't to be the one to take the test.


----------



## mikeaj

opc--the one who designed The Wire, which gets better performance than the O2 (with higher equivalent cost and less features by default)--has an Audio Precision analyzer, and you can see the results on diyaudio.  Obviously all the big pro audio gear manufacturers have equipment like that, not to mention those at TI / AD / Wolfson / whatever that design relevant silicon.  
   
  More relevantly, Tyll has an AP and is looking to put out headphone amp reviews this year, so that should be interesting.  I mean, this whole deal about proving a point or a challenge isn't so compelling, but I'm always a fan of independent testing and verification of any products.
   
  Whatever take you want to have on correlating different measurements to perceived fidelity or audio preferences (based on plenty of established psychoacoustics research), or what metric X / Y / Z mean and how important they are...at least the machines will tell it straight like it is.


----------



## Anaxilus

Quote: 





maverickronin said:


> Well since its not looking likely that anyone will step up ABX it from another amp which measures similarly or better per Voldermort's challenge its probably tied for first place with a lot of other amps.


 

 That's interesting, let me talk to LFF and Purrin about doing it.  That way 3 people are involved and not just one person who can basically BS about whatever they want.  One reason I haven't bothered.  I'd also want to see the money in Escrow of some sort so I know we aren't wasting our time.  Purrin and myself did some ABing w/ his CMoy, my UHA6S and LFF's O2.  I'll post some pics in a sec.


----------



## Anaxilus

Quote: 





rogan said:


> where does one get in contact with said john ;D?


 

 PM'd


----------



## estreeter

Quote: 





anaxilus said:


> That's interesting, let me talk to LFF and Purrin about doing it.  That way 3 people are involved and not just one person who can basically BS about whatever they want.  One reason I haven't bothered.  I'd also want to see the money in Escrow of some sort so I know we aren't wasting our time.  Purrin and myself did some ABing w/ his CMoy, my UHA6S and LFF's O2.  I'll post some pics in a sec.


 

 Anaxilus, as much as I would love to see those results, will they be viewed as 'representative' ? How much better would it be to have people who knew absolutely nothing about the background to the tests ? For that matter, folk who don't even know that they are comparing different *amplifiers* ?
   
  To those who chimed in with 'Benchmark arent the only company with equipment like that', I believe I said 'On a similar level to Benchmark', and clearly Anedio, CEntrance and others are aiming at that level. Compare those companies to the one-man band operations like Just Audio (again, excellent set of measurements for their amps) and it would be interesting to know how many have access to sophisticated measuring equipment. Benchmark may not be Harman International, but they would have a few more dollars than a young guy working out of his basement.


----------



## maverickronin

Quote: 





anaxilus said:


> That's interesting, let me talk to LFF and Purrin about doing it.  That way 3 people are involved and not just one person who can basically BS about whatever they want.  One reason I haven't bothered.  I'd also want to see the money in Escrow of some sort so I know we aren't wasting our time.


 

 Sounds interesting.  What amp are you going try against the O2?


----------



## Anaxilus

I'm not one who puts value in listening tests done by people who are not familiar or interested in audio or related gear.  That is absolutely pointless but is often done in such tests.  It's like asking a soccer mom who makes a better sports car between McLaren, Ferrari and Porsche.
   
  My points are these.
   
  1-Many amps regardless of price sound like crap.
   
  2-It is possible for a someone to design and build an amp that beats many or most of them.
   
  3-Voldemort did this but it's not the best (IMHO) and he isn't the only one.  Nick Leckerton and many others that came before have done so.  But they are few and far between.
   
  Regardless, 'V' did a great job designing an amp at the price which is pretty much 95% of what a Benchmark DAC1 sounds like.  I just want to temper the hype train and keep things real.  Often times champions against hype seem to get carried away w/ their own brand of it.  If people don't see the value in such a test, no sweat, saves me the time and trouble.  Personally I'm tired of hearing about the 'Challenge' and how scared everyone is to take it.  Please.  Counter hype w/ hype I guess.


----------



## Anaxilus

Quote: 





maverickronin said:


> Sounds interesting.  What amp are you going try against the O2?


 


  We could keep the O2, CMoy, UHA6S and maybe add the DAC1 and the BA.   What do you suggest?


----------



## frenchbat

I believe "the challenge" has to be based on an agreed method of testing between the person that takes it and the designer. Of course, that's assuming you're after the 500$.
   
  But regardless, Voldemort would probably be knowledgeable when it comes to decide the test conditions, unless Nick Charles agrees to give some directions, given his alledged experience on the subject.
  
  Quote: 





anaxilus said:


> We could keep the O2, CMoy, UHA6S and maybe add the DAC1 and the BA.   What do you suggest?


----------



## Draygonn

I'm assuming this is the challenge you are talking about:

_THE SUBJECTIVE CHALLENGE: Let’s raise the bar even further for all the subjective guys. For any amp that measures sufficiently well into the desired load (reasonably close to the specs outlined in the O2 Design Principals), regardless of cost, I’ll put the O2 up against it with any popular headphones within its drive capabilities. The challenger can pick the other amp, source, music, and headphones. The listening will be done blind using an A/B/X box and the comparison will be recorded on video for publication on YouTube. The test would be administered by an independent third party (I won’t even be present). The results, win or lose, will be published on this blog. And to sweeten the deal still further, if someone beats the O2 in a valid test, I’ll give $500 to the charity of their choice. If they lose, they give $500 to the charity of my choice._


----------



## maverickronin

Quote: 





anaxilus said:


> We could keep the O2, CMoy, UHA6S and maybe add the DAC1 and the BA.   What do you suggest?


 

 Well the point is to tell the O2 apart from an amp that measures about as well or better to show that the O2 is past the point of diminishing returns for transparency, not to prove that amps can sound different.  That would disqualify the cmoy and BA since proper measurements of them would almost certainly predict audible differences.  The UHA-6S would probably qualify and the DAC1 certainly would.


----------



## Anaxilus

There's certainly a lot to TBD.  I'm certainly not flying or driving out of state to play this game.  I don't even care about the $500 'sweetner'.


----------



## Anaxilus

Quote: 





maverickronin said:


> The UHA-6S would probably qualify and the DAC1 certainly would.


 

 That could be arranged at the Bay Area meet.  The other stuff, however.....


----------



## khaos974

It's good when subjectivists agree to DB testing, because objectivists may increase the likelihood for the test to fail due to their own bias (both terms used loosely).
  Also, the $500 thing is just an opportunity for a good deed, they are offered to any recitative organization of your choice.


----------



## Anaxilus

Quote: 





khaos974 said:


> Also, the $500 thing is just an opportunity for a good deed, they are offered to any recitative organization of your choice.


 

 It also adds pressure to the listener or tested and none to the tester or designer of the experiment.  One records data, the other has to perform.


----------



## estreeter

Quote: 





anaxilus said:


> I'm not one who puts value in listening tests done by people who are not familiar or interested in audio or related gear.  That is absolutely pointless but is often done in such tests.  It's like asking a soccer mom who makes a better sports car between McLaren, Ferrari and Porsche.


 

 No, I didnt say people with no interest in audio gear - I said people with no dog in this fight, philosophically or otherwise. The people Hi-Fi Choice gets in to do their testing arent 'soccer moms', but neither are they the guys who own hi-fi stores or work in the industry. Each has their own kit at home, and that is made clear in the intro to each test - plucking random people off the street isnt going to prove anything in a test like this.
   
  I look forward to the results of your testing.


----------



## khaos974

Quote: 





anaxilus said:


> Quote:
> 
> 
> 
> ...


 

 Also true, but I hadn't realized that audiophilia also comes with performance anxiety


----------



## LizardKing1

Quote: 





anaxilus said:


> It also adds pressure to the listener or tested and none to the tester or designer of the experiment.  One records data, the other has to perform.


 
   
  I would say he has just as many reasons to be pressured as you. In fact, since he most likely won't be there, he has no control over the outcome, which might make him more nervous than you.
  However, this shouldn't be a problem for you:
   
   


anaxilus said:


> There's certainly a lot to TBD.  I'm certainly not flying or driving out of state to play this game.*  I don't even care about the $500 'sweetner'.*


 

  No pressure. Good luck.


----------



## Rawrbington

hey hey hey
  wheres the best place to buy one of these completed?


----------



## PelPix

Quote: 





rawrbington said:


> hey hey hey
> wheres the best place to buy one of these completed?


 

 JDSLabs
http://www.jdslabs.com/item.php?fetchitem=O2Full


----------



## Rawrbington

thanks PelPix.
  anywhere to find the power specs on this thing
  and
  is there a desktop version available?
  or only battery powered?


----------



## maverickronin

Quote: 





rawrbington said:


> thanks PelPix.
> anywhere to find the power specs on this thing
> and
> is there a desktop version available?
> or only battery powered?


 

 On Lord Voldermort's (aka NwAvGuy) blog.  We can't link to it from here but JDS Labs has a link.
   
  A desktop revision is being designed but the biggest difference will just be ergonomics.  You can leave the current version plugged in all the time and it won't hurt anything.


----------



## estreeter

Quote: 





rawrbington said:


> thanks PelPix.
> anywhere to find the power specs on this thing
> and
> is there a desktop version available?
> or only battery powered?


 

 Theoretically, you can have your Objective2 built without batteries and use it as a 'desktop only' amp, but most people seem to be waiting for Voldemort to finalise the design details for the desktop version. I cant recall what sort of numbers he is talking for the desktop version, but you can expect a completed amp to cost more than $150.


----------



## Twinster

I have a question related to the O2 with battery vs no battery. Was it mentioned or tested anywhere for the performance?  My assumption is that battery provide cleaner power so resulting in better sound. Am I wrong?


----------



## khaos974

The measure with or without batteries are available... somewhere online. There are essentially the same except for a slightly higher voltage swing on AC.


----------



## PelPix

Quote: 





rawrbington said:


> thanks PelPix.
> anywhere to find the power specs on this thing
> and
> is there a desktop version available?
> or only battery powered?


 
  Always welcome!
  Removing the batteries from their slots will make the AC power go directly to the circuit, turning it into a proper desktop amp automatically.


----------



## DarknightDK

Are there any more mass orders open for the O2? Or anyone who's taking orders in building these kits? I'd like to get one as well but can't seem to find any information on these. Would appreciate a PM with the Order details.


----------



## PelPix

JDSlabs has an ongoing mass order.


----------



## Ypoknons

I'm posting on the off-chance that someone will have heard or has measured and can advise on both the Fubar IV and the Objective 2. I'm an objectivist with amps and I'd love to get a O2 but the Fubar has dealers in my current location (Hong Kong) and hence better support and the Firestone has a better port layout. And what's the Z-out on the Fubar IV, can't find it anywhere; if it's high I might as well go for a E9.
   
  I want something to tie me over until or if the Gilmore X2 comes out. (edit: I'm not sure there will be an audible difference but I'd love to try. I want the X2 for reasons other than SQ, wierd talking about it in this thread.) I know it'll be a bit of wait.


----------



## Willakan

Interesting to read the phrase "giant-killer" being bandied around: the point of the O2 is indeed that it is the last word in transparency* (along with many other well-measuring amps) at a very competitive pricepoint. If the O2 becomes a "giant-killer" there are quiet a lot of other amps that will need to be admitted to that category by extension.
   
   
  *Into loads that it is designed to drive, ect...


----------



## maverickronin

Quote: 





ypoknons said:


> I'm posting on the off-chance that someone will have heard or has measured and can advise on both the Fubar IV and the Objective 2. I'm an objectivist with amps and I'd love to get a O2 but the Fubar has dealers in my current location (Hong Kong) and hence better support and the Firestone has a better port layout. And what's the Z-out on the Fubar IV, can't find it anywhere; if it's high I might as well go for a E9.
> 
> I want something to tie me over until or if the Gilmore X2 comes out. (edit: I'm not sure there will be an audible difference but I'd love to try. I want the X2 for reasons other than SQ, wierd talking about it in this thread.) I know it'll be a bit of wait.


 

 I don't know much about the Fubar or the schedule on the X2, but if you're concerned about the cramped jacks and/or having a built in DAC you could wait a few months for the Objective Desktop Amp version of the O2 with the optional 24/96 USB DAC.
   
  Quote: 





willakan said:


> Interesting to read the phrase "giant-killer" being bandied around: the point of the O2 is indeed that it is the last word in transparency* (along with many other well-measuring amps) at a very competitive pricepoint. If the O2 becomes a "giant-killer" there are quiet a lot of other amps that will need to be admitted to that category by extension.
> 
> *Into loads that it is designed to drive, ect...


 

 There are other amps like that but a lot of them are pretty expensive or attached to pretty expensive gear and not sold separately.  I think the O2 is the cheapest of the "sufficiently transparent" amps on the market.
   
  Am I wrong on that point?


----------



## Willakan

I suppose if you're going to want to drive a good mix of headphones, the O2 does rather distinguish itself on the price front. If you only want to drive high-impedance headphones, the TPA6120 does pretty well.


----------



## estreeter

Quote: 





khaos974 said:


> The measure with or without batteries are available... somewhere online. There are essentially the same except for a slightly higher voltage swing on AC.


 

 I believe that Voldemort states that you can safely hook up 'home' sources to the Objective2 with the AC connected without overpowering the input stage, but he cautions against doing that when running from batteries. I got away with it from a source notorious for the strength of its output signal, at least among USB-powered devices, but I'm sure its advice worth heeding.


----------



## Reticuli2

I'm in the process of trying to find a Torx T10 within walking distance of campus.  Having difficulty.  Either my batteries are bad, the AC adapter is bad, or something worse.  I got the clicking sound of drained batteries after just a few hours of use.  I was worried that it might be something more serious, but was reassured by the builder it should be minor once I can get the batteries out to check.


----------



## Dixter

Not sure why your batteries are running out so fast but as to the clicking sound...    the amp has circuits that are there to detect a low voltage condition from your batteries and the way it was designed it should not click..  the clicking is the circuit turning off and then back on again...      the designer made a change to a couple of resistors to correct the clicking...
   
  make sure you use the correct WART...   it has to be " AC output "  ... not just plugged into an AC outlet...


----------



## zzffnn

^ my jds o2 made some noise when not fully charged, Especially with 600 ohm Dt880. However, there is no noise at all when fully charged. I bought a charger along with o2 from jds.


----------



## mikeaj

Quote: 





reticuli2 said:


> I'm in the process of trying to find a Torx T10 within walking distance of campus.  Having difficulty.  Either my batteries are bad, the AC adapter is bad, or something worse.  I got the clicking sound of drained batteries after just a few hours of use.  I was worried that it might be something more serious, but was reassured by the builder it should be minor once I can get the batteries out to check.


 

 You know which batteries you have?  What are you powering when it's on, and how loud?  Depending on the batteries and playback conditions, it could possibly be normal.
   
  If the amp works on AC power, then it will charge the batteries with no problem unless the circuit was built wrong.  Even if the AC output voltage is a little low, it will charge the batteries, so most likely you can eliminate the AC adapter from consideration.  Actually, you can just measure the output voltage with a multimeter, if you want.  While you're at it, check the voltage of the batteries after a charge and after you get the low-battery shutdown.


----------



## estreeter

One of the things that this amp could have really used is a circuit to light the LED when it is charging. My uHA-120 starts at cherry red, then orange and green once its charged - handy.


----------



## Ypoknons

It's been a while hasn't maverickronin?

Yes I'm definitely interested in a more refined desktop version of the O2 with all the desktop amp creature comforts down the road but given the particularities in my work schedule I want an amp in the next month or so. 

At any rate I checked the Hong Kong forums and there DIYers making them and selling a few but no commercial venture yet (I wouldn't be surprised if Fiio or someone picked it up down the road though). I presume other hobbyists around the world are doing the same thing. 

As for the X2, indulge me in my fantasies of having a mini-BHSE will ya?  But I do want something that can drive orthos other than he-400 if I ever get a 'nice' headphone amp.


----------



## ClieOS

Received my JDS O2 this morning and haven't spent a lot of time on it yet. First, the overall build quality is really good , kudos to JDS. Out of the limited listening, I still prefer StepDance over it, but it is not to say it isn't quite a good amp for the price. The clean channel separation is the one thing I noticed immediately and it makes it one of the cleanest sounding amp in my collection. Don't really like the size as it is more 'transportable' than it is 'portable', though that is another story of its own. Don't like the fact that it is using AC power-in / charging as these kind of adapter is harder to find in where I live. Good buy overall.


----------



## maverickronin

Quote: 





ypoknons said:


> It's been a while hasn't maverickronin?
> Yes I'm definitely interested in a more refined desktop version of the O2 with all the desktop amp creature comforts down the road but given the particularities in my work schedule I want an amp in the next month or so.
> At any rate I checked the Hong Kong forums and there DIYers making them and selling a few but no commercial venture yet (I wouldn't be surprised if Fiio or someone picked it up down the road though). I presume other hobbyists around the world are doing the same thing.
> As for the X2, indulge me in my fantasies of having a mini-BHSE will ya?
> ...


 

 Based on the efficiency number at InnerFidelity the O2 should probably be OK with anything but the HE-6.  While they're on the more efficient end for planars/orthos I love my O2 with my modded T50RPs and a few people have reported good results with the LCD-2.  The HE-4, 5, and 5LE could be a little iffy if you prefer rock concert levels or like to add a lot EQ to them.  I don't think there are any first hand reports with those combination yet though.


----------



## daigo

Looking for a medium level DIY project and the desktop version of this amp seems interesting.


----------



## DarknightDK

Is there an estimate on when the desktop version of the O2 will be released? 
  
   
  Quote: 





clieos said:


> Don't like the fact that it is using AC power-in / charging as these kind of adapter is harder to find in where I live. Good buy overall.


 

 Me too. I reside in Singapore and am wondering where you got your adaptor from? I'll need to source for one soon.


----------



## 3rdear

I just read somewhere the desktop version will be released around March. But that's probably tentative.
   
  I'm hoping it comes out sooner.


----------



## Ypoknons

The designer has stated he'd stay away from the hungry orthos for now. We'll see, despite the excellent measurements and the all the great listening impressions from listeners I respect, it is a new design and I'll wait for some refinements, give it a little time to see if anything turns up, and see who's good at building them.
  
  Quote: 





maverickronin said:


> Based on the efficiency number at InnerFidelity the O2 should probably be OK with anything but the HE-6.  While they're on the more efficient end for planars/orthos I love my O2 with my modded T50RPs and a few people have reported good results with the LCD-2.  The HE-4, 5, and 5LE could be a little iffy if you prefer rock concert levels or like to add a lot EQ to them.  I don't think there are any first hand reports with those combination yet though.


----------



## mikeaj

There's already been a low/high gain switch added, a tweak to the battery minder circuit, and some other things I'm forgetting, on top of a few PCB revisions (which at one point improved the performance; layout still isn't quite ideal in some aspects).  If you were considering this an early prototype, it's not.  The main suggested change / refinement from others in terms of the design was moving the volume control to before the gain stage rather than after, though of course there's a tradeoff there and the designer wants it right where it is so that's not going to change.
   
  What I mean to say is:  I don't think this is going to be changed significantly.  Some outstanding issues may be addressed in the upcoming desktop version, but the standard (trans)portable O2 is likely how it's going to be, at least in terms of most significant features.  There's really no more space to put stuff on the PCB if you wanted.
  
  Quote: 





ypoknons said:


> The designer has stated he'd stay away from the hungry orthos for now. We'll see, despite the excellent measurements and the all the great listening impressions from listeners I respect, it is a new design and I'll wait for some refinements, give it a little time to see if anything turns up, and see who's good at building them.


----------



## ClieOS

Quote: 





darknightdk said:


> Me too. I reside in Singapore and am wondering where you got your adaptor from? I'll need to source for one soon.


 

 I order mine from element14 Malaysia (formally Farnell). Here is the same one on element14 Singapore. It is 15VAC which is still within spec (14~20VAC)
   
  Good thing it is not expensive, you just have to wait a few days for it to ship from UK.


----------



## Ypoknons

I'm not at all saying it's an early prototype at all, but that general prudence and experience suggests that I will get a better and more reliable product if I wait for a bit.


----------



## DarknightDK

Quote: 





clieos said:


> I order mine from element14 Malaysia (formally Farnell). Here is the same one on element14 Singapore. It is 15VAC which is still within spec (14~20VAC)
> 
> Good thing it is not expensive, you just have to wait a few days for it to ship from UK.


 

 Thanks for the information. Saves me a lot of time in hunting for one here. Will definately check that out. Cheers!


----------



## yenny

Quote: 





3rdear said:


> I just read somewhere the desktop version will be released around March. But that's probably tentative.
> 
> I'm hoping it comes out sooner.


 


  I'm hoping for sooner also! Any ideas when the odac will be out also?


----------



## arirug

I received an Objective O2 from Mr.Slim yesterday. I find it to be an amazing amplifier for a very cheap price. The build quality from Mr.Slim is excellent, and the O2 is now my main headphone amplifier. Headphones used; Sennheiser HD650.


----------



## DarkAudit

Ordered from JDS this morning. Already got a tracking number. Can't wait.


----------



## upstateguy

My O2 arrived today.  It's late but I decided to give it a listen plugged into AC.  Here are my initial impressions.
   
   
 
   
   
  OK, first the O2 is *not* a GS-1 !  Sorry guys, it's just not in the same league.  It's so far away that it's not even worth writing a comparison or going to the trouble of making diffMaker files.
   
  OTOH, it compares favorably with my original Hornet and my Portaphile V2 Maxxed, and it should be noted that I have always felt that the Portaphile was the best portable amp I've ever heard.
   
  On the negative side, hi gain is useless.  Grainy, tinny, sibilant.  Not at all like the difference between hi and low gain on the GS-1.
   
  That it's indistinguishable from the on-board amp in a Benchmark DAC doesn't impress me one little bit.  I've heard that amp, compared it to the GS-1, and was not interested in listening to the Benchmark amp any more.  
   
  The O2 has a "tinniness" to it that reminds me of KICAS amp I returned.
   
  FWIW, the components I used are laptop HD > stock HiFace > North Star 192 MKII > GS-1, Portaphile, Hornet, O2 > 880s.  Music: Chris Isaak, "Beyond the Sun" - 320mp3, Foster The People, "Torches" - flac.
   
  But, maybe it's late and I'm tired, or it needs to be burned in or something, so I'll give it another listen tomorrow under better conditions.


----------



## Anaxilus

Quote:  

  Do let it run in and have another listen.  I pretty much agree w/ your assessment as it stands though.


----------



## limpidglitch

Quote: 





upstateguy said:


> On the negative side, hi gain is useless.  Grainy, tinny, sibilant.  Not at all like the difference between hi and low gain on the GS-1.
> 
> The O2 has a "tinniness" to it that reminds me of KICAS amp I returned.


 


  So far I've used the O2 with HD25-1s, Thunderpants, SM3 and e-Q5, mostly fed straight from my Clip+, but also from a Pico DAC, and never have I witnessed any hint of tinnyness, sibilance or grain. It appears completely transparent.
  If you can hear an audible differance between high and low gain, that is not attributable to either sound level or channel imbalance, I dare say your amplifier is defect.
  Just for further clarification, is your 880s of the 600Ω variety?


----------



## upstateguy

Quote: 





limpidglitch said:


> So far I've used the O2 with HD25-1s, Thunderpants, SM3 and e-Q5, mostly fed straight from my Clip+, but also from a Pico DAC, and never have I witnessed any hint of tinnyness, sibilance or grain. It appears completely transparent.
> If you can hear an audible differance between high and low gain, that is not attributable to either sound level or channel imbalance, I dare say your amplifier is defect.
> Just for further clarification, is your 880s of the 600Ω variety?


 


  I have 2 Clips and a Fuze.  Adequate but mediocre sources.  I also have a Pico DAC that I use with my portables.  My '03 880s are not the 600Ω variety but my T-1s are.
   
  I don't think there's anything wrong with my O2, I just think I'm using a better source.


----------



## limpidglitch

Quote: 





upstateguy said:


> I have 2 Clips and a Fuze.  Adequate but mediocre sources.  I also have a Pico DAC that I use with my portables.  My '03 880s are not the 600Ω variety but my T-1s are.
> 
> I don't think there's anything wrong with my O2, I just think I'm using a better source.


 


  Oh aren't you hoity-toity


----------



## mikeaj

Quote: 





> Originally Posted by *limpidglitch* /img/forum/go_quote.gif
> 
> [snip]
> 
> If you can hear an audible differance between high and low gain, that is not attributable to either sound level or channel imbalance, I dare say your amplifier is defect.


 

 This was where I was going to go as well.  The high gain should sound pretty much identical to the low gain unless the high gain is causing clipping (and the input stage will clip no matter what the volume control is set to, if the input is too high), which is very plausible with many sources.  Default high gain is 6.5X.  If the source outputs any more than say 1.07V, it will clip with that gain.  Most DACs really shouldn't be outputting more than 2.8V but if they do, they'll clip the default low gain of 2.5X as well.
   
  Definitely if the low gain and high gain sound different (uh aside from the volume difference) on the Clip or Fuze, or if you've otherwise confirmed you're not clipping the input stage with whatever it is you're using, something is up.


----------



## Willakan

I can attest to the ease of hearing differences between gain settings due to the difficulties of volume matching - once levels are more carefully controlled they sound identical. If the gain setting difference persists even with volume matching, either your amp is all kinds of broken or your source's input voltage is too high.


----------



## LizardKing1

Quote: 





mikeaj said:


> This was where I was going to go as well.  The high gain should sound pretty much identical to the low gain unless the high gain is causing clipping (and the input stage will clip no matter what the volume control is set to, if the input is too high), which is very plausible with many sources.  Default high gain is 6.5X.  If the source outputs any more than say 1.07V, it will clip with that gain.  Most DACs really shouldn't be outputting more than 2.8V but if they do, they'll clip the default low gain of 2.5X as well.
> 
> Definitely if the low gain and high gain sound different (uh aside from the volume difference) on the Clip or Fuze, or if you've otherwise confirmed you're not clipping the input stage with whatever it is you're using, something is up.


 

 I'm trying to find the output voltage for my E7 and all I get is the output power, which I assume is already considering the amp. Did voldemort ever measure it as a DAC only? Also I don't know what kind of current it uses, so I can't find the voltage using the power even if it related to the DAC part.
  Thanks for helping an undercover noob!


----------



## Willakan

E7 output voltage is about 1.5V from memory: quite high for a USB-powered DAC. This could be completely wrong: will check later.


----------



## shotgunshane

So wait, a 'better' source makes an amp sound tinny? Nothing tinny sounding here and my 2 gain settings sound the same, although they are not default, driving 150 ohm earphones.


----------



## limpidglitch

Quote: 





willakan said:


> E7 output voltage is about 1.5V from memory: quite high for a USB-powered DAC. This could be completely wrong: will check later.


 


  I make it out to be 1.55V into 16Ω and 2.2V into 300Ω.
  I assume the discrepancy is due to current limiting, and that the higher value is what should be counted on when using it as a source.
   
  http://content.miccastore.com/fiio-e7


----------



## Anaxilus

Quote: 





shotgunshane said:


> So wait, a 'better' source makes an amp sound tinny? Nothing tinny sounding here and my 2 gain settings sound the same, although they are not default, driving 150 ohm earphones.


 

 No, but a better source will be more revealing.  If your source is a restriction then the amp will not reveal it or itself.


----------



## shotgunshane

Quote: 





anaxilus said:


> No, but a better source will be more revealing.  If your source is a restriction then the amp will not reveal it or itself.


 

 I read this a lot. It sounds like a prescription for chasing a ghost with ever spiraling and growing costs. I can say this is the first time I've been completely satisfied with the sound I'm getting. Now I only wish I could get it in a more portable, smaller footprint to carry with me on the street.


----------



## Achmedisdead

Subscribed


----------



## LizardKing1

Quote: 





limpidglitch said:


> I make it out to be 1.55V into 16Ω and 2.2V into 300Ω.
> I assume the discrepancy is due to current limiting, and that the higher value is what should be counted on when using it as a source.
> 
> http://content.miccastore.com/fiio-e7


 

 So you can only talk about the output voltage of a source when you're using a load?
  Also do you know wether these refer to the amp output of the line-out?


----------



## stv014

Quote:


lizardking1 said:


> So you can only talk about the output voltage of a source when you're using a load?
> 
> Also do you know whether these refer to the amp output of the line-out?


 
   
  The output voltage decreases with a low impedance load due to these factors:
    - output impedance
    - current limiting (this also causes distortion once the limit is reached)
   
  It is probably the amplified output, since the numbers roughly match those in the NwAvGuy measurements. But limpidglitch apparently just calculated these from the specs (which most likely apply to the amp output), rather than doing actual measurements.


----------



## limpidglitch

Quote: 





stv014 said:


> Quote:
> 
> The output voltage decreases with a low impedance load due to these factors:
> - output impedance
> ...


 

  
  Correct. I saw no mention of a dedicated line out listed among the features, so assumed whatever power ratings were listed would be relevant.
  And yes, the voltages were calculated (V=sqrt(P•Z))


----------



## stv014

Quote: 





limpidglitch said:


> I saw no mention of a dedicated line out listed among the features, so assumed whatever power ratings were listed would be relevant.


 

 True, it only seems to have a line output through the dock, so with standard 1/8" jacks it is only possible to access the amplified output that is about 2 Vrms.


----------



## Twinster

If my O2 sound as good as the KICAS I owned year ago I would be very happy.  
	

	
	
		
		

		
		
	


	



  
  Quote: 





upstateguy said:


> The O2 has a "tinniness" to it that reminds me of KICAS amp I returned.


----------



## upstateguy

Quote: 





twinster said:


> If my O2 sound as good as the KICAS I owned year ago I would be very happy.


 


  Wondering why you sold your KICAS?


----------



## Twinster

The KICAS was one of my first good amplifier at the time and liked it very much. I bought it based on Skylab review and was not disappointed. I sold it to try a Tube amplifier at the time and  realized my mistake later. 
	

	
	
		
		

		
			





 Mine was mod with the Caliente flavor.
  
  Quote: 





upstateguy said:


> Wondering why you sold your KICAS?


----------



## LizardKing1

Quote: 





stv014 said:


> True, it only seems to have a line output through the dock, so with standard 1/8" jacks it is only possible to access the amplified output that is about 2 Vrms.


 

 There is a 1/8" line-out that you buy separately to use with the dock, but I didn't think Voldemort was using that. So my worry is that the E7's DAC output will have a high voltage and clip with the O2. This may be laughabl, but remember I don't know much about this. So if I did try to use the O2 with the headphone-out of the E7 it would clip, since it has 2.2V output voltage into 600ohm? But if I tried it with a very low impedance load (like 16ohm) it wouldn't, that's what I could gather from your post.


----------



## stv014

You can prevent the O2 from clipping by reducing the gain, as suggested by others. If you do want to reduce the voltage on the headphone output, just lower the volume (but it may reduce the SNR). To attenuate the signal with a DIY adapter, it is not enough to use a single resistor as a load, since the E7 has low output impedance; with a 15 Ohm resistor, it will just clip unless you turn down the volume. If necessary, you can build a simple voltage divider, but it is probably best to just adjust the gain of the O2.


----------



## Willakan

It's strange really: I would have expected slightly more people to feel the same as Upstateguy, to be honest. From a psychological perspective, the pressure to hear the O2 as mediocre or nowhere near the true top-league amplifiers must be pretty overwhelming: between expectation bias, cognitive dissonance ect...please don't take this as an insult!
   
  I would say if you're sure about the differences to "DBT it and make $500 for charity" but such challenges are always a little unrealistic due to the effort involved.


----------



## zzffnn

IIRC, Caliente does not sound like O2. The stock KICAS non-Caliente is closer. How close I am not sure, as I sold my KICAS long time ago. I do prefer the non-Caliente than Caliente. 
  
  Quote: 





twinster said:


> The KICAS was one of my first good amplifier at the time and liked it very much. I bought it based on Skylab review and was not disappointed. I sold it to try a Tube amplifier at the time and  realized my mistake later.
> 
> 
> 
> ...


----------



## Twinster

I had modified my KICAS amplifier with a toggle switch for normal to Caliente mode. I remember the KICAS mode to be more neutral but not by much.
   

  
  Quote: 





zzffnn said:


> IIRC, Caliente does not sound like O2. The stock KICAS non-Caliente is closer. How close I am not sure, as I sold my KICAS long time ago. I do prefer the non-Caliente than Caliente.


----------



## PelPix

Since an amplifier is the end-all, be-all coloration of a signal and it only amplifies the signal it's given regardless of its character, I daresay it is completely electrically impossible for a DAC to influence the character of an amp.
   
  The truth is that the difference you're hearing between gains is just volume.  The ears hear different volumes differently.
  Regardless of gain, if I turn the O2 up to a certain volume beyond what I consider comfortable listening, it sounds tinny because the ear perceives that level of sound differently.  The effect is entirely psychoacoustic and is likely the result of evolutionary emphasis on that section of audible treble.
   
  What you should be afraid of is hearing loss, because you're likely listening at way louder than safe levels, and you're depending on colored amps to smooth this effect down for you.


----------



## hekeli

Quote: 





darknightdk said:


> Me too. I reside in Singapore and am wondering where you got your adaptor from? I'll need to source for one soon.


 


  Singapore has UK style socket yes?
   
  http://www.ebay.co.uk/itm/ws/eBayISAPI.dll?ViewItem&item=270438077972
   
  This has been reported to work fine.


----------



## Willakan

Quote: 





pelpix said:


> Since an amplifier is the end-all, be-all coloration of a signal and it only amplifies the signal it's given regardless of its character, I daresay it is completely electrically impossible for a DAC to influence the character of an amp.
> 
> The truth is that the difference you're hearing between gains is just volume.  The ears hear different volumes differently.
> Regardless of gain, if I turn the O2 up to a certain volume beyond what I consider comfortable listening, it sounds tinny because the ear perceives that level of sound differently.  The effect is entirely psychoacoustic and is likely the result of evolutionary emphasis on that section of audible treble.
> ...


 


  I don't think that's entirely fair. It is quite possible to be listening to both amps at a reasonable level, just one slightly louder than the other. Half a decibel would probably do it, and that's before you stagger into the psychoacoustic minefield wholly separate from amp performance.


----------



## PelPix

I get tinniness on every amp I've ever used and with every source when I go beyond the comfortable threshold.  What else could it be but psychoacoustic?


----------



## upstateguy

Quote: 





pelpix said:


> Since an amplifier is the end-all, be-all coloration of a signal and it only amplifies the signal it's given regardless of its character, I daresay it is completely electrically impossible for a DAC to influence the character of an amp.
> 
> The truth is that the difference you're hearing between gains is just volume.  The ears hear different volumes differently.
> Regardless of gain, *if I turn the O2 up to a certain volume beyond what I consider comfortable listening, it sounds tinny *because the ear perceives that level of sound differently.  The effect is entirely psychoacoustic and is likely the result of evolutionary emphasis on that section of audible treble.
> ...


 
  Quote: 





pelpix said:


> I get tinniness on every amp I've ever used and with every source *when I go beyond the comfortable threshold*.  What else could it be but psychoacoustic?


 
   
  Two things about the reported tinniness.  First, this happened below the maximum comfortable levels on the O2, where the (volume balanced) GS-1 was able to play very cleanly.
   
  Second, there are some amps that don't get tinny as the volume goes up.  One such example is the Heed CanAmp.  Although I didn't like the tone of this amp and sold it, I noticed that it would produce a very clean sound way beyond anything that would be considered normal listening levels.  It could reproduce rock concert volume levels easily and as such was potentially dangerous to your hearing because the louder it got the better it sounded.
   

   
  Another such amp was nmaher's Menace.
   

   
   
  And there are easily many others, but you get the idea.
   
  And for the record, I'm not saying that the O2 is a bad amp, I'm saying that it's not up the the level of my GS-1 at any but the softest volumes, and this is because at these quiet levels, the cues that distinguish a better amp from one that is not, cannot be heard.


----------



## Anaxilus

Inetesting, LFF uses a Heed amp as well.  One of the few pieces of kit that has managed to survive his scrutiny.  He does like the O2 and so do I, in context.


----------



## Willakan

The tinnyness is very strange - the O2's performance certainly doesn't suddenly nosedive into questionable areas with increased gain. It isn't as good from an absolute perspective, obviously, but that can be said for prettymuch any amplifier. 
   
  Even stranger considering that nobody else has reported it, even those who compared it with amps such as the Beta22, which are subjectively reported to be good.
   
  Well, perhaps not that strange, as I've said above.


----------



## maverickronin

Quote: 





upstateguy said:


> FWIW, the components I used are laptop HD > stock HiFace > North Star 192 MKII > GS-1, Portaphile, Hornet, O2 > 880s.  Music: Chris Isaak, "Beyond the Sun" - 320mp3, Foster The People, "Torches" - flac.


 

 What's the level of the North Star's line out?  I couldn't find it on their website.


----------



## upstateguy

Quote: 





willakan said:


> The tinnyness is very strange - the O2's performance certainly doesn't suddenly nosedive into questionable areas with increased gain. It isn't as good from an absolute perspective, obviously, but that can be said for prettymuch any amplifier.
> 
> Even stranger considering that nobody else has reported it, even those who compared it with amps such as the Beta22, which are subjectively reported to be good.
> 
> Well, perhaps not that strange, as I've said above.


 

 I don't think it matters what you call it.  Tinniness, grain, clipping, distortion, a vibration in the headphone diaphram on the high frequency notes.  Tinniness seems to be a term some of us can relate to.  I hear it on low gain too if I turn the volume up high enough.  I wouldn't make too big a deal of this as I don't need high gain.
   
  As you can see from the pics I took, all the portables were at relatively the same volume levels and you can see the positions of their volume nobs.... no need for high gain. (Portaphile was set for High gain, Hornet was set for Med. gain, GS-1 (not pictured) set for low gain.)
   
  But that is not the focus of my short evaluation.  All I'm saying is that the O2 is not at the level of a GS-1.  But, it certainly is at the level of a Portaphile, which, if you've ever heard a Portaphile, is saying a lot.
   

  
  Quote: 





maverickronin said:


> What's the level of the North Star's line out?  I couldn't find it on their website.


 

 2v.
   
  Edit:  North Star 192 MKII Specs
   
_[size=10.0pt]Input sampling rates: 32 kHz - 192 kHz[/size]_
_[size=10.0pt]Resolution: 8, 16, 20, 24 bit[/size]
Upsampling: Until 192 kHz
Clock Recovery: Double antijitter with reference clock_
_[size=10.0pt]Dynamic Range: 117 dB[/size]_
_[size=10.0pt]THD[/size]__[size=10.0pt]+Noise: -100 dB[/size]_
_*[size=10.0pt]Max. Output: Voltage 2 Vrms[/size]*
Output Impedance: < 50 Ohm
Output Sockets" Gold plated RCA posts
Inputs: S/PDIF (2 RCA coax and Toslink optical), __[size=10.0pt]AES[/size]__[size=10.0pt]/EBU (XLR balanced) I2S (RJ45)[/size]_
_[size=10.0pt]Mains/Power Consumption: 240/110V 50/60Hz 15VA[/size]
Chassis Size: 17 x 6.7 x 1.95 in, 43,3 x 17 x 5 cm
Weight (with envelope): 11.9 lbs,5,4 Kg_


----------



## Reticuli2

[size=10pt]Maybe the tinny sound is your source, music, or headphones.  It might even be accurate for what's being sent in, assuming it isn't the headphones, for a moment.  Heck, I love the way tubes sound, but I know tubes are usually implimented less accurately than solid state.  I wanted a headphone amp that wouldn't color things more.  I'll leave that to the producer.  The measurements done on these seem about as extensive as we've ever seen on an amp.  If the GS-1 measures just as well or better and doesn't have that issue, then I suppose you might be hearing a subtle difference that is the result of something we don't yet know how to measure.  I should mention mine's gain is set at 1X and 2.5X so it won't clip with the Emu 0204 and I've been mostly using 1X.  It's more than enough even for the DT990 Pro and Fostex.[/size]
   
  [size=10pt]I think the problem was with the second power strip being switched off. I finally got a Boxer screw driver set and opened the O2 up. The batteries are likely fine, but I have them out right now since I don't feel like waiting for them to charge. With them in, there's no way to bypass them when connected to AC so you're always on battery power. Like perfect power conditioning. The clicking is normal on these black units from our Canadian builder as he didn't include the resistor changes. It does seem to work well at telling you when the batteries are out, though. No wondering if they are providing sufficient charge or not. If they're not, they click. So I kind of like that, especially if I put the batteries back in permanently, as eventually they'll need to be replaced when they don't hold the charge.[/size]
  [size=10pt][/size]
   
  [size=10pt]edit: Oh, you're comparing a $900 discrete design to the O2?  O.k. Well I'd be curious how the GS-1 measures.  I really like discrete phono stages... until I found one that was IC-based and blew my cheap discretes away with some cartridges.  I still would use either depending on the material.  Does Head-Amp post measurements?  That'd be cool to see if it does indeed pass muster and you might be hearing even further into the sound.[/size]


----------



## 4nradio

Quote: 





maverickronin said:


> Based on the efficiency number at InnerFidelity the O2 should probably be OK with anything but the HE-6.  While they're on the more efficient end for planars/orthos I love my O2 with my modded T50RPs and a few people have reported good results with the LCD-2.  The HE-4, 5, and 5LE could be a little iffy if you prefer rock concert levels or like to add a lot EQ to them.  I don't think there are any first hand reports with those combination yet though.


 

 x2 on the results with the LCD-2s. My O2 amp has 10X gain resistors in the "high" setting and I find it drives the LCD-2s very well.


----------



## maverickronin

Upstateguy, what gains does your O2 have?


----------



## mikeaj

Quote: 





reticuli2 said:


> [size=10pt]I think the problem was with the second power strip being switched off. I finally got a Boxer screw driver set and opened the O2 up. The batteries are likely fine, but I have them out right now since I don't feel like waiting for them to charge. With them in, there's no way to bypass them when connected to AC so you're always on battery power. Like perfect power conditioning. The clicking is normal on these black units from our Canadian builder as he didn't include the resistor changes. It does seem to work well at telling you when the batteries are out, though. No wondering if they are providing sufficient charge or not. If they're not, they click. So I kind of like that, especially if I put the batteries back in permanently, as eventually they'll need to be replaced when they don't hold the charge.[/size]


 

 Maybe I'm misunderstanding you, but I don't think it's right to say that it's always on battery power.  Check the circuit again.  If the AC power is plugged in, the junction between D1 and D2 (D5 and D6) is a higher voltage than the battery voltage, so the batteries will continue to trickle charge and will not be sourcing power.
   
   
   


upstateguy said:


> As you can see from the pics I took, all the portables were at relatively the same volume levels and you can see the positions of their volume nobs.... no need for high gain. (Portaphile was set for High gain, Hornet was set for Med. gain, GS-1 (not pictured) set for low gain.)


 
  The way your last few posts were structured, I'm still not sure if we're on the same page.
   
  Unlike most audiophile amplifiers, if the input and gain are too high, the O2 will clip *regardless of the volume setting.*  With a 2V input source and 6.5X gain, the O2 will clip (even if the volume is as low as possible), because the input stage gets overloaded. This doesn't happen with most other audiophile amps, which put the volume control in a different place or otherwise implement it differently.  With a 2V input source, we would all obviously expect 2.5X gain to sound different than 6.5X gain whenever there's material close to 0 dBFS, because the 2.5X gain won't clip but the 6.5X gain will.
   
  The behavior of the amp on low gain and high gain has been demonstrated to be almost identical, so if both settings are working properly and you are not clipping the input stage, you should expect them to sound the same.  I'm not going to claim for you which amp sounds better to you, but O2 (low gain) vs. O2 (high gain) should be pretty much tied if level matched.  If this is not the case, then take another listen as something is amiss.
   
  edit: 2.5X and 6.5X are just default though.  You can easily measure what yours are if you don't yet know...or look at the resistors.


----------



## Naim.F.C

I own an O2 now. Used it with my LCD-2's earlier. A very energetic and detailed amp compared to my other portables. I didn't listen for long, but I felt they were quite transparent and detailed. Maybe slightly treble biased in-fact. Compared to my Continental, it's very different. The latter being much warmer, smoother, less detailed and more bassy.
   
  Will test more over the next few days and post more detailed thoughts.


----------



## Br777

considering the O2 has been measured up one side and down the other and has been proven not to create the tinnyness, or other imbalances that it is being blamed for, i dont see how you are calling it tinny or otherwise, cause it's just not.  Unless of course something is wrong with your amp.
   
  you are probably hearing something that sounds tinny, but sorry, its not the amp.  Maybe you are used to a rolled off sound, and in comparison it sounds tinny.   Many people make that mistake, even "pro" reviewers.     
   
  there are certainly a huge number of odds stacked against you in favor of bias or other factors that are not the amp.  If there is any amp you cant accuse of being imbalanced its this one.  sorry, but the measurements dont lie.


----------



## Anaxilus

Quote: 





br777 said:


> considering the O2 has been measured up one side and down the other and has been proven not to create the tinnyness, or other imbalances that it is being blamed for, i dont see how you are calling it tinny or otherwise, cause it's just not.  Unless of course something is wrong with your amp.


 

 When you measure two amps or audio devices that produce the same flat FR and output Z yet one could be called brighter than the other, figure it out and let me know.  There is a tonal character independence somewhere.


----------



## MacedonianHero

Quote: 





upstateguy said:


> My O2 arrived today.  It's late but I decided to give it a listen plugged into AC.  Here are my initial impressions.
> 
> 
> 
> ...


 

 Thanks Eric for the write up. With an incoming GS-1, I guess, I'm happy to hear your results.


----------



## upstateguy

@ Wilikan, Mav, Mike
  
  Quote: 





maverickronin said:


> Upstateguy, what gains does your O2 have?


 

 default gains. 2.5 and 6.5.
   


  Quote: 





mikeaj said:


> <snip>
> 
> 
> *With a 2V input source and 6.5X gain, the O2 will clip (even if the volume is as low as possible), because the input stage gets overloaded. *
> ...


 

 Well, this makes perfect sense and explains why my 2 gain setting do not sound the same.  Since I have the default gain settings, what I've probably experienced is clipping at the high gain setting.
   
  Is everybody else in agreement with this?


----------



## purrin

Quote: 





upstateguy said:


> My O2 arrived today.  It's late but I decided to give it a listen plugged into AC.  Here are my initial impressions.
> 
> 
> 
> ...


 

 Nope. It certainly is not in the league of GS-1 (Dynalo), B22, or Dynahi.
   
  Anax and I compared the O2 to a CHA47 (a fancy parallel CMOY w/ x2 OPA2111) and Leckerton UHA-6. I would say the O2 is one of the more stereotypical "solid-state sounding" amps with some glare and stridency (note that neither the Dynalo or B22 exhibit this behavior) depending upon the headphone. It's a little bit thin on bass too. HD800 is a horrible match for it. LCD3 better. Clarity is excellent on it though. Transparency is poor because it's not very resolving despite the clarity. In other words, I found the CHA47 and to the Leckerton, to even a greater, extent more resolving (I've never found chips to be better than discrete designs in the resolution department.) We used the PWD to feed the O2 to give it the best possible source we had on hand. Both high and low gains were used.


----------



## maverickronin

Quote: 





anaxilus said:


> When you measure two amps or audio devices that produce the same flat FR and output Z yet one could be called brighter than the other, figure it out and let me know.  There is a tonal character independence somewhere.


 

 You're leaving out some other rather important measurements but assuming those all measure similarly I'd like to see those devices properly ABXed.
  
  Quote: 





> Originally Posted by *upstateguy* /img/forum/go_quote.gif
> 
> Well, this makes perfect sense and explains why my 2 gain setting do not sound the same.  Since I have the default gain settings, what I've probably experienced is clipping at the high gain setting.
> 
> Is everybody else in agreement with this?


 

 I am.


----------



## Br777

Quote: 





anaxilus said:


> When you measure two amps or audio devices that produce the same flat FR and output Z yet one could be called brighter than the other, figure it out and let me know.  There is a tonal character independence somewhere.


 


   
  assuming the amp isn't having its input stage overloaded, and is being used properly in other ways, and is being used with headphones that are within its measured compatibility, than I would go back to my original statement and say its not the amp.


----------



## upstateguy

Quote: 





macedonianhero said:


> Thanks Eric for the write up. With an incoming GS-1, I guess, I'm happy to hear your results.


 

 You're going to like the GS-1 a lot Peter.  When will you have it?  
   
  One of the most interesting things to explore is the "holographic effect" Asr wrote about and Shah and I have discussed.  I have always described it as "playing in a larger room".  I'll be curious to know if you hear it too and what you'd call it.
   
  Back on topic, this attribute is something the O2 does not possess.


----------



## PurpleAngel

Where can you buy a pre-built O2?
  Or order parts to DIY build?


----------



## estreeter

Aaah, the joys of trying to subjectively describe sound. Whilst I agree with a lot of what upstateguy has said, and welcome his 'devils advocate' post, I wouldn't have described my initial impression of the amp as 'tinny' - merely flat and (dare I say it ?) uninspiring. There was a hollowness to my overall experience, and I began to wonder if hearing exactly what is on the recording is what I really want.
   
  Before the objectivists come down from the hills with pitchforks, *I reassessed that viewpoint about 50 or so posts back* - fortunately, since most of you dont believe in physical burn-in, I guess you can take the corks off those pitchforks and have at it .....
   
  Given that I have had a few, ahem, altercations with serial offenders who insist on pronouncing every new toy as 'the best eva !', I wont gild the lily - suffice it to say that my personal assessment of the amp changed for the better. Purchase justification ? Possibly. New toy joy ? Hardly - the look and feel of my EHP-02 dont inspire any particular pride-of-ownership, but that's not what the amp was designed for.
   
  upstateguy, without wanting to insult you, *I hope you will give the O2 another 50 or so hours*. If you still find it tinny, c'est la vie - I'm not going to argue the toss with anyone : just as the heart wants what the heart wants, I would suggest that most Head-Fiers want more euphony than they are prepared to admit. Sure, I'm *projecting*, but I look damned good doing it, don't I ?


----------



## MacedonianHero

Quote: 





upstateguy said:


> You're going to like the GS-1 a lot Peter.  When will you have it?
> 
> One of the most interesting things to explore is the "holographic effect" Asr wrote about and Shah and I have discussed.  I have always described it as "playing in a larger room".  I'll be curious to know if you hear it too and what you'd call it.
> 
> Back on topic, this attribute is something the O2 does not possess.


 

 Thanks Eric....hopefully by Friday or early next week is the ETA. That  said, I've sold off some gear (HE-6s and Schiit Lyr) and have about $150 left over in my Paypal...what to do....maybe an O2 for my office?


----------



## xxhaxx

Quote: 





purpleangel said:


> Where can you buy a pre-built O2?
> Or order parts to DIY build?


 
   
  Here you go 

http://www.jdslabs.com/storeAmps.php


----------



## purrin

Quote: 





br777 said:


> assuming the amp isn't having its input stage overloaded, and is being used properly in other ways, and is being used with headphones that are within its measured compatibility, than I would go back to my original statement and say its not the amp.


 

 It most certainly could be the amp. Op-amps have different distortion characteristics that could present different tonal balance to the listener. The current suite of FR measurements typically used are on static state (test tones or sweeps) or very short duration impulse responses - not music.


----------



## upstateguy

Quote: 





> Originally Posted by *estreeter* /img/forum/go_quote.gif
> 
> <snip>
> 
> ...


 

 I will certainly give it some break in time, but 50 hrs is a long time for this little SS amp don't you think?
   
  As it stands now, it seems the tinny sound on high gain was caused by clipping.... although if IIRC low gain also seemed to develop the same "sound" <---insert your own adjective, when driven very hard.  I'll double check this later tonight.
   


  Quote: 





macedonianhero said:


> Thanks Eric....hopefully by Friday or early next week is the ETA. That  said, I've sold off some gear (HE-6s and Schiit Lyr) and have about $150 left over in my Paypal...what to do....maybe an O2 for my office?


 

 I think the O2 is worth collecting as an example of a measurement driven design.  What would be your office source Peter?


----------



## MacedonianHero

Quote: 





upstateguy said:


> I will certainly give it some break in time, but 50 hrs is a long time for this little SS amp don't you think?
> 
> As it stands now, it seems the tinny sound on high gain was caused by clipping.... although if IIRC low gain also seemed to develop the same "sound" <---insert your own adjective, when driven very hard.  I'll double check this later tonight.
> 
> ...


 

 iBasso D4 fed by my iPhone or laptop (Apple Lossless).


----------



## Br777

Quote: 





purrin said:


> It most certainly could be the amp. Op-amps have different distortion characteristics that could present different tonal balance to the listener. The current suite of FR measurements typically used are on static state (test tones or sweeps) or very short duration impulse responses - not music.


 


   
  voldemort tests with music as well.  His whole concept was built around air tight measurements.  He really didnt leave anything to chance.. thats the whole reason this amp and Voldemort have gained the interest they have have in the first place.  There's no wiggle room.


----------



## purrin

Linky or four-five word quote (so I can Google) that he "objectively tests" with music. Unlike AMB's site, his has too much manifesto garbage so it's hard for me to navigate.
   
  Also were measurements into a real load (voice coil, back EMF, temperature) or dummy load?


----------



## upstateguy

Quote: 





macedonianhero said:


> iBasso D4 fed by my iPhone or laptop (Apple Lossless).


 

 Why bother with a giant portable amp?  It looks like you have a really small package in the iBasso dac/amp.
   
  OTOH Peter, we are enablers here, so I'm surprised that you haven't ordered the jdslabs O2 yet.  It might add an entirely new dimension to your office experience.
   
  What headphones do you use in your office?


----------



## MacedonianHero

Quote: 





upstateguy said:


> Why bother with a giant portable amp?  It looks like you have a really small package in the iBasso dac/amp.
> 
> OTOH Peter, we are enablers here, so I'm surprised that you haven't ordered the jdslabs O2 yet.  It might add an entirely new dimension to your office experience.
> 
> What headphones do you use in your office?


 

 Because I have an extra $150 in my Paypal account. 
	

	
	
		
		

		
		
	


	




 Love the enablers comment...ain't that the truth.
   
  I normally use my Ed.8s or Westone 4s. Maybe I'll just pass.


----------



## zeffa

Quote: 





upstateguy said:


> As it stands now, it seems the tinny sound on high gain was caused by clipping.... although if IIRC low gain also seemed to develop the same "sound" <---insert your own adjective, when driven very hard.  I'll double check this later tonight.


 


  I built my own O2, with gain set at 1x and 2.5x. With standard DAC inputs (grubDAC and NFB-3), the sound using 2.5x gain is noticeably harsher than with 1x. It also gets exceedingly loud very quickly, so I just use 1x gain all the time (and I've never had to turn it up to full volume even with 1x gain). At 1x gain, the sound is very, very good. Very neutral & transparent - it easily highlights for me the difference in my sources.
   
  If you're not afraid of getting your hands a little dirty, removing one of the gain resistors completely, will set the gain to 1x. I believe some third party manufacturers were using sockets for the gain resistors, so that end users could easily change the gain themselves.


----------



## mikeaj

Quote: 





purrin said:


> Linky or four-five word quote (so I can Google) that he "objectively tests" with music. Unlike AMB's site, his has too much manifesto garbage so it's hard for me to navigate.
> 
> Also were measurements into a real load (voice coil, back EMF, temperature) or dummy load?


 
   
  The only tests with music (that are published) into real-world loads, as far as I remember, are just descriptions of blind listening tests.  There's high-speed scope shots of square wave testing into real-world loads, but not music.  Search "o2 square wave performance" and then within the page search for "square wave performance" and that's that.
   
   
  This is why I was hoping if somebody with a suitable setup could run an audio differencing test (or pretty much anything) with real music using a real load.  I certainly don't have any interface line in good enough to capture any significant differences, or I would have tried.


----------



## purrin

Quote: 





mikeaj said:


> The only tests with music (that are published) into real-world loads, as far as I remember, are just descriptions of blind listening tests.  There's high-speed scope shots of square wave testing into real-world loads, but not music.  Search "o2 square wave performance" and then within the page search for "square wave performance" and that's that.
> 
> 
> This is why I was hoping if somebody with a suitable setup could run an audio differencing test (or pretty much anything) with real music using a real load.  I certainly don't have any interface line in good enough to capture any significant differences, or I would have tried.


 
   
  Square waves don't cut it. Only clarinets sound like square waves (or was it saw wave) - and even then - not even close. I would like to see objective tests into real-world loads (headphones or even approximate simulations of such - electrical characteristics change depending upon the position of the driver in the voice coil) using music (or even dynamic signals which are of approximate simulations of music). Square waves are summations of multiples of the odd integer harmonics at a certain volume. I want to see variability in volume. In other words, I don't listen to simulated clarinets at a single volume at a single note.
   
  Of particular interest to me is the ability to measure how well amplifiers are able reproduce lower level signals during loud passages or passages of dynamic loudness is music. In addition to the dynamic compression issue I mentioned earlier, I also see this as another major shortcoming  of audio reproduction's inability to give us the immediacy of live music.


----------



## PelPix

Quote: 





purrin said:


> Square waves don't cut it. Only clarinets sound like square waves (or was it saw wave) - and even then - not even close. I would like to see objective tests into real-world loads (headphones or even approximate simulations of such - electrical characteristics change depending upon the position of the driver in the voice coil) using music (or even dynamic signals which are of approximate simulations of music). Square waves are summations of multiples of the odd integer harmonics at a certain volume. I want to see variability in volume. In other words, I don't listen to simulated clarinets at a single volume at a single note.
> 
> Of particular interest to me is the ability to measure how well amplifiers are able reproduce lower level signals during loud passages or passages of dynamic loudness is music. In addition to the dynamic compression issue I mentioned earlier, I also see this as another major shortcoming  of audio reproduction's inability to give us the immediacy of live music.


 


  If you're looking for load tests, I believe ALL of his tests are into simulated loads.  He doesn't even publish loadless results.
  It's only $75 to build.  Build one yourself and test it with your equipment.


----------



## upstateguy

Quote: 





macedonianhero said:


> Because I have an extra $150 in my Paypal account.
> 
> 
> 
> ...


 

 Now Peter, you know those Ed.8s are just screaming for an amp that has specs like the O2.....
	

	
	
		
		

		
		
	


	



   

  
  Quote: 





zeffa said:


> I built my own O2, with gain set at 1x and 2.5x. With standard DAC inputs (grubDAC and NFB-3), the sound using 2.5x gain is noticeably harsher than with 1x. It also gets exceedingly loud very quickly, so I just use 1x gain all the time (and I've never had to turn it up to full volume even with 1x gain). At 1x gain, the sound is very, very good. Very neutral & transparent - it easily highlights for me the difference in my sources.
> 
> If you're not afraid of getting your hands a little dirty, removing one of the gain resistors completely, will set the gain to 1x. I believe some third party manufacturers were using sockets for the gain resistors, so that end users could easily change the gain themselves.


 

 I have extra gain resistors and sockets.  Can I just remove the 6.5 and use the old high gain position for 1x gain?
   
  What headphones are you using?


----------



## purrin

Quote: 





pelpix said:


> If you're looking for load tests, I believe ALL of his tests are into simulated loads.  He doesn't even publish loadless results.


 

 You mean into resistors, or network that simulates the impedance curve of actual headphones, or of actual headphones?


----------



## khaos974

Hmm, I wonder how one could perform such a test, at first glance, it isn't very different from a square wave, the harmonics are lower level signals that are played at the same time as the fundamental. But that's obviously not the metric you want.


----------



## MacedonianHero

Quote: 





upstateguy said:


> Now Peter, you know those Ed.8s are just screaming for an amp that has specs like the O2.....


 

 It's just my "at work" office rig.


----------



## pyrokid

I have one from JDSLabs, and it was fine for a while, but now when I have it running AC sometimes I just hear a loud thump and have the music cut out. Then it starts clipping... What's going on here? AC power supply is just a 16/18V input.


----------



## purrin

Quote: 





khaos974 said:


> Hmm, I wonder how one could perform such a test, at first glance, it isn't very different from a square wave, the harmonics are lower level signals that are played at the same time as the fundamental. But that's obviously not the metric you want.


 
   
  I'm pretty much of the opinion of most of these well known suite of tests are of little use to the consumer or audiophile. They measure steady state signals into simple loads not necessarily reflective of headphones or speakers. The graphs for the most part look nice. But honestly, I don't care if amp X extends the -3db roll-off point to 12Hz compared to amp Y at 18Hz. Or if on amp X, the noise floor at 1kHz is -134db compared to amp Y at -126db. Crosstalk or whatever - heck crosstalk could even be a simple implementation of cross-feed!
   
  Obviously, new metrics developed for hobbyists are needed rather than the same ol' graphs Stereophile has been re-hashing over and over (at least for amps.) The jitter stuff looks neato though and the distortion graphs show clarity. Those measurements actually have some correlation to what I'm hearing - so I am not against everything currently being used.
   
  Another thing to caution: visualization of graphs and choice of tests. Based on his manifesto-ish-ness, we have to be careful what tests are applied and what is presented. There's bias - which has been stated. It would be like for me to invent a headphone and provide excellent measurements of them myself. You would definitely not trust that! Oh wait, I've already been privately accused of doing that with LFF's Paradox. So much for objective shilling. 
	

	
	
		
		

		
		
	


	



   
  But going back to the correlation thing. _Measurements are only meaningful (to the end-user) if we can somehow correlate them to what we hear._


----------



## pyrokid

It's not running without AC input now.


----------



## mikeaj

Quote: 





purrin said:


> Square waves don't cut it. Only clarinets sound like square waves (or was it saw wave) - and even then - not even close. I would like to see objective tests into real-world loads (headphones or even approximate simulations of such - electrical characteristics change depending upon the position of the driver in the voice coil) using music (or even dynamic signals which are of approximate simulations of music). Square waves are summations of multiples of the odd integer harmonics at a certain volume. I want to see variability in volume. In other words, I don't listen to simulated clarinets at a single volume at a single note.
> 
> Of particular interest to me is the ability to measure how well amplifiers are able reproduce lower level signals during loud passages or passages of dynamic loudness is music. In addition to the dynamic compression issue I mentioned earlier, I also see this as another major shortcoming  of audio reproduction's inability to give us the immediacy of live music.


 
   
  Yeah, I agree about the square waves.  And a clarinet won't exactly have much 11th, 13th, etc. harmonics.  Also AFAIK it does have a little bit of even-order harmonics too. Strangely enough I find that it's relatively easy for me to identify what pitch clarinets are playing at compared to some other instruments (I have moderately decent "perfect pitch" or "absolute pitch" or whatever you want to call it.), even though you might think that the strong presence of odd harmonics would be confusing?
   
   
  The question is about the validity of steady-state load testing into resistors with sinusoids or maybe a combination of two sinusoids (i.e. standard audio benchmarking practices), to predict real-world performance with music into non-resistive loads like headphones.  I think this is by far the most valid concern to voice regarding the test data.  There's been plenty of studies correlating measured performance using standard metrics to subjective impressions, but it may not be 100% conclusive.  Certainly that by itself does not rule out the possibility for a device to have good performance into standard benchmarks yet not so good with other tests.  Also the conditions of studies aren't always quite applicable.  But there's also the result of the Carver challenge, with a SS amp tuned to sound like a tube amp by adding in harmonics...
   
  So I'm not particularly convinced that a device with low-Z output that does really well into the standard benchmarks, will suddenly develop problems with actual music into headphones.  But I'm much more interested in seeing results than my own speculation, so if anybody can do it, I'd be interested in seeing the data.
   
   
   

  


pyrokid said:


> I have one from JDSLabs, and it was fine for a while, but now when I have it running AC sometimes I just hear a loud thump and have the music cut out. Then it starts clipping... What's going on here? AC power supply is just a 16/18V input.


 

  I've never heard of this failure mode, but it sounds pretty serious.  Seems strange that it would just cut out by itself.  That implies the comparator is turning off the circuit...but then it comes back on by itself?  Are the batteries in?


----------



## pyrokid

Batteries in, everything is as it came.
   
  Does the amp have to be turned on to charge the batteries?


----------



## upstateguy

Quote: 





macedonianhero said:


> It's just my "at work" office rig.


 


  But it's your favorite ears.


----------



## mikeaj

Quote: 





pyrokid said:


> Batteries in, everything is as it came.
> 
> Does the amp have to be turned on to charge the batteries?


 
  No, the amp need not be turned on to charge the batteries.  The switch comes after the batteries in the circuit.
   
  If you get clipping after it thumps, that could very well be input clipping due to the smaller supply rails when on battery, if somehow the AC input is getting disconnected and then it starts to run on battery.  What's the source and how much does it output?  What are the gains set to?


----------



## khaos974

Quote: 





purrin said:


> Quote:
> 
> 
> 
> ...


 

 The standard test battery ie. THD, IMD, noise, frequency and phase response, analysis of the distortion spectrum, output impedance... would show that most "correctly measuring" amps should sounds the same if not driven to clipping. This doesn't correlate well the subjective impressions of many hobbyists, obviously either there's some bias somewhere or the metrics aren't appropriate. I lean to the former explanation, but I'd really be enthusiastic if someone could come up with a metric that correlates to impressions of transparency and dynamism.
   
  Meanwhile, I'm still waiting.
   
  PS: I do trust the numbers provided with the O2 (and the Paradox), what's more interesting are the measures not provided, but still I'd guess that if provided with a convincing argument, he may actually make them.


----------



## pyrokid

HRT Music Streamer II and the gains are set to 2.5 and 6.5 I believe. (stock?)
   
  Checking source output now...


----------



## mikeaj

Quote: 





pyrokid said:


> HRT Music Streamer II and the gains are set to 2.5 and 6.5 I believe. (stock?)
> 
> Checking source output now...


 

 IIRC 2.25V, enough to clip the O2 with 2.5X gain if on battery power.  Anything above around 4.5V / 2.5 = 1.8V is a no go on 2.5X gain, on battery power.


----------



## pyrokid

On battery power, absolutely nothing comes out... Even when using a DAP as a source...
   
  Are there any solutions? Or should I see if I can get a refund from JDS?


----------



## khaos974

Quote: 





pyrokid said:


> On battery power, absolutely nothing comes out... Even when using a DAP as a source...
> 
> Are there any solutions? Or should I see if I can get a refund from JDS?


 
   
  I'm pretty sure there's a warranty.


----------



## Dixter

I had one of the ones I built to give out for Xmas gifts not work on a set of battery's...   I took the battery's out and put them in a dedicated charger in an attempt to figure out
  which one was bad..   both of them charged up fine, I put them back in the amp and the amp has worked perfectly ever since...   not sure why..
  
   

  
  Quote: 





pyrokid said:


> On battery power, absolutely nothing comes out... Even when using a DAP as a source...
> 
> Are there any solutions? Or should I see if I can get a refund from JDS?


----------



## Reticuli2

Quote: 





zeffa said:


> I built my own O2, with gain set at 1x and 2.5x. With standard DAC inputs (grubDAC and NFB-3), the sound using 2.5x gain is noticeably harsher than with 1x. It also gets exceedingly loud very quickly, so I just use 1x gain all the time (and I've never had to turn it up to full volume even with 1x gain). At 1x gain, the sound is very, very good. Very neutral & transparent - it easily highlights for me the difference in my sources.
> 
> If you're not afraid of getting your hands a little dirty, removing one of the gain resistors completely, will set the gain to 1x. I believe some third party manufacturers were using sockets for the gain resistors, so that end users could easily change the gain themselves.


 


   I agree it's too cheap for people not to have one on this forum. Heck, name a single good, inexpensive design that's capable of being a true zero-gain buffer? 
   
  You should certainly hear a difference between 1X and 2.5X gain.  The measurements improve even more with the former.  It's great at 2.5X gain for an amp of this price -- even a giant killer (or at least giant-annoyer), and it's probably nearly perfect at 1X gain. Sure, I will grant that discrete might be possible to do with more delicacy and finesse.  I don't know why discrete can do that, but both my phono stages and the ESP 950 exhibit that.  So that may be.
   
  The worst thing about about the O2 (besides the size for people who really wanted a tiny amp... I didn't), is the pot.  I have to turn it up slightly louder than I would like on the DT1350s to get the channel imbalance just at 0.6dB as shown in RMAA at 1X gain.  Anything lower and it goes 0.7dB imbalance, 0.8dB, 1.5dB, and then jumps up to 2dB, 3dB, etc.  Much further up I believe I achieved 0.5 or 0.4dB, but it was like 1/3 the way up.  So any less and I must resort to the computer's volume controls.  A digital-controlled or stepped analog pot would provide closer channel matching at low volumes.  I realize it'd drive price up, but I think it'd be worth it.  If I get the desktop version when it comes out, I'll try and splurge for that.
   
  Back to comparing 1X and 2.5X:  Remember, if we compare how the different gains sound, we need to check output levels to ensure they're similar.  Otherwise much of the harshness could just be from having it louder at your higher gain (button pushed in) than you realize due to the need to have the pot higher up than desired because of the unfortunate pot.
   
  Granted, I've encountered pots MUCH worse than this one.  It's alright.  We knew it going in that he was trying to bring the price down and the pot was brought up (including by me).  Just that you get spoiled with Fiio's E6 and E7, you know?
  Quote: 





pelpix said:


> If you're looking for load tests, I believe ALL of his tests are into simulated loads.  He doesn't even publish loadless results.
> It's only $75 to build.  Build one yourself and test it with your equipment.


 

 Right.  Indeed, loadless results wouldn't tell you much.  The near-zero ohm output impedance would make things like stereo separation inferior to something with a higher ohm output if used just as a line out preamp.


----------



## G.Trenchev

I don't get it,what's so great about this amp made with the cheapest components you've listened many times to?
  I think The Wire is a much much better  DIY full-size amp with "objective" quality.


----------



## Reticuli2

Yeah, that would definitely not be subtle if you're running those gains and that input.

  
  Quote: 





upstateguy said:


> @ Wilikan, Mav, Mike
> 
> 
> default gains. 2.5 and 6.5.
> ...


----------



## Anaxilus

Quote: 





g.trenchev said:


> I don't get it,what's so great about this amp made with the cheapest components you've listened many times to?
> I think The Wire is a much much better  DIY full-size amp with "objective" quality.


 

 Ah, but the O2 is designed beyond the limits of human audibility.  Ergo, The Wire and the O2 obviously sound the same so no point to waste your time and money on anything but the O2.  Unless you want some coloration The Wire will introduce.


----------



## Reticuli2

[size=10pt]I think that was the whole point of the design. The assertion by the designer that the "common" components that people think are inferior actually have inherent design specs that are sometimes superior for headphone amps to many of the expensive parts instead sourced in other designs. And that it's the design of the entire amp around these properly-used parts used as they were meant to be that can theoretically produce a real high-end result with proper electrical engineering considerations and testing. This is then backed up with exhaustive measurements of not only this real functioning amp, but others in comparison to it. So yes, you're exactly right that it's cheap components and yet near reference results. Hence the designer's assertions about other company's offerings, the politics and economics of marketing, and all the heated baggage that comes with that related discussion… And our justifiable awe.  You sure you're not being either facetious or a provocateur? ;-P[/size]
  Quote: 





g.trenchev said:


> I don't get it,what's so great about this amp made with the cheapest components you've listened many times to?
> I think The Wire is a much much better  DIY full-size amp with "objective" quality.


----------



## purrin

Quote: 





khaos974 said:


> PS: I do trust the numbers provided with the O2 (and the Paradox), what's more interesting are the measures not provided, but still I'd guess that if provided with a convincing argument, he may actually make them.


 

 Hee hee. No biggie on that one. I'm actually glad that people brought up possible bias issues with the Paradox measurements considering that LFF and I have made it no secret that we are friends in real life. Heck, maybe I subconsciously developed compensating functions to make their graphs look better than they really are. It shows that people are thinking rather than just mindlessly nodding their heads and parroting whatever I've thrown out there. (Although there is a difference between being skeptical and being an ass purely for the sake of being a contrarian needing to add his two cents for everything.)


----------



## purrin

Quote: 





reticuli2 said:


> [size=10pt]I think that was the whole point of the design. The assertion by the designer that the "common" components that people think are inferior actually have inherent design specs that are sometimes superior for headphone amps to many of the expensive parts instead sourced in other designs. And that it's the design of the entire amp around these properly-used parts used as they were meant to be that can theoretically produce a real high-end result with proper electrical engineering considerations and testing. This is then backed up with exhaustive measurements of not only this real functioning amp, but others in comparison to it. So yes, you're exactly right that it's cheap components and yet near reference results. Hence the designer's assertions about other company's offerings, the politics and economics of marketing, and all the heated baggage that comes with that related discussion… And our justifiable awe.  You sure you're not being either facetious or a provocateur? ;-P[/size]


 

  Which other amps were compared to the O2 which did not use common (off-the-shelf cheap op-amps) components? I believe there was a comparison to the AMB mini3, but it wasn't quite an apple-to-apples comparison given the differences in battery voltage and PCB size advantage (and hence extra stage) of the O2.
   


g.trenchev said:


> I don't get it,what's so great about this amp made with the cheapest components you've listened many times to?
> I think The Wire is a much much better  DIY full-size amp with "objective" quality.


 

  LOL, my sentiments exactly. As if other designers (Morsel, KG, Tangent, AMB, etc.) of simple DIY amps in the past such as the PIMETA, PPA, mini3 didn't measure their designs and components, but just randomly slapped parts together. I guess newwavedude is first one to design on such principles as measurements. Give me a break.


----------



## mikeaj

Well I doubt this cost is very significant in the grand scheme of things, but I think there's some substance to the fact that the O2 uses sometimes significantly _cheaper_ off-the-shelf op amps than some other designs, and that there was some nontrivial testing being done to determine which to use.  The three audio op amps are $1.53 total on Mouser.
   
  I'm really not much of a fan of the Mini3 comparison for reasons you mentioned:  smaller size, single battery, etc.  It's not quite playing in the same class, though the O2 cost is a little lower.
   
   



purrin said:


> LOL, my sentiments exactly. As if other designers (Morsel, KG, Tangent, AMB, etc.) of simple DIY amps in the past such as the PIMETA, PPA, mini3 didn't measure their designs and components, but just randomly slapped parts together. I guess newwavedude is first one to design on such principles as measurements. Give me a break.


 
   
  Yeah, such a novel concept, right?  /sarcasm
   
  On the flip side, there were some "disagreements" over the Mini3 performance results, so there's a case to be made that having access to higher-end instrumentation gives an advantage in prototyping, evaluation, etc.  Why would RMAA report -88.4 dB crosstalk with a 33 ohms load for a 3-channel active ground amp using a 1/8" mini jack?


----------



## Willakan

Quote: 





anaxilus said:


> Ah, but the O2 is designed beyond the limits of human audibility.  Ergo, The Wire and the O2 obviously sound the same so no point to waste your time and money on anything but the O2.  Unless you want some coloration The Wire will introduce.


 

  It should sound the same as the Wire. But this is one of those hilarious "Obviously everything sounds different lol /sarcasm" posts is it not?
   
  @purrin:
   
  The stuff about tests with "real music" is a non-sequitur. NwAvGuy actually published a blog post on this, but before you shout "MINDLESS NWAVGUY PARROTING" (just covering my bases here) there are plenty of other sources about the sillyness of declaring that test tones are somehow an easy ride for amps. As Doug Self put it, this comes from a strange urge to personify amplifiers: to imagine they care about what they amplify.
   
  As for measurements, the amps you listed are not comparable as far as verifiable measurements are concerned. I surely don't need to tell you that RMAA with a $30 sound card really doesn't tell you much about the amp you plug into it? Especially considering some of the amps are three-channel active ground designs, some with incredibly dubious crosstalk numbers and reasons to suspect large measureable weaknesses in areas RMAA doesn't touch.
   
  That said, you've already said something about discrete designs being more detailed so I doubt we're going to agree on much. I suppose I can agree with you in that I am all for correlating test results with what can be heard...under controlled conditions. Listening casually to two amps and declaring a slight glassiness in the treble clearly due to the 0.001% THD at 20khz (clearly due to the inferior opamps which are clearly degrading the sound, clearly.) is, in contrast, of absolutely no value whatsoever.


----------



## Anaxilus

Quote: 





willakan said:


> It should sound the same as the Wire.


 

 You mean you don't know?  First for everything I guess.  Thought the measurements would have answered that.  How to tell if we can't fall back on measurements?  Hmmm....


----------



## mikeaj

Okay, slightly patronizing suggestions aside, even if you take no issue with the test tones, there's still the complication of having a real headphone load compared to a resistor.  (Again, amp output impedance is pretty low, so...relevance is maybe arguable)
   
  If you do take issue with the test tones or the load, then please run an alternative yourself like an audio differencing test using real music and a real headphone load.  I hope we can all agree that that scenario would be indicative of real world conditions?  It shouldn't be hard to set up if you have some decent interface.  Anybody?
   
  How do people explain the Carver challenge results, by the way?  I'm sorry if it's an old beaten-to-death subject, but I've not heard the explanation.


----------



## ClieOS

Quote: 





dixter said:


> I had one of the ones I built to give out for Xmas gifts not work on a set of battery's...   I took the battery's out and put them in a dedicated charger in an attempt to figure out
> which one was bad..   both of them charged up fine, I put them back in the amp and the amp has worked perfectly ever since...   not sure why..


 
  Do you use the right AC charger?


----------



## Willakan

Quote: 





anaxilus said:


> You mean you don't know?  First for everything I guess.  Thought the measurements would have answered that.  How to tell if we can't fall back on measurements?  Hmmm....


 


 I sincerely apologise for implying that I was humouring the idea that it sounded different in a clearly foolhardy attempt to imply some respect (if not credence) for the beliefs in audible differences between well-measuring kit. 
   
  I should not have pretended to respect beliefs that I don't.
   
  Measurements are not perfect, but they are the best we've got (controlled comparisons are better, but I have yet to see one between prettymuch any set of products that would refute what we can easily measure) and beat the flying crap out of a load of audiophiles gibbering about how it can't possible match discrete designs for "finesse."
   
  There you go, you now know what I actually think. You can now attack me for having no "real-world experience" instead of implied hypocrisy, which will be vastly more fun and even more full of BS.


----------



## G.Trenchev

Quote: 





reticuli2 said:


> [size=10pt]  You sure you're not being either facetious or a provocateur? ;-P[/size]


 


  Sorry,I did not meant that.I'm just not awed of what an incredible solutions NJM4556 and NE5532 are.They've been in production for decades.I've listened them on whenever on whatever device,you too.So,no progress.Is everything new is well forgotten old?Is audio running in circles of say,20 years?


----------



## Dixter

Quote: 





clieos said:


> Do you use the right AC charger?


 


  Yes,  used correct AC charger...  there was something going on with the battery.. not sure because the problem went away and it works perfect now....


----------



## purrin

willakan said:


> The stuff about tests with "real music" is a non-sequitur. NwAvGuy actually published a blog post on this, but before you shout "MINDLESS NWAVGUY PARROTING" (just covering my bases here) there are plenty of other sources about the sillyness of declaring that test tones are somehow an easy ride for amps. As Doug Self put it, this comes from a strange urge to personify amplifiers: to imagine they care about what they amplify.
> 
> As for measurements, the amps you listed are not comparable as far as verifiable measurements are concerned. I surely don't need to tell you that RMAA with a $30 sound card really doesn't tell you much about the amp you plug into it? Especially considering some of the amps are three-channel active ground designs, some with incredibly dubious crosstalk numbers and reasons to suspect large measureable weaknesses in areas RMAA doesn't touch.
> 
> That said, you've already said something about discrete designs being more detailed so I doubt we're going to agree on much. I suppose I can agree with you in that I am all for correlating test results with what can be heard...under controlled conditions. Listening casually to two amps and declaring a slight glassiness in the treble clearly due to the 0.001% THD at 20khz (clearly due to the inferior opamps which are clearly degrading the sound, clearly.) is, in contrast, of absolutely no value whatsoever.


 
   
  So how do each of those measurements correlate with aspects of audio reproduction? If we are not sure, then how much more value do these measurements offer than subjective impressions (which I concur are unreliable and imprecise)? What measurement or set of measurements offer insight into dynamic compression, retrieval of low level information, etc. I don't see any measurement that supports this claim that op-amps are as equally detailed compared to discrete designs.
   
  It all seems like a lot of misdirection at this point: 1) make wide reaching and controversial proclamations; 2) offer high resolution measurements that show a solid design, but prove nothing of the more controversial claims; 3) confuse the issue further by showing how the O2 measures better than the AMB mini3 (another chip design) and pointing out the flaws in the AMB provided "dubious" crosstalk measurements; 4) fallacious appeal to authority, i.e. Doug Self (as if he was the _only _expert in circuit design.)
   
  Finally, do there exist measurement comparisons between the O2 and other so called amps which use "bogus" discrete components in place of op-amps? And if so, how do these measurements correlate with "detail."


----------



## mikeaj

Quote: 





purrin said:


> So how do each of those measurements correlate with aspects of audio reproduction? If we are not sure, then how much more value do these measurements offer than subjective impressions (which I concur are unreliable and imprecise)? What measurement or set of measurements offer insight into dynamic compression, retrieval of low level information, etc. I don't see any measurement that supports his claim that op-amps are as equally detailed to discrete designs. It seems like a lot of misdirection at this point: 1) make proclamations; 2) offer really good quality measurements that show a solid design, but prove nothing of the more controversial claims; 3) confuse the issue further by showing how the O2 measures better than the AMB mini3 (another chip design) and pointing out the flaws in the AMB provided "dubious" crosstalk measurements.
> 
> Finally, do there exist measurement comparisons between the O2 and other so called amps which use "bogus" discrete components in place of op-amps? And if so, how do these measurements correlate with "detail."


 
   
   
  I agree the whole comparison to other amps and "dubious" measurements is a sidetrack that's not really related.  It was just an example to demonstrate potential issues with previous design-to-the-measurements attempts.  Enough of that, sorry.
   
  Nothing's wrong at all with discrete designs done well.  They just tend to cost more and be easier to screw up in terms of design, so if the goal is to meet certain performance specs X, Y, and Z with as low cost as possible, they may not be the best options (depending on what X, Y, and Z are).  From my perspective it seems like any claim about op amps having inherently different amounts of detail than discrete designs, considewould be controversial.  Not the other way around.
   
  Dynamic compression, retrieval of low-level information, detail, etc. are obviously difficult to define and might mean different things to different listeners anyway.  It would be great if people could dig through all that mess, but I think measuring amps is a lot easier to do than investigate what metrics tend to correlate with what perceptions in most listeners.  Once you carefully establish what actual differences there are between amps, then you can determine how those differences relate to perceived differences when listening, or argue that the differences are so small they probably should be inaudible.
   
  That's why I suggest measuring amps with real music when loaded with real headphones.  If you were to track the output of an amp playing a certain sample of music, and then run the same trial with another amp, and the outputs over time never deviate by more than 0.000001%, surely this means that both amps sound the same (with that music into those headphones)?  What if they never differ by more than 0.01%, which might be realistic?  What if the spectral analysis shows almost exactly the same behavior?
   
  After a certain point of accuracy in many scenarios, I would think that the difference between different high-performance amps would be smaller than the difference between having headphones positioned in spot A on the head as opposed to spot B that's 1mm apart, or something like that.


----------



## purrin

Quote:


mikeaj said:


> That's why I suggest measuring amps with real music when loaded with real headphones.  If you were to track the output of an amp playing a certain sample of music, and then run the same trial with another amp, and the outputs over time never deviate by more than 0.000001%, surely this means that both amps sound the same (with that music into those headphones)?  What if they never differ by more than 0.01%, which might be realistic?  What if the spectral analysis shows almost exactly the same behavior?
> 
> After a certain point of accuracy in many scenarios, I would think that the difference between different high-performance amps would be smaller than the difference between having headphones positioned in spot A on the head as opposed to spot B that's 1mm apart, or something like that.


 

 I hope folks in this thread don't get me wrong. I'm totally in objective measurements (I hope this would be obvious by now considering what I've done so far with help and inspiration from others such as arnaud and Tyll.)
   
  I find a lot of frustration looking deep into my data but not finding differences beyond measurement error for things such as different tubes (which _seem _to sound different - at least different enough where I will prefer one over the other.) For example, one tube may sound like it has deeper bass, but impulse, phase, frequency response, CSDs measure effectively the same. 
   
  Rather that simply disregard the difference between a measurement and subjective impression as "it's all in my head", as some of the more mindless minions will instantly conclude, parrot or proclaim, I prefer to be more circumspect and wonder if we are indeed measuring the right thing.
   
  We have biases and beliefs, but they if are so strong as to cloud our view to the extent that we end up writing manifestos on them, then all we are going to do is rely and bias the experiments to support those beliefs.
   
  As far so your suggestion, LFF and Anax had actually suggested some ideas to me regarding that. It would certainly be an interesting experiment. Figuring what types of analysis to perform would be the hard part. Heck, why not measure the output from the drivers with a mic (although you would be adding a lot of influence from the mic and associated circuitry.)


----------



## Willakan

Quote:
   


purrin said:


> So how do each of those measurements correlate with aspects of audio reproduction? If we are not sure, then how much more value do these measurements offer than subjective impressions (which I concur are unreliable and imprecise)? What measurement or set of measurements offer insight into dynamic compression, retrieval of low level information, etc. I don't see any measurement that supports this claim that op-amps are as equally detailed compared to discrete designs.
> 
> It all seems like a lot of misdirection at this point: 1) make wide reaching and controversial proclamations; 2) offer high resolution measurements that show a solid design, but prove nothing of the more controversial claims; 3) confuse the issue further by showing how the O2 measures better than the AMB mini3 (another chip design) and pointing out the flaws in the AMB provided "dubious" crosstalk measurements; 4) fallacious appeal to authority, i.e. Doug Self (as if he was the _only _expert in circuit design.)
> 
> Finally, do there exist measurement comparisons between the O2 and other so called amps which use "bogus" discrete components in place of op-amps? And if so, how do these measurements correlate with "detail."


 

  I don't feel that the appeal to authority was fallacious - that implies a source was chosen for the express (albeit not necessarily conscious) purpose of misrepresenting the consensus opinion or is not qualified to comment. As for the AMB design, I only bought it up as you listed it as a carefully designed amp with consideration to measured performance
	

	
	
		
		

		
			




   
  The answer to the bulk of your point is simple: these things sound the same because there is no good reason why they shouldn't. Why on earth should a decent (and by decent I don't mean OPA627) audio opamp sound different from a well-performing discrete design, assuming the audio opamp is being used in a reasonable application? This is how it looks as existing science stands (I really don't feel that is a very contentious claim. As the O2 and other designs show, very good measurements are easily within our grasp.)
   
  Until people can hear differences between these things which shouldn't be there (for example, distinguishing two opamps both not designed to drive low impedance loads being used to drive a pair of Grados directly does not require any modification of science, whilst hearing the difference between say, the Wire and the O2 does) under controlled conditions, why should we assume they are there? The subjective evidence is quite happily explained with reference to psychology: if you haven't already seen it the vaguely recent AES "Audio Myths" workshop is quite watchable, especially the section where the listener is compelled to hear nonexistent lyrics by the power of suggestion - so I accept it as the more reasonable explanation (fully explained vs throw all we thought we knew about electronics and human hearing out of the window).
   
  The burden of proof falls crushingly heavily on those who hear differences to show they are not caused by the mechanisms which it currently appears cause them. 
   
  EDIT: Dammit, just read your above post. *Saying it's "all in your head" is not an insult or being closed minded - it's an acknowledgement of humanity!* Once you throw in volume differences it's no wonder people hear so many different things.
  If you feel this is wrong, *then see if you can reproduce the differences under controlled conditions*, after determining that there are no measurements which suggest anything approaching an audible difference. It's not mindless parroting, it's just not rejecting what science says (by saying that these differences are caused by different things than the things which are currently supposed) on no evidence whatsoever.
   
  Also, seeing that you bought up tubes, there are a lot of measurements to be made before you can reasonably say that something is transparent. (Could a tube have high low-frequency distortion, for example?) I would agree that linking large measurable flaws to specific colourations (how does 2% THD in the bass sound?) is potentially more difficult, but when all you're aiming for is as little as possible added to the signal, that isn't a problem.


----------



## mikeaj

Quote: 





purrin said:


> Rather that simply disregard the difference between a measurement and subjective impression as "it's all in my head", as some of the more mindless minions will instantly conclude, parrot or proclaim, I prefer to be more circumspect and wonder if we are indeed measuring the right thing.


 

  I have to also make it clear that I think this kind of skepticism is worthwhile (even if the intuition isn't right 100% of the time; definitely I don't believe all of the challenges levied, though I would be interested in seeing any supporting evidence) and will hopefully lead to some new results and approaches.  In the very least I'm a fan of your headphone CSD plots.


----------



## purrin

willakan said:


> ...


 

 To turn things around, has it been proven by science that the op-amp used in the O2 subjectively sounds different than a discrete design?
   
  I find it interesting that none of my important questions (those dealing with objective measurements correlation with subjective impressions, comparisons of O2 to discrete designs) have been answered so far. They have only been side-stepped. BTW, your "AES Audio Myths" reference seems to be yet another appeal to authority. It has nothing to do with any of the questions I posed above.
   
  Also, what is the consensus opinion of differences in circuit topology, transistor types and materials, etc. among the "followers"? Do those all sound the same? The answer will be of course, they the high precision RMAA measurements show the same results, then they will sound the same. But then this gets back to what I've questioned in the first place? _Where are the measurements comparing the O2 to other amps designed using "bogus" philosophy._


----------



## Willakan

No, that isn't an appeal to authority either. You implied that suggesting that differences that could be produced by bias is something done by "mindless minions," which I not unreasonably took as skepticism about them, so tried to provide an example.
   
  Okay, your questions. Point by point, no place to hide
	

	
	
		
		

		
		
	


	




:
   
  1. Objective measurement correlation to subjective impressions.
  I would agree this can be difficult as I said in the above post: but when you are aiming for simply reproducing the signal _accurately_ this doesn't need to be considered. You just make sure everything that could possibly be objectionable is inaudible by a nice wide margin. Seriously, the targets NwAvGuy sets are not easy: he has thresholds for THD audibility which are particularly brutal and could probably be a fair bit looser IMHO. If you decide you don't like the sound of accuracy, no problem: you now have a perfectly neutral benchmark from which you can EQ and DSP to your heart's content. I am reminded of the infamous Carver amplifier challenge: he didn't need to know the nature of what he was reproducing, he just made sure it was produced in a certain way.
   
  2. Comparisons to discrete designs.
   
  Discrete designs are just another way of doing things. They mainly offer advantages in power amps as I understand it, where ICs tend to be more limited.
  Many discrete designs do sound different, due to the expense and difficulty of matching the performance of ICs: for example, AudioGd's discrete opamps could best be described as a traffic accident. Suggesting their flaws could be audible is entirely reasonable. However, there is absolutely no reason to expect a well-measuring discrete design to sound different from a well measuring opamp, assuming both are being implemented correctly. Where exactly are these audible differences hiding? The only reason to suspect they would sound different is subjective and highly bias-prone sighted listening impressions, which I don't think we can put much stock by.
   
  3. Comparisons to other amplifier measurements.
   
  The O2 is designed based around objective metrics and very safe thresholds of audibility, so I don't see that how other amplifiers perform is directly relevant to the design goals. Unfortunately, very many amplifiers simply are not measured properly, let alone these measurements released into the public domain , so comparisons of that sort are going to be thin on the ground. However, Tyll is going to start pumping them out in a month or so with a bit of luck: what exactly would you hope to establish with them?


----------



## purrin

Quote: 





mikeaj said:


> I have to also make it clear that I think this kind of skepticism is worthwhile (even if the intuition isn't right 100% of the time; definitely I don't believe all of the challenges levied, though I would be interested in seeing any supporting evidence) and will hopefully lead to some new results and approaches.  In the very least I'm a fan of your headphone CSD plots.


 

 To a large extent, I'm trying to be devil's advocate here. I think what the "dude who shall not be named" has done some great stuff; although I question his approach. I've seen a few instances of his followers randomly drop into threads here on HF and proclaim "all op-amps sound the same, it's all in you head, that's what the dude says" or "that op-amp will make the amp explode" - basically parroting Q&A straight from his blog without fully thinking things through or understanding the context what is being discussed.
   
  For everyone who's built an O2, I would advise also building other simple amps such as the PIMETA, PPA, CHA47, and then go on to SOHAs, MilletMaxs, Dynalos, M3s, B22s, etc. and play around with parts. Maybe it's all in your heads. Maybe it isn't. Experience and doing always beats reading.
   
  When I was fixing up and modding Anax's vintage receiver - I joked around and made the following comment: "Of course it's going to sound better - everytime we try a boutique cap that we've never used before - it always sounds better." There's a middle road to take. We can acknowledge the whimsical nature of our senses while not discounting the acuity of our senses (even comparing to measurements which may not be necessarily measuring the right thing in the first place.)


----------



## Willakan

Quote: 





purrin said:


> To a large extent, I'm trying to be devil's advocate here. I think what the "dude who shall not be named" has done some great stuff; although I question his approach. I've seen a few instances of his followers randomly drop into threads here on HF and proclaim "all op-amps sound the same, it's all in you head, that's what the dude says" or "that op-amp will make the amp explode" - basically parroting Q&A straight from his blog without fully thinking things through or understanding the context what is being discussed.
> 
> For everyone who's built an O2, I would advise also building other simple amps such as the PIMETA, PPA, CHA47, and then go on to SOHAs, MilletMaxs, Dynalos, M3s, B22s, etc. and play around with parts. Maybe it's all in your heads. Maybe it isn't. Experience and doing always beats reading.
> 
> When I was fixing up and modding Anax's vintage receiver - I joked around and made the following comment: "Of course it's going to sound better - everytime we try a boutique cap that we've never used before - it always sounds better." There's a middle road to take. We can acknowledge the whimsical nature of our senses while not discounting the acuity of our senses (even comparing to measurements which may not be necessarily measuring the right thing in the first place.)


 


  I'll agree that there has been mindless parroting, but that is done by traditional audiophiles as well: how many times do you read "This amp is supposed to be great" from people who have never tried it: if you adopt the audiophile position then surely that is a cardinal sin?
  And, at the risk of repeating myself ad nauseam, I am all for the evidence of the senses under controlled conditions. If measurements do not show something, which is of course possible, someone should produce these differences under controlled conditions so that science can move on.
   
  It would be fun to play around with lots of designs, but I lack time, money and motive. If I just want audio from my amp that is accurate as far as my ears will ever be concerned and will do justice to most any headphone (save the uber-insensitive) that I care to plug into it, I shouldn't have to go on a sodding voyage of discovery costing thousands when all the evidence suggests the answer is right under my nose!


----------



## purrin

Quote: 





willakan said:


> ... However, Tyll is going to start pumping them out in a month or so with a bit of luck: what exactly would you hope to establish with them?


 

 I would like to see verified by science the claims that op-amps are as detailed as discrete designs.
   
  I see "detail" as having two components: clarity and ability to resolve low level information. In my experience with the headphone measurements, THD (and just as if not more importantly IMD - basically the entire spectrum of non-linear distortion) have a strong correlation with clarity. From my own experience, op-amps have been able to sound very clear, but always lacked the ability to resolve the lowest of low level information present in many recordings.
   
  Finally I would like to ask you if you had much experience (subjective, objective, DIY) with amps such as the PIMETA, M3, B22, Dynalo/Hi with a well designed resolving source (but not necessarily expensive) such as a Buffalo DAC or similar. Or do feel this is unnecessary as you do not trust your senses and prefer to rely on measurements and controlled experiments?


----------



## PelPix

I've been watching this conflict for a while, and you both seem to be working on the same baseless assumption assumption: neutral, transparent amps are preferable.
  Who's to say the human brain even automatically prefers an amp that reproduces the sound well in the first place?  Last I checked, there was absolutely no scientific logic backing this field, and it was all 100% artistic taste.  If neutrality or transparency mattered _at all_ to the human brain, tube amps would be out of the question immediately!
   
  But they aren't.
   
  Just because an amp measures well doesn't mean it's better sounding, just electrically better.  Someone could very well just prefer a distorted mess.  Such a person would find a well-measuring amp intolerable.


----------



## stv014

Quote: 





purrin said:


> I would like to see verified by science the claims that op-amps are as detailed as discrete designs.


 
   
  It would make more sense to look for specific evidence of op-amps lacking details (or anything else), and assuming that it is not true until proven. Otherwise, it is very hard to prove that something vaguely defined (i.e. "detail loss" of some unmeasurable kind in op-amps) does _not_ exist, as you seem to demand it.


----------



## Willakan

Quote: 





pelpix said:


> I've been watching this conflict for a while, and you both seem to be working on the same assumption: neutral, transparent amps are preferable.
> Who's to say the human brain even prefers an amp that reproduces the sound well in the first place?


 


  Well, that is technically what hi-fi is about: reproducing the original recording, which itself tries to reproduce the performance. That said, as I said earlier if you don't like the sound, you now have a neutral base: apply equalisation and other forms of DSP for your perfect sound. Far better than going for something with some deviation from accuracy which you cannot turn off for some silly price.
   
  @purrin:
   
  What would you take as evidence exactly? The "evidence" is more the absence of evidence: the IC opamps designed or well-suited to audio perform extremely well by every known metric, so why would a discrete design that does the same sound different? Whilst absence of evidence is obviously not evidence of absence, it does render a claim rather implausible until such evidence is presented. For example, as far as THD is concerned, the NE5532 (first decent audio opamp to come out AFAIK) performs stupidly well: same for IMD. This is, incidentally, borne out in the measurements of the O2, which uses a cheaper version of that opamp in the voltage gain stage. If there is a difference, the burden of proof is on the audiophiles to say "No, current metrics do not cover X and I can prove it by reproducing it under controlled conditions."
   
  I really don't have the time/money to listen to uber-expensive products, or even moderately expensive. This is normally the time that people shout "AHAHAHA NO EXPERIENCE" then presumably dismiss everything I say. I don't feel it is necessary to throw large sums of money after what I hold to be unfalsifiable and therefore meaningless claims. As you can see from my profile, everything save my headphones was chosen entirely by the numbers. If I had rather more cash, I would change nothing save the headphones, which would be HD800s. If I was feeling particularly affluent, I might splash out on a Benchmark, but I'd have trouble justifying even that.


----------



## zzffnn

Guys, let us sit back and stop arguing. Or this thread will be closed like other O2 threads. The designer is not liked by some Headfiers, we all know that.
   
  As with any other Headfi equipment, some people will like it, while some people not.
   
  I myself do not care to hear all those technical arguments. I like the o2 amp and can certainly understand that some people may not like it. For example, it may sound bright with an already-bright headphone, in view of its neutral sound signature.


----------



## Reticuli2

Who said anything about comparing the O2 to identical style amps?  If there was one that used cheap parts and a great design (and not in a larger product like the Benchmark) in a low price point, he wouldn't have been compelled to do it in the first place.  If you want to send your amps to him for measurement, feel free.

  
  Quote: 





purrin said:


> Which other amps were compared to the O2 which did not use common (off-the-shelf cheap op-amps) components? I believe there was a comparison to the AMB mini3, but it wasn't quite an apple-to-apples comparison given the differences in battery voltage and PCB size advantage (and hence extra stage) of the O2.


----------



## Reticuli2

And the wheel has been around longer.  His assertion is that some of the more "modern" opamps are being misused and you're hearing and liking distortion.  Being around djing boards that are meant to be connected to sound systems that cost more than any of us will make in our lifetime, often the old opamps used with great care sound better than the new stuff.  His results are not enirely unexpected.  Often new opamps are designed for different applications from the old, not meant as replacements.  These aren't GPUs.
  
  Quote: 





g.trenchev said:


> Sorry,I did not meant that.I'm just not awed of what an incredible solutions NJM4556 and NE5532 are.They've been in production for decades.I've listened them on whenever on whatever device,you too.So,no progress.Is everything new is well forgotten old?Is audio running in circles of say,20 years?


----------



## Reticuli2

Anyone tried putting it in their sig?

  
  Quote: 





zzffnn said:


> Guys, let us sit back and stop arguing. Or this thread will be closed like other O2 threads. The designer is not liked by some Headfiers, we all know that.
> 
> As with any other Headfi equipment, some people will like it, while some people not.
> 
> I myself do not care to hear all those technical arguments. I like the o2 amp and can certainly understand that some people may not like it. For example, it may sound bright with an already-bright headphone, in view of its neutral sound signature.


----------



## maverickronin

Quote: 





purrin said:


> Also, what is the consensus opinion of differences in circuit topology, transistor types and materials, etc. among the "followers"? Do those all sound the same? The answer will be of course, they the high precision RMAA measurements show the same results, then they will sound the same. But then this gets back to what I've questioned in the first place? _Where are the measurements comparing the O2 to other amps designed using "bogus" philosophy._


 
   
  Its no secret that I'm a big fan or Voldermort, but here's what I think about the subject.
   
  He's basing it off of research (most of it in the AES library behind a paywall) that supports the idea that when commonly measured modes of distortion such as THD, IMD, crossover, etc are below certain thresholds audible differences between different equipment is no longer detectable.  This research is not complete or exhaustive and exact levels have not been established but it does suggest that his methodology is going in the right direction.
   
  This is further supported by various other blind tests with support the idea that audible differences between equipment of vastly different price, topology, and complexity often disappear as soon as someone doesn't know what they are listening to.
   
  He's used both methods in designing the O2.  He made the numbers as good as possible within the budget and size constraints and then did blind tests against the DAC1 which is generally thought of as transparent.  He has a the blind testing challenge with $500 to charity as well.  Its obviously impractical unless the challenger happens to live nearby but its not like you could expect him to offer a million dollars or something like James Randi.  The challenge is hardly perfect but I think it would be difficult to do better.  I'm sure he'd be interested if you had a better idea.
   
  Regarding comparisons, are you specifically asking for comparative measurements against something else like a discrete or tube design?  That would certainly be interesting but with the large number of such products on the market and their many variations it wouldn't be very useful for setting design goals for the O2 or his goals for the blog.  It would be difficult to get a hold of something expensive or large on loan and no matter what he picked he'd get complaints that it wasn't good enough.  His goal for the O2 was to create an inexpensive and easy to build amp that errs on the cautious side what current research suggests suggest is "good enough" to be transparent and that doesn't require testing against other designs known not to be transparent in order to demonstrate.  From what I can tell his goals for the blog are to provide information about audio gear from an objective engineering perspective and recommend quality products which are good a value for the money.  Since he has a day job and this blog is basically a hobby it doesn't make much sense to spend time measuring and writing up articles on things that aren't likely to advance those goals.  I do think it would be cool and interesting if he did measure more designs of varying topology and transparency but that wouldn't be as useful to as many people.
   
  He's said that there will be future articles which will explain the current data on the correlation between measurements and perceptions.  There's a lot of interesting stuff in the specifics.  The factors the set the boundaries of what is audibly transparent like psychoacoustics which determines how audible and objectionable certain types of distortion are, how well certain tests expose weakness of an amplifier, and how representative they are of its nonlinearities.
   
  I can understand some people thinking that he comes off as terse or rude but that's not really the way I see it.  I think he's simply direct and to the point.  He states his position and asks for evidence if someone questions him.  I know you said you don't like reading his articles but a lot of this stuff is explained through out them.  I agree that he could be a more effective communicator but I don't see him as being rude or intentionally mean spirited.
   
  I'm not sure if this is something you brought up or not but something else he gets a bad rap for is "attacking" certain products, presumably because he doesn't agree with their design philosophy.  Something he's stated, and done in practice as well, is to not call out products or companies who don't make objective claims.  Claims given for the uDAC2 and Mini3 can be measured and verified or falsified but he doesn't take some random tube amp and then complain about how its not transparent to the signal because their manufacturers don't usually make those sorts of claims about it.  He even recommends Bottlehead as an honest company selling such gear.


----------



## Reticuli2

Huh?  I like discrete. Certainly my brain tells me they're doing something special that re-recording will even destroy (opamps sound better in recordings of phonos than they sounded live).  We have no comparison baseline for a further discussion, though.  Send him some discrete designs to test if you want to push that line further.
  
  Quote: 





purrin said:


> I find it interesting that none of my important questions (those dealing with objective measurements correlation with subjective impressions, comparisons of O2 to discrete designs) have been answered so far.


----------



## maverickronin

Quote: 





pelpix said:


> I've been watching this conflict for a while, and you both seem to be working on the same baseless assumption assumption: neutral, transparent amps are preferable.
> Who's to say the human brain even automatically prefers an amp that reproduces the sound well in the first place?  Last I checked, there was absolutely no scientific logic backing this field, and it was all 100% artistic taste.  If neutrality or transparency mattered _at all_ to the human brain, tube amps would be out of the question immediately!
> 
> But they aren't.
> ...


 

 You are correct about that.  Since most people here are listening for pleasure, subjective preference is what matters in the end and obviously the O2 isn't for people who don't want a transparent sound but the fact that someone doesn't like that sort of sound doesn't change the O2's faithfulness to the input signal and doesn't make it objectively worse.  I'd just say that different people have different preferences and should chose their amps accordingly instead of trying to pass judgement on people with different tastes.  I'm still human, but I try not to trumpet my preference as the "correct" way and give balanced presentation of the facts as I understand them instead.
   
  In an abstract or philosophical sense I certainly don't care about what happens to be accurate or transparent but I've found that's what I prefer in amps and DACs for practical reasons.  It provides a neutral base for all kinds of audio and lets me add just the coloration I want with the right headphones or DSPs.


----------



## purrin

Quote: 





maverickronin said:


> ...


 

 I don't have any quarrel personally with Voldemort. He seems like a very intelligent young man and some of his "discoveries" have been very enlightening to say to the least. Even my friends and HF acquaintances such LFF and Anetode are big fans of his. I think what annoys me most is not him, but his less-than-informed followers (it doesn't seem like anyone who has responded to me is one of them) crash in on threads parroting his beliefs as outlined in this manifesto.
   
  I'm of the opinion that with great power (or influence) comes great responsibility. I believe the manifesto-ish nature tends to rub-off the wrong way (meaning badly influence in terms of attitude) on initiates who are newer to the hobby or haven't stopped to think about what is he trying to say.


----------



## Willakan

Yeah, I'll think I'll concede that the O2, despite being a pretty incredible gift in terms of the time and effort put into it, certainly has NwAvGuy's agenda irrevocably intertwined with every aspect of its design and presentation to the headphone hi-fi community, even if the agenda is an entirely admirable one IMHO. That said, some people are going to mindlessly repeat things regardless - surely better to have them mindlessly repeating NwAvGuy than, say, 6Moons?


----------



## purrin

LOL. 6moons can be deciphered though. It just takes time. Perhaps a tool such as this would make things easier:


----------



## Twinster

*[size=small]Star Wars[/size]*[size=small]: [/size]*[size=small]The Old Republic FAN busted! [/size]*





  
  Quote: 





purrin said:


> LOL. 6moons can be deciphered though. It just takes time. Perhaps a tool such as this would make things easier:


----------



## c61746961

*purrin*: What about recording equipment?, does it have to feature an properly designed discrete topology or in this case op-amps are about enough? (this is NOT meant to be sarcastic)

I keep reading your notes about how "low-level" information extraction is your personal benchmark on most equipment's capacity of resolving the signal, would you mind giving us some examples? (I would love to read some description of the sound and try to hear the stuff in a short clip)

Don't get me wrong, I am grateful for all you've done for this community so far. I'm just asking for more


----------



## purrin

Quote:


c61746961 said:


> *purrin*: What about recording equipment?, does it have to feature an properly designed discrete topology or in this case op-amps are about enough? (this is NOT meant to be sarcastic)
> I keep reading your notes about how "low-level" information extraction is your personal benchmark on most equipment's capacity of resolving the signal, would you mind giving us some examples? (I would love to read some description of the sound and try to hear the stuff in a short clip)
> Don't get me wrong, I am grateful for all you've done for this community so far. I'm just asking for more


 

 No doubt. I don't think it was this thread but rather the Senn HD800 appreciation thread where I said what we can get is ultimately limited by the recording and production process. But why stick another two, three, or four op-amps in the way at the end of the chain? It's no surprise why some of the Frank Sinatra recordings in the past (probably recorded, mixed, and mastered using tubes, no IC's yet) sounded so real and immediate. LFF had let me listen to some unadulterated pre-mastered Beatles and Sinatra tracks. Really wonderful very high resolution recordings, especially the Sinatra.
   
  A little bit off topic: not just extraction of low-level information, but also other factors: dynamics - lack of compression, reasonably good tone (flat / neutral), lack of glare or stridency (not necessarily related to tone or measured FR), the ability to dig into the music with authority - that is provide instantaneous dynamic contrasts (particularly with small changes in volume), granularity, range, and continuous-ness of volume, continuity of musical presentation over time (liquidity,) and clarity.
   
  Going back to the the low-level information retrieval aspect: it's better experienced than described. It shouldn't be equated with analytical, but rather more of giving us a _sense _that everything is there. That what is being reproduced is not merely a shadow of the original. It gives us satisfaction that the music is real, that we don't strain to hear what we think is there but not. A proper setup would easily allow an listener to hear the how the individual mixes (especially with the modern recordings with a lot of processing) in a track differ, e.g. microphones used,  microphone placement, EQ and processing applied, etc. I don't hear this on portable amps - maybe at most get a hint of it. The example I provided should not be considered a detail thing (it's an merely indicator that we are there or close), but rather a completeness thing. And I said above, the recording and production process plays a big part of this aspect.
   
  EDIT: It's kind of like how those special edition EMI/Angel 45 rpm classical LPs sounded better than regular 33 rpm LPs. I know this probably doesn't help much...
   
  I'm sure to many in this thread, much of what I've described is just voodoo and nonsense. But listening to music is a subjective experience for me (I do enough measurements already and have really had enough listening for 2nd and 3rd harmonics with test tones.) People know where I live, I organize meets, I go to meets, I lend people my stuff, so folks are always welcome to listen to what I'm talking about for themselves. I may cast a spell upon you to influence your perception as I've done with everyone who's heard my main rig.


twinster said:


> *[size=small]Star Wars[/size]*[size=small]: [/size]*[size=small]The Old Republic FAN busted! [/size]*


 

  Hee hee - forgot about the tabs... major time waster.


----------



## skeptic

Quote: 





purrin said:


> LOL. 6moons can be deciphered though.


 

 How 'bout a visual translation and summary of the contents on 6moons?


----------



## Twinster

Do you think LFF can do something about Coldplay - Mylo Xyloto album or it's just a lost cause 
	

	
	
		
		

		
		
	


	




.


----------



## purrin

Quote: 





skeptic said:


> How 'bout a visual translation and summary of the contents on 6moons?


 

 For me, it's more "Darmok and Jalad at Tanagra"


----------



## PurpleAngel

Hopefully the O2 with AC adapter design is finished soon, that what I'm waiting on.


----------



## Willakan

Quote: 





purpleangel said:


> Hopefully the O2 with AC adapter design is finished soon, that what I'm waiting on.


 


  The current version works with an AC adaptor: it's just that it can work with batteries as well.


----------



## Twinster

The current O2 has an AC adapter and can be use without batteries to my knowledge. I got the bigger case too with the RCA input and full size headphone jack.
  
  Quote: 





purpleangel said:


> Hopefully the O2 with AC adapter design is finished soon, that what I'm waiting on.


----------



## Anaxilus

Quote: 





twinster said:


> Do you think LFF can do something about Coldplay - Mylo Xyloto album or it's just a lost cause
> 
> 
> 
> ...


 

 Ask him, he does great work and might be willing to let you hear a sample to see if you approve.


----------



## Maxvla

purrin said:


> For me, it's more "Darmok and Jalad at Tanagra"




When the walls fell!


----------



## PelPix

Quote: 





purrin said:


> I don't have any quarrel personally with Voldemort. He seems like a very intelligent young man and some of his "discoveries" have been very enlightening to say to the least. Even my friends and HF acquaintances such LFF and Anetode are big fans of his. I think what annoys me most is not him, but his less-than-informed followers (it doesn't seem like anyone who has responded to me is one of them) crash in on threads parroting his beliefs as outlined in this manifesto.
> 
> I'm of the opinion that with great power (or influence) comes great responsibility. I believe the manifesto-ish nature tends to rub-off the wrong way (meaning badly influence in terms of attitude) on initiates who are newer to the hobby or haven't stopped to think about what is he trying to say.


 

 I can't help but agree.  He came to try and get people to think, not to convert them from HeadFiism to the newly-created religion NwAVGuyism.  It's ridiculously annoying.


----------



## maverickronin

Quote: 





purrin said:


> I don't have any quarrel personally with Voldemort. He seems like a very intelligent young man and some of his "discoveries" have been very enlightening to say to the least. Even my friends and HF acquaintances such LFF and Anetode are big fans of his. I think what annoys me most is not him, but his less-than-informed followers (it doesn't seem like anyone who has responded to me is one of them) crash in on threads parroting his beliefs as outlined in this manifesto.
> 
> I'm of the opinion that with great power (or influence) comes great responsibility. I believe the manifesto-ish nature tends to rub-off the wrong way (meaning badly influence in terms of attitude) on initiates who are newer to the hobby or haven't stopped to think about what is he trying to say.


 

 I suppose some people will make a dogma out of anything...


----------



## sphinxvc

My second O2 came in today.  This time cased.  It weirdly matches my Zodiac perfectly.  Everything from the silver front panel, black shell, to the red LEDs & black lettering.  Ditto for my Pure i20 dock. 
   
  I'm using it in "power amp" mode, maxed volume and using the Zodiac's much more refined volume pot.  It's exactly the "upgrade" over the internal head-amp I was looking for.
   
  Also, John's build and casework is awesome.  Having owned the uncased version of the O2 I can tell how much weight is added because of the JDS cases.  It's a solid feel.  It also came in less than three days, I can't recommend John enough, provided you aren't a DIYer.


----------



## DarkAudit

Ordered from JDS on Tuesday morning. Arrived Thursday lunchtime. All is well.


----------



## Dzhozef

I love it when a revolutionary, ground-breaking value audio product comes out.


----------



## arirug

I have, and have had a lot of headphone amps. With this objective O2 I feel that it fulfills all that I need in a headphoneamp. I will now sell all my other headphoneamps which consist of Stax, Decware Audio, Meier audio, Ibasso, and other companies. I will make one more heaphoneamp buy, and that will be the desktop version with DAC from the O2 creator.


----------



## Maxvla

arirug said:


> I have, and have had a lot of headphone amps. With this objective O2 I feel that it fulfills all that I need in a headphoneamp. I will now sell all my other headphoneamps which consist of Stax, Decware Audio, Meier audio, Ibasso, and other companies. I will make one more heaphoneamp buy, and that will be the desktop version with DAC from the O2 creator.




High praise. Makes me want one even more. Glad you found something you like, and is a huge money saver.


----------



## Deep Funk

Quote:


purrin said:


> I don't have any quarrel personally with Voldemort. He seems like a very intelligent young man and some of his "discoveries" have been very enlightening to say to the least. Even my friends and HF acquaintances such LFF and Anetode are big fans of his. I think what annoys me most is not him, but his less-than-informed followers (it doesn't seem like anyone who has responded to me is one of them) crash in on threads parroting his beliefs as outlined in this manifesto.
> 
> I'm of the opinion that with great power (or influence) comes great responsibility. I believe the manifesto-ish nature tends to rub-off the wrong way (meaning badly influence in terms of attitude) on initiates who are newer to the hobby or haven't stopped to think about what is he trying to say.


 
  Agreed.
   
  Just to add something: what he has done is not entirely new. There are various audio fora where whatever he has written was already known and tested. Given he at least made new audio enthusiasts think about what makes audio work is a good thing. I am not that interested in his efforts though...


----------



## Willakan

I don't think anyone is saying that NwAvGuy invented sensible audio design - but then again it wasn't invented by people on interent forums either.


----------



## Deep Funk

I know but his efforts have been somewhat hyped up.
   
  With a bit of research and reading from various sources: old electric engineering books; libraries and audio fora for instance you can educate yourself a lot...


----------



## DarkAudit

Headphones plugged straight into the front panel jack of my desktop PC had a lot of noise from the inner workings of the machine, even when volume was down to zero. Nothing of the sort with the O2 connected. (Granted, I opened up the case, blew out a mess of dust and slightly rearranged the front cables before attaching the O2.)
   
  So now the options for the DAC are the PC audio (Realtek ALC892), or the Creative X-Fi Go! Pro USB stick.


----------



## stv014

Quote: 





darkaudit said:


> Headphones plugged straight into the front panel jack of my desktop PC had a lot of noise from the inner workings of the machine, even when volume was down to zero.


 

 The amount of noise on the front panel does not decrease with lower volume settings, as it is added after the output stage of the sound card. It only decreases if you connect a less sensitive headphone to the front panel, or just avoid using it.


----------



## sphinxvc

Some listening impressions from last night.  There's a bit more bass presence on the O2 than the Zodiac's HP out.  That's probably a tell-tale sign I've been under-powering the LCDs with the Zodiac.  I kind of feel like there's been a little loss in spatial definition, but that might be because the Zodiac's output is thinner and high frequencies & air come across more, those usually help with spatial positioning.  Now the O2's bass masks a bit of that air & spatial information.  
   
  All in all though, I think I can say without a doubt that this is an really good amp with the LCD-2s.  And at it's cost, it needs no apologies.


----------



## Deltron 3030

How does it compare to the Ibasso zero? Also would it be a good match for the beyer dt150 (250 ohms)


----------



## Willakan

Quote: 





sphinxvc said:


> Some listening impressions from last night.  There's a bit more bass presence on the O2 than the Zodiac's HP out.  That's probably a tell-tale sign I've been under-powering the LCDs with the Zodiac.  I kind of feel like there's been a little loss in spatial definition, but that might be because the Zodiac's output is thinner and high frequencies & air come across more, those usually help with spatial positioning.  Now the O2's bass masks a bit of that air & spatial information.
> 
> All in all though, I think I can say without a doubt that this is an really good amp with the LCD-2s.  And at it's cost, it needs no apologies.


 


  Unless I'm much mistaken, the Zodiac Silver has an output impedance of 120 ohms, which is really very high. This is almost certain to have an audible effect as far as damping is concerned: what you are describing fits rather well with a comparison of a headphone when electrically underdamped and driven properly.
   
  There are plenty of other possible reasons for the difference, but that sounds like the obvious one.


----------



## maverickronin

Quote: 





deep funk said:


> I know but his efforts have been somewhat hyped up.
> 
> With a bit of research and reading from various sources: old electric engineering books; libraries and audio fora for instance you can educate yourself a lot...


 
   
  You still couldn't build an amp like the O2 without an audio analyzer though.  You can certainly make something pleasant sounding with just some know-how and a good o'scope but you'll need more than that to squeeze every last bit of performance out of a given set of parts
   
  I think the O2 is a big deal because its combination of performance and price is pretty new to the headphone world.  Its like the gainclone of the headphone world or something.
  
  Quote: 





deltron 3030 said:


> How does it compare to the Ibasso zero? Also would it be a good match for the beyer dt150 (250 ohms)


 

 Just from ibasso's and Beyer's specs it looks like the DT150s might want a bit more voltage than the D Zero can provide.
  
  Quote: 





willakan said:


> Unless I'm much mistaken, the Zodiac Silver has an output impedance of 120 ohms, which is really very high. This is almost certain to have an audible effect as far as damping is concerned: what you are describing fits rather well with a comparison of a headphone when electrically underdamped and driven properly.
> 
> There are plenty of other possible reasons for the difference, but that sounds like the obvious one.


 

 IME planars aren't usually affected much by lack of electrical damping from high output impedance.  Its probably a little off topic but I wonder how much it does matter.  They do have some back EMF which can be demonstrated by trying to use your planar 'phones as a mic but I wonder how important the electrical damping is compared to all the acoustic/mechanical damping that they already require.


----------



## DarkAudit

Quote: 





stv014 said:


> The amount of noise on the front panel does not decrease with lower volume settings, as it is added after the output stage of the sound card. It only decreases if you connect a less sensitive headphone to the front panel, or just avoid using it.


 


  My point was that is no longer an issue now that the O2 is in place. The issue now is which to use the onboard Realtek HD or the Creative X-Fi Go! USB stick as my DAC.


----------



## mikeaj

Quote: 





darkaudit said:


> My point was that is no longer an issue now that the O2 is in place. The issue now is which to use the onboard Realtek HD or the Creative X-Fi Go! USB stick as my DAC.


 

 Which Realtek (not like it really matters)?  In theory the higher-end Realtek models can have better performance than the X-Fi Go!  (I think; I didn't just go check a spec sheet but IIRC it does), but it would be pretty surprising to get that kind of performance in practice when sitting on a computer mainboard, since the audio performance has got to be one of the lowest priorities on those things.
   
  Actually, a certain amp designer whose name you may recognize, did a review of the X-Fi Go! and the results are all pretty good for the price except the noise level.  If the noise level is not a problem I'd just use that.


----------



## DarkAudit

Quote: 





mikeaj said:


> Which Realtek (not like it really matters)?  In theory the higher-end Realtek models can have better performance than the X-Fi Go!  (I think; I didn't just go check a spec sheet but IIRC it does), but it would be pretty surprising to get that kind of performance in practice when sitting on a computer mainboard, since the audio performance has got to be one of the lowest priorities on those things.
> 
> Actually, a certain amp designer whose name you may recognize, did a review of the X-Fi Go! and the results are all pretty good for the price except the noise level.  If the noise level is not a problem I'd just use that.


 


  It's the ALC892 on the ASRock P67 Extreme 4. Drivers on the ASRock site are at least one version behind Realtek's. Maybe more.
   
I picked up the stick before I read that review you mentioned.  Now that I've found the noise problem is gone, it's now a matter of swapping back and forth to see which I like better... as if I can really tell the difference. I'm not as trained as I should be to hang out here.


----------



## Twinster

Manage to complete my first O2 amplifier today and it worked on the first try.  It was really easy to build with all the documented process. Listening to it while I'm typing and source from my DACmini it sound very good. I can attest to the clarity and the good bass others have reported. Even my SRH-940 gets a good kick on the lower notes.


----------



## pekingduck

How's the O2 compared to the amp part of your DACmini?
  
  Quote: 





twinster said:


> Manage to complete my first O2 amplifier today and it worked on the first try.  It was really easy to build with all the documented process. Listening to it while I'm typing and source from my DACmini it sound very good. I can attest to the clarity and the good bass others have reported. Even my SRH-940 gets a good kick on the lower notes.


----------



## Eisenhower

Quote: 





stv014 said:


> The amount of noise on the front panel does not decrease with lower volume settings, as it is added after the output stage of the sound card. It only decreases if you connect a less sensitive headphone to the front panel, or just avoid using it.


 

 Wouldn't sensitive headphones also decrease the signal? Or would they actually improve the S/N ratio?


----------



## stv014

Quote: 





eisenhower said:


> Wouldn't sensitive headphones also decrease the signal? Or would they actually improve the S/N ratio?


 

 No, I meant with less sensitive headphones the volume needs to be increased to sound equally as loud, and since the noise voltage (at least the part of it that is added by using the front panel) does not increase as much, the SNR will improve. Or, from another point of view, if the noise voltage is roughly constant, then its loudness will depend on the headphone sensitivity (dB/V). Obviously, the disadvantage is that the maximum possible SPL will be lower, too. With an external amplifier, the line output volume is normally set to the maximum that is possible without increased distortion/clipping, so it will achieve optimal SNR.


----------



## Naim.F.C

Anyone compared one of these to a Violectric V100/V200?


----------



## FritzS

Quote: 





naim.f.c said:


> Anyone compared one of these to a Violectric V100/V200?


 

 or to LPA-2 module?
   
http://www.funk-tonstudiotechnik.de/SYMM-VERST.htm#Headmaster
   
http://www.funk-tonstudiotechnik.de/LPA-2%20englisch.pdf


----------



## tseliottt

How would you guys compare this amp to the Matrix M Stage sound wise?


----------



## 129207

Quote: 





tseliottt said:


> How would you guys compare this amp to the Matrix M Stage sound wise?


 


  Amps aren't supposed to sound like anything.


----------



## caracara08

Quote: 





negakinu said:


> Amps aren't supposed to sound like anything.


 


  but they do. so way to add to the discussion.


----------



## Twinster

That look very interesting Fritzs. Do you know where it can be bought and the cost?
   
   
  Quote: 





fritzs said:


> or to LPA-2 module?
> 
> http://www.funk-tonstudiotechnik.de/SYMM-VERST.htm#Headmaster
> 
> http://www.funk-tonstudiotechnik.de/LPA-2%20englisch.pdf


----------



## 129207

Quote: 





caracara08 said:


> but they do. so way to add to the discussion.


 


  It might not have been the most useful addition I agree, but I'd be seriously impressed if anyone in here could identify either the M-Stage or the O2 in a blind test. The O2 is designed to be nothing more than a wire-with-gain, so it can't really have a sound signature of itself. The whole idea of buying amps for their sound is a flawed concept as well in my opinion. An amp is meant to amplify, not EQ. Get an EQ if you want to change the sound of your headphones. You'll get much more reliable results this way. Cheaper too.
   
  EDIT: now that I think of it, it does actually piss me off a little and I feel my remark is justified. The differences between amps and dacs are vastly exaggerated. Newbs buying their first gear after reading the comments here end up either disappointed or adding to the information pollution by mimicking others in their description of a piece of gear. Just say it like it is.


----------



## caracara08

in an ideal world. truth is, there are differences.  the o2 is suppose to be exactly what youre looking isnt it? amplify without adding coloration. yet you have an arrow and e5 both with their own tweaks. do all the amps you own sound exactly the same?


----------



## 129207

Quote: 





caracara08 said:


> in an ideal world. truth is, there are differences.  the o2 is suppose to be exactly what youre looking isnt it? amplify without adding coloration. yet you have an arrow and e5 both with their own tweaks. do all the amps you own sound exactly the same?


 

 You're doing a mental hiccup. The Arrow has EQ options. Those EQ options EQ. The amp itself amplifies. The bassboost is a hardware EQ and advertised as such. The original question was what the difference between the M-Stage and the O2 sound-wise are, obviously expecting an answer like "This one has romantic mids and smooth treble with a black background while the other has a more neutral sound but a really big soundstage" and more of those random non-sensical audiophile-linguistics.


----------



## tseliottt

Quote: 





negakinu said:


> You're doing a mental hiccup. The Arrow has EQ options. Those EQ options EQ. The amp itself amplifies. The bassboost is a hardware EQ and advertised as such. The original question was what the difference between the M-Stage and the O2 sound-wise are, obviously expecting an answer like "This one has romantic mids and smooth treble with a black background while the other has a more neutral sound but a really big soundstage" and more of those random non-sensical audiophile-linguistics.


 


  Actually, I was looking for an answer like yours. I actually made a thread asking for an amp that adds no coloration. I was considering the O2 already, and an answer like yours justified the decision. Cool your pants.


----------



## 129207

Quote: 





tseliottt said:


> Actually, I was looking for an answer like yours. I actually made a thread asking for an amp that adds no coloration. I was considering the O2 already, and an answer like yours justified the decision. Cool your pants.


 

 My pants are always on fire. It's nothing personal.


----------



## khaos974

Doesn't anyone get tired of this?
   
  One camp says that theoretically the O2 or any decently designed amp (Benchmark, GS1, Violectric...) is akin to wire aith gain and should sound like nothing, for this camp, their subjective impressions match the theory. As for the other camp, they hear differences between amps that theoretically should sound the same, thus no measurement based argument will convince them.
   
  This type of argument is gust going round in circles, unless the other guy is an objectivist, objectivists arguments won't convince, and if he's already an objectivist, he already is convinced.


----------



## mikeaj

Quote: 





khaos974 said:


> Doesn't anyone get tired of this?
> 
> One camp says that theoretically the O2 or any decently designed amp (Benchmark, GS1, Violectric...) is akin to wire aith gain and should sound like nothing, for this camp, their subjective impressions match the theory. As for the other camp, they hear differences between amps that theoretically should sound the same, thus no measurement based argument will convince them.
> 
> This type of argument is gust going round in circles, unless the other guy is an objectivist, objectivists arguments won't convince, and if he's already an objectivist, he already is convinced.


 

  Well yeah, same old, same old.
   
  I'd just say that some of the options maybe don't exactly perform close enough to wire with gain, so there's maybe some differences there.  Also I would say that some decently-designed amps aren't intended to be the wire-with-gain type.  If the design goal is something else, then that's not necessarily a bad design.
   
   
  The issue is the body of credible evidence (e.g. peer-reviewed publications, any type of testing with the bare minimum of scientific controls) supporting one argument versus the other.  Some people treat their own perceptions and limited experiences--which generally don't include any testing with the bare minimum of scientific controls--as strong evidence, even though they're generally not.  It's understandable but misinformed thinking.
   
  edit: and that came out sounding a lot more condescending than intended, but I'll let the idea stand.


----------



## khaos974

Quote: 





mikeaj said:


> Quote:
> 
> 
> 
> ...


 
   
  Yes, you have point amps not designed to sound like wire with gain.
   
  As for the other part, you are quite right, there is literally zero credible evidence (as in peer reviewed papers, serious ABX, comparing parameters to academically accepted limits of human hearing) that suggest that any amp designed with a wire with gain philosophy (baring any huge flaws) should sound different from each other.


----------



## Willakan

Bleh, mindsets will change eventually, if only by virtue of an influx of new blood thanks to Beats and co. into audiophilia. Until then, I'll keep on arguing


----------



## Digital-Pride

To disagree is to be human I say!


----------



## purrin

One thing to add about the "wire-with-gain" concept: there's the thought of not adding anything, not adding coloration. The opposite should also be considered and is just as critical: is it missing anything? Errors of commission and errors of omission. I hear the first point mentioned the most often, the second point less.


----------



## Head Injury

Quote: 





purrin said:


> One thing to add about the "wire-with-gain" concept: there's the thought of not adding anything, not adding coloration. The opposite should also be considered and is just as critical: is it missing anything? Errors of commission and errors of omission. I hear the first point mentioned the most often, the second point less.


 

 What would an uncolored amp be missing besides coloration?


----------



## purrin

Quote: 





head injury said:


> What would an uncolored amp be missing besides coloration?


 

 The term coloration usually implies changes to tonal balance or timbre of sound. Using this definition, a lot could be missing: information, dynamic contrast, etc.
   
  In other words, wire-with-gain = uncolored (doesn't add anything) and transparent (doesn't lose anything.)


----------



## LFF

Quote: 





purrin said:


> The term coloration usually implies changes to tonal balance or timbre of sound. Using this definition, a lot could me missing: information, dynamic contrast, etc.


 


   Indeed!


----------



## maverickronin

Quote: 





purrin said:


> One thing to add about the "wire-with-gain" concept: there's the thought of not adding anything, not adding coloration. The opposite should also be considered and is just as critical: is it missing anything? Errors of commission and errors of omission. I hear the first point mentioned the most often, the second point less.


 

 Maybe its just semantics but I'd count an error of omission as a coloration too.  Its essentially just changing the sign and adding a negative right?  The issue is the difference between the input and the output so any difference of any kind is a coloration whether it adds some tube-y harmonics or filters something out.
   
  With a good ADC you could probably do some pretty interesting differencing tests.  I wonder what the difference between the BA and the O2 sounds like.


----------



## Naim.F.C

I'd personally hate it if all amps aimed to be completely neutral. Don't get me wrong, having neutral amps is necessary and important. But not all. Sometimes you want amps that focus on the highs to bring out detail in warmer cans, and like wise, you want amps that smoothen brighter cans, or add bass, body etc. That's why selecting amps is such a tricky decision, because neutral might not be what you're after, unless the balance of the cans/DAC you own are perfect and not something you'd want to change in any way. But I've yet to come across a can, that by default is absolutely 'perfect'.


----------



## maverickronin

Quote: 





purrin said:


> The term coloration usually implies changes to tonal balance or timbre of sound. Using this definition, a lot could be missing: information, dynamic contrast, etc.
> 
> In other words, wire-with-gain = uncolored (doesn't add anything) and transparent (doesn't lose anything.)


 

 Maybe we're coming at it from different perspectives.  I'd define transparent as something like, "when any changes the component in question make to the signal are no longer detectable by human ears".
   
  Quote: 





naim.f.c said:


> I'd personally hate it if all amps aimed to be completely neutral. Don't get me wrong, having neutral amps is necessary and important. But not all. Sometimes you want amps that focus on the highs to bring out detail in warmer cans, and like wise, you want amps that smoothen brighter cans, or add bass, body etc. That's why selecting amps is such a tricky decision, because neutral might not be what you're after, unless the balance of the cans/DAC you own are perfect and not something you'd want to change in any way. But I've yet to come across a can, that by default is absolutely 'perfect'.


 

 There's something to be said for that because there is no perfect headphone.  I certainly inject a lot of coloration in to my signal chain but I like to do it in controlled and switchable amounts using EQ, DSPs, or filter circuits.  I just think its easier and cheaper to start from a neutral base since its more versatile.  Switching to a different DSP preset in foobar is a lot easier and cheaper than buying a different amp to switch to.


----------



## purrin

Honestly I'm more worried about coloration from headphones and the recording/production process.


----------



## maverickronin

Quote: 





purrin said:


> Honestly I'm more worried about coloration from headphones and the recording/production process.


 
   
  I thought we were talking about amps.  That's what I was talking about.  The ADC is to record an amp's output so it can be compared with a tool like this.


----------



## Willakan

I think it would be advisible to keep the discussion at least tangentially related to the O2 or the principles behind it, seeing that the record as regards to thread locks when the O2 is discussed is hardly stellar.
   
  Also, DSPing and EQ renders coloured amps redundant and their pricing even more silly, IMHO. Hell, you can even simulate a tube amp if you feel so inclined.


----------



## 129207

Quote: 





willakan said:


> Also, DSPing and EQ renders coloured amps redundant and their pricing even more silly, IMHO. Hell, you can even simulate a tube amp if you feel so inclined.


 

 My point exactely, ergo we can conclude that everyone should buy the O2, stop buying any other amps forever since those are redundant and start learning about proper EQ'ing. That way, maybe, we can finally get something done after all.


----------



## Anaxilus

Quote: 





negakinu said:


> My point exactely, ergo we can conclude that everyone should buy the O2, stop buying any other amps forever since those are redundant and start learning about proper EQ'ing. That way, maybe, we can finally get something done after all.


 

 So how do I EQ the O2 to be as transparent and as my Leckerton if they are both flat?  If only my expectation bias for the O2 was greater than it was.  Oh well.


----------



## Willakan

As nobody has ever publically measured the Leckerton (although what they do have on their site looks OK, although highly limited in what we can derive from it) and we don't know what it does to the sound (if indeed what it supposedly does to the sound is audible under controlled conditions) that could prove difficult. If you're rolled opamps it gets even murkier.
   
  Once Tyll has got his "measure popular amps based on NwAvGuy's template" plan underway, we should have some interesting numbers to look at.


----------



## Maxvla

Speaking of EQing 'properly' anyone have a link to a guide to do this? Also is software or hardware EQ better? (As in digital vs analog)

I've always been a proponent of never EQing, especially headphones since the space should be almost the same for everyone unlike rooms with speakers. I'm willing to try anything though.


----------



## 129207

Quote: 





maxvla said:


> Speaking of EQing 'properly' anyone have a link to a guide to do this? Also is software or hardware EQ better? (As in digital vs analog)
> I've always been a proponent of never EQing, especially headphones since the space should be almost the same for everyone unlike rooms with speakers. I'm willing to try anything though.


 


  This is a great start: http://www.head-fi.org/a/tutorial-on-how-to-equalize-headphones


----------



## Willakan

Quote: 





maxvla said:


> Speaking of EQing 'properly' anyone have a link to a guide to do this? Also is software or hardware EQ better? (As in digital vs analog)
> I've always been a proponent of never EQing, especially headphones *since the space should be almost the same for everyone *unlike rooms with speakers. I'm willing to try anything though.


 

  The HRTF for headphones, at least as far as frequency response is concerned, varies hugely with position, head size, age ect.


----------



## Maxvla

willakan said:


> The HRTF for headphones, at least as far as frequency response is concerned, varies hugely with position, head size, age ect.




Well, I was comparing to speakers in a room. The variability in rooms is far greater than differences in biology. Stepping back further, you realize that speaker rooms have the HRTF to deal with as well. By comparison headphones are MUCH easier to work with.


----------



## sphinxvc

Quote:


anaxilus said:


> So how do I EQ the O2 to be as transparent and as my Leckerton if they are both flat?  If only my expectation bias for the O2 was greater than it was.  Oh well.


 

 Didn't you know transparency is a flaw?  
   
  If only everyone had little blue eyed, blond haired O2s they wouldn't be as misinformed. Have you ever measured the face plate of any O2?  It's invariably of perfect proportions...all others have anthropometric-ally inferior faceplates.  
  
 [*made these measurements myself, outside, in public.]


----------



## 129207

Quote: 





sphinxvc said:


> Quote:
> 
> Didn't you know transparency is a flaw?
> 
> ...


 
   
  From now on all amps but O2 shall be addressed as Unteramps.


----------



## Naim.F.C

I'm willing to bet you £2000 I could tell my ALO Continental and SR-71A apart in a complete blind test (haven't yet A/B'd directly with my O2 to be able to make such a bold challenge). And I disagree, not all amps have to be neutral. I personally believe that DAC's should stay neutral, and amps can, if desired add a little colour or change. For example, smoother or warmer sounding amps definitely compliment cans like the T1's and HD800's. And EQ's are finicky and affect optimum SQ in other ways.
   
  I agree, often differences between amps are grossly exaggerated, such is the case with almost every element of the audiophile world, but there are also real world differences at play in much of it, and you shouldn't be so quick to dismiss them. Personally, I don't think I've ever just gone with the status quo of how something is "supposed" to sound based on feedback from others. I trust only my own ears which is why often my opinions end up clashing or differing with others
    
   
  Quote:


negakinu said:


> It might not have been the most useful addition I agree, but I'd be seriously impressed if anyone in here could identify either the M-Stage or the O2 in a blind test. The O2 is designed to be nothing more than a wire-with-gain, so it can't really have a sound signature of itself. The whole idea of buying amps for their sound is a flawed concept as well in my opinion. An amp is meant to amplify, not EQ. Get an EQ if you want to change the sound of your headphones. You'll get much more reliable results this way. Cheaper too.
> 
> EDIT: now that I think of it, it does actually piss me off a little and I feel my remark is justified. The differences between amps and dacs are vastly exaggerated. Newbs buying their first gear after reading the comments here end up either disappointed or adding to the information pollution by mimicking others in their description of a piece of gear. Just say it like it is.


----------



## Satellite_6

I don't think it is unreasonable to say that one could possibly tell the difference between a colored amp like the M-Stage and a transparent amp like the O2. . . NwAvGuy himself said that amps can have audible consequences and interfere with the music. I'm sure a blind test would be harder than most would think though.


----------



## 129207

Quote: 





satellite_6 said:


> I'm sure a blind test would be harder than most would think though.


 


  My point exactely. Try putting three similar-ish midrange amps next to each other, wear a blindfold and let someone else mix 'em up. Try to identify them. It's a lot harder than you'd think, especially when you read all these superlative descriptions people use to describe them.


----------



## Willakan

Wait, how did we get from "The O2 will sound the same as any other amp that measures equally well or better (could probably get off with a fair bit worse TBH)" to "The O2 will sound the same as a given popular SS amp that has never been measured?"


----------



## purrin

Quote: 





anaxilus said:


> So how do I EQ the O2 to be as transparent and as my Leckerton if they are both flat?  If only my expectation bias for the O2 was greater than it was.  Oh well.


 

 Going back to coloration, I find the O2 more colored and less transparent compared to the Dynalo and B22.
   
  Heck a CHA47 (paralleled CMOY) is more transparent and cheaper too.


----------



## upstateguy

Quote: 





negakinu said:


> My point exactely. Try putting three similar-ish midrange amps next to each other, wear a blindfold and let someone else mix 'em up. Try to identify them. It's a lot harder than you'd think, especially when you read all these superlative descriptions people use to describe them.


 


  +1   
   
  You can add high end amps to this as well. 
   
  Play them all at a volume that is equal to 9:30, low gain, on the standared O2 connected to a 2V source... which is a comfortable listening level for 650s, 880s and T-1s.
   
  Good luck telling them apart.


----------



## purrin

Quote: 





upstateguy said:


> +1
> 
> You can add high end amps to this as well.
> 
> ...


 
   
  Exactly, no need for an even O2. A CMOY with the JRC4556 opamp should do.


----------



## upstateguy

Quote: 





purrin said:


> Going back to coloration, *I find the O2 more colored and less transparent compared to the Dynalo and B22.*
> 
> Heck a CHA47 (paralleled CMOY) is more transparent and cheaper too.


 


  At what position is your volume set and what gain are you using on the O2, when you find it more colored than a Dynalo or B22?  What headphones were you using?
   
  I would like to reproduce your findings.


----------



## purrin

Quote: 





upstateguy said:


> At what position is your volume set and what gain are you using on the O2, when you find it more colored than a Dynalo or B22?


 

 Low gain on O2 from PWD source. Volume is set to to 10 position using HD800 and 12 11 position with HE500. I'm normalizing the output to the DAC so output levels are less hot.


----------



## zzffnn

Well, I have O2, Beta22, Lcd-2s and DT880s/600.
  Beta22 does sound better and provides bigger soundstage and better instrument separation. However, I would not say that O2 is more "colored" than Beta22. In view of the part cost and the power supply of Beta22 vs. O2, a direct comparison is not fair IMHO. The fact that we are comparing these two suggests that O2 is indeed very good.
  Not sure about CHA47 but I doubt it is better than O2, if both are on battery power.
  
  Quote: 





purrin said:


> Going back to coloration, I find the O2 more colored and less transparent compared to the Dynalo and B22.
> 
> Heck a CHA47 (paralleled CMOY) is more transparent and cheaper too.


----------



## sphinxvc

Quote:


zzffnn said:


> Well, I have O2, Beta22, Lcd-2s and DT880s/600.
> Beta22 does sound better and *provides bigger soundstage and better instrument separation*. However, I would not say that O2 is more "colored" than Beta22. In view of the part cost and the power supply of Beta22 vs. O2, a direct comparison is not fair IMHO. The fact that we are comparing these two suggests that O2 is indeed very good.
> Not sure about CHA47 but I doubt it is better than O2, if both are on battery power.


 

 I guess those things don't show up in measurements.


----------



## zzffnn

^ I agree, and I did not say "*bigger soundstage and better instrument separation"  *can show up in measurements (glad to learn if someone can teach me otherwise). Also I would love to see some measurement showing O2 is more or less "colored" than Beta22.


----------



## Satellite_6

I see you people are missing the point of the O2 entirely, but that's not surprising. . .


----------



## sphinxvc

So to extrapolate further, we can't really call the O2 a "wire with gain" either, because there is obviously some spatial information missing.


----------



## sphinxvc

Quote:


satellite_6 said:


> I see you people are missing the point of the O2 entirely, but that's not surprising. . .


 

 What are we missing here?  I thought the point was to "amplify".


----------



## Anaxilus

Pics


----------



## purrin

Quote: 





sphinxvc said:


> Quote:
> 
> I guess those things don't show up in measurements.


 

 Lots of stuff doesn't show up in measurements. What we have is this:
   

 Use our ears - high acuity (of course this is for for debate), but unreliable and subject to our moods and influence of dollars spent.
 Use measurements - of which current methods at best only hint at basic neutrality and clarity, but are unable to measure (correlating to human experience) other critical aspects: macro-dynamics; "sound-floor" - the floor where lowest level sounds are able to be reproduced; range, granularity, and continuity of dynamic contrasts, etc.
   
  I always though the point of audio reproduction was to try to make the recording sound more real. Measuring stuff that doesn't matter or inaudible to humans (i.e. noise floor at -134db, standard cheesy IMD test, etc.), isn't anything different from headphone manufacturers stating their headphones go up 54kHz.
   
  It's like trying to decide on whether a car is better for road racing based on 0-60 times and lateral G on a skidpad. It's probably best to test drive it to see how it handles under acceleration and braking in and out of large and small turns. And yes, the O2 is a nice Toyota that really isn't that much different from the Lexi. But it ain't no Acura NSX.
   
  As for pocket portability, the O2 fails. It's footprint is too large to slap under an iPhone.


----------



## sphinxvc

^
  Good post...I want to say more on your points, and the direction of this thread in general but I'm heading out the door right, hopefully I'll have some time later.  Anyway, for now, good post.


----------



## Twinster

Just a recommendation. You should cut the Gain resistors legs a bit before they short each others. 
	

	
	
		
		

		
			




  
  Quote: 





anaxilus said:


> Pics


----------



## sphinxvc

Quote: 





purrin said:


> Lots of stuff doesn't show up in measurements. What we have is this:
> 
> 
> Use our ears - high acuity (of course this is for for debate), but unreliable and subject to our moods and influence of dollars spent.
> ...


 

 On second thought, I don't feel like writing a paragraph, so I'll just say that the points written above extremely important to keep in mind while reading this thread and while "researching" the O2.  Some here are getting _carried away_ without sensible posts like these to temper the tide.


----------



## Shike

Quote: 





purrin said:


> It's like trying to decide on whether a car is better for road racing based on 0-60 times and lateral G on a skidpad. It's probably best to test drive it to see how it handles under acceleration and braking in and out of large and small turns. And yes, the O2 is a nice Toyota that really isn't that much different from the Lexi. But it ain't no Acura NSX.


 

 If we're talking numbers the O2 is more like a Skyline or heavily upgraded vette', while there's numerous others that have the price and low performance in an empirical sense.  Still, I think car analogies aren't suited for this in the least . . .
   
   
  Either way someone call me when these immeasurable amp phenomena can be proven in some fashion beyond basic sighted testing >_>


----------



## stv014

Quote: 





> Originally Posted by *purrin* /img/forum/go_quote.gif
> 
> I always though the point of audio reproduction was to try to make the recording sound more real. Measuring stuff that doesn't matter or inaudible to humans (i.e. noise floor at -134db, standard cheesy IMD test, etc.), isn't anything different from headphone manufacturers stating their headphones go up 54kHz.


 
    
  Anything can be measured if you have an accurate physical definition of what it actually is. And only once you can describe (from a scientific/engineering point of view) and measure an alleged problem in an amplifier is it possible to fix it without resorting to randomly throwing around expensive components, "opamp rolling", etc. in the hope that it will get better and not too many other issues will be introduced in the process.
   
  Quote:


> Originally Posted by *purrin* /img/forum/go_quote.gif
> 
> It's like trying to decide on whether a car is better for road racing based on 0-60 times and lateral G on a skidpad. It's probably best to test drive it to see how it handles under acceleration and braking in and out of large and small turns. And yes, the O2 is a nice Toyota that really isn't that much different from the Lexi. But it ain't no Acura NSX.


 
   
  Yet the design and engineering of modern cars is based on science, it is just that more - quantifiable and measurable - information is used than 0-60 times and lateral G on a skidpad.


----------



## upstateguy

Quote: 





purrin said:


> Low gain on O2 from PWD source. Volume is set to to 10 position using HD800 and 12 11 position with HE500. I'm normalizing the output to the DAC so output levels are less hot.


 

 What are you using to normalize?
   

  
  Quote: 





zzffnn said:


> Well, I have O2, Beta22, Lcd-2s and DT880s/600.
> Beta22 does *sound better* and provides bigger soundstage and better instrument separation. However, I would not say that O2 is more "colored" than Beta22. In view of the part cost and the power supply of Beta22 vs. O2, a direct comparison is not fair IMHO. The fact that we are comparing these two suggests that O2 is indeed very good.
> Not sure about CHA47 but I doubt it is better than O2, if both are on battery power.


 
   
  How does it "sound better"?  <--- just asking
  
   


  Quote: 





sphinxvc said:


> So to extrapolate further, we can't really call the O2 a "wire with gain" either, because *there is obviously some spatial information missing.  *


 

 Is there any proof of this?
   


  Quote: 





shike said:


> <snip> .
> 
> *Either way someone call me when these immeasurable amp phenomena can be proven in some fashion beyond basic sighted testing >_>*


 
   
  +1


----------



## mikeaj

Quote: 





shike said:


> Either way someone call me when these immeasurable amp phenomena can be proven in some fashion beyond basic sighted testing >_>


 

 Likewise, call me up too.  Or even, for that matter, if somebody comes up with measurable amp phenomena that are not at all predicted by the traditional metrics.
   
   
  Canned benchmarks of noise, IMD, etc. are really mostly for comparative purposes, both to other amps reviewed by the same person, as well as to amps reviewed by other people.  However, there should be a little deeper meaning than just the results themselves.
   
  It should be that low distortion by the traditional benchmarks is a fairly good measure of linearity.  Lower distortion -> higher linearity, closer to the mathematical ideal (which is not necessarily any particular person's sonic preference).  If you had a perfect LTI system, the impulse response would be perfectly described by the frequency response, through the inverse transform.  And the input/output relationship would be known for any input.  There would be zero distortion of any kind:  nothing added or missing compared to the original, so there's no possibility for any change that would result in differences of sound stage, macro-dynamics, range, granularity, or anything else--at least when compared to the signal given to the amp by the source.
   
  Furthermore, if the frequency response were flat over the audible range, then for any input containing only those frequencies, the output would be exactly the same as the input except for a flat scaling factor.  In practice the input will also contain some noise, including ultrasonic noise that gets filtered out somewhat.
   
  Also it's not perfectly linear in reality.  The benchmarks just imply that it's pretty close (and that some other devices are even closer), so the behavior should be close to what a mathematically ideal LTI system should be like, under these operating conditions.


----------



## Naim.F.C

The funny thing about this thread is that even NwAvGuy himself believes the O2 can be improved upon, and only offers his $500 prize blind test challenge with comparisons with the O2 amp vs other mid-tier amps up to $500 value only.
   
  He clearly states that there are other very accomplished amps and manufacturers out there, but that they charge a hefty premium (he brings up Violectric quite often as an example of one getting it right, but still charging too much). Add to that, he is currently developing a better amp (ODA, Objective Desktop Amp) which also throws this notion that there's no difference between amps, no need for one full stop etc, clear in the water.


----------



## purrin

Quote: 





stv014 said:


> Yet the design and engineering of modern cars is based on science, it is just that more - quantifiable and measurable - information is used than 0-60 times and lateral G on a skidpad.


 

 And they also test drive on tracks to fine tune the suspension and handling characteristics.
   
  For nwaguy (or at least his more blind followers) to suggest that he is the only one (or the select all-knowing few) who designs amps using bench tests is preposterous. I've seen test equipment and 'scopes on the benches of all the well known reputable amp builders. Not only do the good builders test, but they listen.


----------



## purrin

Quote: 





upstateguy said:


> What are you using to normalize?
> 
> 
> How does it "sound better"?  <--- just asking
> ...


 
  Is there any proof that the O2 sounds as good as discrete designs such as the Dynalo and B22? The maker is the one writing the manifesto and making these claims. I think the burden of proof is upon him. Where are the measurements that show the O2 is as "detailed" as the discrete designs?


----------



## upstateguy

Quote: 





naim.f.c said:


> The funny thing about this thread is that even NwAvGuy himself believes the O2 can be improved upon, and only offers his $500 prize blind test challenge with comparisons with the O2 amp vs other mid-tier amps up to $500 value only.
> 
> He clearly states that there are other very accomplished amps and manufacturers out there, but that they charge a hefty premium (he brings up Violectric quite often as an example of one getting it right, but still charging too much). Add to that,* he is currently developing a better amp (ODA, Objective Desktop Amp) which also throws this notion that there's no difference between amps, no need for one full stop etc, clear in the water.*


 

 I was under the impression that the desktop amp wouldn't *sound* any better than the portable.  Is this incorrect?
   
  OTOH, I wouldn't mind a *better* version that includes heavy duty jacks and switches, a line out, preamp out and 2 inputs.


----------



## mikeaj

The ODA is mostly about having a larger form factor, 6.35mm jacks, things like power cords on the back rather than everything on the front, a daughterboard option for a DAC, relays to eliminate the turn on/off transients (which are already small) and offer additional headphone protection, and so on.  There's no claim about audibly improving sound quality with this version (unless you count using the DAC)--and there really shouldn't be since the down-and-dirty part of the amp is going to be the same, if I'm reading between the lines correctly.  A different PCB layout and possibly very slightly improved power supply performance, may make a small measurable improvement in overall performance.


----------



## upstateguy

Quote: 





purrin said:


> Is there any proof that the O2 sounds as good as discrete designs such as the Dynalo and B22? The maker is the one writing the manifesto and making these claims. I think the burden of proof is upon him. *Where are the measurements that show the O2 is as "detailed" as the discrete designs?*


 


  That's a silly statement.  You can just as well ask where are the measurements that show the O2 is not as detailed as discrete designs?


----------



## Naim.F.C

Put it this way, if there were no audible upgrades available to the current O2 design, why would his challenge be to amps costing only up to $500 and not _*any*_ amp of _*any*_ value? Clearly NwAvGuy recognises there is an audible difference (even if it is slight) the higher up the ladder you go.


----------



## purrin

Quote: 





upstateguy said:


> That's a silly statement.  You can just as well ask where are the measurements that show the O2 is not as detailed as discrete designs?


 
   
  Our ears - the ultimate measurement device.
   
  EDIT: On that note - so you agree that there is no measurement that scientifically proves or indicates the O2 is as detailed as the Dynalo or B22?


----------



## Anaxilus

Is there proof that one headphone has better separation or soundstage than another?  Wake me up when you find it.  Till then it's all in your head or most likely voodoo.
   


Spoiler: Rant



 
  GTR is a bad example, it's $100K.  Evo + $20K in mods is better but that's not an O2 either.  O2 would be like a beater Honda CRX w/ mods tuned for the track and barely streetable.  Speaking of cars I find it funny that person 'X' uses a Miata as an example w/ what looks like 17" chromed wheels.  Physics FAIL!
   
  Anyway, the point purrin was making and is obviously lost on some, is that yes science is involved in cars and amps.  That has nothing to do w/ putting measurements and benchmarks first.  You can make a dyno queen pumping out 1500hp that falls apart on the way home and can't turn a corner.  You can target skidpads or acceleration numbers but that won't tell you how the package is balanced or even if it's capable in real world conditions or even livable for that matter.  I could build you a car to blast every benchmark out of the water and do it for less than any manufacturer, you wouldn't want to drive it or you'd probably kill yourself.  How does that relate to amps?  Benchmarks are nice, useful things.  Are they the whole story?  No.  The only thing we know is that we don't know everything.  We may know a lot about some things but that's not the same and is no excuse to run around smacking down or being condescending to others when you think you've got it all figured out.


----------



## Shike

Quote: 





purrin said:


> Our ears - the ultimate measurement device.
> 
> EDIT: On that note - so you agree that there is no measurement that scientifically proves or indicates the O2 is as detailed as the Dynalo or B22?


 


  Judging from the measurements, assuming nothing is deficient (let's see them on a bench first) then neither is going to be more accurate or inaccurate.  You're going to need proof of your claims, and saying "but I heard it" isn't enough.  If that was the case, would you immediately believe anyone that "saw a ghost"?  Equally, if they told you the problem was with your eyes or ghost catching technique would you believe them?  Furthermore, if they claimed the proof is upon you to disprove ghosts could you do it?
   
  See what you're asking us to do for a moment, register it, and reconsider your position for a moment.  Considering the above, your statements are both unreasonable and dare I say illogical.


----------



## sphinxvc

USG, I don't think I can offer you any "proof" when the whole contention was that something like imaging (for example) doesn't have metrics for it (yet).  I find it ironic that you're asking for "evidence."


----------



## maverickronin

Quote: 





naim.f.c said:


> The funny thing about this thread is that even NwAvGuy himself believes the O2 can be improved upon, and only offers his $500 prize blind test challenge with comparisons with the O2 amp vs other mid-tier amps up to $500 value only.
> 
> He clearly states that there are other very accomplished amps and manufacturers out there, but that they charge a hefty premium (he brings up Violectric quite often as an example of one getting it right, but still charging too much). Add to that, he is currently developing a better amp (ODA, Objective Desktop Amp) which also throws this notion that there's no difference between amps, no need for one full stop etc, clear in the water.


 

 Err...No.
   
  The one limited by price is for anything that measures better.  The ABX listening test is _not _limited by price and is to demonstrate that the O2's distortion levels have reached the point of transparency and you can't actually hear that something else has lower distortion.  The desktop version is just about ergonomics so everything isn't crammed on to one panel.
   
  Of course its not perfect.  It could use some more power to handle those last few fringe cases.
  
  Quote: 





purrin said:


> For nwaguy (or at least his more blind followers) to suggest that he is the only one (or the select all-knowing few) who designs amps using bench tests is preposterous. I've seen test equipment and 'scopes on the benches of all the well known reputable amp builders. Not only do the good builders test, but they listen.


 

 Well he seems to have demonstrated that some people don't test their amps with much more than RMAA and an oscilloscope...


----------



## purrin

Quote: 





shike said:


> Judging from the measurements, assuming nothing is deficient (let's see them on a bench first) then neither is going to be more accurate or inaccurate.  You're going to need proof of your claims, and saying "but I heard it" isn't enough.  If that was the case, would you immediately believe anyone that "saw a ghost"?  Equally, if they told you the problem was with your eyes or ghost catching technique would you believe them?  Furthermore, if they claimed the proof is upon you to disprove ghosts could you do it?
> 
> See what you're asking us to do for a moment, register it, and reconsider your position for a moment.  Considering the above, your statements are both unreasonable and dare I say illogical.


 
   
  My claims are only this:_ I hear X. Look past meaningless canned measurements and listen for yourself._
   
  The claims here seem to be: _There is no difference between the O2 and more expensive discrete component amps such as the B22 or Dynalo based on canned measurements of just the O2. Because of this, I'm not even going to bother listening with my ears to the other amps because the canned measurements of the O2 (just the O2) are awesome._


----------



## sphinxvc

Quote:


anaxilus said:


> The only thing we know is that we don't know everything.  We may know a lot about some things but that's not the same...


 

 Thank you - it's almost like some forget the purpose of science is to better understand the world, not the other way around.
   
  What's interesting is I see Jason of Schiit hanging out here.  It'd be interesting to hear his input on this.


----------



## Satellite_6

Quote: 





purrin said:


> Is there any proof that the O2 sounds as good as discrete designs such as the Dynalo and B22? The maker is the one writing the manifesto and making these claims. I think the burden of proof is upon him. Where are the measurements that show the O2 is as "detailed" as the discrete designs?


 

 How about the measurements that show that the O2's levels of distortion are _a fraction_ of what is considered audible distortion. Do they not count? I would imagine that would make for the most detailed sounding amp possible. 
   
  The only counter argument is ignoring the numbers and supposing that there are magical immeasurable forces at work, as others have said. 
   
  You have to fight numbers with numbers not feelings. So until these magical forces can be somehow quantified this side of the argument is simply irrational.


----------



## purrin

Quote: 





sphinxvc said:


> Quote:
> 
> Thank you - it's almost like some forget the purpose of science is to better understand the world, not the other way around.
> 
> What's interesting is I see Jason of Schiit hanging out here.  It'd be interesting to hear his input on this.


 
   
  Exactly, and this was always my approach with the headphone measurements. What do I observe, or hear? How do I measure. What do I measure? How do I present or visualize the data? Do the results concur with what I observe? How do I refine the measurement and visualization process, ad. inf.
   
  Even then, I would be the first one to acknowledge that the CSDs I crank out are very limited and only tell a part of the picture.


----------



## Grev

Quote: 





negakinu said:


> My point exactely. Try putting three similar-ish midrange amps next to each other, wear a blindfold and let someone else mix 'em up. Try to identify them. It's a lot harder than you'd think, especially when you read all these superlative descriptions people use to describe them.


 


  Also play music they are unfamiliar with.


----------



## purrin

Quote: 





satellite_6 said:


> You have to fight numbers with numbers not feelings. So until these magical forces can be somehow quantified this side of the argument is simply irrational.


 

 First step is to understand what the numbers mean. As you mentioned: "fraction of audible distortion". This would indicate that we are measuring the wrong thing. Why are we measuring things that can't be heard? As I said earlier, who cares if a manufacturer says their headphone goes up to 54kHz.
   
  So I repeat, where is the scientific data that shows the O2 sounds as transparent as the discrete designs?
   
   



negakinu said:


> My point exactely. Try putting three similar-ish midrange amps next to each other, wear a blindfold and let someone else mix 'em up. Try to identify them. It's a lot harder than you'd think, especially when you read all these superlative descriptions people use to describe them.


 
   
  This I do not disagree with. Most middle-tier (meaning 90%) amps are kinda _bleh_, especially in terms of transparency. Unless you want to shell out over 1k USD, stick with the O2 or desktop CMOY with a good power supply.


----------



## mikeaj

Quote: 





purrin said:


> First step is to understand what the numbers mean. As you mentioned: "fraction of audible distortion". This would indicate that we are measuring the wrong thing. Why are we measuring things that can't be heard? As I said earlier, who care if a manufacturer says their headphone goes up to 54kHz.
> 
> So I repeat, where is the scientific data that shows the O2 sounds as transparent as the discrete designs?


 

 And you measure those things (1) for comparative purposes and (2) because they indicate other things, as I mentioned before.  Any response to that?
   
  Performance aside, what would you describe as the difference between a design that uses op amps and a discrete design?  You have RLC elements and individually nonlinear electronics components constructed from doped silicon with both, just in different configurations (circuit layouts, size).  Why would this be a distinguishing factor in sound quality?  (in amount of power or supply rails that can be handled in practice, sure)


----------



## purrin

Quote: 





mikeaj said:


> Performance aside, what would you describe as the difference between a design that uses op amps and a discrete design?  You have RLC elements and individually nonlinear electronics components constructed from doped silicon with both, just in different configurations (circuit layouts, size).  Why would this be a distinguishing factor in sound quality?  (in amount of power or supply rails that can be handled in practice, sure)


 
   
  That's a good question. Open up an amp with discrete components and you see all the parts and layout - pretty simple. I'm not sure that's the case with op-amps. I've noted some manufacturers hide the design / schematics for their top-tier op-amps (e.g. LM4562) . Even when the designs are indicated in the data sheet, it's my understanding it's a very simplified representation of what's actually implemented on the die. I would have to defer this question to those who design semi-conductors or are experts in op-amp design.


----------



## Shike

Quote: 





purrin said:


> My claims are only this:_ I hear X. Look past meaningless canned measurements and listen for yourself._
> 
> The claims here seem to be: _There is no difference between the O2 and more expensive discrete component amps such as the B22 or Dynalo based on canned measurements of just the O2._


 


  Really?  It sounds like your claim is similar to  "go chase ghosts for yourself because I know they exist/saw one".  We aren't going to do the chasing for you, I've heard more expensive amps besides the O2 and couldn't tell them apart (after the review I've had hands on with M3 and gilmore amps + some others).  This leaves the excuse that the problem is my ears.  Thus, the proof of burden is on the one claiming a difference, because otherwise we have a conflict of interest or the "tin ears" scape' goat.
   
  This is why we can't provide you with evidence of it being as detailed, because you're wanting us to prove the effective non-existence of something.  It's like trying to disprove God, and using the lack of evidence as evidence contrary.  Unless you took our words over yours that there isn't a difference (unlikely, because you've claimed to here the existence of a difference and argue for it) then it's up to you to prove that one actually exists.
   
  Prove to us the wrong thing is being measured.  This is an amp based on empirical evidence with the primary audience being those that value quantifiable performance first and foremost.  If you want your argument taken seriously, then you need to provide some serious evidence.  For those of us that want an amp based on quantifiable performance, you're going to have to prove it's inferiority using the same metric.  If you feel it's impossible to do this, then it's probably best to up and drop it because you aren't going to sway us based on what you've said so far.
   
  Hopefully this is crystal clear as I don't know how to make it simpler at this point.


----------



## Satellite_6

Quote: 





purrin said:


> First step is to understand what the numbers mean. As you mentioned: "fraction of audible distortion". This would indicate that we are measuring the wrong thing. Why are we measuring things that can't be heard? As I said earlier, who cares if a manufacturer says their headphone goes up to 54kHz.
> 
> So I repeat, where is the scientific data that shows the O2 sounds as transparent as the discrete designs?


 

 Why are we measuring things that can't be heard? To ensure they can't be heard in order to ensure absolute transparency. :|  
   
  The O2's THD is *~.002%*, IMD is simlar. What else is there (in terms of detail or transparency?) 
   
  Really, what else am I missing, someone tell me? I am not an expert, but I just cannot believe in something that has no evidence behind it.
   
  The "it" being that a more expensive amp can be more transparent than an amp designed to be _completely_ transparent with numbers to back it up. BTW, the whole point of his blog is to disprove this "it" and as far as I know he does not recognize anything of the sort. 
   
   
"Put it this way, if there were no audible upgrades available to the current O2 design, why would his challenge be to amps costing only up to $500 and not _*any*_ amp of _*any*_ value? Clearly NwAvGuy recognises there is an audible difference (even if it is slight) the higher up the ladder you go." - Naim.F.C


----------



## Shike

Those claiming NwAvGuy has a limit on what amps can be used in the O2 DBT:
   
  "Let’s raise the bar even further for all the subjective guys. For any amp that measures sufficiently well into the desired load (reasonably close to the specs outlined in the O2 Design Principals), _regardless of cost_, I’ll put the O2 up against it with any popular headphones within its drive capabilities."
   
  That's the beginning sentence of his challenge.  I see nothing in regards to limits of what amps can be used in regards to cost.  The $500 is in regards to how much is paid to charity.


----------



## mikeaj

Quote: 





purrin said:


> That's a good question. Open up an amp with discrete components and you see all the parts and layout - pretty simple. I'm not sure that's the case with op-amps. I've noted some manufacturers hide the design / schematics for their top-tier op-amps (e.g. LM4562) . Even when the designs are indicated in the data sheet, it's my understanding it's a very simplified representation of what's actually implemented on the die. I would have to defer this question to those who design semi-conductors or are experts in op-amp design.


 
   
  Yes, the schematic given for a more complicated op amp circuit is just a user's guide, a simplification of the "equivalent" key parts of the topology.  It tells you general system characteristics and maybe how it will interface with components you use with the op amp, not so much about the entire internal circuit composition, which would be much more difficult to read and understand.  For some of these systems, if you printed out the entire schematic, even the ones who designed them would struggle to understand what's being represented.


----------



## idletime1213

I love basketball. It's my favorite sport in the whole world, and I think it's the perfect blend of excitement and intensity. it has the simplest statistics to dissect, and you can get a good feel of who the best players are in the world just by glancing at statistics.
   
  Well, basically there's this guy named Bill Russell. By every measurable metric, he shouldn't rank as one of the greatest players in NBA history. He was a subpar scorer, a mediocre shooter. He was an excellent rebounder and defender, but nothing about him stood out. This man won 5 MVPs and 11 championships and by the time he retired in 1970, nearly everybody agreed that this is the greatest player ever (until MJ arrived).
   
  40 years later, I see a large gap between the opinions of those who saw him and those who never did. Those who didn't point out the statistical inadequacies he had compared to contemporaries like Wilt Chamberlain or Oscar Roberston. Those people who saw him, of the older generation, try to point out that what made Russell great cannot be measured in statistical value. They pointed out that such things like leadership, team defense, nitty gritty plays cannot be measured statistically, that one had to see him play to realize why the man won 11 championships - by far the greatest winner in any sport. How could a man who wasn't outstanding statistically, win so much with a team that wasn't that much better than everyone else's? That's why they call it *intangibles*, because they go beyond what you can see in a boxscore. That's why it's so hard to quantify Bill Russell in a modern world.
   
  The debate rages on today.


----------



## Naim.F.C

Thanks for correcting me above. Seems I may have miss-read. I assumed the challenge was only for amps up to $500 in value. Didn't realise it wasn't, nor that it was subject to any op amps.
   
  I can't wait to conduct my own listening tests between my amps. I actually own the O2, which currently I use exclusively with the LCD-2, since it doesn't seem to give as much warmth as the ALO Continental with my T1's. I find the T1's are a little dryer with the O2's. The high's have a sort of grain to them.
   
  If the O2 is neutral, this leads me to believe the Continental is intentionally coloured or smoother. Likewise, I find the LCD-2's aren't as quite as clear with the Continental as the O2. I wonder if this could have anything to do with sensitivity or ohm's of the cans in relation to the amps?
   
   
  EDIT: Just to clarify, the above testing was iPhone > LOD > amp, so it's possible once I add one of my DAC's to the equation it could change things.


----------



## purrin

Quote: 





shike said:


> Really?  It sounds like your claim is similar to  "go chase ghosts for yourself because I know they exist/saw one".  We aren't going to do the chasing for you, I've heard more expensive amps besides the O2 and couldn't tell them apart (after the review I've had hands on with M3 and gilmore amps + some others).  This leaves the excuse that the problem is my ears.  Thus, the proof of burden is on the one claiming a difference, because otherwise we have a conflict of interest or the "tin ears" scape' goat.


 

 So I assumed you heard the amps in question and heard no difference? That's OK and fine by me. I do think it's a little self-righteous to tell _many _others who've designed, built, and listened to the discrete designs mentioned that it's all in their heads.
   


  Quote: 





satellite_6 said:


> Why are we measuring things that can't be heard? To ensure they can't be heard in order to ensure absolute transparency. :|
> 
> The O2's THD is *~.002%*, IMD is simlar. What else is there (in terms of detail or transparency?)
> 
> Really, what else am I missing, someone tell me? I am not an expert, but I just cannot believe in something that has no evidence behind it.


 
   
  What you are missing is that THD or IMD does not measure detail and transparency. Do you know what 2% THD sounds like for a 100Hz signal at 90db? I don't - because that's not enough information. In this case for example, I would then ask: What comprises the THD? Is the second order distortion higher than third order (or vice versa), because these types of distortion sound totally different to the ear.
   
  And then it gets more complex. What about non-linear distortion (THD + IMD) for more complex signals (say 3 tones, or 5 tones). Then things get really hairy and complex. Music of course is even more than 3 or 5 tones, and certainly not steady state.
   
  That being said, I do hear the lack of distortion of the O2. It's very very clean sounding up and down the volume range.


----------



## Shike

Quote: 





idletime1213 said:


> I love basketball. It's my favorite sport in the whole world, and I think it's the perfect blend of excitement and intensity. it has the simplest statistics to dissect, and you can get a good feel of who the best players are in the world just by glancing at statistics.
> 
> Well, basically there's this guy named Bill Russell. By every measurable metric, he shouldn't rank as one of the greatest players in NBA history. He was a subpar scorer, a mediocre shooter. He was an excellent rebounder and defender, but nothing about him stood out. This man won 5 MVPs and 11 championships and by the time he retired in 1970, nearly everybody agreed that this is the greatest player ever (until MJ arrived).
> 
> ...


 

  
  This isn't a valid comparison, because the performance of players will vary in-spite of average statistical performance.  For all we know they choked when facing the statistically inferior team.  The difference here between amps and these teams is one is likely to have consistent performance versus basketball players having varied performance.  It would be like one day comparing a broken benchmark to another amp then going "AHA! This amp is clearly better than the benchmark now!".

  
  Quote: 





purrin said:


> So I assumed you heard the amps in question and heard no difference? That's OK and fine by me. I do think it's a little self-righteous to tell _many _others who've designed, built, and listened to the discrete designs mentioned that it's all in their heads.


 

 I haven't said anything is in your head, though it's very possible.  I HAVE asked for evidence of your claim that it's different in a quantifiable form (yes, this means numbers where your influence in minimized on the outcome).  The normal stance in testing is assuming a null until otherwise proven.  The current set of audio electronics understanding shows that within a certain set of parameters these amps will sound the same.  You're saying these findings are wrong, but have yet to provide evidence.  Your entire argument has been "but you're wrong, I hear X, Y, and Z" and then ask for evidence that there isn't difference which makes no sense because it can never be good enough in this case.  On the other hand the potential of a difference CAN be proven _if_ it exists.
   
  Basically: If I told you Santa Claus is alive and kicking, would you believe me?  Surely not (I hope), but then I ask you to disprove his existence . . . how could you possibly do such a thing?  That's what you've been asking us to do for so many posts.  You've run up to us saying these sound different.  We say "no they don't", but then you want us to prove that a difference doesn't exist.  Then you throw a tantrum saying we're mindlessly parroting or calling you crazy.
   
  Quote: 





naim.f.c said:


> Thanks for correcting me above. Seems I may have miss-read. I assumed the challenge was only for amps up to $500 in value. Didn't realise it wasn't, nor that it was subject to any op amps.
> 
> I can't wait to conduct my own listening tests between my amps. I actually own the O2, which currently I use exclusively with the LCD-2, since it doesn't seem to give as much warmth as the ALO Continental with my T1's. I find the T1's are a little dryer with the O2's. The high's have a sort of grain to them.
> 
> If the O2 is neutral, this leads me to believe the Continental is intentionally coloured or smoother. Likewise, I find the LCD-2's aren't as quite as clear with the Continental as the O2. I wonder if this could have anything to do with sensitivity or ohm's of the cans in relation to the amps?


 

 The Continental if I'm not mistaken is an OTL design, which means it's likely to have a larger output impedance.  This can definitely modify frequency response of headphones by creating a voltage divider depending on the headphones impedance in regards to frequency.  Read NwAvGuy's write-up on why output impedance is important, or if you don't trust him I'm sure there's articles on Google that can explain it by now ^_^


----------



## mikeaj

Quote: 





idletime1213 said:


> I love basketball. It's my favorite sport in the whole world, and I think it's the perfect blend of excitement and intensity. it has the simplest statistics to dissect, and you can get a good feel of who the best players are in the world just by glancing at statistics.
> 
> Well, basically there's this guy named Bill Russell. By every measurable metric, he shouldn't rank as one of the greatest players in NBA history. He was a subpar scorer, a mediocre shooter. He was an excellent rebounder and defender, but nothing about him stood out. This man won 5 MVPs and 11 championships and by the time he retired in 1970, nearly everybody agreed that this is the greatest player ever (until MJ arrived).
> 
> ...


 

 That's pro basketball, which is worlds apart from the input/output relationship of an audio amplifier.  "Who's the best basketball player?" is a much different question than "how different is one amp compared to another?"  If the output is supposed to be 1.93571 at time 4.351 and it's 1.93589 instead, we can score that.  Saying something is the "best" is always subject to a lot of interpretation over what "best" means, context, and so on.  
   
  What some people are saying is that the traditional stats aren't everything that matters.  As one example, huge points and rebounds guys with lots of production can actually be quite mediocre players because of low efficiency, stealing actions that others would have gotten, and so on.  That's the primary reason why I'd say that traditional basketball stats are much less indicative than traditional audio metrics.  Probably +/- and other more advanced metrics probably correlate better with how good a player actually is.  For many legendary players, the teammates are probably better than they are given credit for, at least relative to the other players in the league at a given time.  Also, some people act as if championships and success are perfect indicators of ability.  It's random.  11 championships could have been 8 or 12 or something else, with different luck.  This doesn't really have much to do with the audibility of certain effects and measuring amplifiers.
   
   
   
   


> Originally Posted by *purrin* /img/forum/go_quote.gif
> 
> I do think it's a little self-righteous to tell _many _others who've designed, built, and listened to the discrete designs mentioned that it's all in their heads.


 
   
  I'd almost never trust listening impressions from people who build things or design them, since they've got to be attached.  But there's definitely reasons to go discrete, such as (1) more power output possible even though most people probably won't need it, (2) better marketing.  In theory you can also get measurably better performance which some of us would clearly argue is way past the point of audibility for humans.  If you want to best the O2's performance using stock op amps and buffers, you end up with a design like The Wire.  If you want something even better for a particular application, maybe it's possible with your own topology, rather than more general-use parts.
   
  Even more importantly, from a headphone amp designer's point of view, _using op amps is relatively boring and easy_.  In general, particularly if there's not a confounding challenge like portability, size, or price, doing it the easy way is no fun, with no feeling of accomplishment at the end.  People want to innovate.


----------



## Naim.F.C

Can anyone knowledgable on output impedance etc educate me on what sort of specifications would best suit the T1's? And whether by default design, the O2 is more likely to match with the LCD-2 over the T1 based on such factors. I'm genuinely curious.


----------



## maverickronin

Quote: 





shike said:


> The Continental if I'm not mistaken is an OTL design, which means it's likely to have a larger output impedance.  This can definitely modify frequency response of headphones by creating a voltage divider depending on the headphones impedance in regards to frequency.  Read NwAvGuy's write-up on why output impedance is important, or if you don't trust him I'm sure there's articles on Google that can explain it by now ^_^


 

 I'm pretty sure its a hybrid with a transistor output stage.


----------



## Anaxilus

Quote: 





shike said:


> This isn't a valid comparison


 

  Yes, it only makes sense to talk about ghosts or Santa Claus in relation to audio electronics.  You should stop appealing to logic in the deductive sense you are misapplying it because the fallacies are racking up quickly.


----------



## Anaxilus

Quote: 





maverickronin said:


> I'm pretty sure its a hybrid with a transistor output stage.


 

 Yup.  Still, the Continental is largely irrelevant to the real discussion that purrin and mikeaj have been having.  But it's nice to have more data and input to evaluate.  That's how I feel, I'm sure others disagree.


----------



## Jzbass25

I haven't read every post on this thread so I apologize if it was answered but I couldn't find it with the search. Can anyone compare the  Zo2 vs the O2 vs. maybe even a maverick D1. I have been thinking about the O2 but I don't have a dedicated dac yet and I'm not exactly sure if I need/want a portable rig at this moment so that's why I added the D1 to the list. I can make a new thread if it is too off topic.


----------



## Naim.F.C

Specs of the O2 and ALo Continental.
   
*ALO* _(which I feel sounds better with the T1, a bit smoother and darker, more boomy, unless it's in my head lol)._
   
Tube type; one Raytheon 6111 NOS tube
Battery: Lithium-Polymer 
Battery Play Time: Approximately 6 - 7 hours per charge 
Recharge Time: Approximately 3-4 hours 
Frequency Response: 40Hz-20KHz +/- 1dB 
Signal-to-Noise Ratio: >100dB 
Total Harmonic Distortion: 1% 
Stereo Crosstalk: >85dB @ 1KHz 
Input Impedance 30K ohms Output 
Output 300mW@ 32 ohms 
Dimensions: 120mm (L) x 72mm (W) x 27mm (H)
One Year Limited Warranty
   
---
   
*Epiphany O2* _(Which I feel sounds better with the LCD-2. First listen I felt like it was cleaner and had a bit more punch)_
   

 THD @ 1kHz: 0.0017%
 Noise level (ref 400mV): -105dB
 IMD: 0.001%
 Power output @ 33Ω : 641mW
 Crosstalk: 65dB
 Channel balance 0.6dB
 Battery life: 8 hours
   
   
Given the T1 and LCD-2 specs, someone please help me make sense of output impedance compatibility. 
   
T1: Impedance @ 1kHz: 600
LCD-2: Impedance @ 1kHz: 50 Ohms
   
   
Thanks for the responses people. Just trying to educate myself on the science behind all this lol.


----------



## purrin

Quote: 





mikeaj said:


> Even more importantly, from a headphone amp designer's point of view, _using op amps is relatively boring and easy_.  In general, particularly if there's not a confounding challenge like portability, size, or price, doing it the easy way is no fun, with no feeling of accomplishment at the end.  People want to innovate.


 

 Yup, it's like Legos. The O2 really isn't all that different from other DIY starter chip amps (other than the nice measurements to go with it and having the volume pot between the stages - presumably for lower noise.)
   
  I suggest to all O2 owners that they swap the input op-amp just for kicks - see if sounds different - that is hear the different variations of "wire-with-gain." Need to becareful of the replacement op-amps' voltage swing, but most likely won't be an issue with a portable source.
   
   


mikeaj said:


> I'd almost never trust listening impressions from people who build things or design them, since they've got to be attached.


 
  
 Yup. This is one indicator of who you can trust. The really good amp makers tend to be evasive when asked how their amps sound. They don't make claims that their amp sounds as good as amps costing twice, five times, or ten times as much. They don't dedicate entire blogs on why their amps measure good.


----------



## Anaxilus

Quote: 





jzbass25 said:


> I haven't read every post on this thread so I apologize if it was answered but I couldn't find it with the search. Can anyone compare the  Zo2 vs the O2 vs. maybe even a maverick D1. I have been thinking about the O2 but I don't have a dedicated dac yet and I'm not exactly sure if I need/want a portable rig at this moment so that's why I added the D1 to the list. I can make a new thread if it is too off topic.


 

 I only have the ZO original but it's a device from the other side of the spectrum from the O2.  The O2 is supposed to remove itself from the source upstream while the ZO shapes sound using programmed contours or signatures.  One is portable, the other is transportable.  The ZO2 is weaker than my ZO and will drive less phones adequately while the O2 has greater driving capacity than either especially w/ headphones.


----------



## Shike

Quote: 





anaxilus said:


> Yes, it only makes sense to talk about ghosts or Santa Claus in relation to audio electronics.  You should stop appealing to logic in the deductive sense you are misapplying it because the fallacies are racking up quickly.


 

  
  Nice posturing you're doing.  The point I was making to purrin is that he holds the _burden of proof_.  I'm sure you've heard of it.  I used fictitious items to drive home why his demands were logically unreasonable at best and disingenuous at worst (quite like your post).
   
  In regards to amps, they don't vary the extent that a professional performer may from day to day . . . unless they were built wrong not operating properly.  Are you arguing contrary to this point?
   
  Speaking of fallacies, I see you enjoy partaking in poisoning the well right?  Well, I'd like you to point out what fallacies I've made exactly pertaining to these two instances too.

 @maverickronin
   
  I see, I only checked ALO's site and didn't see anything besides the tubes there.
   
  @Purrin
   
  Changing the opamps could cause oscillation or other effects that would be audible.  It doesn't make sense unless you can insure that the circuit is stable with the opamp in question.
   
  Also, this:
   
   
  Quote: 





> Yup. This is one indicator of who you can trust. The really good amp makers tend to be evasive when asked how their amps sound. They don't make claims that their amp sounds as good as amps costing twice, five times, or ten times as much. *They don't dedicate entire blogs on why their amps measure good.*


 
   
 ಠ_ಠ


----------



## mikeaj

Quote: 





purrin said:


> Yup, it's like Legos. The O2 really isn't all that different from other DIY starter chip amps (other than the nice measurements to go with it and having the volume pot between the stages - presumably for lower noise.)
> 
> I suggest to all O2 owners that they swap the input op-amp just for kicks - see if sounds different - that is hear the different variations of "wire-with-gain." Need to becareful of the replacement op-amps' voltage swing, but most likely won't be an issue with a portable source.


 

 Well more properly it should be 1) build two O2s, one with a different op amp for the gain stage, 2) get an ABX box, and 3) blind compare, but yeah.
   
  NJM2068 is what was used.  There are a few measurements on the blog for what happens if you use NE5532, OPA2134, OPA2227, OPA2277, LM4562, and TL072 instead, so surely those can be used as alternatives.  NE5532 has a little better distortion performance at high gains, while the others are mostly just worse except for OPA2277 having lower power consumption.
   
  By "worse" I mean an expensive audio analyzer can pick it up, not necessarily human hearing, so regardless...still something to do.


----------



## maverickronin

Quote:


purrin said:


> Yup. This is one indicator of who you can trust. The really good amp makers tend to be evasive when asked how their amps sound. They don't make claims that their amp sounds as good as amps costing twice, five times, or ten times as much. They don't dedicate entire blogs on why their amps measure good.


 

 Because Creative Commons is the choice of greedy unscrupulous bastards everywhere...


----------



## purrin

Quote: 





maverickronin said:


> Quote:
> 
> Because Creative Commons is the choice of greedy unscrupulous bastards everywhere...


 

 Some people are greedy for money. Others for attention.


----------



## purrin

Quote: 





shike said:


> @Purrin
> 
> Changing the opamps could cause oscillation or other effects that would be audible.  It doesn't make sense unless you can insure that the circuit is stable with the opamp in question.


 
   
  Just pick a stable op-amp that will work with the lowest gain and the circuitry in the O2. In other words, read the spec sheet. Looking at O2 schematic and layout, I wouldn't expect the more stable commonly used op-amps to oscillate. In any case, it's not like the amp will explode if you put a sensitive op-amp like the OPA637 in it.
   
   


mikeaj said:


> Well more properly it should be 1) build two O2s, one with a different op amp for the gain stage, 2) get an ABX box, and 3) blind compare, but yeah.
> 
> NJM2068 is what was used.  There are a few measurements on the blog for what happens if you use NE5532, OPA2134, OPA2227, OPA2277, LM4562, and TL072 instead, so surely those can be used as alternatives.  NE5532 has a little better distortion performance at high gains, while the others are mostly just worse except for OPA2277 having lower power consumption.
> 
> By "worse" I mean an expensive audio analyzer can pick it up, not necessarily human hearing, so regardless...still something to do.


 

  I've actually already rolled a few including some of the above you mentioned. They all do sound different. I wonder which op-amp would be considered wire-with-gain.


----------



## Jzbass25

Quote: 





anaxilus said:


> I only have the ZO original but it's a device from the other side of the spectrum from the O2.  The O2 is supposed to remove itself from the source upstream while the ZO shapes sound using programmed contours or signatures.  One is portable, the other is transportable.  The ZO2 is weaker than my ZO and will drive less phones adequately while the O2 has greater driving capacity than either especially w/ headphones.


 


  Very true, does the Zo2 have a dac built in? I am almost leaning towards just doing the maverick D1 but all the other options seem so good! Also I'm on the fence because I don't really need much amping with my current headphones...but this forum has made me want some more gear... haha


----------



## Digital-Pride

Whether or not this amp(O2) sounds the same or better than other more expensive options, it gives users an affordable quality amp that works well almost any headphone.  I'd say that is the most important aspect of this amp.  I know it is for me.


----------



## mikeaj

Quote: 





purrin said:


> I've actually already rolled a few including some of the above you mentioned. They all do sound different. I wonder which op-amp would be considered wire-with-gain.


 

 Did you have a second stock O2 to compare to for quick A/B?  If yes, was it compared blind?
   
  If the answer is "no" to either, I hate to be so dismissive in such a boring and repetitive way, but this goes again into the pile of "personal anecdotes that don't pass a bare minimum of experimental controls" evidence.  i.e. of limited but non-zero use.  We have lots of this already in general anyhow, so the value is deprecated.


----------



## purrin

Quote: 





mikeaj said:


> Did you have a second stock O2 to compare to for quick A/B?  If yes, was it compared blind?
> 
> If the answer is "no" to either, I hate to be so dismissive in such a boring and repetitive way, but this goes again into the pile of "personal anecdotes that don't pass a bare minimum of experimental controls" evidence.  i.e. of limited but non-zero use.  We have lots of this already in general anyhow, so the value is deprecated.


 
   
  We'll be having another O2 soon. If not AB/X then simple AB. Planning on matching levels (which obviously I can do with better precision than most others) too. Gotta build a switch box - shouldn't be too difficult.


----------



## mikeaj

Quote: 





purrin said:


> We'll be having another O2 soon. If not AB/X then simple AB. Planning on matching levels (which obviously I can do with better precision than most others) too. Gotta build a switch box - shouldn't be too difficult.


 

 Cool, well then you can at least do it single-blind at least a couple times for kicks, if you want.  Level matching is definitely key.
   
  On a side note, if you could A/B/X one stock O2 from another O2 (stock or with say the NJM2068 swapped for NE5532), that would count as winning the challenge.


----------



## purrin

Quote: 





mikeaj said:


> Cool, well then you can at least do it single-blind at least a couple times for kicks, if you want.  Level matching is definitely key.
> 
> On a side note, if you could A/B/X one stock O2 from another O2 (stock or with say the NJM2068 swapped for NE5532), that would count as winning the challenge.


 

 I don't know about single-blind. The smile or wink on Anax's face before he presses the button would likely give it away, not to mention his Force telepathy powers.


----------



## upstateguy

Quote: 





anaxilus said:


> *Is there proof that one headphone has better separation or soundstage than another? * Wake me up when you find it.  Till then it's all in your head or most likely voodoo.


 

 My T-1s have a wider soundstage than my 650s.  Do I need proof?
   
   
  Quote: 





> Originally Posted by *Naim.F.C* /img/forum/go_quote.gif
> <snip>
> 
> EDIT: Just to clarify, the above testing was *iPhone* > LOD > amp, so it's possible once I add one of my DAC's to the equation it could change things.


 
   
  An iPhone is not a good enough source.  Try HD > High quality transport > high quality DAC > amp.
  

  
  Quote: 





purrin said:


> So I assumed you heard the amps in question and* heard no difference*? That's OK and fine by me. I do think it's a little self-righteous to tell _many _others who've designed, built, and listened to the discrete designs mentioned that it's all in their heads.
> 
> <snip>


 
   
  FWIW, my M^3 does *not* sound like my GS-1.  The GS-1 is more resolving and the M^3 has more bass... and the M^3 with 637/627 opamps and the Woo3 with Centron 7236 and Jan 6922s have extremely similar sound signatures and are difficult to tell apart.  My O2 sounds like the GS-1 at volumes around 9:30 on the volume dial.


----------



## maverickronin

Quote: 





purrin said:


> Some people are greedy for money. Others for attention.


 

 A cunning plan!  Clearly Jude is in on the conspiracy as well.  How else would Voldermort's blog be so high up Google's results when you search for "head fi"?


----------



## Anaxilus

Quote: 





shike said:


> *I see you enjoy partaking in poisoning the well right? *
> 
> You don't need me for that.  'V's camp is more capable or interfering w/ his agenda more than anyone else.  I'm just balancing Dogma which seems to reign supreme here whether objective or subjective.  I'd rather just have purrin and mikeaj have a constructive discussion and others post their impressions which obviously are meaningless to folks like yourself since that hardly qualifies as any evidence unless it supports your suppositions.
> 
> ...


 

  Edit - For the record, purrin and myself both come from science backgrounds and we both like and enjoy conversing with many in the Objectivist camp.  I have a few friends here who are also zealous 'V' fans and that's fine.  But I'll be damned if I sit back and idly watch rampant kool-aid drinking no matter who happens to be drinking it.
   
  Also, we aren't trying to single out the O2.  We've been pissing off a lot of people on many threads.  It is a good amp at a good price.  Just a bit too much superfluous strutting about IMHO.


----------



## Anaxilus

Quote: 





upstateguy said:


> My T-1s have a wider soundstage than my 650s.  Do I need proof?


 
   
  According to some O2 faithful here, YES!


----------



## upstateguy

Quote: 





anaxilus said:


> According to some O2 faithful here, YES!


 


  Like who, for instance?


----------



## Anaxilus

Quote: 





jzbass25 said:


> Very true, does the Zo2 have a dac built in? I am almost leaning towards just doing the maverick D1 but all the other options seem so good! Also I'm on the fence because I don't really need much amping with my current headphones...but this forum has made me want some more gear... haha


 

 Careful, it's easy to spend on non performing gear due to hype.  The ZO2 has no DAC.  No experience w/ the maverick, only Head-fi's maverick.  
	

	
	
		
		

		
		
	


	




  Ask yourself what you think you are looking for and do a lot of research.  It's clear you are looking to spend money to improve sound but what are you not happy with?


----------



## Anaxilus

Quote: 





upstateguy said:


> Like who, for instance?


 

 You didn't see the posts asking for measurements of soundstage in amps?  If it hasn't been measured it doesn't exist?  I think you missed my sarcasm.


----------



## maverickronin

Quote: 





jzbass25 said:


> Very true, does the Zo2 have a dac built in? I am almost leaning towards just doing the maverick D1 but all the other options seem so good! Also I'm on the fence because I don't really need much amping with my current headphones...but this forum has made me want some more gear... haha


 

 I also happen to have that Maverick.  No relation....
   
  IMO the D1's main selling point is its versatility for the price.  If you don't need all the different ins an outs you're probably better off getting something else.
   
  Quote: 





anaxilus said:


> According to some O2 faithful here, YES!


 
   
  Quote: 





anaxilus said:


> You didn't see the posts asking for measurements of soundstage in amps?  If it hasn't been measured it doesn't exist?  I think you missed my sarcasm.


 

 I don't know if I should take this seriously or not but it probably deserves a response for any newbies standing on sidelines...
   
  While there isn't a specific measurement for soundstage but I don't think many people would argue that the measured differences between the T1 and the HD650 shouldn't be audible in one manner or another...


----------



## Anaxilus

Quote: 





maverickronin said:


> While there isn't a specific measurement for soundstage but I don't think many people would argue that the measured differences between the T1 and the HD650 shouldn't be audible in one manner or another...


 

 Absolutely.


----------



## upstateguy

Quote: 





anaxilus said:


> You didn't see the posts asking for measurements of soundstage in amps?  If it hasn't been measured it doesn't exist?  I think you missed my sarcasm.


 

 I think soundstage can be measured.  The cues for left-right and depth are in the high frequency range and can be measured.  Bass reflections can be measured as well as ambiance.  Soundstage has been measured and reproduced for years.  It is found in DSP aps and your surround sound receiver.  Various venues have been accurately measured and reproduced, like the Royal Albert Hall.  Recording engineers can increase or decrease the soundstage according to their taste.  Even cheap TVs have a setting that increases the soundstage beyond the sides of the TV.


----------



## Shike

@Anaxilus
   
*Straw man:*
   
  Who's position did I misrepresent and when?  Point to specific post and when I misrepresented what they were saying?
   
*non-sequitur:*
   
  Sorry, not seeing it.  Please quote exactly in reference to what and where the logic supposedly did not follow.
   
*Analogies:*
   
  Which analogy?  If you're arguing in regards to the car analogies I believe all of them have been relatively pointless to pursue.  If you're arguing my picking of ones with clearly defined outcomes is bad, it's merely to exhibit the level of skepticism we enforce in regards to claims such as amps sounding different without a proper testing methodology.  In regards the the sport one, the only possible analogy there is that a really good player was maybe acting like a broken amp on that day.
   
*Structure*
   
  I have not seen a fallacy named "structure" before, please provide supporting documentation of this fallacy and how it relates specifically.
   
*Appeal to motive*
   
  I never challenged a thesis based on motive, I challenged that you on purposely misrepresenting my point.  Your thesis is your thesis, I never accused you of why your thesis is what it is.
   
*Ad hominem*
   
  You're misusing another fallacy.  If I said "you're wrong because of insult x" or "you're wrong because you're being disingenuous"  then you would be right.  Contrary to popular belief, just because someone interprets something as an insult does not make it ad-hominem.  The logic must follow that because you're X you're wrong.
   
  I could call you a slew of names or insult you up and down, but unless I use that as a point of why you're wrong then it isn't ad-hominem.  Poisoning the well maybe.
   
*Equivocation*
   
  Which word did I try to change the meaning or context of exactly?
   
* Post hoc ergo propter hoc*
   
  Saying it's possibly psychological doesn't mean it is, it's just one possibility.  Even if you're tired of hearing it, it still stands.  I never said it WAS, and asked for proof that it (phenomena) was at least observable.
   
   
  Looks like you may have two, maybe three, if you can make a valid case for them.
   
   
  I take accusations that I've done these things very seriously as I consider it an attack on my credibility.
   
   
   
*"Then again, I'm just being disingenuous because I don't agree with you." *
   
  Is an actual strawman and poisoning the well.
   
  "*eductio ad Hitlerum"*
   
  Poisoning the well again, possibly a strawman since you've tried claiming I'll make a point I have not (one that wouldn't even make sense).
   
   
   
  Still, I suggest you take this to PM if you wish to continue.  Further derailing of this thread isn't helping anyone unless there is a motive of some sort.
   
   
  Quote: 





> Also, we aren't trying to single out the O2.  We've been pissing off a lot of people on many threads.  It is a good amp at a good price.  Just a bit too much superfluous strutting about IMHO.


 
   
  I'm sorry, but superfluous strutting isn't exactly a good reason to post in this thread.  You either have an interest, you don't, or are apathetic.  Only one of those reasons seems suitable for posting here in my view.
   
   
  PS:
   
  As for soundstage, it can be measured but it's always going to be a collimation of measurements at this point.  Time domain, dispersion characteristics, and FR immediately come to mind as potentially effecting interpretation.  This is why something like the Smyth Realizer can do what it can.


----------



## mikeaj

This is pretty unrelated to recent topics of discussion, but I think it's still worth throwing this thought out there...
   
   
  I think there's one valid objective criticism of the O2 with regards to sound quality that people have not explicitly explored, as far as I've seen.  As we all know, our senses and perceptions are all linked.  If we want to evaluate the performance of an amp by how good it sounds in practice (perceived sound quality), we should be looking at areas other than sound quality!  In other words, we're interested in more than just the electrical performance.  When cooking, chefs are evaluated in part on the presentation of food on the plate, since the visual appeal will influence diners' perception of the taste.  Similar things could be said for headphone amplifiers.  This is also why much of the cost of audiophile equipment is in the enclosure, yet that may not be as true for pro amps and gear that the listeners will not see or touch.
   
  The default O2 enclosure, the Box Enclosures B2-080, looks pretty fine to me, but the power jack and input jack really are in awkward places on the front panel.  It's not just visually poor, but ergonomically suboptimal.  You could very well argue that those should have been on the back.  The primary reason they're on the front is to reduce the cost of the amp, by only making one custom panel necessary rather than two.  Considering the entire cost of the amp, particularly if bought assembled and not done DIY, this is arguably worse price/performance (including functionality) in a sense.


----------



## Anaxilus

Quote: 





upstateguy said:


> I think soundstage can be measured.  The cues for left-right and depth are in the high frequency range and can be measured.  Bass reflections can be measured as well as ambiance.  Soundstage has been measured and reproduced for years.  It is found in DSP aps and your surround sound receiver.  Various venues have been accurately measured and reproduced, like the Royal Albert Hall.  Recording engineers can increase or decrease the soundstage according to their taste.  Even cheap TVs have a setting that increases the soundstage beyond the sides of the TV.


 

 Sure, can you post a graph?  Otherwise how do I believe what you are saying.  Maybe it's a conspiracy or all in your head.  Evidence?  Amps have been producing more detail and transparency than the O2 for years too but apparently this is not possible according to some in the 'O2 is pure wire w/ gain and cannot be improved' camp.  Although it is interesting that the O2 is brighter sounding than my Leckerton but more compressed sounding as well.  Sorry I don't have a graph to support that observation.  >.<


----------



## Shike

Quote: 





> Originally Posted by *mikeaj* /img/forum/go_quote.gif
> 
> The default O2 enclosure, the Box Enclosures B2-080, looks pretty fine to me, but the power jack and input jack really are in awkward places on the front panel.  It's not just visually poor, but ergonomically suboptimal.  You could very well argue that those should have been on the back.  The primary reason they're on the front is to reduce the cost of the amp, by only making one custom panel necessary rather than two.  Considering the entire cost of the amp, particularly if bought assembled and not done DIY, this is arguably worse price/performance (including functionality) in a sense.


 


  This is an argument I can get behind, I tend to have issues with the front panel wiring getting tangled on and off.  This part of the default build should probably be fixed by those offering it commercially or having the cash to do it themselves.


----------



## Anaxilus

Spoiler: Warning%3A%20Spoiler!



I like how you acknowledge that SS is a culmination of things in a complex system but provide not measurements.  Yet someone observes things like detail and transparency and they have to **** you a graph ASAP.  Really now....
   


shike said:


> @Anaxilus


 

  When you can't even critically examine your own arguments presented to you on a platter you should probably stop.  Funny how the burden is on everyone else except for you.  Yes, I made a few fallacies, ones I directly copied from you that you claim not to see!  I'm satisfied w/ what I  presented regardless of whether it escapes you or not.  Probably best for us to move along and get back to the O2.


----------



## Anaxilus

Quote: 





mikeaj said:


> The default O2 enclosure, the Box Enclosures B2-080, looks pretty fine to me, but the power jack and input jack really are in awkward places on the front panel.  It's not just visually poor, but ergonomically suboptimal.


 

 I was actually thinking about this earlier.


----------



## Shike

Quote: 





anaxilus said:


> Spoiler: Warning%3A%20Spoiler!
> 
> 
> 
> ...


 
   
  You make claims, you're expected to prove them.  I'd appreciate it if you would stop libeling me further, kthx?  If you want to continue it, take it to PM.


----------



## upstateguy

Quote: 





> Originally Posted by *mikeaj* /img/forum/go_quote.gif
> 
> <snip>
> 
> The default O2 enclosure, the Box Enclosures B2-080, looks pretty fine to me, but the power jack and input jack really are in awkward places on the front panel.  It's not just visually poor, but ergonomically suboptimal.  You could very well argue that those should have been on the back.  The primary reason they're on the front is to reduce the cost of the amp, by only making one custom panel necessary rather than two.  Considering the entire cost of the amp, particularly if bought assembled and not done DIY, this is arguably worse price/performance (including functionality) in a sense.


 


   


  Quote: 





anaxilus said:


> Sure, can you post a graph?  Otherwise how do I believe what you are saying.  Maybe it's a conspiracy or all in your head.  Evidence?  Amps have been producing more detail and transparency than the O2 for years too but apparently this is not possible according to some in the 'O2 is pure wire w/ gain and cannot be improved' camp.  Although it is interesting that the O2 is brighter sounding than my Leckerton but more compressed sounding as well.  Sorry I don't have a graph to support that observation.  >.<


 

 You're just being silly.
   


  Quote: 





shike said:


> This is an argument I can get behind, I tend to have issues with the front panel wiring getting tangled on and off.  This part of the default build should probably be fixed by those offering it commercially or having the cash to do it themselves.


 

 I like everything on the front panel when it comes to a portable/transportable.  If you have it in a coat pocket, bag, center console of a car, or next to your laptop, everything is easily accessible.  If I'm using it with my Fuze, I like front panel access as well.


----------



## mikeaj

Quote: 





upstateguy said:


> I like everything on the front panel when it comes to a portable/transportable.  If you have it in a coat pocket, bag, center console of a car, or next to your laptop, everything is easily accessible.  If I'm using it with my Fuze, I like front panel access as well.


 

 Yeah as transportable, input location is kind of arguable.  I still think power makes no sense on front, but a custom back panel just for the power jack?  I don't know.
   
  If used on a desk, maybe gain switch could also be on the back.  I'm not a huge fan of LEDs on devices giving me the one-eyed staredown, so I wouldn't mind it somewhere else either.


----------



## maverickronin

Quote: 





upstateguy said:


> I think soundstage can be measured.  The cues for left-right and depth are in the high frequency range and can be measured.  Bass reflections can be measured as well as ambiance.  Soundstage has been measured and reproduced for years.  It is found in DSP aps and your surround sound receiver.  Various venues have been accurately measured and reproduced, like the Royal Albert Hall.  Recording engineers can increase or decrease the soundstage according to their taste.  Even cheap TVs have a setting that increases the soundstage beyond the sides of the TV.


 
   
  I'm not talking about what's in the source material, I'm talking about some sort of useful metric that would indicate what changes a headphone or amp might impart to it on the way to your ears.
   
  I don't really hear amps changing soundstage much at all so I don't know how you'd go about trying to measuring its influence.   I suppose a really wonky phase response could mess it up.
  
  With headphones just closely inspecting its construction and seeing how the driver and enclosure will interact with the ear will tell me more about its soundstage than any of Tyll's graphs.  Its not going to rank a bunch of 'phone precisely in order or anything but it could be the start of finding some different things to measure which would indicate something about soundstage.


----------



## maverickronin

Quote: 





mikeaj said:


> I'm not a huge fan of LEDs on devices giving me the one-eyed staredown, so I wouldn't mind it somewhere else either.


 

 At least its not one of blue ones that doubles as a flashlight.
   
  My XM6 literally has a "flashlight mode" where the LEDs go to full power...


----------



## Anaxilus

Quote: 





maverickronin said:


> With headphones just closely inspecting its construction and seeing how the driver and enclosure will interact with the ear will tell me more about its soundstage than any of Tyll's graphs.


 

  Don't you think that's true of all phones or largely non planar dynamics?


----------



## maverickronin

Quote: 





anaxilus said:


> Don't you think that's true of all phones or largely non planar dynamics?


 

 IME and FWIR it works with anything but BA IEMs.
   
  The FWIR is about dynamic IEMs where finding a vent will apparently give you a big clue but I don't have much experience with that.  I don't think there are too many people who know how to make heads or tails of BA IEM's tuning even after breaking it open and I sure don't though there has to some method.
   
  Planars play by slightly different rules than dynamics but much of it still applies with some changes here and there.  Its often less obvious than with dynamics and some of the tricks you can use with dynamics don't work with planars but I managed to wring a nice sound stage out of my T50RPs considering that they're closed and planar magnetic.  It was quite a bit larger than the HD650 I used to have and a few steps larger than the K601s I have now.  Soundstage size is hard to remember and I haven't A/Bed with any other good open headphones so that's all the data points I have so far.
   
  I don't have much experience with 'stats so there might be some other differences besides the level of damping required and it effects on soundstage.


----------



## upstateguy

Quote: 





mikeaj said:


> Yeah as transportable, input location is kind of arguable.  I still think power makes no sense on front, but a custom back panel just for the power jack?  I don't know.
> 
> If used on a desk, maybe gain switch could also be on the back.  I'm not a huge fan of LEDs on devices giving me the one-eyed staredown, so I wouldn't mind it somewhere else either.


 

 A little piece of electrical tape on the LED is your friend.  I got used to the connections and switches on the front very quickly.  Convenient.


----------



## Willakan

I really don't see on what logical basis claiming the O2's measurements are not comprehensive is made* unless these comparisons are done under blind, volume-matched conditions*. Likewise, I'm not entirely sure what Anaxilius is on, regardless of his "scientific background." Perhaps he could explain himself in a post that uses logic instead of cheap humour?
   
  I still think there is this incredibly annoying perception whereby people think "Well, it's not all in my head. How insulting to suggest it!" Cognitive bias is not some crappy effect made up to justify people hearing differences by a group of people whose only occupation is to shout "EVERYTHING SOUNDS THE SAME" on internet forums. It is of considerable importance. For example, Harmon Kardon hired a Manager of Subjective Evaluation to introduce blind testing into R&D - by his own admission he was met with oppostion by marketeers and engineers alike, who felt that they didn't need all this blind-testing crap to hear the obvious. The blind tests run by the manager are very illuminating, in that people prefer different speakers under blind conditions: under sighted conditions they invariable opt for the expensive, audiophile-review-approved models, whereas they would opt for different models once they didn't know what they were listening to.
   
  And this with speakers, where God knows the differences are much bigger than with friggin' amps, especially those designed for accuracy.
   
  If anyone believes they can hear these differences and/or that they are not shown by the measurements (the O2 sounding different from a high-impedance tube amp, for example, isn't very surprising and makes reasonable sense), *make them appear under blind, volume-matched conditions*. We can then remember the results of the comparison and look at the numbers when Tyll's amp-measuring program gets under way.


----------



## PelPix

Quote: 





purrin said:


> Lots of stuff doesn't show up in measurements. What we have is this:
> 
> 
> Use our ears - high acuity (of course this is for for debate), but unreliable and subject to our moods and influence of dollars spent.
> ...


 


  As a mixing/mastering engineer, I couldn't disagree more.  The purpose of audio REPRODUCTION is not to try and do anything at all.  I want the waveform I'm seeing on the oscilloscope to come out of my headphone drivers.  If you want a real-sounding recording, RECORD it real with well-performing equipment.
   
  I don't want any equipment I own to be listen-tested *at all*.  The only thing listen tests can do is ruin the results.  If it makes my client's music sound good on its own, I can't do my job, can I?


----------



## Digital-Pride




----------



## purrin

Quote: 





willakan said:


> I really don't see on what logical basis claiming the O2's measurements are not comprehensive is made* unless these comparisons are done under blind, volume-matched conditions*.


 
   
  Exactly. Any claims about the O2 sounding as good, i.e. uncolored, transparent, etc. as discrete component amps must be further verified under blind, volume-matched conditions - given the lack of any meaningful (correlating to human observation) measurements comparing the O2 with such amps.


----------



## Il Mostro

Quote: 





pelpix said:


> As a mixing/mastering engineer, I couldn't disagree more.  The purpose of audio REPRODUCTION is not to try and do anything at all.  I want the waveform I'm seeing on the oscilloscope to come out of my headphone drivers.  If you want a real-sounding recording, RECORD it real with well-performing equipment.
> 
> I don't want any equipment I own to be listen-tested *at all*.  The only thing listen tests can do is ruin the results.  If it makes my client's music sound good on its own, I can't do my job, can I?


 

  
  There is an old saying that describes the ideal amplifier being as close as possible to "straight wire with gain".  No additions or embellishment -- no subtractions or compensation.


----------



## sphinxvc

Quote:


purrin said:


> Exactly. Any claims about the O2 sounding as good, i.e. uncolored, transparent, etc. as discrete component amps must be further verified under blind, volume-matched conditions - given the lack of any meaningful (correlating to human observation) measurements comparing the O2 with such amps.


 

 +1
   
  How many have actually done the ABX, volume matched tests?  Or even seen results from a decent sample?  I would think that's important before you give yourself up to straddling V's "position."


----------



## purrin

purrin said:


> Lots of stuff doesn't show up in measurements. What we have is this:
> 
> 
> Use our ears - high acuity (of course this is for for debate), but unreliable and subject to our moods and influence of dollars spent.
> ...


 
   
  Quote: 





pelpix said:


> As a mixing/mastering engineer, I couldn't disagree more.  The purpose of audio REPRODUCTION is not to try and do anything at all.  I want the waveform I'm seeing on the oscilloscope to come out of my headphone drivers.  If you want a real-sounding recording, RECORD it real with well-performing equipment.


 

 LOL. I think you are twisting my words for the sake of winning an argument. If "you couldn't disagree more", I assume you mean:_ *the point of audio reproduction is to make things sound less real??? *_(that would be the inverse of what I said - and me being an ass - not to different from what you just did.) Now, I actually don't disagree with what you _really _mean - it's best to mess less with things rather than over-produce. I assume you come from the minimalist school of music production: simpler mic arrangements, use of wide-band flat mics, minimized steps in workflow of the mixing and mastering process, adulteration of the signal if and only absolutely necessary, etc. And finally, yes, as an audio engineer, you have to assume the equipment at the user-end faithfully reproduces your work.


----------



## purrin

Quote: 





sphinxvc said:


> Quote:
> 
> +1
> 
> How many have actually done the ABX, volume matched tests?  Or even seen results from a decent sample?  I would think that's important before you give yourself up to straddling V's "position."


 
   
  LOL. Funny how the scientific method gets thrown out the window with one view but needs to be applied rigorously with the other. "Objectively", nothing can be said either way at this time.


----------



## Willakan

Quote: 





purrin said:


> LOL. Funny how the scientific method gets thrown out the window with one view but needs to be applied rigorously with the other. "Objectively", nothing can be said either way at this time.


 


  No, not at all. Claiming that nothing can be said either way is simply bollocks and a horrendous distortion of the burden of proof.
   
  There are recognised numbers for the audibility of measurable imperfections. The O2 keeps everything at least 86db below the signal and the distortion is generally of a relatively benign nature. 
  There are established thresholds of audibility. The O2 takes the stricter ones, makes them a bit more paranoid for good measure and then makes sure everything is well under them.
  When everything that could possibly affect what you hear to the best of our current knowledge is at the very least 86db below the music and generally considerably more (THD at 1khz is about 20% of that) there is absolutely no reason to expect them to be audible, by established science. NwAvGuy hardly broke new ground here: this stuff has been spelled out in the AES archives years ago. 
   
  The reason why blind listening is asked for when people declare other amps that it is likely measure well sound different. How does the burden of proof constitute double standards: one claim makes sense, the other less. You don't demand science proves itself simply because you reckon it might be wrong with absolutely no evidence at all. When someone suggests something that clashes directly with current scientific thought, however, it is considered a good idea to present at least a shred of semi-credible proof and casual listening impressions don't even get that far.


----------



## purrin

Quote: 





willakan said:


> The reason why blind listening is asked for when people declare other amps that it is likely measure well sound different. How does the burden of proof constitute double standards: one claim makes sense, the other less. You don't demand science proves itself simply because you reckon it might be wrong with absolutely no evidence at all. When someone suggests something that clashes directly with current scientific thought, however, it is considered a good idea to present at least a shred of semi-credible proof and casual listening impressions don't even get that far.


 

 Exactly, so where is the proof - objective measurements showing the O2 sounds the same as the discrete component amps such as the B22, Dynalo, etc? Keep in mind we haven't seen the more _interesting _measurements, i.e. full spectrum non-linear distortion measurements at specific frequency sets (or multiple frequency sets) for the B22 and Dynalo (or the O2 for that matter.)
   
  All we've seen so far is that the O2 measures beyond what humans can hear in tests A, B, C, etc. This is hardly proof that the O2 sounds the same as discrete component amps (where no measurements have even been applied.) The only thing that can be inferred so far is that the O2 measures beyond what humans can hear in tests A, B, C, etc. - just that - nothing more (other than that it measures better than the mini3 in many of these tests.)
   
  And finally, where's the science that says that the set of measurement tests applied to the O2 explains all aspects of human perception? In other words, are we measuring the right things?


----------



## Shike

Quote: 





> full spectrum non-linear distortion measurements at specific frequency sets


 
   
  Do you have a link to this test procedure, evidence this test will show meaningful data that other tests do not, and a quantity in regards to this test that will show an audible impact?  Preferably from a recognized source please.


----------



## purrin

Quote: 





shike said:


> Do you have a link to this test procedure, evidence this test will show meaningful data that other tests do not, and a quantity in regards to this test that will show an audible impact?  Preferably from a recognized source please.


 
   
  I love these tests (and full spectrum visualizations) because they show more and are better differentiator of non-linear distortion. In other words, as I've been saying, what the heck does 0.3% THD at 100Hz mean? With these types of visualizations, you see a lot more of what's actually going on. The disadvantage is that you need to run a lot of them and that can be a pain.

http://www.head-fi.org/t/566929/headphone-csd-waterfall-plots/120#post_7743752 (there are a few sets of these in the CSD thread)
   
http://www.audioheuristics.org/measurements/Testing/mdt33/mdt33_supreme110.htm (scroll down a bit to see the tri-tone tests)
   
  I swear there was something similar on V's website, but I can't seem to find it. (EDIT: see the full spectrum THD and IMD graphs.)
   
  But basically I'd like to see a full suite of these at different sets of frequencies with single tones, tri-tones (grouped closer together), or even more tones, i.e. ~5


----------



## maverickronin

Quote: 





purrin said:


> I swear there was something similar on V's website, but I can't seem to find it.
> 
> But basically I'd like to see a full suite of these at different sets of frequencies with single tones, tri-tones, or even more.


 

 There are graphs like that into different loads for single tone THD and SMPTE and CCIF IMD in the first O2 article.


----------



## mikeaj

There have definitely been plenty of multi-tone tests developed other than SMPTE and CCIF, many of which probably tell a little more interesting things about the performance than SMPTE or CCIF and may be more interesting.  But since those two are more established, that's more often than not what we get.  At least those cover kind of low frequencies as well as high frequencies.
   
  But again, for reasons stated before, I would be pretty surprised if one device could ace SMPTE and CCIF tests and fall flat on its face with something else.  If you can find an example of a device that does, I'd be interested to see that.


----------



## purrin

Quote: 





mikeaj said:


> There have definitely been plenty of multi-tone tests developed other than SMPTE and CCIF, many of which probably tell a little more interesting things about the performance than SMPTE or CCIF and may be more interesting.  But since those two are more established, that's more often than not what we get.  At least those cover kind of low frequencies as well as high frequencies.
> 
> But again, for reasons stated before, I would be pretty surprised if one device could ace SMPTE and CCIF tests and fall flat on its face with something else.  If you can find an example of a device that does, I'd be interested to see that.


 

 I'm curious and I feel it's worth trying more than the two-tone SMPTE and CCIF - don't you think? Maybe something along the lines to the closely grouped tri-tone and penta-tone tests on Mark K's website.


----------



## Willakan

Quote: 





purrin said:


> Exactly, so where is the proof - objective measurements showing the O2 sounds the same as the discrete component amps such as the B22, Dynalo, etc? Keep in mind we haven't seen the more _interesting _measurements, i.e. full spectrum non-linear distortion measurements at specific frequency sets (or multiple frequency sets) for the B22 and Dynalo (or the O2 for that matter.)
> 
> All we've seen so far is that the O2 measures beyond what humans can hear in tests A, B, C, etc. This is hardly proof that the O2 sounds the same as discrete component amps (where no measurements have even been applied.) The only thing that can be inferred so far is that the O2 measures beyond what humans can hear in tests A, B, C, etc. - just that - nothing more (other than that it measures better than the mini3 in many of these tests.)
> 
> And finally, where's the science that says that the set of measurement tests applied to the O2 explains all aspects of human perception? In other words, are we measuring the right things?


 


  The reason they *should* sound the same is because these amps have supposedly been designed around being wonderful at reproducing audio, not simply adding some pleasant colouration. The O2 is provably transparent to the best of our knowledge by virtue of the fact it excels in every known parameter. As for more complex tests, why would you expect they are needed to characterise performance? NwAvGuy has written moderately extensively about why he feels absolutely fine armed with relatively standard test-signals and what he has said is hardly new or revolutionary. That said, I'm sure he would at least discuss any test you would care to suggest on his blog that the O2 would not excel in.
   
  As it stands, the current tests will be insufficient the day someone hears something that shouldn't be there under controlled conditions, in common with how the rest of science works.
   
  Anyway, to the crux of the point, it is maintained that the uber-expensive discrete amps are transparent and wonderful, conveying soundstage and other such things with superb fidelity - try suggesting on the high-end forums that really high-end amps just colour the sound in a nice way. So far I'll admit I have been slightly inconsistently granting them the benefit of the doubt. I strongly suspect that some of them do not measurably excel.
   
  Anyway, there are two possibilities:
   
  1) The expensive discrete amps measure as well or better than the O2 and should (should in the context that I would happily bet lots on the outcome: if I lose I'll be too excited about the revolutionary new audio parameters discovered to care about my loss!) sound the same as it into loads they are designed to drive and volume-matched. If they are held to sound different this could easily be verified with a blind test.
   
  2) The expensive discrete amps measure decidedly dubiously and it is entirely possible they sound different from the O2.
   
*As I said, I have, so far, been assuming that these other amps measure reasonably well*. It is entirely possible they do not, in which case we should ask the question of why people spend a fortune to accomplish what could be done with ease in the digital domain.


----------



## purrin

Quote: 





willakan said:


> The reason they *should* sound the same is because these amps have supposedly been designed around being wonderful at reproducing audio, not simply adding some pleasant colouration. The O2 is provably transparent to the best of our knowledge by virtue of the fact it excels in every known parameter. As for more complex tests, why would you expect they are needed to characterise performance? NwAvGuy has written moderately extensively about why he feels absolutely fine armed with relatively standard test-signals and what he has said is hardly new or revolutionary. That said, I'm sure he would at least discuss any test you would care to suggest on his blog that the O2 would not excel in.


 

 Well, I wouldn't say "every known parameter". Perhaps a more precise statement would be that the O2 excels with the RMAA suite, and SMPTE/CCIF distortion tests. I don't believe any of those standards ever state that performing well in those tests equates with transparency. I'm also pretty sure those standards were never designed for the purpose of measuring _high_-fidelity. The only thing that is proven is that the O2 measures well with those set of measurements.
   
  I'm puzzled why you are against more complex tests that could possibly show more differences among different amps (there's even no guarantee of this.) As I've said, it doesn't hurt, and aren't you at least curious to see if we can push the boundaries of current measurements? The "Bah humbug! No need for such tests, V says that these existing ones are good enough!" attitude hardly sounds inquisitive and smacks of someone who wants to stay in his little box.


----------



## Shike

I want to know why you believe these tests will actually benefit finding transparency, and if these tests are needed to gauge it when ABX would be sufficient myself.
   
  Would it not make sense to first prove audibility between them before assuming the tests even matter?


----------



## Satellite_6

Can more complex tests be done with Voldemort's equipment? I think it's already been said that you could contact him.
   
  Reversing the burden of proof and claiming the numbers don't mean anything doesn't seem like much of an argument to me, but I suppose it's the only way to be on the other side. . .


----------



## purrin

Quote: 





shike said:


> I want to know why you believe these tests will actually benefit finding transparency, and if these tests are needed to gauge it when ABX would be sufficient myself.


 
   
  Measurements that provide more data and greater differentiation give us more opportunities to find correlations with human experience. If these tests are meaningful (they may not be), then they come in handy since ABX tests are much more difficult to conduct.
   
   


> Would it not make sense to first prove audibility between them before assuming the tests even matter?


 

 About as much sense as for V to first ABX the O2 against the supposedly voodoo rip-off amp designs using discrete components _before _making claims and taking non-comparative isolated measurements of the O2.


----------



## Willakan

Wait a second, the O2 was not tested with RMAA. It was tested with a $10k piece of specialised audio measuring equipment and he ran rather more tests than RMAA could ever hope to manage (including the aforementioned specialised IMD tests.) Have you looked at the blog? It measures distortion relative to frequency, phase, noise floor differences with batteries and AC, uber wide-band THD, slew rate...it is pretty comprehensive and the individual tests are run at a resolution far beyond anything RMAA could hope to pull off.
   
  I'm still not quite sure what you're getting at with measurement correlation. The point of the O2 isn't to get numbers to specific ideal values, it is just to get rid of everything that isn't the audio signal as much as possible to the point where it is irrelevant to the listener regardless of hearing acuity. Who cares exactly how different distortion harmonics sound when you can't possibly hear any of them?
   
  Also, I may be being quite astoundingly thick, but could you kindly rephrase the last line of your post for clarity?


----------



## purrin

Quote: 





willakan said:


> Wait a second, the O2 was not tested with RMAA. It was tested with a $10k piece of specialised audio measuring equipment and he ran rather more tests than RMAA could manage (including the aforementioned specialised IMD tests.) Have you looked at the blog? It measures distortion relative to frequency, phase, noise floor differences with batteries and AC, uber wide-band THD...it is pretty comprehensive.
> 
> I'm not quite sure what you're getting at with measurement correlation. The point of the O2 isn't to get numbers to specific ideal values, it is just to get rid of everything that isn't the audio signal as much as possible to the point where it is irrelevant to the listener regardless of hearing acuity. Who cares exactly how different distortion harmonics sound when you can't possibly hear any of them?


 

 I stand corrected - it's a Prismsound dscope running a suite of tests more comprehensive than RMAA.


----------



## maverickronin

Quote: 





purrin said:


> I stand corrected - it's a Prismsound dscope running a suite of tests more comprehensive than RMAA.


 

 That's pretty important.
   
  Quote: 





purrin said:


> For nwaguy (or at least his more blind followers) to suggest that he is the only one (or the select all-knowing few) who designs amps using bench tests is preposterous. I've seen test equipment and 'scopes on the benches of all the well known reputable amp builders. Not only do the good builders test, but they listen.


 

 What is being suggested is that many designers aren't using proper audio analyzers.


----------



## Grev

Quote: 





purrin said:


> I stand corrected - it's a Prismsound dscope running a suite of tests more comprehensive than RMAA.


 


  I don't know if you're being sarcastic or not... 
   
  I do really enjoy your waterfall plots, just hope that you might be able to test SOMETHING for the amp... haha


----------



## Willakan

You didn't think we were kicking up all this fuss over something that looked OK with RMAA
	

	
	
		
		

		
			





? It doesn't even come close to providing anything like decent amp performance metrics. Only thing it really has any use for is FR and crosstalk tests and even they are a bit dodgy. 
   
  You certainly couldn't make anything within a thousand miles of the statements being made about the O2 based on a set of RMAA results.


----------



## Shike

Quote: 





willakan said:


> You didn't think we were kicking up all this fuss over something that looked OK with RMAA
> 
> 
> 
> ...


 

 Which is exactly what the M3 is based on including a basic oscilloscope iirc . . .


----------



## BGRoberts

I freely admit I don't understand much of this "discussion", if that's what it is.
   
  I DO know I just got my O2 a couple of nights ago.  Plugged in my Sansa Fuze with the modded Fostex T50's, and I'M LOVIN' IT!!!!!
   
  Please hold down the noise while I listen to some SWEET music.


----------



## PelPix

Hey Purrin, if you'd like to measure these amps yourself and see what's up, I could TRY and talk to my friends (who own the each individual amp respectively) to haul them to you for testing.
   
  Also, there are measurements for the B22 here:
http://www.ibiblio.org/tkan/audio/beta22.html
   
  There is a problem with comparing the earlier measurements, however.  They're using an audio interface to play back/record signals, and it isn't of the highest quality.
  The oscilloscope measurements shouldn't present a problem though.


----------



## Anaxilus

Quote: 





willakan said:


> Likewise, I'm not entirely sure what Anaxilius is on, regardless of his "scientific background." Perhaps he could explain himself in a post that uses logic instead of cheap humour?


 
   
  Hah.  My sillyness or drug induced rethor was a mimic to illustrate the absurdity of some of those that claim 'objective' standards here.  Nothing more to say on the matter than what has been said already if one simply reads properly.  Not an easy thing for those predisposed to another perspective already.


----------



## Willakan

Nobody can ever claim absolute objectivity with regards to anything: but I still don't see what you're getting at.


----------



## Anaxilus

Quote: 





satellite_6 said:


> *Reversing the burden of proof and claiming the numbers don't mean anything* doesn't seem like much of an argument to me, but I suppose it's the only way to be on the other side. . .


 

 Case in point.


----------



## Satellite_6

wat. 
   
  I think Willikan has already explained why shifting putting the burden of proof is ridiculous but if you choose to continue to view it differently then I guess that's your prerogative.


----------



## Anaxilus

Quote: 





satellite_6 said:


> wat.
> 
> I think Willikan has already explained why* shifting *putting *the burden of proof* is ridiculous but if you choose to continue to view it differently then I guess that's your prerogative.


 


  Who do you imagine is doing that.


----------



## Satellite_6

Quote: 





anaxilus said:


> Who do you imagine is doing that.


 


  wat. 
   
  I suggest you go read the last few pages.


----------



## Deltron 3030

For the Beyerdynamic dt150 's (250 ohm) with an ipod touch 4g will the o2 be any better than a FiiO E7 USB DAC and Portable Headphone Amplifier. Would the DAC in the FiiO make it better sound quality wise?


----------



## upstateguy

Quote: 





willakan said:


> The reason they *should* sound the same ....
> 
> <snip>
> 
> ...


 

  
  It occurs to me that the *O2* is a *known quantity* that has been measured every which way to Sunday.
   
  What is this *hypothetical* expensive discrete amp the O2 is being compared to?  If it exists, what is it?  Name it.  Let's take a look at it's measurements before we compare it to the O2.
   
  If it's only hypothetical or if it doesn't have the same kind of meaningful measurements, it's not germane to this discussion.


----------



## Digital-Pride

Quote: 





deltron 3030 said:


> For the Beyerdynamic dt150 's (250 ohm) with an ipod touch 4g will the o2 be any better than a FiiO E7 USB DAC and Portable Headphone Amplifier. Would the DAC in the FiiO make it better sound quality wise?


 

 Hmm, how about paring the O2 with the E7?  I think that would be a good pairing.


----------



## Deltron 3030

Quote: 





digital-pride said:


> Hmm, how about paring the O2 with the E7?  I think that would be a good pairing.


 
   
   
   
  Well I can only get one atm so which should I get first?


----------



## mikeaj

If you're using it from a non-computer device like an iTouch iPod Touch (whoops I invented a new product)...there's no way to make use of the DAC portion of the E7.  Actually, you probably wouldn't even want to bother because the modern iPod internal DAC is pretty good already.
   
  E7 costs as much as it does because it's a USB-connected computer DAC + amp.  It can also be used as an amp alone.  The amp part of the E7 is really not that much different than a $20 E5 though.
   
  So from an iTouch, especially if you're looking for more volume, you want a dedicated headphone amplifier and that's it.  O2 is a very good choice for the money if you don't mind the size and don't mind spending up to that level.  Generally it's much too large for usage in pocket, so something else would be more appropriate for that.  E11 is neither as good nor as powerful, but it's cheaper and smaller.


----------



## Deltron 3030

I don't need it for portable use. Would the e11 be any different than the o2 sq wise for a pair of 250 ohm headphones?


----------



## khaos974

Quote: 





deltron 3030 said:


> Quote:
> 
> 
> 
> ...


 


  How cute, it seems that from time to time, we still get someone not interested in the measurements debate and interested in getting an amp 
	

	
	
		
		

		
			





.
  So to answer your question:
  - Epiphany Acoustics if you're not in the US (remember to specify your country's voltage)
  - Jdslabs if you're in the US
  - Join Diyaudio.com, if you're interested in building it yourself.


----------



## Deltron 3030

Quote: 





khaos974 said:


> How cute, it seems that from time to time, we still get someone not interested in the measurements debate and interested in getting an amp
> 
> 
> 
> ...


 
  But would it improve the sound quality any more than the e11 on a pair of 250 ohm headphones? If not I'd rather not spend the extra $90. Also would a e7 paired with a pc be much better than the e11 with an itouch?


----------



## mikeaj

Quote: 





deltron 3030 said:


> But would it improve the sound quality any more than the e11 on a pair of 250 ohm headphones? If not I'd rather not spend the extra $90. Also would a e7 paired with a pc be much better than the e11 with an itouch?


 

 According to the O2 designer's criteria and the accepted levels of audibility etc. that people have been discussing in the past few pages, the O2 shouldn't perform audibly better with 250 ohms headphones like that.  The O2 will do somewhat better with lower-impedance headphones, which are harder to drive accurately in general.  The O2 would also have more power available, but the E11 should be enough for the DT 150 unless you feel like the current level with the iPod Touch is way too quiet.
   
  Also keep in mind that the E11 cannot be used while charging.  If you're willing to be unplugging it and plugging it back in every day, then go for it.
   
   
  E7 by itself with PC is probably worse than E11 with iPod Touch?  The E11 is also a bit more powerful.
   
  By the way, if you were considering E7 for home-only use, the newer and cheaper E10 is pretty much better in every single way.  E10 apparently has some quality-control issues regarding the headphone jack liking to eject headphones with slight tugs and a borderline high DC offset voltage (in theory maybe somewhat objectionable, for lower-impedance and more sensitive headphones), but in pretty much every performance parameter it beats the E7.


----------



## Deltron 3030

Quote: 





mikeaj said:


> According to the O2 designer's criteria and the accepted levels of audibility etc. that people have been discussing in the past few pages, the O2 shouldn't perform audibly better with 250 ohms headphones like that.  The O2 will do somewhat better with lower-impedance headphones, which are harder to drive accurately in general.  The O2 would also have more power available, but the E11 should be enough for the DT 150 unless you feel like the current level with the iPod Touch is way too quiet.
> 
> Also keep in mind that the E11 cannot be used while charging.  If you're willing to be unplugging it and plugging it back in every day, then go for it.
> 
> ...


 

 I think I'm gonna go for the e11. Thanks so much for the help!!
   
  edit: what about the jdslabs cMoyBB? I've read it's smoother and fuller than the e11, but less powerful. Would it not be able to drive 250 ohm phones?


----------



## Mad Lust Envy

Wondering how well it performs with the D7000.


----------



## Pars

Quote: 





willakan said:


> You didn't think we were kicking up all this fuss over something that looked OK with RMAA
> 
> 
> 
> ...


 
  Even Voldemort doesn't completely dismiss RMAA in his blogs, at least the ones that I've read. He even said he uses it some :eek:
   
  Sure, it isn't as competent as his dscope, but still not entirely worthless as you infer if done properly (which is the target of much of his criticism of RMAA, and I would agree). It would be interesting to see him run both RMAA and dscope tests on the same device and compare the results.


----------



## Pars

Quote: 





pelpix said:


> Hey Purrin, if you'd like to measure these amps yourself and see what's up, I could TRY and talk to my friends (who own the each individual amp respectively) to haul them to you for testing.
> 
> Also, there are measurements for the B22 here:
> http://www.ibiblio.org/tkan/audio/beta22.html
> ...


 

 What's the problem with an M-Audio Firewire Audiophile?


----------



## mikeaj

Indeed I wouldn't necessarily say there's that much wrong with the sound card approach except that you're not going to be able to catch ultrasonic garbage or oscillation, and other things like that.  You also can't get an idea of output levels just through software.  However, there's a scope, multimeter, and other bench gear to help you with those things.  Also you may need some kind of step-down voltage divider or transformer, or something clever to be able to reduce high output levels to a range where a sound card input can handle it...if you want to test those high output levels.
   
  It's more an issue with RMAA just being super-buggy and not inspiring a lot of confidence, and as you say, many users of RMAA having no idea what they're doing and not supplementing the approach with other gear (if even just a multimeter to check the output level).  There's got to be better software?  Or maybe just do your own spectral analysis and test tones.  The M-Audio Firewire should have good enough hardware for quite reasonably good noise and distortion measurements.


----------



## stv014

Quote: 





> Originally Posted by *Deltron 3030* /img/forum/go_quote.gif
> 
> edit: what about the jdslabs cMoyBB? I've read it's smoother and fuller than the e11, but less powerful. Would it not be able to drive 250 ohm phones?


 

 It depends on the exact parameters of that particular CMOY. If it has a sufficiently high power supply voltage (e.g. 18V), and enough gain to actually output the higher voltage, then it may in fact even be more powerful for high impedance headphones. For low impedance, CMOYs (unbuffered op-amp based amplifiers) are weaker because most op-amps can only output low current.
   
  Quote: 





pars said:


> Even Voldemort doesn't completely dismiss RMAA in his blogs, at least the ones that I've read. He even said he uses it some :eek:
> 
> Sure, it isn't as competent as his dscope, but still not entirely worthless as you infer if done properly (which is the target of much of his criticism of RMAA, and I would agree). It would be interesting to see him run both RMAA and dscope tests on the same device and compare the results.


 
   
  Indeed, the usefulness of RMAA also depends on the competence of the person using it, which is often questionable with the various RMAA results posted on internet forums. But even having a cheap setup of PC, sound card, digital multimeter, soldering iron, and cables, connectors and resistors (for simulating loads and creating voltage dividers if needed) only, you are not limited to just using RMAA. So while the electrical/analog limitations of such testing equipment compared to e.g. dScope obviously cannot be overcome, it is still possible to perform the tests missing from (or limited/buggy in) RMAA with other software.


----------



## Willakan

Certainly, RMAA is better than nothing, but I certainly wouldn't start making any serious assumptions about the quality of an amp based on results from it: it is both limited in scope and flawed in results. Even in uber-best case scenarios, RMAA results are only comparable with other RMAA results from exactly the same setup and even then they are not sufficiently broad or of sufficient resolution to really say much about what is being measured.
   
  He did actually measure one product with RMAA and the Dscope, but only to demonstrate how RMAA showed no evidence of significant flaws in the design apparent with the vastly better equipment.


----------



## Pars

Do you actually use RMAA and other test equipment? Also, do you have a link to the results in your last statement? Thanks.


----------



## Digital-Pride

Quote: 





mad lust envy said:


> Wondering how well it performs with the D7000.


 

 I think it would be a good fit.  The O2 has worked well with all of my low impedance headphones, so the 25Ohm D7000 should be a piece of cake.


----------



## limpidglitch

Quote: 





pars said:


> Do you actually use RMAA and other test equipment? Also, do you have a link to the results in your last statement? Thanks.


 


  It was in his Clip+ and Cowon i9 reviews, I believe.


----------



## Satellite_6

I assume linking is still not allowed.


----------



## Willakan

@Satellite: Indeed.
   
  @Pars: The flaws of RMAA are many and documented: as I said above and I believe NwAvGuy has said as well in his post on RMAA, results are not really comparable across RMAA setups, whilst the lack of any concept of absolute levels and the general opacity of operation are also problematic (could say more, but I would just be quoting NwAvGuy's list at this stage.) It also doesn't cover a great deal of parameters and according to NwAvGuy some of the maths behind it seems to be somewhat broken.
  This is before you get into the problem of the performance of the recording interface.
   
  It is better than nothing and you can't complain too much about free software, but it is totally inadequate if you want to completely ensure an amp is transparent to prettymuch the best of our current knowledge. I suppose it is reasonable for spotting some of the really big possible measurable flaws but even then has to be set up very carefully.


----------



## upstateguy

I've had the O2 for a while now.
   
  I don't believe in solid state burn in but a curious thing has occurred. 
   
  My O2 seems to have improved from it's initial sound, to one that is better than my M^3 or Woo3 and is on a Par with my GS-1.  With careful volume balancing, it becomes hard to tell the O2 (low gain and 9:00 volume setting) from the GS-1.  Not so against the M^3 and the Woo3 which seem to have more, but less articulated bass and not as much HF resolution or clarity.
   
  The only problem I continue to have is the default high gain setting which clips and remains useless, even with my Fuze as a source.  If I turn the volume down on high gain to what I can achieve on low gain, it will not clip, but it seems to sound a little better on low gain.... this with my T-1s.
   
  There is also a limit on how loud the unit will go before the signal deteriorates.  This is in line with the other portables but not the desktops.
   
  Still, the O2 is not a GS-1, which has no issues with the gain settings, or volume settings and is just a marvelous little full featured amp.


----------



## Mad Lust Envy

Anyone have a picture of the rear? Or is the only input the 3.5mm on the front? I don't like front facing inputs.


----------



## purrin

Quote: 





willakan said:


> It is better than nothing and you can't complain too much about free software, but it is totally inadequate if you want to completely ensure an amp is transparent to prettymuch the best of our current knowledge. I suppose it is reasonable for spotting some of the really big possible measurable flaws but even then has to be set up very carefully.


 

 I think the "totally inadequate" is too much of a stretch. If set up properly with care and quality components, very good results could be obtained. The lab grade tools do have much better accuracy, precision, lower noise floors, etc. Even sloppy results could be obtained with lab grade tools if the person doing the testing isn't careful.


----------



## purrin

Quote: 





upstateguy said:


> I've had the O2 for a while now.
> 
> I don't believe in solid state burn in but a curious thing has occurred.
> 
> My O2 seems to have improved from it's initial sound, to one that is better than my M^3 or Woo3 and is on a Par with my GS-1.


 

 You've just gotten used to the sound, unless you believe in voodoo capacitor burn in. Typically I've found that bench measurements of equipment get worse over time.


----------



## maverickronin

Quote: 





mad lust envy said:


> Anyone have a picture of the rear? Or is the only input the 3.5mm on the front? I don't like front facing inputs.


 

 Everything's on the front so it doesn't cost an extra $15-20 for another cut panel.
   
  If you want to wait for it, there's "desktop" version coming out in a few months with RCA inputs, 1/4" jack, rear inputs, 'normal' layout, etc.  By ditching the batteries for AC only operation and a few other parts it should only end up a little bit more expensive


----------



## TooPoor

Newbie question, but how well/poorly would the O2 mate up with my Denon D2000 and Senn HD598. I realize they have very different sound signatures, hence my curiosity.


----------



## purrin

Quote: 





toopoor said:


> Newbie question, but how well/poorly would the O2 mate up with my Denon D2000 and Senn HD598. I realize they have very different sound signatures, hence my curiosity.


 

 Should go good with D2000. D2000 really needs bass control (low impedance +current). HD598 should be OK. I don't feel the O2 (as equipped with the op-amp used for voltage gain) does deep bass as well as others.


----------



## upstateguy

Quote: 





purrin said:


> *You've just gotten used to the sound*, unless you believe in voodoo capacitor burn in. Typically I've found that bench measurements of equipment get worse over time.


 

 Um, no.  I compared it to my GS-1 when I first got it and I'm comparing it to the same GS-1 now. 
   


  Quote: 





maverickronin said:


> Everything's on the front so it doesn't cost an extra $15-20 for another cut panel.
> 
> If you want to wait for it, there's "desktop" version coming out in a few months with RCA inputs, 1/4" jack, rear inputs, 'normal' layout, etc.  By ditching the batteries for AC only operation and a few other parts it should only end up a little bit more expensive


 

 OTOH, is MadLust looking for SQ or a jack on the back?  I like everything on the *front* of this amp.  It gives me more flexibility in positioning.


----------



## Mad Lust Envy

maverickronin said:


> Everything's on the front so it doesn't cost an extra $15-20 for another cut panel.
> 
> If you want to wait for it, there's "desktop" version coming out in a few months with RCA inputs, 1/4" jack, rear inputs, 'normal' layout, etc.  By ditching the batteries for AC only operation and a few other parts it should only end up a little bit more expensive




Hmm, the desktop version has me more intrigued, as I don't need a portable.


----------



## arirug

I just love my Objective O2 amp. I have used it for several hours each day since I got it from Mr.Slim. It is paired with a Cambridge Dacmagic and a desktop computer. I like it more than my Decware CSP2 and Stax Srm-1/Mk2 with Stax lambda Pro. My Decware is for sale, and the Stax system was sold today. Some of the money from the Stax sale will be invested in another O2.


----------



## Satellite_6

Quote: 





upstateguy said:


> Um, no.  I compared it to my GS-1 when I first got it and I'm comparing it to the same GS-1 now.
> 
> 
> OTOH, is MadLust looking for SQ or a jack on the back?  I like everything on the *front* of this amp.  It gives me more flexibility in positioning.


 


  He's probably right. 
   
   
  I want an ODA!
   
  If all goes well I will build one over my spring break, instead of doing whatever normal people with lives do over spring break. . .


----------



## Pars

Quote: 





pars said:


> Do you actually use RMAA and other test equipment? Also, do you have a link to the results in your last statement? Thanks.


 
  Quote: 





willakan said:


> @Pars: The flaws of RMAA are many and documented: as I said above and I believe NwAvGuy has said as well in his post on RMAA, results are not really comparable across RMAA setups, whilst the lack of any concept of absolute levels and the general opacity of operation are also problematic (could say more, but I would just be quoting NwAvGuy's list at this stage.) It also doesn't cover a great deal of parameters and according to NwAvGuy some of the maths behind it seems to be somewhat broken.
> This is before you get into the problem of the performance of the recording interface.
> 
> It is better than nothing and you can't complain too much about free software, but it is totally inadequate if you want to completely ensure an amp is transparent to prettymuch the best of our current knowledge. I suppose it is reasonable for spotting some of the really big possible measurable flaws but even then has to be set up very carefully.


 

 I take it the answer to my 1st question is "no".
   
  All test equipment (or anything for that matter) has anomalies and flaws. I agree with Purrin in that if you are careful and examine the results, you can get useful data from RMAA. DMMs, oscilloscopes and such don't run themselves either, and getting useful data from them requires knowledge of measurement technique in order to get what you are looking for. I would agree that just tossing a couple of cables on your soundcard and blindly running RMAA can be problematic. And also that any measurements or values coming from it should not be taken as absolute values. Most of the time when I am doing measurements (of DIY stuff), I'm not necessarily interested in the absolute value anyhow, but relative. This includes use of DMMs, scopes etc.
   
  Obtaining solid absolute values would require something like the dscope or AP units, and that their hardware is kept in calibration. Since RMAA has little knowledge of the hardware being used, it obviously cannot be counted on for these types of measurements.


----------



## upstateguy

Quote: 





arirug said:


> I just love my Objective O2 amp. I have used it for several hours each day since I got it from Mr.Slim. It is paired with a Cambridge Dacmagic and a desktop computer. I like it more than my Decware CSP2 and Stax Srm-1/Mk2 with Stax lambda Pro. My Decware is for sale, and the Stax system was sold today. Some of the money from the Stax sale will be invested in another O2.


 

 Mine is a Mr.Slim unit too.  Do you have issues with the high gain (clipping) like I do?
   

  
  Quote: 





satellite_6 said:


> *He's probably right. *
> 
> 
> I want and ODA!
> ...


 

 I'm not sure what you mean. 
   
  I firmly don't believe in SS burn in and I'm an extreme objectivist, but I a-b 'd the O2 with the GS-1 when I got it and the differences I heard then, I don't seem to hear now.... and I certainly know how to a-b something... <shrug>
   
  (I don't even want to tell you that the GS-1 matured in a similar way when it was new....)


----------



## Anaxilus

Quote: 





mad lust envy said:


> Hmm, the desktop version has me more intrigued, as I don't need a portable.


 

 Do the desktop as this is not portable either.


----------



## mikeaj

Not sure what "not portable" means.  For sure it's much too large and heavy to use in a pocket for most people, but it should be reasonable in a bag or in an automobile or transit of some kind.


----------



## Maxvla

"Transportable"


----------



## shotgunshane

It's smaller than I thought from pics.  The footprint is small enough to be portable but it's too thick for pockets, so transportable is a good description.


----------



## ClieOS




----------



## Maxvla

So yeah.. It's kinda big.


----------



## Mad Lust Envy

Looks like it's take up as much space as the Fiio E9, which isn't huge, but bigger than can be considered portable.


----------



## Draygonn

vizzle said:


> 3. Size comparison (from left, Samsung Galaxy SII, o2 itself, mouse, Fiio e7, Sansa Clip+, Fiio e9)


----------



## MacedonianHero

Quote: 





maxvla said:


> So yeah.. It's kinda big.


 


  I wonder how big the desktop version will be?


----------



## Maxvla

About the size of the current Schiit amp/dac lineup would be excellent. Small but not too small.

Asgard: 9 x 6.75 x 2.25”


----------



## upstateguy

re-posting this pic for size comparisions.


----------



## Mad Lust Envy

So it isn't that big. The E9 looks huge in that pic, but in person, it's just a light brick.


----------



## MacedonianHero

Quote: 





upstateguy said:


> re-posting this pic for size comparisions.


 

 Thanks Eric. I miss my Hornet...never should have sold it.


----------



## mikeaj

I probably should have just posted this before, but the enclosure is this:
http://www.boxenclosures.com/category/product_details.html?product__id=211292
   
  1.18" H x 4.27" W x 3.15" L (30mm x 108mm x 80mm), so roughly palm-sized.


----------



## Mad Lust Envy

I'll most likely be getting this amp for now, and keeping an eye on future products. I like the gusto this guy has, and backs it up with some pretty good info. 

edit: Scratch that, I'm gonna wait for the desktop version as well as the DAC.


----------



## tekdemon

upstateguy said:


> I've had the O2 for a while now.
> 
> I don't believe in solid state burn in but a curious thing has occurred.
> 
> My O2 seems to have improved from it's initial sound, to one that is better than my M^3 or Woo3 and is on a Par with my GS-1.  With careful volume balancing, it becomes hard to tell the O2 (low gain and 9:00 volume setting) from the GS-1.  Not so against the M^3 and the Woo3 which seem to have more, but less articulated bass and not as much HF resolution or clarity.


 


   
  I don't believe in solid state burnin either but it's somewhat possible in hand-soldered units like this that heat generated from actually using the unit helps stabilize (or destabilize) less than optimal solder joints.  That said, it's probably in your head.


----------



## Willakan

@Upstateguy:
   
  I'm not sure about the Fuze's output level, but if clipping is occurring on high gain it will occur at any setting of the volume pot. The problem isn't in the output stage, it's the input stage that clips: by the time the signal reaches the pot the clipping has already occurred.  This can only be fixed with either switching from batteries to AC if you are using the former (which I don't believe you are) or by swapping the gain resistors for a lower amount of gain on the high-gain setting. Apologies if you have already said, but high gain is 6.5X presumably for your amp?
   
  I'm not sure where this deterioration with higher volume settings could come from: the only explanation would be if you are using a borderline voltage (12VAC under load) AC adaptor. This can cause the power rails to drop out of regulation at higher volume settings, which increases distortion, albeit not by much (opamps having a stupidly high PSRR).
   
  The limitation is a compromise for price and size reasons, as I understand it. However, the first problem at least (the second problem not existing AFAIK with a decent AC/AC adaptor) will be fixed in the forthcoming desktop version.


----------



## arirug

re upstateguy
   
  My O2 is not clipping. headphones I use are Sennheiser HD650 and AKG K601.


----------



## stv014

Quote: 





> Originally Posted by *upstateguy* /img/forum/go_quote.gif
> 
> and I certainly know how to a-b something... <shrug>


 
   
  Do you mean it was a blind test ?


----------



## limpidglitch

Quote: 





arirug said:


> re upstateguy
> 
> My O2 is not clipping. headphones I use are Sennheiser HD650 and AKG K601.


 


  What headphones you use will not in a direct manner affect the amplifiers susceptibility to clip in this case.
   
  The kind of clipping we're talking about here is an effect of the relationship between input vultage, supplied voltage, and voltage gain.


----------



## MacedonianHero

Quote: 





tekdemon said:


> I don't believe in solid state burnin either but it's somewhat possible in hand-soldered units like this that heat generated from actually using the unit helps stabilize (or destabilize) less than optimal solder joints.  That said, it's probably in your head.


 

 Eutectic Tin-Lead reflows (melts) at 183'C, I seriously doubt that the components are getting to that temperature. The O2 would most likely use lead-free solder....reflows at a higher temperature.


----------



## Reticuli2

Meh.  O2 and Emu 0204 works much better.  The DAC on the E7 is pretty average, and you'd be going from a headphone jack into the O2... and not a great headphone jack into line-out loads like on the Emu.

  
  Quote: 





deltron 3030 said:


> Well I can only get one atm so which should I get first?


----------



## Mad Lust Envy

Umm you can buy an L7 LOD for the E7 to have a direct line out. The headphone jack issue unused.


----------



## upstateguy

Quote: 





willakan said:


> @Upstateguy:
> 
> I'm not sure about the Fuze's output level, but if clipping is occurring on high gain it will occur at any setting of the volume pot. The problem isn't in the output stage, it's the input stage that clips: by the time the signal reaches the pot the clipping has already occurred.  This can only be fixed with either switching from batteries to AC if you are using the former (which I don't believe you are) or by swapping the gain resistors for a lower amount of gain on the high-gain setting. Apologies if you have already said, but high gain is 6.5X presumably for your amp?
> 
> ...


 

 Hi W
   
  We'll have to discuss this further....
   
  I'm using the AC adapter that came with the amp... what ever nwav spec'd out I guess.... and the high gain is the default 6.5
   
  Not sure why there's distortion at very high volumes.  It almost seems like there is a maximum volume, past which, it distorts regardless of which gain is used.
   


  Quote: 





arirug said:


> re upstateguy
> 
> My O2 is not clipping. headphones I use are Sennheiser HD650 and AKG K601.


 

 You don't get any distortion or clipping with high gain? 
 What is your source?
   


  Quote: 





stv014 said:


> Do you mean it was a blind test ?


 


  No, not a blind test, just an a-b comparison.  Been doing them for years with all my equipment.  Certainly not scientific by any means, but it gives me an idea about how the various components sound.


----------



## maverickronin

Quote: 





upstateguy said:


> I'm using the AC adapter that came with the amp... what ever nwav spec'd out I guess.... and the high gain is the default 6.5
> 
> Not sure why there's distortion at very high volumes.  It almost seems like there is a maximum volume, past which, it distorts regardless of which gain is used.
> 
> ...


 

 In to loads above 50 ohms or so where the JRC4556s in the output stage don't have to worry about running out of current the O2 should never be driven into clipping by changing the volume control.  With higher impedance loads it should always clip or never clip regardless of the volume pot's setting.  The pot is in between the gain and output stages so turning down the volume will have no effect on whether the input voltage is to high for the gain stage to amplify without clipping.  The only thing that should change whether or not it clips into those loads is changing the gain or increasing the input voltage.
   
  None of the 'phones in your profile are low enough impedance to reach the 4556's current limit like that so if it really is clipping at one volume setting and not another then it may be broken or something.


----------



## Draygonn

upstateguy said:


> I'm using the AC adapter that came with the amp... what ever nwav spec'd out I guess.... and the high gain is the default 6.5




I remember MrSlim mentioning something about wanting to upgrade the AC adapter for users with power hungry cans. I went with the upgraded adapter and I'm having no problems running High Gain(6.5) with my T50RPs. I don't know if this could cause your clipping but thought I'd toss it out in case its something to look into:


> There was some discussion that the 12v 200ma adapter may be a little "under spec'd " for the job. Earlier, NwAVGuy had re-assured me that there should not be any issues with this adapter for anyone but those that have very power hungry headphones, and I decided to just keep things as they were. This is the adapter that I have been testing with, and I can confirm that anyone with reasonably efficient headphones, will not have any problem with using this adapter, at all. The reason I am bringing this discussion back up, is that since I'll have to place an order with Mouser anyway, I would like to offer any North American users who have more power hungry headphones( I know at least one person mentioned "Thunderpants" and/or Fostex TP-50's ) the opportunity to upgrade to a more powerful AC Adapter (either the 16V 400ma or 16V 1000ma units depending on availability) for the cost of the price difference


----------



## maverickronin

Quote: 





draygonn said:


> I remember MrSlim mentioning something about wanting to upgrade the AC adapter for users with power hungry cans. I went with the upgraded adapter and I'm having no problems running High Gain(6.5) with my T50RPs. I don't know if this could cause your clipping but thought I'd toss it out in case its something to look into:  Quote:
> 
> 
> 
> ...


 
   
  My modded T50RPs are at least a little more power hungry than the K701 which is USG's most power hungry 'phone and they're fine a 2.5x from a ~2.2V DAC on AC with the 12V adapter and at 6.5x from my Cowon D2+ on batteries.


----------



## LizardKing1

Quote: 





maverickronin said:


> My modded T50RPs are at least a little more power hungry than the K701 which is USG's most power hungry 'phone and they're fine a 2.5x from a ~2.2V DAC on AC with the 12V adapter and at 6.5x from my Cowon D2+ on batteries.


 

 You're using the D1 DAC or the Maverick? Also what is the maximum input voltage the O2 needs without clipping? Is there a minimum treshold as well?


----------



## maverickronin

Using the Maverick D1's solid state output.
   
  Max input before clipping is  7/gain on AC and 4.5/gain on battery.
   
  I don't know why there would a threshold beyond whatever you could manage to hear.


----------



## PelPix

Is that voltage peak or RMS?
  
  Quote: 





maverickronin said:


> Using the Maverick D1's solid state output.
> 
> Max input before clipping is  7/gain on AC and 4.5/gain on battery.
> 
> I don't know why there would a threshold beyond whatever you could manage to hear.


----------



## mikeaj

Quote: 





pelpix said:


> Is that voltage peak or RMS?


 
   
  That's rms (pure sine wave).  Multiply 2 * sqrt(2) for peak-to-peak.


----------



## upstateguy

Quote: 





draygonn said:


> I remember MrSlim mentioning something about wanting to upgrade the AC adapter for users with power hungry cans. I went with the upgraded adapter and I'm having no problems running High Gain(6.5) with my T50RPs. I don't know if this could cause your clipping but thought I'd toss it out in case its something to look into:  Quote:
> 
> 
> 
> ...


 


  I opted for the upgraded adapter, but to be sure, the one I have says Triad model WAU16-400.  (Output is 16VAC @ 400mA)  Is this what you have?


  Quote: 





maverickronin said:


> My modded T50RPs are at least a little more power hungry than the K701 which is USG's most power hungry 'phone and they're fine a 2.5x from a ~2.2V DAC on AC with the 12V adapter and at 6.5x from my Cowon D2+ on batteries.


 

 I'm using my T-1s.  Not very power hungry.  Maybe it's not clipping, maybe it's some kind of distortion?  But the funny thing is that what ever it is, it seems to be decreasing with use. (maybe I'm just tired tonight)


----------



## arirug

re upstateguy
   
  My source is a desktop computer paired with a Cambridge DacMagic,


----------



## Draygonn

upstateguy said:


> I opted for the upgraded adapter, but to be sure, the one I have says Triad model WAU16-400.  (Output is 16VAC @ 400mA)  Is this what you have?




Yes


----------



## stv014

Quote:


> No, not a blind test, just an a-b comparison.


 

 That is not too reliable when the differences are small, like they are supposed to be between good amplifiers. But if the change is real, maybe you have a faulty unit ?


----------



## Willakan

Quote: 





upstateguy said:


> I opted for the upgraded adapter, but to be sure, the one I have says Triad model WAU16-400.  (Output is 16VAC @ 400mA)  Is this what you have?
> 
> I'm using my T-1s.  Not very power hungry.  Maybe it's not clipping, maybe it's some kind of distortion?  But the funny thing is that what ever it is, it seems to be decreasing with use. (maybe I'm just tired tonight)


 


  16VAC is plenty enough to ensure the power rails never drop out of regulation. As long as the input stage isn't overloaded, your amp should be working fine. It shouldn't overload even on high gain with the Fuze (pretty sure the Fuze doesn't pump out over 1.1V RMS) although it will clip with prettymuch anything higher - high gain is really only meant for use with MP3 players and other low-output sources as even 1.5V RMS USB DACs will clip with it.
   
  Nice to see your enjoyment of the O2 is increasing,anyhow.


----------



## upstateguy

Quote: 





stv014 said:


> That is not too reliable when the differences are small, like they are supposed to be between good amplifiers. But if the change is real, *maybe you have a faulty unit* ?


 

 That thought has been bothering me, but what ever the problem was, it seems to be dissipating.... why it should do that eludes me.
   


  Quote: 





willakan said:


> 16VAC is plenty enough to ensure the power rails never drop out of regulation. As long as the input stage isn't overloaded, your amp should be working fine. It shouldn't overload even on high gain with the Fuze (pretty sure the Fuze doesn't pump out over 1.1V RMS) although it will clip with prettymuch anything higher - high gain is really only meant for use with MP3 players and other low-output sources as even 1.5V RMS USB DACs will clip with it.
> 
> Nice to see your enjoyment of the O2 is increasing,anyhow.


 

 W -
   
  I'm not sure clipping is the right diagnosis.  What I initially reported was 'some' type of distortion on high gain, which was diagnosed by a number of guys, a few pages back, as "clipping".
   
  the other thing I notice is that if I turn the volume up really high, like past 3:00 the sound gets strained.  Do you notice this?


----------



## mikeaj

It's hard for circuits like these to be marginally faulty in terms of performance.  (The power management may be more finicky.)  Either it will work 100% or it won't work at all, mostly.
   
  The position of the volume control should have next to no difference on the sound other than volume, with less change than most other amps.  The exception is if you're using headphones with impedance maybe under 64 ohms or so, and you're maxing out the volume with a certain gain and source level, such that you're clipping the output of the device.  And that would sound really obvious (suddenly with a small change in the volume knob, you go from a clean sound to extreme clipping), so that's not what you're hearing.  To run into volume issues on lower-impedance headphones, you'd pretty much need to be using HE-6.  Many amps have similar characteristics or worse into lower-impedance headphones, in terms of clipping behavior.


----------



## upstateguy

Quote: 





mikeaj said:


> It's hard for circuits like these to be marginally faulty in terms of performance.  (The power management may be more finicky.)  Either it will work 100% or it won't work at all, mostly.
> 
> The position of the volume control should have next to no difference on the sound other than volume, with less change than most other amps.  The exception is if you're using headphones with impedance maybe under 64 ohms or so, and you're maxing out the volume with a certain gain and source level, such that you're clipping the output of the device.  And that would sound really obvious (suddenly with a small change in the volume knob, you go from a clean sound to extreme clipping), so that's not what you're hearing.  To run into volume issues on lower-impedance headphones, you'd pretty much need to be using HE-6.  Many amps have similar characteristics or worse into lower-impedance headphones, in terms of clipping behavior.


 

 So what do you think is going on?


----------



## limpidglitch

Quote: 





mikeaj said:


> It's hard for circuits like these to be marginally faulty in terms of performance.  (The power management may be more finicky.)  Either it will work 100% or it won't work at all, mostly.
> 
> The position of the volume control should have next to no difference on the sound other than volume, with less change than most other amps.  The exception is if you're using headphones with impedance maybe under 64 ohms or so, and you're maxing out the volume with a certain gain and source level, such that you're clipping the output of the device.  And that would sound really obvious (suddenly with a small change in the volume knob, you go from a clean sound to extreme clipping), so that's not what you're hearing.  To run into volume issues on lower-impedance headphones, you'd pretty much need to be using HE-6.  Many amps have similar characteristics or worse into lower-impedance headphones, in terms of clipping behavior.


 


  What about the potentiometer, could it be causing this?
   
  I remember the first times I used the O2 the pot was really scratchy, but it smoothed out in practically no time.
  From a lack of any other clear suspects, I assumed it to be caused by some slight oxidation on the windings inside the pot.


----------



## MikeW

I agree with the above, it does sound like it could be a problem with the pot, might want to make sure that S2 (gain switch) was properly installed and is not shorting to the VIA (small hole on the PCB). As it was a design problem that was later addressed. It's unlikely but possible.
   
   
  Quote: 





> *S2 PROBLEM – *The September version of the PCB artwork (9/14/11 release) has the via between R21 and S2 located too close to the corner “foot” on S2. While most have not had any problem, it’s highly recommended to slightly bend the leg in that corner of the switch inward, or if you have some heavy cutters, trim that leg shorter (don’t use small “precision” cutters as you’ll likely damage the blades). At the least, _make sure there is no contact when you’re soldering S2 in place_.


----------



## Willakan

Quote: 





upstateguy said:


> I'm not sure clipping is the right diagnosis.  What I initially reported was 'some' type of distortion on high gain, which was diagnosed by a number of guys, a few pages back, as "clipping".
> 
> the other thing I notice is that if I turn the volume up really high, like past 3:00 the sound gets strained.  Do you notice this?


 

 In the interests of science, I turned up my volume to 3:00 (which is coincidentally 3X my normal listening level if we go by degrees of rotation.) I'm afraid I was unable to maintain this listening volume for very long (with my normal setting of unity gain) due to the fact it was uncomfortably loud.
   
  I'm not entirely sure what an amplifier straining sounds like: I presume some subjective failure to deliver the dynamics and bass impact associated with a high listening level (Good God I hate this kind of terminology!) On that front the O2 did not appear to be straining: drum hits shook my eardrums unpleasantly violently and everything seemed to be in dischordant order.
   
  I would repeat this experiment on the 3X gain setting, but at that point it would be so loud that any commentary on the sound would be confined to expletives.
   
  Anyhow, as you say, it appears your problem is slowly fixing itself.
   
  EDIT: It is unlikely that the gain switch is shorting to the feed-thru via, as that would result in *massive* channel imbalance.


----------



## upstateguy

Quote: 





willakan said:


> In the interests of science, I turned up my volume to 3:00 (which is coincidentally 3X my normal listening level if we go by degrees of rotation.) I'm afraid I was unable to maintain this listening volume for very long (with my normal setting of unity gain) due to the fact it was uncomfortably loud.
> 
> I'm not entirely sure what an amplifier straining sounds like: I presume some subjective failure to deliver the dynamics and bass impact associated with a high listening level (Good God I hate this kind of terminology!) On that front the O2 did not appear to be straining: the drum hits shook my eardrums unpleasantly violently and everything seemed to be in dischordant order.
> 
> ...


 

 This in itself is really weird.  What's up with that?????
   
  With low default gain, slowly advance your volume.  Do you find a place (around 3:00 with my T-1s) where the SQ changes and gets grainy/shrill?  If you can't find the change in low gain, try high gain, and slowly advance the volume.  See if there is a place where the SQ changes.
   
  I agree with you, I can't keep it up there very long... too loud and it doesn't feel like it's doing the headphones any good.


----------



## Willakan

I have previously experimented with gradually raising the volume out of curiosity: I could perceive no shift in tone or anything else that I wouldn't expect from turning it up.
  As I built my O2 myself and it was my first audio-related DIY build, I experienced a certain paranoia as to its performance, not helped by the fact I wired the output jack backwards initially! In the end, however, I have been unable to find the O2 reproducing anything that isn't on the original recording - and my paranoia has led me to check several times!
   
  EDIT: As regards your comments on the GS-1 thread (thought I would respond here to keep everything together), I'd agree that the O2 doesn't use the nicest jacks/switches by default. That said, the input/output jacks are spec'd for 5000 insertions whilst the on/gain switches boast 10,000 cycles.
  Regarding Dynalo parts cost, I think it is around $200, but I don't think that includes casework or a linear power supply (have to use a switching DC wallwart). I built my O2 for about $100 (tad over £60 once I added up postage), with nice jacks (Neutrik) and all - I did DIY the front panel though, which saved me a little. And it is an incredibly ugly build to look at, as I broke all the clear acrylic I ordered off Ebay with my first three attempts at the front panel so had to use some yellowish stuff instead.


----------



## maverickronin

Quote: 





upstateguy said:


> With low default gain, slowly advance your volume.  Do you find a place (around 3:00 with my T-1s) where the SQ changes and gets grainy/shrill?  If you can't find the change in low gain, try high gain, and slowly advance the volume.  See if there is a place where the SQ changes.
> 
> I agree with you, I can't keep it up there very long... too loud and it doesn't feel like it's doing the headphones any good.


 

 The warmer sounding T1 which Tyll measured and is how USG previously described his T1 to me would reach about 111dB from 5V.  (2V from DAC, 2.5x gain)  Lots of voltage and not much current.
   
  Does/did it do that same kind of thing with weaker source like your DAP?  I don't turn mine anywhere near that loud unless I've EQed up the deep bass for movies and that's not a place where distortion is likely to be very audible.


----------



## mikeaj

Sometimes I crank it all the way to max, and I don't hear anything differently.  This is with a ~1V source on 1x gain into K601 (around 100 dB SPL / 1V input), so it's actually not loud enough for some classical music recordings.
   
  A while back I did several RMAA tests at 1x gain and max volume dial setting into three different headphones, and they didn't show anything strange.  I tested 1x gain with max volume and 5.1x gain with volume turned down (such that the effective total gain was 1x), and the distortion results were pretty much exactly the same.  The distortion products were at least like 10 dB above the noise floor of the sound card audio chain, so it wasn't a lack of resolution there.  So most likely at most gain levels, the performance of the amp is generally being limited by the output stage and not the gain stage, which is probably what you'd expect when it's driving headphones.


----------



## upstateguy

Quote: 





mikeaj said:


> Sometimes I crank it all the way to max, and I don't hear anything differently.  This is with a ~1V source on 1x gain into K601 (around 100 dB SPL / 1V input), so it's actually not loud enough for some classical music recordings.
> 
> A while back I did several RMAA tests at 1x gain and max volume dial setting into three different headphones, and they didn't show anything strange.  I tested 1x gain with max volume and 5.1x gain with volume turned down (such that the effective total gain was 1x), and the distortion results were pretty much exactly the same.  The distortion products were at least like 10 dB above the noise floor of the sound card audio chain, so it wasn't a lack of resolution there.  So most likely at most gain levels, the performance of the amp is generally being limited by the output stage and not the gain stage, which is probably what you'd expect when it's driving headphones.


 
  Quote: 





maverickronin said:


> The warmer sounding T1 which Tyll measured and is how USG previously described his T1 to me would reach about 111dB from 5V.  (2V from DAC, 2.5x gain)  Lots of voltage and not much current.
> 
> Does/did it do that same kind of thing with weaker source like your DAP?  I don't turn mine anywhere near that loud unless I've EQed up the deep bass for movies and that's not a place where distortion is likely to be very audible.


 

 I'll see if I can make an Audacity recording tonight that illustrates what I'm hearing as I turn up the volume.  No promises though. 
	

	
	
		
		

		
			




   
  Regarding loudness:  I never listen loudly except when testing/comparing.


----------



## sphinxvc

Took my O2 to a meet this weekend, people ♥'ed it for it's performance/cost.


----------



## upstateguy

Quote: 





sphinxvc said:


> Took my O2 to a meet this weekend, people ♥'ed it for it's performance/cost.


 

 Were there amps at the meet that sounded better?


----------



## sphinxvc

Quote:


upstateguy said:


> Were there amps at the meet that sounded better?


 

 Well yes, from closest to farthest, the Apache, the Audez'e Edition Isabellina, and a custom tube headphone amplifier that was there.  The transparency, control, speed, reach and _dynamics _on that custom tube amplifier are some of the best I've heard.  The KGSSHV is probably better as well.


----------



## kyoshiro

definetly a good amp for its money, may be even more powerful with lithium polymers, will have to try some ipowers later 
  btw since we have the u1 and u2 for output, which one do i roll? I currently replaced U1 with a OPA2134 I had lying around and ordered like 4 more op amps to try with my gear.


----------



## bellsprout

Quote: 





maverickronin said:


> The warmer sounding T1 which Tyll measured and is how USG previously described his T1 to me would reach about 111dB from 5V.  (2V from DAC, 2.5x gain)  Lots of voltage and not much current.
> 
> Does/did it do that same kind of thing with weaker source like your DAP?  I don't turn mine anywhere near that loud unless I've EQed up the deep bass for movies and that's not a place where distortion is likely to be very audible.


 

 dunno about the dbSPL/V. the T1 is listed as 102dB/1mw. 1mw is 0.77V into 600ohm. 5V would result in an increase of 20log(5/0.77) which is ~= 16dB, which is a lot more than the nominal 111dB the amp should be designed for. i know that T1 has about the same V sensitivity as AKG k701, which would die from 5V (well m years would die first, dunno about the cans)


----------



## Mad Lust Envy

How many MW does the O2 push into 600ohm? Merely curious.


----------



## mikeaj

Quote: 





kyoshiro said:


> definetly a good amp for its money, may be even more powerful with lithium polymers, will have to try some ipowers later
> btw since we have the u1 and u2 for output, which one do i roll? I currently replaced U1 with a OPA2134 I had lying around and ordered like 4 more op amps to try with my gear.


 

 U1 -- NJM2068 -- gain stage op amp
  U2 -- NJM2903 -- comparator for the power management circuit -- I don't think anybody considers rolling this one
  U3 -- NJM4556 -- right channel (either that or it's left channel) output stage op amp; two ICs on one package are used in parallel
  U4 -- NJM4556 -- left channel (either that or it's right channel) output stage op amp; two ICs on one package are used in parallel
   
  Check the third entry in the blog in August.  NJM2068, NE5532, OPA2134, OPA2227, OPA2277, LM4562, and TL072 were all tested for U1, and there are some results shown for those alternatives.  Others were tested for U3 and U4 but he didn't bother putting any graphs for those because the 4556 was supposed to be a lot better.
   
  There seems to be little motivation to choose something other than the 2068, or possibly the 5532 for high gains, or the 2277 for lower power draw, at least according to that small amount of data.  There's also the op amps he didn't test obviously.  But of course you're free to try whatever you fancy.
   
   


mad lust envy said:


> How many MW does the O2 push into 600ohm? Merely curious.


 

 88 mW (per channel) at 1% THD, more like 79 mW at < 0.002% THD.  It gets to about 7V for 80 ohms and higher loads.


----------



## Digital-Pride

Thanks, Mikeaj.


----------



## Mad Lust Envy

mikeaj said:


> 88 mW (per channel) at 1% THD, more like 79 mW at < 0.002% THD.  It gets to about 7V for 80 ohms and higher loads.




Hmm, so comparable to the E9 in terms of power. I like those numbers. Considering the T1 which is as efficient as 600ohms get, and I heard the E9 paired up well with them, so safe to assume the O2 will as well.


----------



## kyoshiro

Quote: 





mikeaj said:


> U1 -- NJM2068 -- gain stage op amp
> U2 -- NJM2903 -- comparator for the power management circuit -- I don't think anybody considers rolling this one
> U3 -- NJM4556 -- right channel (either that or it's left channel) output stage op amp; two ICs on one package are used in parallel
> U4 -- NJM4556 -- left channel (either that or it's right channel) output stage op amp; two ICs on one package are used in parallel
> ...


 

 Thanks! Guess I was smart to order 2 of each op amp. I was quite confused when I saw U1 to potentiometer to U3/U4


----------



## Naim.F.C

Just to chime in and say I have exactly the same issue, round about the same 3:00 mark too with the T1's. Maybe actually just under. Before that threshold, it's amazing, detailed, sharp, punctual and amazingly revealing (lacking in sub bass a touch though, and perhaps a little too energetic at top, but only ever so slightly). But past that point? Sibilance starts rearing its ugly head, barging other sounds out the way and essentially forcing me to tone down the volume.
   
  Shrill is exactly how I'd describe it too.
   
  In a way it's good because I hate when I sometimes creep up to this stupidly high volume, but also weird that it happens. I don't have this same level of sibilance, or such a point of immediate sharpness with my other amps, as I do the O2. Wonder what the reason could be for it?
  
  Quote: 





upstateguy said:


> This in itself is really weird.  What's up with that?????
> 
> With low default gain, slowly advance your volume.  Do you find a place (around 3:00 with my T-1s) where the SQ changes and gets grainy/shrill?  If you can't find the change in low gain, try high gain, and slowly advance the volume.  See if there is a place where the SQ changes.
> 
> I agree with you, I can't keep it up there very long... too loud and it doesn't feel like it's doing the headphones any good.


----------



## limpidglitch

Quote: 





naim.f.c said:


> Just to chime in and say I have exactly the same issue, round about the same 3:00 mark too with the T1's. Maybe actually just under. Before that threshold, it's amazing, detailed, sharp, punctual and amazingly revealing (lacking in sub bass a touch though, and perhaps a little too energetic at top, but only ever so slightly). But past that point? Sibilance starts rearing its ugly head, barging other sounds out the way and essentially forcing me to tone down the volume.
> 
> Shrill is exactly how I'd describe it too.
> 
> In a way it's good because I hate when I sometimes creep up to this stupidly high volume, but also weird that it happens. I don't have this same level of sibilance, or such a point of immediate sharpness with my other amps, as I do the O2. Wonder what the reason could be for it?


 

  
  Heve you tried EQing down the upper frequecies (~3kHz and above) dow a bit, say 3dB?
   
  My best suggestion for what is going on is still this:


----------



## Naim.F.C

I could, but won't that affect SQ in other ways? In any case, sibilance is still rare, and the trade off is immense detail retrieval. Might perhaps set up an EQ preset as you mentioned, just for that rare sibilant recording.
  
  Also, could you explain or elaborate on the diagram?
   
  Quote: 





limpidglitch said:


> Heve you tried EQing down the upper frequecies (~3kHz and above) dow a bit, say 3dB?
> 
> My best suggestion for what is going on is still this:


----------



## limpidglitch

Quote: 





naim.f.c said:


> I could, but won't that affect SQ in other ways? In any case, sibilance is still rare, and the trade off is immense detail retrieval. Might perhaps set up an EQ preset as you mentioned, just for that rare sibilant recording.
> 
> Also, could you explain or elaborate on the diagram?


 


  The curves show how the frequency response must look at different sound pressures for it to be perceived as flat by the human ear.
  It shows that your ear is most sensitive to sounds in the 2-4kHz region (speech), and less sensitive in both extreme ends of the range.
  But more importantly in our case now, it shows that respective to the middle frequecies, your ears get more sensitive to the extreme high/lows as sound pressure rises, and that by dialing down these these frequencies you will counteract this effect.


----------



## kyoshiro

by the way anyone considered throwing in those 9.6V 9V Nimh? will it get too much voltage? lol


----------



## Grev

Quote: 





kyoshiro said:


> by the way anyone considered throwing in those 9.6V 9V Nimh? will it get too much voltage? lol


 

 Sort of on topic, I have the 9.6v NiMh ones from Imedion/Maha and I asked John from JDSLabs if I could use them in the cmoys and he said it's fine, and I've since been using them along with the tenergy ones in the cmoy.  Since I've ordered two of the O2 amps from him pretty much today, want me to ask if they're ok just to make sure?


----------



## Willakan

The v-regs can cope with up to 20V, although they'll get a little warm at that stage (obviously exact warmth is somewhat dependant on power as well.) For example, I operate my O2 with an 18VAC adaptor, which results in it getting quite warm at 3X gain (with a 2.1V source) but it stays only slightly above room temperature when operated at unity gain (its normal mode of operation for me).


----------



## mikeaj

With 9.6V batteries, it should just charge to max capacity slower, unless I'm overlooking something stupid.  I didn't check all the max charge rates from every data sheet (actually I couldn't find one quickly so I gave up in one minute) and so on, but the trickle charging should still work within safe limits.
   
  Certainly there's no problem with having sub-12V power rails, which is what you'd get when running on battery.  The extra voltage over a 8.4V battery is no problem.  It's less than what the amp runs on normally when on AC power, and the amp is still going to cut the circuit off when the batteries drop too low.
   
  Possibly with some batteries other than the Tenergy, which were tested more thoroughly, you could get some hysteresis with the power management circuit resulting in the amp shutting itself on and off rapidly when the battery gets too low.  It depends.  That's not a huge deal as that just tells you you need to shut the amp off and recharge the batteries.


----------



## Grev

John replied very quickly and said it's fine.  Also said thr Tenergy when charged up goes as bit above 9.6v.


----------



## mikeaj

Quote: 





grev said:


> John replied very quickly and said it's fine.  Also said thr Tenergy when charged up goes as bit above 9.6v.


 

 Yeah mine (Tenergy 200mA low self-discharge) goes to like 10V.  I was just thinking that 9.6V batteries are likely to go higher than that on a completely full charge, which shouldn't be a problem.  But I couldn't find a derating curve for voltage over time on a very quick search.


----------



## maverickronin

Quote: 





bellsprout said:


> dunno about the dbSPL/V. the T1 is listed as 102dB/1mw. 1mw is 0.77V into 600ohm. 5V would result in an increase of 20log(5/0.77) which is ~= 16dB, which is a lot more than the nominal 111dB the amp should be designed for. i know that T1 has about the same V sensitivity as AKG k701, which would die from 5V (well m years would die first, dunno about the cans)


 

 Well that's what it says on Beyer's site but if its available I go with some independent numbers that someone like Tyll actually measured.  This pair is about 95dB/mW which is a pretty big departure from the official specs.  This sample is a little more efficient at about 97.5dB/mW but still pretty far from the official numbers.  I went with the less efficient one because its FR is closer to how USG described his T1 when we were discussing how their sound varied.
   


mad lust envy said:


> Hmm, so comparable to the E9 in terms of power. I like those numbers. Considering the T1 which is as efficient as 600ohms get, and I heard the E9 paired up well with them, so safe to assume the O2 will as well.


 

 There are comprehensive measurements on Voldermort's site but into 600 ohms the power output is pretty much identical


----------



## Mad Lust Envy

The thing that turns me off is that people seem to be having issues with clipping.


----------



## Willakan

You don't have issues with clipping unless you are using a high-voltage source with a high gain setting. There isn't a great deal that can be done about that: the O2 can only swing so much voltage. It's not as if the O2 clips due to some design flaw or is unable to drive hard-to-drive headphones.


----------



## Digital-Pride

Quote: 





willakan said:


> You don't have issues with clipping unless you are using a high-voltage source with a high gain setting. There isn't a great deal that can be done about that: the O2 can only swing so much voltage. It's not as if the O2 clips due to some design flaw or is unable to drive hard-to-drive headphones.


 


  Actually, according to Lord Voldemort's blog, the O2 can handle sources up to 2.8V on low gain with the AC adapter plugged in and 1.8V on battery power.  So, on low gain(which should be enough for most headphones) clipping should not be a problem.


----------



## Anaxilus

Quote: 





mad lust envy said:


> The thing that turns me off is that people seem to be having issues with clipping.


 

 Only the people NOT hearing the issues are calling it 'clipping'.


----------



## Willakan

I fail to see how, even by silly subjective standards, two people saying they felt the O2 sounded strained at higher volumes, one of which stated repeatedly that the effect seems to be diminishing, can be termed an issue, let alone multiple issues.


----------



## mikeaj

The only thing different about this amp compared to many audiophile amps (apparently it's not so for many pro amps, where undoubtedly the users can set the levels correctly), is that the volume control is after the gain stage.  This introduces an additional place for clipping to occur, other than the output.
   
  If somebody is using a gain of 7 / {source output voltage} or less on AC power, they are not clipping the gain stage.  If you have no idea what your source outputs, a M/M TRS cable or similar + $5 multimeter + test tone @ 60 Hz and 0 dBFS can give you a sufficiently-accurate reading.  Thus they're not hearing clipping (unless they're trying to drive something like HE-6 at a loud volume).  It's something else.
   
  What that "something" is:
  (1) some kind of explanation involving somebody's changing perception with increased volumes, maybe related to equal-loudness contours
  (2a) some kind of nebulously-defined amplifier property that causes an audible performance issue past a certain rotation of the volume control, despite an extensive array of traditional audio benchmarks and theory implying that there is probably no significant difference to be heard
  (2b) some kind of half-failed amplifier build causing the audible performance issue only at particular volumes, which may not apply to correctly-functioning amplifiers like the ones that were benchmarked
  (3) something else?
   
  Take your pick.


----------



## sphinxvc

I sometimes hear a slight crackling in the background during loud passages.  It's very subtle.  Is this the same thing you clippers are hearing?


----------



## wje

My Triad power adapter died after 2 months this past weekend.  I've never kept it plugged into a socket for more than 8 hours.  I'd move the amp around, so it would have time to cool, etc.  I did find an adapter at Radio Shack that is adjustable from 9V AC to 13V AC.  The end plug was the same size as that on the O2 amp, so no additional modifications were needed.  However, Radio Shack does charge $22.99 for the adapter, plus tax.


----------



## upstateguy

Quote: 





anaxilus said:


> Only the people NOT hearing the issues are calling it 'clipping'.


 


  What do the people hearing the issues call it?  
	

	
	
		
		

		
			





  
  Quote: 





willakan said:


> I fail to see how, even by silly subjective standards, two people saying they felt the O2 sounded strained at higher volumes, one of which stated repeatedly that the effect seems to be diminishing, can be termed an issue, let alone multiple issues.


 

 It should be noted that on default low gain, the O2 amp sounds incredible, and my unit is starting not to have issues on high gain either. 
   
  As far as the strained sound I thought I heard, I'm not sure what's going on at the very end of the pot, but no one listens there anywhere, it's too loud.  For all I know it's an issue with the wipers in the pot that might be going away with use.
   
  If I have time, I still intend to try to record what I'm hearing.
   


  Quote: 





sphinxvc said:


> I sometimes hear a slight crackling in the background during loud passages.  It's very subtle.  Is this the same thing you clippers are hearing?


 

 Nope.  No crackling.  Dead quiet background.
   
  I'm not convinced that what I heard was clipping.  I called it distortion.  But what ever it was it sounded like when you turned a radio up too loud, past the point of maximum sound quality.  I'll check again later tonight and see if it's still there.
   
  @ wje:  Regarding the Triad adapter:  I have it plugged in all the time.  I hope it doesn't fail.


----------



## MikeW

Well, my O2 definitely  has clipping in High Gain with a 2.1 V dac output. but it's completely expected. No surprise there, I knew it would before I even built it. High gain is for weak sources like a dap(.5 V output).. this is working as intended.
   
  It's a design limitation, and well documented. You can get around it when you build it if you set low-gain to 1x, and high gain to 3x, it will never clip. But that gives you less flexibility when using weak source.


----------



## Anaxilus

Quote:


upstateguy said:


> What do the people hearing the issues call it?


 
   
  Some examples below.  To me it's just a similar treble signature to what I get from the Bechmark DAC1 via HO and I doubt that is clipping.  Seems more akin to what has been referred to as digititus or digital glare effect found in some SS gear.  Some notice it others don't for a number of possible reasons.  It's a tonal character I am very sensitive to and do not appreciate personally.  Do you have a 'darker' phone like the HD650 or LCD2 r.1 to try?  I bet you won't notice it as much if at all.
  
  Quote: 





upstateguy said:


> I'm not sure clipping is the right diagnosis.  What I initially reported was 'some' type of distortion on high gain, which was diagnosed by a number of guys, a few pages back, as "clipping".
> 
> the other thing I notice is that if I turn the volume up really high, like past 3:00 the sound gets strained.  Do you notice this?


 
   
  Quote: 





upstateguy said:


> Do you find a place (around 3:00 with my T-1s) where the SQ changes and gets grainy/shrill?


 
   
  Quote: 





naim.f.c said:


> Shrill is exactly how I'd describe it too.
> 
> In a way it's good because I hate when I sometimes creep up to this stupidly high volume, but also weird that it happens. I don't have this same level of sibilance, or such a point of immediate sharpness with my other amps, as I do the O2. Wonder what the reason could be for it?


 
   
   
  Quote:Originally Posted by *sphinxvc* /img/forum/go_quote.gif 





> I sometimes hear a slight crackling in the background during loud passages.  It's very subtle.  Is this the same thing you clippers are hearing?


 

 ^ That sounds like something else altogether.  I haven't heard that from either of the O2 builds I've sampled.


----------



## Willakan

@Upstateguy
  I have a cunning plan theory as to where some of the harshness could be coming from. It is still a psychoacoustic trick, but now with 100% more reasons!
  As others have said, changes in volume affect perceived FR, to the point where the O2 could seem harsher at higher volumes. Seems strange that it is only harsh in a specific section of the volume control's travel - roughly the last quarter or so, would you say?
   
  The reason I'm asking is because the pot used in the O2 comes in two different tapers: both have been used in builds as the O2 has proved to be remarkably good at burning through Mouser's stock. Likewise, both tapers provide the same ultimate degree of volume adjustment, but one has the volume change perceptually spread out over the whole range of the pot, whilst the other has volume increasing relatively slowly, until it increases perceptually faster in the last 1/4 of the pot's travel.
   
  Volume suddenly increasing faster than expected at around 3:00 onwards (
	

	
	
		
		

		
		
	


	




) could quite possibly give the impression of the O2 suddenly becoming "harsh" sounding.


----------



## upstateguy

Quote: 





willakan said:


> @Upstateguy
> I have a cunning plan theory as to where some of the harshness could be coming from. It is still a psychoacoustic trick, but now with 100% more reasons!
> As others have said, changes in volume affect perceived FR, to the point where the O2 could seem harsher at higher volumes. Seems strange that it is only harsh in a specific section of the volume control's travel - roughly the last quarter or so, would you say?
> 
> ...


 

 That's interesting, but I didn't notice that the last quarter got louder faster....  I'll have to check it out tomorrow.  I've lost my perspective for tonight.
   
  Did you get the PM?


----------



## upstateguy

Quote: 





anaxilus said:


> Quote:
> 
> Some examples below.  To me it's just a similar treble signature to what I get from the Bechmark DAC1 via HO and I doubt that is clipping.  Seems more akin to what has been referred to as digititus or digital glare effect found in some SS gear.  Some notice it others don't for a number of possible reasons.  It's a tonal character I am very sensitive to and do not appreciate personally.  *Do you have a 'darker' phone like the HD650 or LCD2 r.1 to try?*  I bet you won't notice it as much if at all.
> 
> ...


 


  It seemed just as noticeable with my 650s.  But on the other hand, I'm not sure what it is or even if it is really there.  I'm going to have to listen some more.


----------



## upstateguy

*Anaxilus, **Naim.F.C, & Co.....*
   
   
  I made Audacity recordings of both low and hi gain last night, and there is a difference in the waveform.
   
*It seems that the 2v output from my North Star is indeed the clipping culprit.*
   
  PM me if you would like to listen to them yourself.


----------



## ballcall2

Folks do you know where I can order the parts for the O2? I want to build it myself but I don't find a store where I can order all the necessary parts


----------



## Willakan

Mouser is probably your best bet, with Farnell also of use if you're in the UK: but this is all documented in great detail on the blog. I can't even joke about NwAvGuy helping you put the items in your basket because he explains that as well.


----------



## limpidglitch

Quote: 





upstateguy said:


> *Anaxilus, **Naim.F.C, & Co.....*
> 
> 
> I made Audacity recordings of both low and hi gain last night, and there is a difference in the waveform.
> ...


 


  That's a relief 
  Did you use sine waves or music?


----------



## MikeW

Im not really understanding whats' going on here. 
   
  If you use a dac with more then 1.8 V RMS output, (most are 2.0 V) it WILL CLIP ON HIGH GAIN. There's no question about this, it's not broke, it's not maybe it will clip, it will clip, period. It's by design, and on purpose. So what is the issue again? 
   
  Most DAPs have half a volt... .5 V RMS, that is why you need high gain.


----------



## upstateguy

Quote: 





limpidglitch said:


> That's a relief
> Did you use sine waves or music?


 
  Music.  PM me if you want to hear it.
  
   


  Quote: 





mikew said:


> Im not really understanding whats' going on here.
> 
> If you use a dac with more then 1.8 V RMS output, (most are 2.0 V) it WILL CLIP ON HIGH GAIN. *There's no question about this, it's not broke, it's not maybe it will clip, it will clip, period. It's by design, and on purpose.* So what is the issue again?
> 
> Most DAPs have half a volt... .5 V RMS, that is why you need high gain.


 
  Why didn't you say so in the first place....


----------



## maverickronin

You know, I think I have another idea about what's up with USG's O2.
   
  The O2 has no charging indicator so if the AC was plugged in but not making contact for some reason you wouldn't know apart from testing for the clipping point.  If you keep using it like that the battery will run down and the clipping point will get lower and lower making the sound worse.  If after a few cycles of plugging and unplugging it finally does make contact it will charge, run off the rails you expect, and the problem will go away.
   
  On battery power 4.5/gain give you the maximum input before clipping and 4.5/2.5 = 1.8 which would make a 2V input clip.  On stuff with a decent amount of dynamic range it might even end up being pretty subtle and only obvious at higher volumes.
   
  I'm not sure that this really explains everything that USG said he heard but I don't really know how else it could have got better over time.


----------



## Twinster

Hi Naim.F.C,  how do you like the T1 with the O2?  Do you have to use the High gain (6.5x) on the O2 and where is the volume position at normal listening level?
   
  I'm asking because I'm waiting for my T1 now and just build my O2 last week and I'm hoping to be able to pair them.  My O2 have the gain set to 1x & 3x.  I may have to increase the high gain.
   
   
  Quote: 





naim.f.c said:


> Just to chime in and say I have exactly the same issue, round about the same 3:00 mark too with the T1's. Maybe actually just under. Before that threshold, it's amazing, detailed, sharp, punctual and amazingly revealing (lacking in sub bass a touch though, and perhaps a little too energetic at top, but only ever so slightly). But past that point? Sibilance starts rearing its ugly head, barging other sounds out the way and essentially forcing me to tone down the volume.
> 
> Shrill is exactly how I'd describe it too.
> 
> In a way it's good because I hate when I sometimes creep up to this stupidly high volume, but also weird that it happens. I don't have this same level of sibilance, or such a point of immediate sharpness with my other amps, as I do the O2. Wonder what the reason could be for it?


----------



## Twinster

Hey Wayne,  be sure to measure the voltage out of your new adapter because 13 volt might not be enough.
   
  Nwavguy explain it in the "Using the O2, Power jack" section. The O2 expect at least 14 volts and not more then 20. The 12 volt 200 mah from the BOM is actually putting out about 14 volts as per NwAvGuy. Also it need at least 200 mah min.
   
  To be safe I went with the 16 volts 400 mah like many other did.
   
   
  Quote: 





wje said:


> My Triad power adapter died after 2 months this past weekend.  I've never kept it plugged into a socket for more than 8 hours.  I'd move the amp around, so it would have time to cool, etc.  I did find an adapter at Radio Shack that is adjustable from 9V AC to 13V AC.  The end plug was the same size as that on the O2 amp, so no additional modifications were needed.  However, Radio Shack does charge $22.99 for the adapter, plus tax.


----------



## upstateguy

Quote: 





maverickronin said:


> You know, I think I have another idea about what's up with USG's O2.
> 
> The O2 has no charging indicator so if the AC was plugged in but not making contact for some reason you wouldn't know apart from testing for the clipping point.  If you keep using it like that the battery will run down and the clipping point will get lower and lower making the sound worse.  If after a few cycles of plugging and unplugging it finally does make contact it will charge, run off the rails you expect, and the problem will go away.
> 
> ...


 

 No batteries installed.  Don't know if that makes a difference.


----------



## maverickronin

Quote: 





upstateguy said:


> No batteries installed.  Don't know if that makes a difference.


 

 You don't have any batteries in it?
   
  Well my idea is shot then.  If it wasn't making contact like I was guessing then it wouldn't play at all because it would have no power.


----------



## Naim.F.C

I thoroughly enjoy them. In-fact, I don't currently have an amp that retrieves more detail from my music than with the O2. It is incredibly revealing. Only downside is it is a tiny bit harsher or sharper sounding than other amps I've tested. On rare occasion you can come across sibilance on certain tracks but only listening at high volumes. Don't get me wrong, it's not artificial or narrow sounding, it's still very natural and realistic, just has a teeny bit of edge sharpness at higher volumes.
   
  I do miss the warmth of the Continental somewhat (trust me it's not placebo, the difference is there), but I can definitely hear more micro details using the O2. So it's a trade off with some mellowness in place of intricacy and outright detail. Soundstage wise they are the same, which is great as the soundstage on the ALO is greater than the cMoyBB, Pico and SR-71A, and about on par with my old Concerto.
   
  My V200 should be with me this week so I'll compare the O2 with that as well. Clash of the titans really. One pushing the high value stakes, the other mid-fi.
   
  Volume wise, I actually use both the LCD-2 and T1 on low gain (with AC plugged in). Haven't really tested it much on battery. But on low gain, with the AC in, with the T1's on average I'm listening to them at around the 11 to 2:30 position, and with the LCD-2's around 1 to 4pm. T1's tend to favour low-mid volume listening, and the LCD-2's mid-high. High not being recommended, unless you want to lose the quality of your hearing over time.
   
  Quote: 





twinster said:


> Hi Naim.F.C,  how do you like the T1 with the O2?  Do you have to use the High gain (6.5x) on the O2 and where is the volume position at normal listening level?
> 
> I'm asking because I'm waiting for my T1 now and just build my O2 last week and I'm hoping to be able to pair them.  My O2 have the gain set to 1x & 3x.  I may have to increase the high gain.


----------



## sphinxvc

Quote:


naim.f.c said:


> Only downside is it is a tiny bit harsher or sharper sounding than other amps I've tested. On rare occasion you can come across sibilance on certain tracks but only listening at high volumes. Don't get me wrong, it's not artificial or narrow sounding, it's still very natural and realistic, just has a teeny bit of edge sharpness at higher volumes.


 
   
  Are the other amps you've tested softer?  I find_ just a bit_ of harshness & sharpness in every T1 I've heard.


----------



## kyoshiro

i've also noticed that 1 night of charging cant charge 2 200mah nimh 9vs fully with a 20VAC 1000ma charger 
  I only got like 6~7 hrs of play time then shut down mode
  sooo I went and bought a Powerex charger which should hopefully allow me to get the full 10 expected hrs


----------



## mikeaj

Quote: 





kyoshiro said:


> i've also noticed that 1 night of charging cant charge 2 200mah nimh 9vs fully with a 20VAC 1000ma charger
> I only got like 6~7 hrs of play time then shut down mode
> sooo I went and bought a Powerex charger which should hopefully allow me to get the full 10 expected hrs


 

 Wait, you sure about this, or don't you think you might be drawing the wrong conclusion?  6-7 hours runtime is normal for a couple of 200 mAh batteries.  Why and how would one charger not be able to charge them to capacity, while another one can?
   
  Anyway, what were the battery voltages after charging and then in shutdown mode?  For many models there should be some kind of capacity vs. voltage curve you can look at.


----------



## wje

Quote: 





twinster said:


> Hey Wayne,  be sure to measure the voltage out of your new adapter because 13 volt might not be enough.
> 
> Nwavguy explain it in the "Using the O2, Power jack" section. The O2 expect at least 14 volts and not more then 20. The 12 volt 200 mah from the BOM is actually putting out about 14 volts as per NwAvGuy. Also it need at least 200 mah min.
> 
> To be safe I went with the 16 volts 400 mah like many other did.


 

 Simon,
   
  Thanks.  I wasn't aware of that much variance that would be allowed / tolerated.  However, it is good to know.  The replacement adapter I purchased from Radio Shack is adjustable up to 13VAC with 800mA.  It seems as though I might be able to step up to the next level of power supply and set it in the 18V or so range.
   
  The Triads are quite cheap from the vendors that sell electronic components - usually a little under $6.00 (US $$.)   However, I think with so many O2 amps being built, most vendors are either in a low stock situation or out of stock for a month or so for that particular power adapter.  The only thing that rubbed me on the R.S. adapter was spending nearly $27.00 on it, including taxes.  There is a 30-day return policy, though, if I can locate something else.


----------



## kyoshiro

Quote: 





mikeaj said:


> Wait, you sure about this, or don't you think you might be drawing the wrong conclusion?  6-7 hours runtime is normal for a couple of 200 mAh batteries.  Why and how would one charger not be able to charge them to capacity, while another one can?
> 
> Anyway, what were the battery voltages after charging and then in shutdown mode?  For many models there should be some kind of capacity vs. voltage curve you can look at.


 


  Sorry should have said the AC 20VAC 1000mah wall adapter using the internal charging circuitry. But yeah I was actually expecting more hours with these 200mah  
  and i was referring to amount charged in the same amount of time. 
  As for battery voltage, I'll get it to shut down again tmr and have a test, didnt have a multimeter with me @ work 
  Also not having a charge indicator does create a few problems with not knowing when the battery is charged or not. 
  Am charging my 200mah GP 8.4V with my powerex charger, the imedions 9.6v charged in like an hr or so, these are still charging, prob cuz the 90ma isnt enough to kick it into rapid charge mode or something (it needs 100ma+)


----------



## Willakan

Wow: NwAvGuy has just revealed the board for 24/96 USB DAC capability will fit inside the existing O2 in the space otherwise occupied by the batteries. I find the idea of a tiny yet completely transparent signal chain quite appealing: USB cable goes in, sound for my headphones come out, all in a relatively tiny box (It will all fit in the smaller of the O2 enclosures apparently).
   
  And he bought a new scope to peer at I2S streams


----------



## DarknightDK

Saw that too. Looks like the this is going to be one hell of a portable source / amp combo.


----------



## Maxvla

Well if it's instead of batteries, it's no longer portable (for anyone) but truly transportable.


----------



## Draygonn

Am I correct in thinking If you are using USB input for the DAC you can't hook it to any DAPs anyway so the batteries would be moot?


----------



## Maxvla

Didn't look at the DAC, but I guess you are right. If it were a spdif input it could, but battery life would be even shorter.


----------



## kyoshiro

we could probably make it a riser card and just get a bigger enclosure while still having the batteries in place.


----------



## kiertijai

I apologize if this question has been asked,  I have followed this thread for some time
  and would like to know the performance of O2 amplifier comparing to the AMB mini3 amplifier


----------



## stv014

Quote: 





kiertijai said:


> I apologize if this question has been asked,  I have followed this thread for some time
> and would like to know the performance of O2 amplifier comparing to the AMB mini3 amplifier


 
   
  These measurements are from the NwAvGuy site.
   

 *[size=small]Measurement[/size]* *FiiO E11* *[size=small]O2[/size]* *[size=small]FiiO E9[/size]* *[size=small]AMB Mini3[/size]* [size=small]Frequency Response[/size] +/- 0.1 dB A [size=small]+/- 0.1 dB A[/size] [size=small]+/- 0.1 dB A[/size] [size=small]+/- 0.1 dB A[/size] [size=small]THD 1 Khz 150 Ohms[/size] 0.004% A [size=small]0.0016% A[/size] [size=small]0.005% A[/size] [size=small]0.002% A[/size] [size=small]THD 1 Khz 15 Ohms[/size] 0.011% B [size=small]0.0023% A[/size] [size=small]0.037% C[/size] [size=small]0.017% B[/size] [size=small]THD 20 hz 15 Ohms[/size] 0.017% B [size=small]0.0023% A[/size] [size=small]0.05% Good[/size] [size=small]0.01% B[/size] [size=small]THD 20 Khz 15 Ohms[/size] 0.011% B [size=small]0.010% A[/size] [size=small]0.003% A[/size] [size=small]0.45% F[/size] [size=small]IMD CCIF 15 Ohms[/size] 0.002% A [size=small]0.001% A[/size] [size=small]0.05% C[/size] [size=small]0.043% D[/size] [size=small]IMD SMPTE[/size] 0.0079% A [size=small]0.002% A[/size] [size=small]0.002% A[/size] [size=small]0.009% B[/size] [size=small]Noise A-Wtd[/size] -101.3 dBu B [size=small]-114 dBu A[/size] [size=small]-94.7 dBu C[/size] [size=small]-103.2 dBu B[/size] [size=small]Max Output 15 Ohms[/size] 63 mW B [size=small]337 mW A[/size] [size=small]1067 mW A[/size] [size=small]104 mW A[/size] [size=small]Max Output 33 Ohms[/size] 101 mW C [size=small]613 mW A[/size] [size=small]883 mW A[/size] [size=small]98 mW C[/size] [size=small]Max Output 150 Ohms[/size] 52 mW C [size=small]355 mW A[/size] [size=small]317 mW A[/size] [size=small]38 mW C[/size] [size=small]Output Impedance[/size] 0.5 Ohms A [size=small]0.54 Ohms A[/size] [size=small]10 Ohms C[/size] [size=small]0.9 Ohms A[/size] [size=small]Crosstalk 15 Ohms[/size] 48 dB B [size=small]65 dB A[/size] [size=small]63 dB A[/size] [size=small]40 dB C[/size] [size=small]Channel Balance[/size] 1.1 dB B [size=small]0.6 dB A[/size] [size=small]1.8 dB C[/size] [size=small]1.14 dB B[/size] Battery Life ~10 hours ~8 hrs / ~30 hrs AC Only ~5 hours
   
  Note: the maximum power of the O2 is specified for AC operation. When using batteries, the power output into 150 Ohms is reduced to 180-200 mW (depending on the battery voltage); the 15 and 33 Ohm maximum power values do not change as much, because these are current limited.


----------



## kiertijai

@stv014,   thanks so much for the info.
  soundwise which is better? or which genre of music the O2 or mini3 are more appropriate
  it seems like the O2 has more driving power so it can drive more difficult headphone, I think
  it should be able to drive the HD800, LCD2 , T1   but it may not be able to drive the HE6, is that correct?


----------



## mikeaj

Right, O2 is larger and heavier, and part of that is because of using two 8.4V batteries rather than one like the Mini3 uses.  They're not really comparable in that sense.  So of course the O2 can output more power.
   
  People report using HD 800, LCD2, T1, etc. with O2, and this can also be told by looking at the measurements at InnerFidelity.  Check out the data sheets and the power needed to reach 90 dB SPL and the impedance for a given headphone.  You need 100 times more power to reach 110 dB SPL as compared to 90 dB SPL, and 110 dB SPL peaks is about as loud as most people will listen for very quiet music with a lot of dynamic range (some may listen a little bit louder than that).  e.g. if headphones are 33 ohms and need 2 mW for 90 dB SPL, they will need 200 mW for 110 dB SPL so the O2 and E9 and many others can do, but some smaller portable amps may not be able to do.
   
  For those kinds of volumes, HE-6 needs more power than something like O2 can provide.


----------



## wje

Quote:


twinster said:


> Hey Wayne,  be sure to measure the voltage out of your new adapter because 13 volt might not be enough.
> 
> Nwavguy explain it in the "Using the O2, Power jack" section. The O2 expect at least 14 volts and not more then 20. The 12 volt 200 mah from the BOM is actually putting out about 14 volts as per NwAvGuy. Also it need at least 200 mah min.
> 
> To be safe I went with the 16 volts 400 mah like many other did.


 

 Being that my current Radio Shack adapter is within my 30-day return windown and tops out at a 13V AC setting, I think I'm going to exchange it today for their next level up model - the one that can do 18V or 22V AC.  I'll keep it on the 18V AC setting.  It's also capable of delivering 1,000mA, if required.


----------



## Willakan

Quote: 





kiertijai said:


> @stv014,   thanks so much for the info.
> soundwise which is better? or which genre of music the O2 or mini3 are more appropriate


 

 The O2 reproduces the input signal, but louder, with no perceivable colouration. It is your headphones which will decide the appropriateness of your setup for different genres.


----------



## sonitus mirus

Just received my JDS Labs-built O2 last night.  I plan on using this amp to replace my Headroom Micro Amp that I am currently using in my office.  I already yanked the batteries out, as I am only going to use this with AC power anyway.
   
  The build quality is generally very good, however, after pulling out the batteries, I noticed that a leg of the through hole resistor on the back left of the PCB (when viewed from the front) was extremely close to  the fastening screw for the back panel.  I just left that screw out to be safe, as I did not want to short the resister to the case.
   
  It runs cool, and it sounds good with my typical source of 320 mp3 (MOG) or Q9 Ogg Vorbis (Spotify) subscription music service tracks from my Squeezebox Touch.  I have been using the SB's internal DAC, which does a fairly good job for the source quality being used, but I'm not able to keep the volume at a fixed level (100%) like I was with my Micro Amp using the low gain setting.  The O2 amp is simply way too loud for my ears using the easy-to-drive ATH-M50s (38Ω 99dB) without significantly lowering the volume on the SB Touch. 
   
  I have been on a quest for new headphones to use at work, and I suppose that I will have to make sure these are not overly efficient.  I need a closed design at work, and I know the Denon's do not isolate enough (have D5000's), and I did not prefer the Beyer DT-770 (250Ω) over the M50s on a 2 week trial a few weeks back.  The Fischer Audio 003 is what I want to try, but they are impossible to find in stock from any site I feel comfortable with making a purchase.  I looked into the AKG K550, but AKG does not have the bass impact I crave.
   
  Anyway, the O2 is an amp, and it shouldn't change the sound, just make it louder.  That said, there are 2 things that I noticed in my very short audition between my Micro Amp and the O2.  I seem to enjoy the classic rock genre more with the O2 setup.  I used the crossfeed with the Micro Amp, so that may be the difference I believe I hear.  Also, the lower frequencies with the O2 seem to cut off more immediately, without as much resonance, if that makes any sense.  Listening to a BASS-heavy track from Deadmau5, when there is no bass present, it is absolutely gone with the O2, but with the Micro Amp, each deep note seemed to carry over a bit more into the next.  It appeared to be a tad bit sloppier before, where it sounds more precise now. 
   
  These are all very small differences that I probably cannot possibly notice outside my own imagination, and I have no way to properly ABX anything in my office.  Just going by the objective numbers, and having listened for a while now, I am keeping the O2 in my office and retiring the Micro Amp for now.


----------



## maverickronin

Quote: 





sonitus mirus said:


> I have been on a quest for new headphones to use at work, and I suppose that I will have to make sure these are not overly efficient.  I need a closed design at work, and I know the Denon's do not isolate enough (have D5000's), and I did not prefer the Beyer DT-770 (250Ω) over the M50s on a 2 week trial a few weeks back.  The Fischer Audio 003 is what I want to try, but they are impossible to find in stock from any site I feel comfortable with making a purchase.  I looked into the AKG K550, but AKG does not have the bass impact I crave.


 
   
  The Audio Technica W1000x are probably worth a look.  They don't have a ton of isolation but they sure beat the Denons in that area.  If you're up for a little DIY modded T50RPs sound really great too.


----------



## mikeaj

Quote: 





sonitus mirus said:


> It runs cool, and it sounds good with my typical source of 320 mp3 (MOG) or Q9 Ogg Vorbis (Spotify) subscription music service tracks from my Squeezebox Touch.  I have been using the SB's internal DAC, which does a fairly good job for the source quality being used, but I'm not able to keep the volume at a fixed level (100%) like I was with my Micro Amp using the low gain setting.  The O2 amp is simply way too loud for my ears using the easy-to-drive ATH-M50s (38Ω 99dB) without significantly lowering the volume on the SB Touch.
> 
> I have been on a quest for new headphones to use at work, and I suppose that I will have to make sure these are not overly efficient.


 
   
  Consider opening up the case and removing (snipping out) R19 and R23, which are around the gain switch area.  You needn't actually desolder them, just break the connection.  The leads are thin, so this is not difficult:

   
  That will drop the high gain setting (switch in) from 6.5x to 1x.  The low gain is default at 2.5x.  This should help with the volume being too high.


----------



## Willakan

The JDS Labs front panel looks very nice: if I have need of another O2 I'll think I'll cough up as opposed to DIYing it.
  I wouldn't bother with keeping the screw out: the proximity of the screw thread and the resistor lead is a known potential issue and JDS Labs have excellent quality control AFAIK, so the lead will have been clipped so it can never quite come into contact.
   
  +1 on clipping the High Gain setting resistors: you couldn't use high gain with the Squeezebox Touch anyway, as its 2.06V outputs would result in the input stage clipping (high gain is just for MP3 players and low-voltage sources rather than more volume). The O2 makes a lovely unity-gain buffer, and if you ever need more volume it's just a button press away.


----------



## sonitus mirus

Great information, and I will consider it.  I have found that it is easier to adjust the volume with the Squeezebox.  The screen is always on anyway when the music is playing, and there is no mechanical movement and wear over time as there would be using the amp's volume knob.  I like good sound quality, but I am certainly not going for critical listening.  The only thing I don't like is having to re-adjust the amp volume when I shut it off and back on, as I normally turn the volume all the way down before shutting off an amp or removing the headphones.  I'll get used to it, I'm sure.
   
  Thanks again!


----------



## Twinster

+1 on removing (cutting) the High gain resistors. I got mine set with 1x & 3x. As for a good set of headphone for work I personnaly use the Beyerdynamic DT1350 but also eyeing the Sony MDR-Z1000 if you don't mind on-ear headphone.
   
  For Fisher Audio Headphone try Dimitri. He will take care of you. 
	

	
	
		
		

		
			




   
   
 [size=medium]  Dimitri Trush 
  President/Manager,  
  Musica Acoustics 
trush@musicaacoustics.com
  tel +81 422 38-7452
  fax +81(0)422-38-7457
  skype: musicaacoustics
www.musicaacoustics.com
www.musicaacoustics.jp
[/size]
 [size=medium]




[/size]


  Quote: 





sonitus mirus said:


> Just received my JDS Labs-built O2 last night.  I plan on using this amp to replace my Headroom Micro Amp that I am currently using in my office.  I already yanked the batteries out, as I am only going to use this with AC power anyway.
> 
> The build quality is generally very good, however, after pulling out the batteries, I noticed that a leg of the through hole resistor on the back left of the PCB (when viewed from the front) was extremely close to  the fastening screw for the back panel.  I just left that screw out to be safe, as I did not want to short the resister to the case.
> 
> ...


----------



## DarknightDK

Quote: 





sonitus mirus said:


> Also, the lower frequencies with the O2 seem to cut off more immediately, without as much resonance, if that makes any sense.  Listening to a BASS-heavy track from Deadmau5, when there is no bass present, it is absolutely gone with the O2, but with the Micro Amp, each deep note seemed to carry over a bit more into the next.  It appeared to be a tad bit sloppier before, where it sounds more precise now.
> 
> These are all very small differences that I probably cannot possibly notice outside my own imagination, and I have no way to properly ABX anything in my office.  Just going by the objective numbers, and having listened for a while now, I am keeping the O2 in my office and retiring the Micro Amp for now.


 

 These are my observation of the O2 as well. The bass does not go as deep, but very tight and punchy. There is not much extension of lower bass notes. Hope this changes after burn-in (right now its probably sitting at 40 hours). However, the O2 is very enjoyable with great PRaT. Will post more impressions of the O2 after some extensive listening.


----------



## stv014

Quote: 





darknightdk said:


> There is not much extension of lower bass notes.


 
   
  It does not seem to lack extension (due to the low output impedance, it should stay flat enough with a headphone load as well), the roll-off is insignificant at audible frequencies. Although more bass is not added, either.


----------



## jmwreck

I hope pictures are enough for now, I cant comment on the audio aspect since I just recently finished boxing up my o2 from this
   


   
  to this
   



   
  never had a time to listen thoroughly


----------



## wje

Quote: 





wje said:


> Quote:
> 
> Being that my current Radio Shack adapter is within my 30-day return windown and tops out at a 13V AC setting, I think I'm going to exchange it today for their next level up model - the one that can do 18V or 22V AC.  I'll keep it on the 18V AC setting.  It's also capable of delivering 1,000mA, if required.


 

 Actually, last evening, I went to Radio Shack with the intention of exchanging the adapter.  They have the 18V / 24V adapter for $25.99, but it doesn't include the tip.  You have to buy that piece for an additional $6.99.  However, they didn't have the correct 2.1mm size version at the moment, so I didn't do the exchange.  Then, just for the fun of it, I asked the guy if he'd test the voltage of the adapter that I had purchased from them a few days earlier.  When set in the 13V position, it actually puts out 16.09V - or, on mine it does and I later confirmed that too when I got home.  Plus, the $22.99 adapter features the correct sized barrel connector already in place, so no additional funds are required.  I'm keeping what I have being that things should be running smooth at 16V for my O2.


----------



## sphinxvc

@jmwreck.
   
_Beautiful_.


----------



## Naim.F.C

Been A/B comparing the O2 vs with the V200 for the last few hours. Interesting findings...


----------



## uelover

Quote: 





naim.f.c said:


> Been A/B comparing the O2 vs with the V200 for the last few hours. Interesting findings...


 


  What have you found?


----------



## olor1n

Quote: 





naim.f.c said:


> Been A/B comparing the O2 vs with the V200 for the last few hours. Interesting findings...


----------



## Twinster

Please please report back 
	

	
	
		
		

		
		
	


	




. I'm assuming you are using the T1?  I'm curious on your finding because I have been reading on the Lake Poeple Amplifier this week and almost pull the trigger on the V90 that was in the FS to match the T1.  But if you come back with the O2 being impressive or comparable well even better 
	

	
	
		
		

		
		
	


	



  Quote: 





naim.f.c said:


> Been A/B comparing the O2 vs with the V200 for the last few hours. Interesting findings...


----------



## Willakan

The difference is either:
  1) Night and day.
  2) Nonexistent.
  3) "Just the last little bit of extra X in favour of amp Y."
   
  Think that's covered all the bases


----------



## Naim.F.C

I'm scared to post my impressions lol...
   
  But in any case, I spent about 2-3 hours direct A/B'ing yesterday. First I compared entire tracks, had a note pad and jotted down any elements of music heard, time stamps and everything. Compared. After that, I compared 10 second snippets of different songs.
   
  I'm not sure if volume was perfectly matched, probably close enough. I used an iPhone app, placed exactly the same spot near the T1 placed also in a set spot (neither were moved during db testing), and recorded DB using both the V200 and O2 till they showed roughly the same averages.
   
  In any case, I plan to do further testing before posting anything. Let's just say, the O2 is impressive to say the least. 
   
   
  Bear in mind, the DAC in question can have a big affect. Macbook Pro > Mini to Optical > Rein Audio X-DAC is an absolutely amazing sound. I doubt it's neutral, but it's so subtly musical, bassy and natural sounding.
  Unlike using it from say, an iPhone (LOD) or even (to a lesser degree) USB from X-DAC, there's little to none of that sibilance you can on rare occasion get with the T1. It's a slightly smoother more analogue sounding like affair.


----------



## shadow419

Quote: 





naim.f.c said:


> I'm scared to post my impressions lol...
> 
> snip......


 

  
  Please do share you impression.  While no one has to agree with your opinion, it's still your's to share if you choose.


----------



## MikeW

might want to sell your vio b4 you destroy it lol  nobodies gonna want it if you tell the world how your 85$ amp matched a 1000$ amp.
   
  edit: im being a little sarcastic, a half truth. I don't really think you'd have a hard time selling it though


----------



## wje

Quote: 





mikew said:


> might want to sell your vio b4 you destroy it lol  nobodies gonna want it if you tell the world how your 85$ amp matched a 1000$ amp.
> 
> edit: im being a little sarcastic, a half truth. I don't really think you'd have a hard time selling it though


 

 There's always Audiogon.  I'm sure it would sell quickly.


----------



## Crazy*Carl

Someone actualy conducted a blind test, I can't wait to hear the results against 1000 dollar gear.
   
  As soon as I get a mailing address, I am gonna get a JDS O2.


----------



## Naim.F.C

Bare in mind though, aside from the sonic differences, you have to consider the actual build quality and design as well. I'd imagine we put at least £200-£300 on the build and design of say, a Macbook Pro alone. The V200 is literally a tank with the most impressive engineered design compared to the nimble and rather flimsy design and chassis of the O2. One has a casing and connector's that feel like they'd survive a nuclear attack, the other feels like it would split open if dropped.
   
  I was talking about it to my other half, and she brought up an interesting point. She mentioned that the O2, is supposedly designed or originally built by one man, at least with respect to R&D, whereas the Violectric would have been researched and designed, potentially by a team of people since it is an actual company with staff paid to do such things. Comparative to NwAvGuy who's basically done it on charity. All these things, including rent and other costs factor in to the final production cost of an item.
   
  There is also the fact that you can potentially use two headphones on the V200 simultaneously. A small thing but actually quite useful. Literally my other half can just sit beside me, pick up another pair of headphones and plug them in to join my world. It's a welcome feature. A dual volume knob would have made it even better though.


----------



## Crazy*Carl

I don't really think the 1000 dollar price unjustified.  It takes alot to make those devices and people have to get paid.  And there is some to be said for features and build quality.  However, to often hear people equate that with placebo sound effects.  Sound is the most important thing to me.  I thank you for actually doing a blind test and I really want to see the results!  If your interested, I am conducing an mp3 vs lossless blind test in the sound science forum:

 http://www.head-fi.org/t/594167/blind-test-128kbps-mp3-vs-lossless#post_8118013


----------



## Willakan

I suppose it's a personal question. I treat my gear carefully (this is not meant as an insult, I'm not trying to imply that anyone else doesn't) and am not that bothered about aesthetics.
  My O2 cost £60, including postage, even though I went for the larger case and added Neutrik RCA and headphone jacks to ensure long-term durability on that front. It is, however, as ugly as hell, due to me skimping on the front panel, and smells slightly of Araldite, which is quite clearly splattered on the front panel on the inside, as I'm not very good at gluing things.
   
  I find many times that price, even for an exquisitely designed case that casts awe and wonder into all who look upon it/would survive me hitting it with a hammer, not really very appealing (having said that, I think you'll find the O2's case is tougher than it looks). I'd quite happily pay an extra £10-20 for a nice front panel though, in hindsight, but that's as much as I would throw after making my equipment look nice.
   
   
  Regarding the dual headphone jack: Think how many O2s you could buy for the cost of a V200
	

	
	
		
		

		
			





! They'll even have their own volume jacks!


----------



## shadow419

Quote: 





crazy*carl said:


> I don't really think the 1000 dollar price unjustified.  It takes alot to make those devices and people have to get paid.  And there is some to be said for features and build quality.  However, to often hear people equate that with placebo sound effects.  Sound is the most important thing to me.  I thank you for actually doing a blind test and I really want to see the results!  If your interested, I am conducing an mp3 vs lossless blind test in the sound science forum:
> 
> http://www.head-fi.org/t/594167/blind-test-128kbps-mp3-vs-lossless#post_8118013


 


  I agree with you.  If the O2 were a commercial offering with a larger desktop form factor, internal power supply, and nicer case/ergonomics would people balk at paying $200-300 for it?  Possibly, but if it sounds well and has enough power for your requirements it's definitely worth a listen imo.


----------



## Willakan

What's actually wrong with the current cases? The photos of the JDS Labs amps in particular I've seen look very nice. Nobody is about to wax lyrical for a paragraph about their beauty, but they certainly don't embarrass themselves. I don't think it's fair to paint something like the JDS Labs offering as vastly visually/structurally inferior to other commercial offerings.


----------



## Crazy*Carl

The only problem I have with the design is all front inputs.  Its not that bad though, I can minimize the affect with 90 degree male cables.


----------



## shadow419

Quote: 





willakan said:


> What's actually wrong with the current cases? The photos of the JDS Labs amps in particular I've seen look very nice. Nobody is about to wax lyrical for a paragraph about their beauty, but they certainly don't embarrass themselves. I don't think it's fair to paint something like the JDS Labs offering as vastly visually/structurally inferior to other commercial offerings.


 


  Nothing is wrong with the case.  I love all the  O2's I've put together, but when being realistic about it I know the enclosure was chosen for functionality and cost first and looks a distant second.  I like the way the O2 looks, but it could be improved.


----------



## MikeW

The stock case is quite sturdy. Honestly, it looks like it could easily withstand a 5 foot drop onto pavement. Especially as light as the unit is. As far as internal build quality?
   
  I built it myself, I took my time, and I used good quality solder and parts. It's built extremely well. Proudly, made in the USA.
   
  The only thing that could be improved is the jacks, and rear plugs for power/input. But this was designed for mobile use, not desktop. So all the front connections make sense.
   
  There have been quite a few (DIYAUDIO Thread) that have made custom cases and moved the power/input/ac in to the rear, and used higher quality RCA and 1/4 jacks. It's really all up to the builder.
   
  is 1000? unjustified? For the V200?
   
  I don't know, it's hard to say, R&D, payroll, small company, profit margin.. If some giant consumer electronics company made the same thing it'd probably cost 200$. But a giant consumer electronics company would not make such a product to begin with (for whatever reason). I'd imagine the actual parts cost to be well under 200$. But perhaps not to a small company.
   
  If you take a look at the V90, remove the blue transformer from it's case, there's not a whole lot of electronics there, about as much as an O2.
   
  If I can build this thing for 85 bucks, Sony could build it en mass for 30$. But they are too busy making products for 8$ to be bothered.


----------



## Naim.F.C

It's certainly an interesting debate. I still actually believe the V200 is reasonably priced given the performance, competition pricing, discussed facets and the actual quality and build of the product itself. It really is exceptionally built and designed. I also believe it to be the best solid state amp I've ever tried or used, however small the lead margin may be, it's still there after all. It's kind of like everything in life really, premium's to be paid for the very best. You ever ask yourself why people pay £600 for top end graphics cards that offer only 5-10% extra performance? And then double or triple card SLI set ups where diminishing returns are worse.
   
  The O2 is without doubt a game changer. It was necessary as I honestly feel the audio-fi world is and has been getting well out of control for some time. Could the V200 be cheaper? Sure. But given some of the prices of ultimate tier gear, I'm going to assume they offer very little difference in performance or quality compared to even the V200, again for probably 2-3 times the price if not more. But then that's like everything in the audio world, even between headphones etc.
   
  The V200 is far from being ludicrously priced. If you want controversial opinions or comparisons, there are so many other things that are worse in the audio world. Even with hugely popular products, like for example, the LCD-3's. I'm sorry, but that right there is a bigger price gouge if I ever saw one.


----------



## uelover

Why do I seems to infer that the O2 performs respectably well (if not on par) with the V200 on SQ alone??
   
  I am still waiting out to see if there is version of O2 that uses a clean external PSU and accepts RCA inputs.


----------



## MikeW

the PSRR on the 02 is so insanely good that the power supply hardly matters at all. Why a design like this can't be done on other gear? Why do we need 400$ separate boxes for PSU? Hell if I know, the O2 outperforms those models, with it's mere 10$ wallwart, no excess needed.
   
  600 euro graphics cards? what is that like 800 usd?
   
  The only graphics cards at that price are Dual GPU on a single card solutions, and the performance gain is more like 70%.
   
  The next closest would be AMD's best 79xxx series that was just released, it's not 600 euro though, and it's about 30% faster.
   
  5-10% faster? your talking about a mid-range to high end product. With a price bump of of 325 > 400$.. 75$ increase. 
   
  SLI is almost double the performance, so that whole argument is silly.
   
  A bad analogy, but yes, in life, with everything you do pay massive premium for that last 10%.
   
   
  Quote: 





> *Single AC/AC Wall Adapter* - An inexpensive AC/AC two wire wall transformer can provide a true split supply using half-wave rectification. While half-wave might seem less than ideal, the performance is in the implementation and the advantages are numerous. Wall transformers are already safety agency approved and available for local power/plugs in various countries. They come with standard barrel connectors allowing the use of a small inexpensive power jack on the amp. The amp can operate perfectly without the batteries installed. There’s no high frequency switching “hash” to worry about. All that makes an AC wall transformer the best choice for the O2. Anyone doubting the performance of a half-wave power supply should check out the performance results in the first O2 article including the incredible noise performance. All those measurements (marked “AC”) were using this power supply. It works great!
> 
> *POWER SOURCE:* To geek out for a moment. An often unappreciated parameter of audio circuits is PSRR—Power Supply Rejection Ratio. It’s basically the ability of the circuitry to reject noise, ripple and variations on the power supply. In a lot of discrete designs PSRR is relatively poor and it’s really awful in most single-ended amps. That makes those designs sensitive to even small amounts of noise or variations on their power supply. By comparison, _you can listen to the O2 even at full volume on the high gain setting, and attach or disconnect the AC power and there’s zero noise in the headphones_. The entire power supply is abruptly jumping up and down by 30% and it’s inaudible! Try that on a single-ended zero feedback and you might damage your headphones the transient at the output will be so large.


----------



## Crazy*Carl

Yeah, you actually get what you pay for in gfx cards - and there is a very quantifiable benefit.


----------



## maverickronin

Quote: 





uelover said:


> Why do I seems to infer that the O2 performs respectably well (if not on par) with the V200 on SQ alone??
> 
> I am still waiting out to see if there is version of O2 that uses a clean external PSU and accepts RCA inputs.


 

 The desktop version is going to have a 1/4" TRS and RCA jacks.  The power supply is going to improved a bit too.  The specifics haven't been finalized but given the PSRR or the rest of the circuit its not like you'll be able to hear the difference even though it will probably show up on the dScope.


----------



## uelover

Quote: 





maverickronin said:


> The desktop version is going to have a 1/4" TRS and RCA jacks.  The power supply is going to improved a bit too.


 

 Sounds interesting.


----------



## Naim.F.C

I'm willing to bet that the mark up made on high end graphics cards is more than Violectric makes on the V200. So I disagree personally.
   
  In-fact, mid and high end graphics cards generally use chipsets and shared components from the same process. Often the main difference between upper tier GPU's and CPU's etc, is that the higher end one's were cherry picked one's that happen to perform better despite being from the same manufacturing process and line. The cherry picked chipsets are put together in a better package with a few extra additions to make the difference. I purchased an Intel i7 920 near release for pretty cheap (around £180), on air cooling I was able to OC it to 4ghz. The best CPU at the time performed worse, and cost nearly £1k. Took years before a stock i7 chip actually competed with my OC'd cheaper one.
   
  I remember also purchasing numerous lesser priced graphics cards in the past and simply unlocking them to the upper model (bios flash), and then OC'ing past it's performance too, (i.e 5850 to 5870) all for half the price.

 Bear in mind Carl, you mentioned that amps, DAC's etc made no difference to sonic performance, and from your iPod. This I also strongly disagree with. I bet you £500 in an earlier thread that I could do blind tests telling your iPod and an amp of choice apart, just as I did telling specific amps apart too, namely lesser priced or portable one's, i.e SR-71A, cMoyBB, ALO Continental etc. There is a quantifiable difference between a lot of amps, not all mind, though generally these differences are quite slight, like nearly everything else in the audio world. And it's a similar thing with the V200, just on a very miniscule degree. The V200 is not a completely neutral amp. It actually has a very slight emphasis on sub bass, smoother highs and musicality. The O2 as far as I can tell, is strictly neutral across the board.
   
   
  Quote: 





crazy*carl said:


> Yeah, you actually get what you pay for in gfx cards - and there is a very quantifiable benefit.


----------



## DarknightDK

The O2 is a very very good headphone amplifier at any price and I am surprised at how good it sounds. I have been comparing the amp section with my 10SE and I now know what neutral should sound like. The O2 is a fantastic listen and am enjoying it immensely.
   
  Will pick up the desktop version as well. Hoping for better rear connectors, volume control and audiophile grade components. I think if NwAvGuy takes the time to design a high-end amplifier without it being limited to a budget, its going to be the one to beat. Already the O2 is a giant killer.


----------



## mikeaj

Quote: 





darknightdk said:


> The O2 is a very very good headphone amplifier at any price and I am surprised at how good it sounds. I have been comparing the amp section with my 10SE and I now know what neutral should sound like. The O2 is a fantastic listen and am enjoying it immensely.
> 
> Will pick up the desktop version as well. Hoping for better rear connectors, volume control and audiophile grade components. I think if NwAvGuy takes the time to design a high-end amplifier without it being limited to a budget, its going to be the one to beat. Already the O2 is a giant killer.


 

 Out of curiosity, which components would you consider not to be audiophile grade?  The op amps, resistors (they're 1% metal film, so this I doubt), electrolytic / ceramic / film capacitors used, AC/AC adapter, or what?  Note that several more expensive op amps were tested, and they performed worse for this application than the cheaper ones chosen.  Also a few other audio coupling capacitors were also tested, and they performed pretty much the same.  Performance on AC vs. battery power is pretty much the same, so the power supply isn't a limitation either.  Sure, there were compromises made to keep the cost down, the board not larger than it already is, and the battery life not lower than it already is at like 6-8 hours with standard batteries, but there weren't too many big compromises made that ultimately detract a lot from the performance.
   
  The Wire is more of a no-holds-barred higher-performance DIY headphone amplifier if you want something like that. There are some measurements in the diyaudio thread that show (probably inaudibly) better performance than the O2.  Unfortunately for users who just want an amp and aren't interested in building for the sake of building, the design is pretty much just the amp itself, leaving things like the case, topology (balanced or unbalanced inputs and outputs), volume control, etc. up to the builder.  There's less support and sources for getting the amp.


----------



## Shike

Quote: 





naim.f.c said:


> I'm willing to bet that the mark up made on high end graphics cards is more than Violectric makes on the V200. So I disagree personally.


 
   
  And who presumably has higher R&D costs?  Those have to be recouped, so a larger margin is reasonable IMO.


----------



## Anaxilus

Quote: 





naim.f.c said:


> I'm willing to bet that the mark up made on high end graphics cards is more than Violectric makes on the V200. So I disagree personally.


 

  You'd be wrong actually.  Maximum PC had a spread about it a few years back.  The margins are surprisingly thin but obviously increase the more upscale you get.  Computer silicon is quite a cut throat business unless you can monopolize some aspect of it.  
   
  Most high end amps have way more margin than just about anything in electronics I've seen.  It's pretty ridiculous.  Doesn't mean they all fail to perform though most seem to IME.


----------



## MikeW

Quote: 





> I remember also purchasing numerous lesser priced graphics cards in the past and simply unlocking them to the upper model (bios flash), and then OC'ing past it's performance too, (i.e 5850 to 5870) all for half the price.


 
   
  Coming from another computer enthusiast, who also has a I7 920 (D0 Stepping) @ 4 Ghz, i call BS on this.
   
  For one, the 5870 was not nearly twice the cost of the 5850. It was at most 100$ more, likely closer to 75$. And yes, there was about a 10% performance lead. We're talking 300$ vs 350, or 350 vrs 400$ here..
   
  Also, yes you can use bios updates and overclock a 5850 to stock 5870 performance or higher, however the 5870 can overclock that much further and maintain it's lead.
   
  Your exagerating here, neither of those cards where "high end" either, the 5870 was, at one time the top "single gpu solution" but if we are talking strictly "high end" we must consider  5900, dual GPU solution, it's the only thing close to the previous mentioned 600 euro's, and it's almost twice as fast as a 5870.


----------



## maverickronin

My i7 920 only runs at 3.9GHz....


----------



## Anaxilus

Quote: 





maverickronin said:


> My i7 920 only runs at 3.9GHz....


 

 Lol, I'm still rockin' the Core 2 duo E8400 3.0ghz on an X48.  Can't believe how long I've been able to extend this PC compared to my past builds.  Got 2 SSDs in RAID0 and a 6970 though.
   
  Personally I don't OC anymore as I just prefer rock solid reliability to BSODs.


----------



## maverickronin

Quote: 





anaxilus said:


> Personally I don't OC anymore as I just prefer rock solid reliability to BSODs.


 

 I test all my OCs thoroughly.  If 24 hours of Prime95 doesn't take it down then I don't see what else will.  I could have gone to 4GHz but it only lasted a few hours at that speed.  Just about the only time my PC is ever off is if I'm switching out parts or the power dies.  Currently rockin' 51 days of uptime since the last power interruption.
   
  I get to have my cake and eat it too.


----------



## Naim.F.C

No BS at all. 4ghz on a D0 step indeed, with a Noctua in an Antec 1200 case. I used some thermo paste that came like 3rd best on some massive HardOCP comparison, and honestly, it made an amazing difference. Ran it through Prime95 among others for prolonged periods and it was stable. OCZ Platinum ram at the time. Admittedly, these days I've pipped it down to 3.8ghz as I started getting a few anomalies after a year or so (I'm guessing my fan or case just needs a clean or something).
   
  And I remember the 5850 was on offer at OCUK at one point for like £180 whilst the 5870 was at like £320 to £350 (I know because I picked up two of them for the price of one 5870!). Can't comment for US prices, I'm based in the UK here. Also, I regard the best single GPU platform on the market as "high end". I regard dual and multi card set ups as "ultra high end", and most often than not they do not scale up to double the performance, unless things have improved in the last few years. I've been out of the PC game for a while.
   
   
  Anyway, I know the pressures on. And I need to be completely sure none of my opinions are remotely placebo affected, which lets face it is a powerful mental affliction that anyone can and probably has been affected by. Been conducting further tests all night. Problem before was that I was comparing RCA-Mini from the X-DAC to the O2, with Balanced from the X-DAC to the V200. I will say there were audible differences, one's I have pinned down to specific frequency changes, the problem is however, I don't know if these differences are from the X-DAC itself or the V200. 
   
  In any case, I'll be doing further comprehensive comparisons, this time with "X-DAC > RCA to Mini > O2" vs "X-DAC > RCA > V200".
   
  On a side note, NwAVGuy needs to design an O2 with balanced connections lol.
  
  Quote: 





mikew said:


> Coming from another computer enthusiast, who also has a I7 920 (D0 Stepping) @ 4 Ghz, i call BS on this.
> 
> For one, the 5870 was not nearly twice the cost of the 5850. It was at most 100$ more, likely closer to 75$. And yes, there was about a 10% performance lead. We're talking 300$ vs 350, or 350 vrs 400$ here..
> 
> ...


----------



## Anaxilus

Quote: 





maverickronin said:


> I test all my OCs thoroughly.  If 24 hours of Prime95 doesn't take it down then I don't see what else will.  I could have gone to 4GHz but it only lasted a few hours at that speed.  Just about the only time my PC is ever off is if I'm switching out parts or the power dies.  Currently rockin' 51 days of uptime since the last power interruption.
> 
> I get to have my cake and eat it too.


 

 I could do that but if or when something happens that lost time I'm never getting back for diagnostics.  Don't want to deal with it anymore for the relatively minimal gain (in most cases).  It's fun though.  I remember the old pencil graphite days.


----------



## Naim.F.C

Dude, with CPU's over the last few years the gains have been anything but minimal. Heck if you use Photoshop, Lightroom, Premiere Pro, After Effects etc like me, the differences are sometimes night and day.
  
  Quote: 





anaxilus said:


> I could do that but if or when something happens that lost time I'm never getting back for diagnostics.  Don't want to deal with it anymore for the relatively minimal gain (in most cases).  It's fun though.  I remember the old pencil graphite days.


----------



## Anaxilus

Quote: 





naim.f.c said:


> Dude, with CPU's over the last few years the gains have been anything but minimal. Heck if you use Photoshop, Lightroom, Premiere Pro, After Effects etc like me, the differences are sometimes night and day.


 

 Dude, I said in *most *cases.  Not everything ramps up to a 'night and day' difference.  I doubt your 4ghz Oc is getting you double the performance.


----------



## maverickronin

Quote: 





anaxilus said:


> I could do that but if or when something happens that lost time I'm never getting back for diagnostics.  Don't want to deal with it anymore for the relatively minimal gain (in most cases).  It's fun though.  I remember the old pencil graphite days.


 

 I guess it depends what you use it for.  You can get some pretty huge gains in serious number crunching applications like video encoding and post processing.


----------



## maverickronin

Quote: 





anaxilus said:


> Dude, I said in *most *cases.  Not everything ramps up to a 'night and day' difference.  I doubt your 4ghz Oc is getting you double the performance.


 

 That would be pretty impressive for a 50% OC.


----------



## Anaxilus

Quote: 





maverickronin said:


> You can get some pretty huge gains in serious number crunching applications like video encoding and post processing.


 
   
  Like what 20-30% at best?  Now he's got 'anomalies' after a year that might be dustbunnies?  It's cool if you need it and can burn hardware or upgrade every cycle.  I just prefer reliably upgrading during revolutionary tech cycles not evolutionary ones.  If I made my money by squeezing out an extra 30% from floating point I'd be down and I totally understand.  Luckily I'm not in that spot as evidenced by my E8400.


----------



## Anaxilus

Quote: 





maverickronin said:


> That would be pretty impressive for a 50% OC.


 

 I know right!  Like night and day!


----------



## maverickronin

Quote: 





anaxilus said:


> Like what 20-30% at best?  Now he's got 'anomalies' after a year that might be dustbunnies?  It's cool if you need it and can burn hardware or upgrade every cycle.  I just prefer reliably upgrading during revolutionary tech cycles not evolutionary ones.  If I made my money by squeezing out an extra 30% from floating point I'd be down and I totally understand.  Luckily I'm not in that spot as evidenced by my E8400.


 

 You just have to go overkill in your stress testing.  It me took like a week and a half to dial mine in.  Change some settings, fire up Prime95, find it crashed after 14 hours, turn it down a hair, try again, etc.  I checked when I put this build together and it was in July '09.  I've been rock solid for 2 and a half years now.
   
  It takes some effort to do it properly but for those of us on a budget its not much different from any other type of DIY.


----------



## kyoshiro

building a fabrication plant goes into billions, yields are not high until near end of life. The chips that have bad transistors goes out as lower models (thus the reason why we can Overclock, we really just try and use the deem "broken" transistors which were binned).
  card makers make more money with reference boards because those boards are given by nvidia and they just package it, 2-3 months later, those ones are the customized cards by the card maker. 
  (just my random info for you guys from someone who works in the IT industry and know people in the hardware industry  )


----------



## mikeaj

It's the reference board designs (not the boards themselves) that are given by AMD and Nvidia.  Of course chip designers want to help out those manufacturers buying chips, so they make helpful reference designs to help products get to market faster, among other things.  Quite differently than for other IC/chip makers making more mundane things like transistors / op amps / DSPs / etc., AMD and Nvidia control when the board partners are allowed to release cards based on non-reference design; it takes some time to design a new PCB (well less for just a custom cooler), but that's not the only reason why there's the delay.
   
  There's huge costs to recoup for the fabs, but the chips themselves aren't cheap due to the size, latest process technology, and yields.  Add in lots of GDDR5 memory, lowish RDS(on) MOSFETs, etc., and a cooling mechanism, and the cost isn't that low.  Of course they make much larger margins on the high-end stuff though.  
   
  Now the question for me is:  wait for Ivy Bridge or Haswell?  Unfortunately I don't think any of you can look into the future for me, so your guess is probably as good as mine.  I'm stuck on 45nm Core 2 Duo.


----------



## kyoshiro

Actually in Nvidia's case its actually given to them and made at Foxconn (I know the CEO of one of the card makers) But yeah card makers make the most money out of reference boards.
  Ivy Bridge is a good upgrade for you lol, Im using a i7 920 as my main with a Q6600 and E7200 machine as my fileserver/VM server and development server. 
  
  Quote: 





mikeaj said:


> It's the reference board designs (not the boards themselves) that are given by AMD and Nvidia.  Of course chip designers want to help out those manufacturers buying chips, so they make helpful reference designs to help products get to market faster, among other things.  Quite differently than for other IC/chip makers making more mundane things like transistors / op amps / DSPs / etc., AMD and Nvidia control when the board partners are allowed to release cards based on non-reference design; it takes some time to design a new PCB (well less for just a custom cooler), but that's not the only reason why there's the delay.
> 
> There's huge costs to recoup for the fabs, but the chips themselves aren't cheap due to the size, latest process technology, and yields.  Add in lots of GDDR5 memory, lowish RDS(on) MOSFETs, etc., and a cooling mechanism, and the cost isn't that low.  Of course they make much larger margins on the high-end stuff though.
> 
> Now the question for me is:  wait for Ivy Bridge or Haswell?  Unfortunately I don't think any of you can look into the future for me, so your guess is probably as good as mine.  I'm stuck on 45nm Core 2 Duo.


----------



## Crazy*Carl

Quote: 





mikeaj said:


> Now the question for me is:  wait for Ivy Bridge or Haswell?  Unfortunately I don't think any of you can look into the future for me, so your guess is probably as good as mine.  I'm stuck on 45nm Core 2 Duo.


 

 I still have the e8400, but I am in no rush for upgrade.  The only reason I have for upgrading is bf3, and that's not cause enough for to get a $1500 rig yet.  Maybe kepler and ivy bridge...


----------



## Maxvla

Wait.. is this an amplifier thread?


----------



## firev1

Quote: 





naim.f.c said:


> On a side note, NwAVGuy needs to design an O2 with balanced connections lol.


 


  I'm gonna bring this topic back on track =P.
   
  Guess we all know that we will never design it. But self designing a balanced topology to add on using a taller casing isn't out of order for the folks at diyaudio. That being said, its been around 2 months with my 2 O2 amps, I really love um, they provide the resolution that I only found in the much higher end amps that I tried at jaben but could never afford(college-fi). I really have fun reexploring my collection again on my TF10s, digital or disk. I don't really use headphones these days but having them 2 amps makes me wanna get a replacement fast( still deciding).


----------



## maverickronin

Quote: 





maxvla said:


> Wait.. is this an amplifier thread?


 
  Quote: 





firev1 said:


> I'm gonna bring this topic back on track =P.


 

 Exactly.  What's an Objective2 thread without silly criticisms?
   

   
  I still love mine.
   
  I can't wait for the desktop version either.  I'm probably going to build a customized version with lots of inputs, a crossfeed circuit, and maybe a remote controlled resistor ladder stepped volume control.


----------



## Naim.F.C

I'm loving mine too. Just wish it was better built and designed physically and aesthetically (though the JDS front panel looks ace, I have an Epiphany one, but would have bought a JDS one had it come out sooner!). What I wouldn't give for an RSA quality build of an O2. I asked John about doing a premium model, and he said he'd consider it except the possibility that using different components could change the sound signature somewhat, and with the ODA not too far away, there might be little point.


----------



## Crazy*Carl

Is JDS the preferred method of obtaining an O2 right now?  I can't really find them elsewhere.


----------



## maverickronin

Quote: 





naim.f.c said:


> I'm loving mine too. Just wish it was better built and designed physically and aesthetically (though the JDS front panel looks ace, I have an Epiphany one, but would have bought a JDS one had it come out sooner!). What I wouldn't give for an RSA quality build of an O2. I asked John about doing a premium model, and he said he'd consider it except the possibility that using different components could change the sound signature somewhat, and with the ODA not too far away, there might be little point.


 

 The PCB layout and the specific op amps are probably the most important parts.  It shouldn't change the performance much unless you really mess around with the other stuff.
   
  I think it would be nicer if there was a smaller version.  The O2 is so big because lithium batteries aren't as practical for DIY projects requiring large 9V rechargeables and because it uses large through-hole parts to make it easy to build.  With lithium batteries, DC-DC converters, a multi layer surface mount board, and Chinese manufacturing the Objective2's basic design could probably be implemented in half the size at the same cost or less.
   
  Lord Voldermot probably wouldn't even mind as long as they sent him a sample so he could verify its performance.
   
  Quote: 





crazy*carl said:


> Is JDS the preferred method of obtaining an O2 right now?  I can't really find them elsewhere.


 

 If you don't want to build it yourself its either JDS or Epiphany AFIK.  Choice is pretty much down to aesthetics or how cost varies based on exchange rates and shipping.


----------



## shotgunshane

Quote: 





maverickronin said:


> I think it would be nicer if there was a smaller version.  The O2 is so big because lithium batteries aren't as practical for DIY projects requiring large 9V rechargeables and because it uses large through-hole parts to make it easy to build.  With lithium batteries, DC-DC converters, a multi layer surface mount board, and Chinese manufacturing the Objective2's basic design could probably be implemented in half the size at the same cost or less.
> 
> Lord Voldermot probably wouldn't even mind as long as they sent him a sample so he could verify its performance.


 

  This.  Sign me up!


----------



## Crazy*Carl

I am planning in running the O2 right out of my computers analog out, which is not line level.  I am gonna do some testing on that vs ipod LOD to see if it really degrades anything.  If it does then maybe I will consider some cheap usb DAC to get line level (I don't really believe in high end DAC's).  I don't expect the desktop version to be out for quite some time, especially for non DIYers like myself.  I can upgrade then.

 My basic philosophy is I don't really expect dedicated DAC/AMPs to do very much, I just want to get proper power and a clean signal to my Sennheisers.


----------



## maverickronin

Quote: 





crazy*carl said:


> I am planning in running the O2 right out of my computers analog out, which is not line level.  I am gonna do some testing on that vs ipod LOD to see if it really degrades anything.  If it does then maybe I will consider some cheap usb DAC to get line level (I don't really believe in high end DAC's).  I don't expect the desktop version to be out for quite some time, especially for non DIYers like myself.  I can upgrade then.
> 
> My basic philosophy is I don't really expect dedicated DAC/AMPs to do very much, I just want to get proper power and a clean signal to my Sennheisers.


 

 Most USB DACs (especially the cheap ones) don't get up to the 2V Redbook standard if that's what you're looking for.
   
  Integrated sound cards are pretty hit or miss.  You'll probably know right away if you need a USB DAC though since the bad integrated sound cards are usually disastrously awful with plainly audible levels of noise, static, and distortion, noise that modulates with the computer's activity, or $DEITY forsaken drivers that have DSPs you can't disable.


----------



## zzffnn

I really hope Fiio will adopt the design of O2 and make it more portable;
I will buy one for sure.


----------



## Crazy*Carl

Quote: 





maverickronin said:


> Most USB DACs (especially the cheap ones) don't get up to the 2V Redbook standard if that's what you're looking for.
> 
> Integrated sound cards are pretty hit or miss.  You'll probably know right away if you need a USB DAC though since the bad integrated sound cards are usually disastrously awful with plainly audible levels of noise, static, and distortion, noise that modulates with the computer's activity, or $DEITY forsaken drivers that have DSPs you can't disable.


 


  Mine is definitely a hit.  Its a media desktop mobo.  Whats the 2V standard?  I would still be using the O2 to get proper power.
   
  And despite what people say, I have listened to a wide variety of onboard sound, any almost anything recent sounds pretty good.  If you get to the Pentium 4 era, they start to sound pretty bad.


----------



## Anaxilus

Quote: 





crazy*carl said:


> And despite what people say, I have listened to a wide variety of onboard sound, any almost anything recent sounds pretty good.  If you get to the Pentium 4 era, they start to sound pretty bad.


 

 Hmm, I have an XFi elite pro with a breakout box and excellent SNR.  I can still hear low level noise and things like platters spooling and heads actuating.  Though only on cans that can dig it out.


----------



## MikeW

Well, I've been building PC's for about 15 years. It's certainly possible to have a 100% rock stable o/c. As the above poster mentioned, it just takes ridiculous amounts of testing and stress. I use LinX, for 4 hours or so, it's much more stressful then Prime95, and will spot error's alot quicker. When that has passed, I use 24 hours of Prime95 BLEND. If that passes I use OCCT power supply torture test. Which is a combination of LinX and Furmark, it's absolutely brutal. Putting max load on the PSU, Video card, AND CPU. I only run that for a couple hours. I have not had a bsod since i finished stability testing.. not one. That was a couple years ago now. I'm hardcore when it comes to stability, if I get a BSOD for any reason I'm already tearing my system down to figure out What, because that's not normal, ever.
   
  All the above said, I can certainly empathize with someone who just does not want to go though the hassle, the above took me a couple weeks of trail and error, logging settings, what works what don't etc. And it's not something I do to my family's PC's or friends, because it can be more trouble then it's worth.
   
  With regards to performance, the difference can be dramatic, depending on usage. If your just doing word processing, browsing the web, and email, it's not going to matter if it's 1.5 ghz or 4.5. If you play games, encode video, or do lots of compression, photoshop, etc it can be a large difference in performance. I'm sitting around a 52% overclock, and the performance seems to scale pretty matter of factly.
   
  AMD has made great strides with SLI in the last generation, if you read the reviews you will see that SLI scaling is at something like 90% efficiency now.
   
  I have derailed this thread a bit, and it's my fault. Sorry about that guys. This PC talk is pretty irrelevant.
   
  Naim. Thanks for your comparisons, also NwAVGuy has some good reasons not to use balanced connections, it's in his blog. Expensive, with no benefit, and sometimes a disadvantage. Also if you like the JDS labs faceplate, they sell it by itself for 10$, should be a super easy swap.


----------



## Anaxilus

I've been building my PC's for over 20+ now too.  Never owned a prefab PC other than laptops and a IBM PC/XT from the early 80's.
  Quote: 





mikew said:


> And it's not something I do to my family's PC's or friends, because it can be more trouble then it's worth.


 
   
  That's where my time ends up being sucked.  Fixing other peoples PC's and even the occasional Mac issue.   95% of the time it's user error and I'm just tired of dealing w/ other people breaking their gear and having me figure it out.  I guess it's just really demotivated any desire to tweak around anymore.  There's a saying among auto technicians I know when friends or family come to them w/ problems.  "My car works."
   
  Back to the regularly scheduled programming.


----------



## Grev

I will be getting 2 of these from JDSLabs soon, one with the normal gain levels and the other one with 1x/3x gain, should be great!


----------



## wje

Quote: 





anaxilus said:


> That's where my time ends up being sucked.  Fixing other peoples PC's and even the occasional Mac issue.   95% of the time it's user error and I'm just tired of dealing w/ other people breaking their gear and having me figure it out.  I guess it's just really demotivated any desire to tweak around anymore.  There's a saying among auto technicians I know when friends or family come to them w/ problems.  "My car works."


 
  I hear you there.  Fortunately, for me, it's really never hardware issues that I have to get involved with.  For example, my 82 y.o. mother-in-law has a laptop and periodically, she'll hit the wrong "F" key and turn off wireless networking, or Comcast will have a "burp" and interrupt her service.  Fortunately, she's only 4 miles away.  However, when it comes to the Comcast outages, she busts on them for not having 100% reliability in their service.  I then explain to her how much -- in thousands of dollars, companies spend to have redundant connections in the event one service provider goes out.  She then stops complaining and happily pays her $45.00 a month cable Internet bill.
   
  Now, regarding the O2 - I've read and heard about some people opting for a bass-boost addition as a modification.  To me, if the bass boost needs to be utilized, something else in the chain of components needs to be reviewed.  Are the headphones capable of adequate bass?  How about the source player? Is it something like an iPod with a LOD cable?  Or, is it connected via the headphone / out jack?  There are easier ways to cure lower bass issues, too, instead of fiddling with the O2 amp itself.  For example, if one is using iTunes or any other MP3 software for that matter, they could go through their music and embed some EQ adjustments into the songs themselves.  This might seem a bit time consuming - but, to me, it's better than risking an issue by damaging your O2 amp with the addition of the bass boost that it was never designed to have.
   
  The O2 itself, is strictly an amplifier.  A great amplifier for the price.  An amplifier that essentially doesn't "color" the sound by altering certain frequencies as they leave your source player.  However, some people prefer a bit more color in the music, and in those cases, just the simple input and output of the O2 might not be enough for them if they're craving some change in the sound.


----------



## sphinxvc

Quote:


wje said:


> The O2 itself, is strictly an amplifier.  A great amplifier for the price.  An amplifier that essentially doesn't "color" the sound by altering certain frequencies as they leave your source player.  However, some people prefer a bit more color in the music, and in those cases, just the simple input and output of the O2 might not be enough for them if they're craving some change in the sound.


 

 I was actually quite astonished at the O2's performance this weekend.   I received my PS for my DAC and the cleaner power just brought my system into the high-end, that is not something I expected with the O2 in my chain.  For anyone claiming the O2 is analytical or thin sounding in any way, you need to come over to my house and listen to this thing in my system.
   
  To elaborate, the O2 wasn't a hindrance to the gains brought by the PS.  The timbre, weight, and imaging were truly of a high-end level.
   
  I'm still down for the DIY commissioned amp I'm supposed to get in 2 months, but honestly, even if I wasn't, I would be 100% happy with where I am right now.  I will update in 2 months if I feel differently, and hopefully I will given that it the other amp is 6-7x the price.  
	

	
	
		
		

		
			





 
	

	
	
		
		

		
		
	


	



   
  I'm curious to see what it will add or detract compared to the O2.  To be frank, I'm not of the camp that believes the O2 is a perfect wire with gain.  While I can't find anything wrong with it, I still think I have heard other amps more transparent to the recording, with more spatial details etcetera, so it will be interesting to do the compare.


----------



## DarknightDK

Im very much enjoying my time with the O2 and the LCD-3. They are a fantastic pairing and the LCD-3 really sings with the O2 with clarity, resolution and PRaT. I would not believe it but the O2 really takes my system to another level altogether.


----------



## Crazy*Carl

Quote: 





wje said:


> I
> 
> Now, regarding the O2 - I've read and heard about some people opting for a bass-boost addition as a modification.  To me, if the bass boost needs to be utilized, something else in the chain of components needs to be reviewed.  Are the headphones capable of adequate bass?  How about the source player? Is it something like an iPod with a LOD cable?  Or, is it connected via the headphone / out jack?  There are easier ways to cure lower bass issues, too, instead of fiddling with the O2 amp itself.  For example, if one is using iTunes or any other MP3 software for that matter, they could go through their music and embed some EQ adjustments into the songs themselves.  This might seem a bit time consuming - but, to me, it's better than risking an issue by damaging your O2 amp with the addition of the bass boost that it was never designed to have.


 
   
  Ya, bass boost is a terrible thing.  I hope this never becomes part of the O2 design.  If you want more bass, then get bassy headphones.


----------



## wje

Quote: 





sphinxvc said:


> Quote:
> 
> For anyone claiming the O2 is analytical or thin sounding in any way, you need to come over to my house and listen to this thing in my system.


 
  It is statements like yours that prove out that the amp is not the culprit in many of these cases.  As I mentioned, the source or even the headphones themselves could be to blame.
   
  Also, since this amp is a DIY amp - or, could be assembled by many types of individuals, it's hard to tell how consistent the assembly process has been carried out.  If the assembler is new to DIY and soldering in general, what's stopping him or her from holding the soldering iron on a connection too long and having the heat damage one of the caps?  It is assemblies like that which could present a problematic O2 amplifier.  So, then, we have an individual that comes along and has a moment to listen to the amp - when it's not capably running at spec due to the damaged caps, and they hear a sound variation or weakness.  Then, before taking the time to thoroughly listen to a 2nd O2 amp from another source, they type up some comments about the O2 amp being thin, weak, etc.
   
  The purpose of my last paragraph wasn't intended to stir the coals in any way.  It was simply done to point out that many variables are at play here and one build can easily vary from the next by some small deviation in the build process.
   
  I do know one thing though, my O2 amp is stellar.  It carries forward the right mix of lows, mids and highs from my source and presents them to me in a great and enjoyable manner.


----------



## maverickronin

Quote: 





crazy*carl said:


> Ya, bass boost is a terrible thing.  I hope this never becomes part of the O2 design.  If you want more bass, then get bassy headphones.


 

 Well there's nothing wrong with tone controls as long as they can be turned off.  I think that they're actually a very good thing since if you want to listen at low volumes to save your hearing you'll need extra bass and treble to make it sound natural due to the equal loudness curves.  Personally, I think having some way to change the FR like tone controls or EQ is usually a lot easier and cheaper than getting two pairs of good headphones with different FRs and switching between them or something.
   
  Of course something like that will never get added to the O2's or ODA's design because they're supposed to max out the price/performance ratio and tone controls that not everyone would use are bad for that.


----------



## juman231

To anyone with experience with JDS,
   
  I was wondering, does JDS offer the service of changing the gain settings from the default settings according to customer's preference?


----------



## shotgunshane

Quote: 





juman231 said:


> To anyone with experience with JDS,
> 
> I was wondering, does JDS offer the service of changing the gain settings from the default settings according to customer's preference?


 


  Yes, John will change it to your request.


----------



## juman231

thanks


----------



## syphen606

Just finished making mine with PCB and faceplate from JDSlabs.   Haven't had a chance to listen to it yet, but it fired up first shot without any problem.  Total time making it was ~ 3 hours and several beers.


----------



## Maxvla

Pretty good speed. Have you done DIY before?


----------



## syphen606

Quote: 





maxvla said:


> Pretty good speed. Have you done DIY before?


 


  I think I can make em faster now. The 3 hours was from all parts bagged and packed from Mouser/JDSLabs & Allied Electronics/Beer Store, to a fully assembled product tested and function checked.  I have parts for a 2nd one that I'm making for a friend later this week.
  Haven't done any DIY audio stuff, no. I did go to school for electrical engineering back in the day and did a short stint at an electronics company in the engineering department troubleshooting boards and assembling prototypes.   I guess the experience helped.
   
  Just giving it a quick listen now. Haven't pulled out my HD650's but tried a set of ATH-M50's and HD558's on it.  This amp is CLEAR.  REALLY clear and detailed. It made my HD558's really bright. Much brighter and detailed then I've heard them.  It makes the ATH-M50's sound fantastic. Really gives me a new appreciation for these headphones. Clears them right up and gives me a sound that I like. Super detailed sounding with enough bump to be fun.   Noticed minor minor channel imbalance with the HD558's with the pot at the near-off position, but it cleans up and goes away with virtually 1/32" of a turn on the dial. Nothing to be worried about.  
   
  My C421 is in my car and I'm not feeling like getting it at this moment, but compared to the E10 and CmoyBB I have on my desk in front of me, this amp is very very detailed.  I played a couple songs that I hadn't heard a bit of noise in the background. I thought maybe I had assembled something bad and was getting distortion. Ran the amp through several slow frequency sweeps from 20hz-16khz (I can't hear above that so didn't bother pushing it) and at several volumes without any distortion.  Gave it some more listening time before realizing I was just hearing garbage in the background of a bad recording hah!   Love the detail this amp has for sure.


----------



## Crazy*Carl

Quote: 





syphen606 said:


> I think I can make em faster now. The 3 hours was from all parts bagged and packed from Mouser/JDSLabs & Allied Electronics/Beer Store, to a fully assembled product tested and function checked.


 


  Did you get all the parts in a kit, or did you have to go on a wild goose chase to obtain everything.  I am open to the idea of trying a build, but the task of finding all the parts seems daunting.


----------



## syphen606

Quote: 





crazy*carl said:


> Did you get all the parts in a kit, or did you have to go on a wild goose chase to obtain everything.  I am open to the idea of trying a build, but the task of finding all the parts seems daunting.


 

 "Wild Goose Chase" was my route. Its not that bad to be honest.     I got the enclosure from Allied Electronics. PCB & Faceplate from JDSlabs, and all the internals and ac adapter came from from Mouser.  There is an .XLS bill of materials on the internet that you can upload onto Mouser once you have an account and it will fill your shopping cart based on the xls file. It was actually all quite easy and only took about 2 weeks to get all the parts from the time I decided to make an O2.
   
   
  I just added a set of rubber feet and changed the volume knob to an kilo ml-50-6 knob. The same one that the JDSLabs finished units ship with I think. It was on a CmoyBB I had kicking around here and it looks sharp so on it went!!


----------



## Anaxilus

^  Not sure about your E10 but the one I sampled was bass light.  I heard they were or did a revision to it FYI.  The O2 is definitely the strongest part of your chain.  If you ever want to upgrade I'd look at the DAC first then headphones.


----------



## scoopbb

i just received the pair of hd650s i ordered and man it sounds amazing with the o2. i am using an e10 but i wanna upgrade to a better dac. debating the ms or ms+. any ideas/.


----------



## syphen606

Quote: 





anaxilus said:


> ^  Not sure about your E10 but the one I sampled was bass light.  I heard they were or did a revision to it FYI.  The O2 is definitely the strongest part of your chain.  If you ever want to upgrade I'd look at the DAC first then headphones.


 
  The E10 amp component has weak bass on its own, yes.  I have HD650's as well but couldn't be bothered to pull them out of the case last night as I was only testing functionality of the amp (make sure I didn't mess up the assembly) and the 558's and M50's were on the desk when I got home.  
  
   


  Quote: 





scoopbb said:


> i just received the pair of hd650s i ordered and man it sounds amazing with the o2. i am using an e10 but i wanna upgrade to a better dac. debating the ms or ms+. any ideas/.


 

 I'd wait for the ODAC. The design is expected to be released this spring and by the looks of things, will be offered as a retro-fit for existing O2's.  It looks like you will lose the batteries and "portability" of the O2 but gain what no doubt will be a good DAC. It will require a new back plate also:


----------



## Twinster

*** For all O2 owners ***
  I have extra aluminium knobs so if you want to upgrade from the basic plastic knob here are some option for you.
   
   
 *[size=small](3x) AlcoKnobs model kn700b Knurled in Black Aluminum.*[/size] 

   
  I also have one silver Kilo that I bought from JDS Lab
   

   
   
  I'm asking $10 each including shipping in CONUS/Canada only. Please send me a PM if interested. Thanks!


----------



## sphinxvc

Quote:


sphinxvc said:


> I sometimes hear a slight crackling in the background during loud passages.  It's very subtle.  Is this the same thing you clippers are hearing?


 
   
  Quote:


upstateguy said:


> Nope.  No crackling.  Dead quiet background.
> 
> I'm not convinced that what I heard was clipping.  I called it distortion.  But what ever it was it sounded like when you turned a radio up too loud, past the point of maximum sound quality.  I'll check again later tonight and see if it's still there.


 

 Ok, I finally figured out what the crackling was, and I was correct, it was clipping.  The good news is it wasn't from the O2.  The bad news, it was from my new and rather expensive DAC.


----------



## sonitus mirus

Was your Antelope causing the clipping?  Hope not. 
   
  I thought I was hearing things on the second day with my O2.  When I read about your experience with crackling sound, it matched the description I was hearing.  The sound was like the "popping" heard between songs on a vinyl record, and at times it sounded like feint static from a radio tuner.  After a bit of troubleshooting, it appeared to be the quality of the recording.  The song I was listening to was actually dubbing sounds from old records, and I was picking this up with the clarity of the O2.  A few days later I thought I heard the issue again, but upon further examination it turned up being the sound created from the scraping of a guiro in a latin song that was playing.
   
  This amp is very revealing, and I didn't think that amps were supposed have that type of impact on the sound.  I don't know, it just seems like every odd beep, whistle, or bump causes me to freak a bit until I determine that it is not a problem with the amp.  I listen to a lot of new stuff every day, so I am usually hearing songs for the first time.  I went back and listened to a playlist of my older favorites, and the experience with the O2 was much more relaxing. Still, this amp is definitely a bit different than my previous amp it replaced. (HeadRoom Micro Amp)


----------



## upstateguy

Quote: 





sphinxvc said:


> Quote:
> 
> Quote:
> 
> Ok, I finally figured out what the crackling was, and I was correct, it was clipping.  The good news is it wasn't from the O2.  The bad news, it was from my new and rather expensive DAC.


 
   
  How is  your DAC clipping?


----------



## sphinxvc

Quote:


upstateguy said:


> How is your DAC clipping?


 

 Antelope has a application to control the DAC and see a "peak meter" which has a clipping indicator.  It lights up at the exact times I hear the crackling, so I'm assuming it's clipping.  The only unknown in all of this is whether it's just inherent in the recording, and would clip on any normal DAC, or if there's something wrong with the Zodiac.  Edit: I should probably dial back the volume pot and see if there's any crackling then.  Anyway, sorry to take this thread off topic, just wanted to clear up that it wasn't the O2.


----------



## upstateguy

Quote: 





sphinxvc said:


> Quote:
> 
> Antelope has a application to control the DAC and see a "peak meter" which has a clipping indicator.  It lights up at the exact times I hear the crackling, so I'm assuming it's clipping.  The only unknown in all of this is whether it's just inherent in the recording, and would clip on any normal DAC, or if there's something wrong with the Zodiac.  Edit: I should probably dial back the volume pot and see if there's any crackling then.  Anyway, sorry to take this thread off topic, just wanted to clear up that it wasn't the O2.


 


  Just to be clear, you mean dial back the volume of the DAC, right?  Does this happen on low gain?  Does it happen with all your recordings?  Does changing the volume on the DAC effect the sound quality in any way?  What headphones?  Any other pertinent information?


----------



## sphinxvc

Quote:


upstateguy said:


> Just to be clear, you mean dial back the volume of the DAC, right? *Yeah.*





> Does this happen on low gain? *Yes.*





> Does it happen with all your recordings?  *No, just some.  Albums with good dynamic range don't have the problem.*





> Does changing the volume on the DAC effect the sound quality in any way? * It shouldn't, since the Zodiac doesn't have digital volume control, I'm assuming I wouldn't be losing bits/quality.*





> What headphones?  *LCD-2s.*





> Any other pertinent information?  *Afraid not, trying to understand it myself.*


----------



## mikeaj

I am not at all familiar with this DAC, but to me this description almost certainly seems like a signal clipping detector. It's just saying that the input bits themselves (from the music file) go to 0 dBFS.  Or maybe 0 dBFS for multiple samples, or something like that?  It depends on how it's set up to report clipping.  So that's not the DAC clipping but the music file itself containing clipping.  Blame the guy who mastered it.  The whole peak meter thing is just reading the digital values being sent through to the D/A chain, including whatever might be approaching clipping levels.  Open up the files in something like Audacity and look for clipping there and see if it's happening where the signal goes to 0 dBFS.
   
  It would take an incompetent design to have the DAC itself be causing the clipping.  Or a "design decision" according to some.  
	

	
	
		
		

		
		
	


	




  That's a totally off-topic potshot though, so I'll let it go now.


----------



## sphinxvc

Quote:


mikeaj said:


> I am not at all familiar with this DAC, but to me this description almost certainly seems like a signal clipping detector. It's just saying that the input bits themselves (from the music file) go to 0 dBFS.  Or maybe 0 dBFS for multiple samples, or something like that?  It depends on how it's set up to report clipping.  So that's not the DAC clipping but the music file itself containing clipping.  Blame the guy who mastered it.  The whole peak meter thing is just reading the digital values being sent through to the D/A chain, including whatever might be approaching clipping levels.  Open up the files in something like Audacity and look for clipping there and see if it's happening where the signal goes to 0 dBFS.
> 
> It would take an incompetent design to have the DAC itself be causing the clipping.  Or a "design decision" according to some.
> 
> ...


 

 Incompetent, but I wouldn't put it past anyone.  
	

	
	
		
		

		
		
	


	




  I vaguely remember hearing something similar on my NFB-3 DAC, so I am leaning toward it being inherent in the recording.  Thanks for the input.


----------



## jseaber

This may be answered earlier, but this is by design. The O2's power management circuitry shuts off the opamps (no sound) when batteries are low, but the LED is tied directly to the batteries/power switch (it stays lit). If you get no sound from the O2, it's time to charge!
  
  Quote: 





dixter said:


> I had one of the ones I built to give out for Xmas gifts not work on a set of battery's...   I took the battery's out and put them in a dedicated charger in an attempt to figure out
> which one was bad..   both of them charged up fine, I put them back in the amp and the amp has worked perfectly ever since...   not sure why..


----------



## Crazy*Carl

I  am trying to figure out if the O2 is going to benefit me and could us some help. I have heard other amps such as the audio gd sparrow with a very powerful 10v output and I was never able to tell a difference or pass a blind test with it against my computers onboard sound. Because of this I am doubtful I am goIng to hear any difference with the O2. Is there any reason the o2 will do something for me these other amps did not? Thanks.


----------



## maverickronin

Quote: 





crazy*carl said:


> I  am trying to figure out if the O2 is going to benefit me and could us some help. I have heard other amps such as the audio gd sparrow with a very powerful 10v output and I was never able to tell a difference or pass a blind test with it against my computers onboard sound. Because of this I am doubtful I am goIng to hear any difference with the O2. Is there any reason the o2 will do something for me these other amps did not? Thanks.


 

 If your onborad has enough power for you then you probably won't notice a difference by adding the O2 in between


----------



## Crazy*Carl

It's quite powerful. My iPod usually is about at 75% volume but the pc is around 25% for normal listening


----------



## maverickronin

Well the O2 is all about clean power, low noise, and low output impedance.  The 580s aren't going to be bothered by any output impedance an onboard sound card is likely to have and isn't sensitive enough for you to hear the noise floor so if you've got enough power then you probably don't need the O2


----------



## Crazy*Carl

Do you think it's more likely to affect a denon ahd2000?


----------



## maverickronin

Quote: 





crazy*carl said:


> Do you think it's more likely to affect a denon ahd2000?


 

 Yeah.  They're sensitive enough that there might be some audible hiss and a few ohms of output impedance could end up making the bass sound loose or boomy.
   
  An O2 would help with those issues.


----------



## Crazy*Carl

Does an iPod have a low output impedance That I could compare my pc to?


----------



## sonitus mirus

According to the references I could find, the iPod headphone output impedance is about 5Ω and the line out is 100Ω.
   
http://members.chello.nl/~m.heijligers/ipod/Performance/measurements.html


----------



## maverickronin

Which one?  For the most part they're all different and I don't have all of them memorized.


----------



## Crazy*Carl

I just tried my beyer earbuds and they did not sound any different on my pc vs iPod 
   
  Iphone 4


----------



## shotgunshane

Quote: 





crazy*carl said:


> I just tried my beyer earbuds and they did not sound any different on my pc vs iPod
> 
> Iphone 4


 


  As far as I recall, the iPhone 4 has .9 ohm.


----------



## Crazy*Carl

So I take it denons run really well outa iPhone 4


----------



## Anaxilus

Not to derail the O2/iDevice dialogue but just wanted to toss out an idea for a Voldemort project.  Electrostatic amp.  I'd really really be curious to hear what could be done on the cheap w/ his measurement routine.  If someone finds the idea compelling perhaps they could give a shout out over on the blog.


----------



## mikeaj

Quote: 





anaxilus said:


> Not to derail the O2/iDevice dialogue but just wanted to toss out an idea for a Voldemort project.  Electrostatic amp.  I'd really really be curious to hear what could be done on the cheap w/ his measurement routine.  If someone finds the idea compelling perhaps they could give a shout out over on the blog.


 

 Now that's an interesting idea I haven't heard, but I doubt it would come to pass.  My impression is that he fancies himself foremost as the champion of the little guy--or starting audiophile, or just borderline regular consumers.  Hence there's the focus on FiiO amps and DACs, all those sub-$40 DAC reviews, the aggressive rhetoric (which probably turns off many who have been around for a while, but may make a stronger impression on those whose opinions have not hardened as much), and so on.  Additionally, he markets the O2 as a kind of one-size-mostly-fits-all solution.  I don't get the feeling he would ever spend time designing for a niche of the niche audio market, which may be unfortunate for the Stax crowd.


----------



## firev1

Quote: 





anaxilus said:


> Not to derail the O2/iDevice dialogue but just wanted to toss out an idea for a Voldemort project.  Electrostatic amp.  I'd really really be curious to hear what could be done on the cheap w/ his measurement routine.  If someone finds the idea compelling perhaps they could give a shout out over on the blog.


 


  Maybe one day when Electrostats get wider use, his blog has always been about doing something for the masses and Electrostats, despite their popularity with the headphone community, has not seen widespread use yet. Maybe one day, when distribution channels for stats get better(and cheaper)(with Edifier) he would try making a electrostatic amplifier. On the other note, the other problem with electrostat amps is also the availability of high voltage devices which sad to say is dwindling(if I'm not wrong). That would be another factor too as you can see, all of O2's parts can be gotten from one or 2 sources at most.


----------



## maverickronin

Quote: 





anaxilus said:


> Not to derail the O2/iDevice dialogue but just wanted to toss out an idea for a Voldemort project.  Electrostatic amp.  I'd really really be curious to hear what could be done on the cheap w/ his measurement routine.  If someone finds the idea compelling perhaps they could give a shout out over on the blog.


 

 That would be seriously awesome, but as others have mentioned its just too niche for him to dedicate the time too it.  He's basically doing this sort of thing for other people.  With the time and money he's spent on the O2, ODA, and ODAC designs he could have easily bought a few more DAC1s (which he's already perfectly happy with) for his personal use or something.  OTOH the impression I get from the Kevin Gilmore designs (correct me if I'm wrong) is that he designs something he would like to have for himself anyway and then documents it, releases it, does board runs, etc.


----------



## kyoshiro

i have ordered parts for another 3 O2s  
  gonna make some variations like RCA input and such and make one for a friend


----------



## evanft

I'm thinking of getting one of these, but I have a question about proper gain.
   
  I used that spreadsheet floating around, I figured out that I need a gain of 3.2 for my DT880 600 ohm and my E-MU 0204 (2.16 Vrms) for listening at 115 dB. Is this safe? Can I go any higher without clipping? I wouldn't mind some head room.
   
  I only plan on using this with AC power, BTW.


----------



## stv014

Quote: 





> Originally Posted by *evanft* /img/forum/go_quote.gif
> 
> Can I go any higher without clipping? I wouldn't mind some head room.


 
   
  If you want headroom, then a lower gain is preferred. The default 2.5x gain would mean a 5.4 Vrms signal level at the output of the gain stage, which should be loud enough while keeping the signal somewhat more than 2 dB below the clipping level (so no distortion on occasional peaks above the specified output level of the DAC). I would just keep the default gain settings.


----------



## shadow419

Quote: 





evanft said:


> I'm thinking of getting one of these, but I have a question about proper gain.
> 
> I used that spreadsheet floating around, I figured out that I need a gain of 3.2 for my DT880 600 ohm and my E-MU 0204 (2.16 Vrms) for listening at 115 dB. Is this safe? Can I go any higher without clipping? I wouldn't mind some head room.
> 
> I only plan on using this with AC power, BTW.


 

  
  Sounds about right.  I'd install the gain sockets so you can test with different gain levels for any music you might have that is much lower in level.  The headphones I have are pretty sensitive so I use 1x gain almost exclusively, but I also installed 3x gain for insurance.


----------



## Crazy*Carl

does anyone have any result from a O2 + Denon ahd2000 combo?


----------



## evanft

Quote: 





shadow419 said:


> Sounds about right.  I'd install the gain sockets so you can test with different gain levels for any music you might have that is much lower in level.  The headphones I have are pretty sensitive so I use 1x gain almost exclusively, but I also installed 3x gain for insurance.


 


  Gain sockets? You mean the resistors?


----------



## shadow419

Quote: 





evanft said:


> Gain sockets? You mean the resistors?


 


  Yes, sockets for the gain resistors.


----------



## Crazy*Carl

Does anyone run the HD650 with the O2?


----------



## maverickronin

Quote: 





crazy*carl said:


> does anyone have any result from a O2 + Denon ahd2000 combo?


 
  Quote: 





crazy*carl said:


> Does anyone run the HD650 with the O2?


 
   
  FWIW Voldermort has both of those 'phones. and likes how they work with the O2.


----------



## uelover

maverickronin said:


> FWIW Voldermort has both of those 'phones. and likes how they work with the O2.




Made me imagine of Voldermort wearing a pair of Hd650 driven by O2 in some Harry Potter scene.


----------



## Crazy*Carl

Why is he called Voldemort anyways?  More accurate to call him Ghandi.


----------



## juman231

Quote: 





crazy*carl said:


> Why is he called Voldemort anyways?  More accurate to call him Ghandi.


 


  Cus he's "he who must not be named"


----------



## maverickronin

Quote: 





crazy*carl said:


> Why is he called Voldemort anyways?  More accurate to call him Ghandi.


 

 Because normally on Head-Fi you're not allowed to talk about people who have been banned or anything else they do.  The O2 became so popular they had to give in and let us talk about his projects even if we can't link to his blog.  For a time we weren't allowed to even mention his name and he became "He-Who-Must-Not-Be-Named".
  .
  I think Obi-Wan would be better ("Ban me and I shall become more powerful than you can possibly imagine.") and I'm not a big Harry Potter fan either but Voldermort stuck.  I find it hilarious that he's been promoted to the status of a fantasy supervillain though.


----------



## Crazy*Carl

Does anyone have any blind tests with the O2 they care to share?  If not can anyone conduct them?  I would be much more likely to get one if I could actually be shown it does something.  Peoples opinions and statements in the hi-fi world are meaningless.  Its an industry built on snake oil and BS, but there is some truth in good sound.  Plus its the Objective AMP!   Make audio objective - Blind tests guys!  I swear its like pulling teeth to get any useful information on audio on the internet.
   
  In Voldemorts review of the HD650, he said a dedicated Amp may not be required.
   
  "Generally you need about 2 volts RMS (5.7 volts peak-to-peak) for wide dynamic range music at realistic levels. PC and portable audio gear is typically limited to around 1 volt or less with many managing only about 0.5 volts. So you might need a headphone amp. While the 650 may deserve better, even the $20 FiiO E5 can manage about 1.3 volts which might be enough for many tastes."
   
  I am pretty sure my PC has alot more than 1V, it gets the HD580s ridiculously loud.  I usually listen at 25%.  And if you listen at reasonable levels always on a decently powered computer, is an dedicated amp really gonna do much?


----------



## maverickronin

Quote: 





crazy*carl said:


> Does anyone have any blind tests with the O2 they care to share?  If not can anyone conduct them?  I would be much more likely to get one if I could actually be shown it does something.  Peoples opinions and statements in the hi-fi world are meaningless.  Its an industry built on snake oil and BS, but there is some truth in good sound.  Plus its the Objective AMP!   Make audio objective - Blind tests guys!  I swear its like pulling teeth to get any useful information on audio on the internet.
> 
> In Voldemorts review of the HD650, he said a dedicated Amp may not be required.
> 
> ...


 

 An ABX won't demonstrate anything useful to you unless they use the same equipment as you.
   
  I have an external DAC and amp because it takes the soundcard out of the equation.  It more convenient and its one less factor to consider when buying a new laptop or motherboard.  Once I add in some EQ for the LFE channel in movies I end up needing a lot of power too.
   
  If none of those things, or the stuff I mentioned earlier applies to you then you don't need it.


----------



## Crazy*Carl

Quote: 





maverickronin said:


> An ABX won't demonstrate anything useful to you unless they use the same equipment as you.
> 
> I have an external DAC and amp because it takes the soundcard out of the equation.  It more convenient and its one less factor to consider when buying a new laptop or motherboard.  Once I add in some EQ for the LFE channel in movies I end up needing a lot of power too.
> 
> If none of those things, or the stuff I mentioned earlier applies to you then you don't need it.


 
  Sure it will, all I am looking for is to see if someone can actually pass a blind test.  I gave results to head-fi showing that I could not with Audio gd hardware.  Other people raved on how impressive the gear was.


----------



## maverickronin

Quote: 





crazy*carl said:


> Sure it will, all I am looking for is to see if someone can actually pass a blind test.  I gave results to head-fi showing that I could not with Audio gd hardware.  Other people raved on how impressive the gear was.


 

 You're missing the point.  What you're supposed to tell the O2 from makes all the difference.  I could ABX it from my OTL tube amp but that won't tell you anything useful because it has about as little in common with your soundcard as it possible for 2 audio amplifiers to have.
   
  The O2 is designed to be transparent.  Its not supposed to sound like anything so obviously if you try and ABX it against something else that's supposed to be transparent then you probably won't be able to tell the difference.  That's the entire point of the O2.  Its transparent, can power a wide variety of 'phones, and most importantly is the cheapest thing on the market with those capabilities.
   
  The O2 isn't supposed to magically make anything sound better.  Its supposed to amplify what you feed it and add as little else as possible.  If you need more power then buy it.  If you need less hiss for sensitive IEMs then buy it.  If you need a lower output impedance to increase the damping factor of low impedance headphones then buy it.  If you just want an amp that you don't have to worry about being a weak link in your signal chain then buy it.  If you don't need any of that then don't buy it.  That's all there is to it.


----------



## Crazy*Carl

I'm not missing the point.  I would love to see any results from blind tests.


----------



## firev1

maverick you are missing HIS point, the O2 is great amp but still to satisfy our curiosity, how would it fare against other more venerable amps like say the V200 or RSA Shadow in blind listening? (behind cloth cover, with no blindfold) Such a test would prove that going upgrading from an O2 may(or not) be justified.


----------



## sphinxvc

This has been covered before recently.  There have been no such blind tests, to my knowledge at least.


----------



## mikeaj

The only blind tests of the O2 vs. other amps, that I've heard reported, are by Voldemort himself and a couple other of his friends.  He claims not to hear differences between the Benchmark DAC1 Pre headphone out and the O2, using an A/B/X testing box IIRC.  I don't particularly think a negative result (couldn't tell the difference) means much from people who are expecting not to hear a difference, at least in general.  For reference, he does claim to hear issues with some other gear, where the distortion or noise or output impedance figures would imply potential problems.  Take that what you will.
   
  The main issue is that people who believe more in blind tests don't bother because they don't believe they'd be hearing differences, or maybe they're more frugal and rational in purchases and don't own anything worth comparing the O2 to.  And then a lot of people don't really see the point in blind tests or don't think they're worthwhile for one reason or another.


----------



## Naim.F.C

If you guys bare with me I will do a full review and comparison of both the V200 and the O2. I can tell you now they do sound slightly different, picked up even in blind testing and naturally general A/B testing too. At first it was quite tricky, but once I knew the sig of each amp and knew what differences to look out for, it became much easier.
   
  To the point where with certain tracks I'd actually swap amps just to get the desired sound. Ultimately, it's a tricky comparison because they don't aim to do the same thing. The O2 is near enough completely neutral, whereas the V200 is intentionally coloured, albeit subtly. There's pro's and cons to both really.
   
   
  EDIT: Are we really not even allowed to mention his name? Because not being able to even do that seems just a tad draconian. Is there a thread somewhere where the rules on this are outlined? It's very difficult to keep up!


----------



## arirug

I have both the Denon d2000 and HD650, and the O2 does an excellent job driving them. I do not have the urge to try any other headphoneamplifier after having listened to the O2. And i have owned more than 20 headphoneamplifiers from various well known  manufacturers. For my ears it fullfills all my expectations from a headphoneaamplifier.


----------



## Digital-Pride

I love that with its very low output impedance, you can confidently pair it with any low impedance headphone or iem.


----------



## Crazy*Carl

Quote: 





naim.f.c said:


> If you guys bare with me I will do a full review and comparison of both the V200 and the O2. I can tell you now they do sound slightly different, picked up even in blind testing and naturally general A/B testing too. At first it was quite tricky, but once I knew the sig of each amp and knew what differences to look out for, it became much easier.
> 
> To the point where with certain tracks I'd actually swap amps just to get the desired sound. Ultimately, it's a tricky comparison because they don't aim to do the same thing. The O2 is near enough completely neutral, whereas the V200 is intentionally coloured, albeit subtly. There's pro's and cons to both really.
> 
> ...


 
  Could you just do your PC sound vs the O2.  I would like to see that one more.


----------



## maverickronin

Quote: 





crazy*carl said:


> I'm not missing the point.  I would love to see any results from blind tests.


 

 So _any _blind test will do...


----------



## juman231

Quote: 





crazy*carl said:


> Could you just do your PC sound vs the O2.  I would like to see that one more.


 


  Since all PCs are built so differently from each other to different specs, I doubt such comparison would help? =/


----------



## firev1

Its getting a little ridiculous. For me its no competition since my card has massive EMI issues anyway,,,,


----------



## shadow419

Quote: 





crazy*carl said:


> Could you just do your PC sound vs the O2.  I would like to see that one more.


 


  Hell i don't even have to do it blind with my pc onboard.
   
  My onboard sound can't make my headphones go as loud as the O2.  They don't sound bad out of the onboard, and I'm not sure if I could pick out which was powering the headphones blind 100% of the time.  If I asked someone to keep increasing the volume I'd know soon enough though.


----------



## Crazy*Carl

Thats why the person performing the test sets the volume at a reasonable fixed level before you listen.


----------



## shadow419

I've built mine because I needed more volume and I like having a volume knob.  I don't have to worry about background hiss if I'm using very sensitive headphones/iem.  At <$100 for everything, I have what I want.
   
  Edit:  I'm not trying to be mean, but I never put this amp together to [insert flowery prose about bringing music to life].  I needed something relatively inexpensive that could provide plenty of volume with any of the headphones I own or might consider purchasing in the future.  I could have bought a commercially built amp or a soundcard with a better amp, but I had much more fun and satisfaction building it up myself.


----------



## Grev

I should have mine O2s this week, I will see how good this is compared to the other cheaper amps I have.


----------



## uelover

Quote: 





grev said:


> I should have mine O2s this week, I will see how good this is compared to the other cheaper amps I have.


 


  What are the other amps you have?


----------



## Grev

Quote: 





uelover said:


> What are the other amps you have?


 


  JDSLabs cmoy, PA2V2, ZO2.
   
  Thinking of buying The Continental too but that would be luxury compared to my existing amps, haha.


----------



## palmfish

I have an O2 (JDS Labs built) and a Violectric V90. Both have output impedance ratings below 1 ohm. My main amp is a Peachtree Nova that I use as a DAC, integrated amp (speakers) and headphone amp.
   
  Since I have not conducted any blind tests, I won't mention the differences that I (think I) hear, but I do want to mention something that I have noticed that surprised me.
   
  It was mentioned way earlier in this thread that the differences between amps, DAC's, etc. are typically blown way out of proportion to the point where newcomers to the hobby can really be convinced that product 'A' is superior to product 'B'. I think this is a real shame.
   
  With my Nova's 30 ohm output impedance, I was convinced that my Denon D7000's (which are rated at 25 ohms impedance) would sound terrible. Well, they don't. In fact, I can barely tell the difference between any of these amps. If damping factor is so important to the performance of dynamic headphones, then how can my Nova drive the Denon's basically as well as the others - with an output impedance that's HIGHER than the headphones impedance?
   
  I'm really at a loss here. Could it be the D7000's were designed with a high output impedance source in mind so the frequency response was purposely engineered to sound "normal" with  the expected FR shifts that that occur with underdamped drivers? I really can't explain it. As I mentioned before, I do hear subtle differences, so perhaps the effects of damping are simply overblown?
   
  My brain wants to hear bloated bass from the Nova so I can replace it with a "properly designed" amp, but my ears just aren't hearing it.


----------



## mikeaj

Quote: 





palmfish said:


> With my Nova's 30 ohm output impedance, I was convinced that my Denon D7000's (which are rated at 25 ohms impedance) would sound terrible. Well, they don't. In fact, I can barely tell the difference between any of these amps. If damping factor is so important to the performance of dynamic headphones, then how can my Nova drive the Denon's basically as well as the others - with an output impedance that's HIGHER than the headphones impedance?
> 
> I'm really at a loss here. Could it be the D7000's were designed with a high output impedance source in mind so the frequency response was purposely engineered to sound "normal" with  the expected FR shifts that that occur with underdamped drivers? I really can't explain it. As I mentioned before, I do hear subtle differences, so perhaps the effects of damping are simply overblown?


 
   
  Yeah the effects of electrical damping factor, for many headphones, is probably overblown by many, though maybe you're right about the Denon possibly being tuned that way.  Maybe it is, maybe it's not?  There's an argument about headphone drivers being much smaller than speaker drivers (less momentum, maybe less back EMF I suppose?  it's been a while since I looked at the physics here, and I never did like electromagnetics much) and there being more mechanical damping, but I don't really know enough to comment on that.
   
  The main issue with output impedance is just the change in frequency response if the headphones have impedance that varies over frequency between 20Hz - 20kHz.  You don't get frequency response shifts with more or less constant impedance over frequency that the Denon has.


----------



## palmfish

Quote: 





mikeaj said:


> The main issue with output impedance is just the change in frequency response if the headphones have impedance that varies over frequency between 20Hz - 20kHz.  You don't get frequency response shifts with more or less constant impedance over frequency that the Denon has.


 

 Now that is something I didn't consider. I thought all dynamic headphones had "wandering" impedance. I didn't know that the Denons were particularly stable. If that is true, it would explain what I'm hearing.


----------



## mikeaj

Quote: 





palmfish said:


> Now that is something I didn't consider. I thought all dynamic headphones had "wandering" impedance. I didn't know that the Denons were particularly stable. If that is true, it would explain what I'm hearing.


 

 It depends on the model.  See below.  HeadRoom uses a linear scale on the y axis for some reason, so I included a graph from a second source that's probably easier to read.


----------



## 129207

Quote: 





palmfish said:


> It was mentioned way earlier in this thread that the differences between amps, DAC's, etc. are typically blown way out of proportion to the point where newcomers to the hobby can really be convinced that product 'A' is superior to product 'B'. I think this is a real shame.
> 
> ...
> 
> My brain wants to hear bloated bass from the Nova so I can replace it with a "properly designed" amp, but my ears just aren't hearing it.


 

 I think you're referring to my post here. But yeah, I'm not surprised at all to read your comment. I think in general the best thing is to be brutally honest to yourself. This can be rather difficult if you just spent another $1K on the next FOTM wunderDAC though. 

 I think a lot of people WANT to hear something and then believe they do instead of actually hearing it.


----------



## ballcall2

Quote: 





negakinu said:


> I think you're referring to my post here. But yeah, I'm not surprised at all to read your comment. I think in general the best thing is to be brutally honest to yourself. This can be rather difficult if you just spent another $1K on the next FOTM wunderDAC though.
> 
> I think a lot of people WANT to hear something and then believe they do instead of actually hearing it.


 


  Exactly 
	

	
	
		
		

		
		
	


	



   
  This is one of the most intresting threads in this forum.


----------



## palmfish

Quote: 





negakinu said:


> I think you're referring to my post here. But yeah, I'm not surprised at all to read your comment. I think in general the best thing is to be brutally honest to yourself. This can be rather difficult if you just spent another $1K on the next FOTM wunderDAC though.
> 
> I think a lot of people WANT to hear something and then believe they do instead of actually hearing it.


 

 Yes, it was your post. I actually only found this discussion yesterday and got through the first 40 pages (phew!) and I remembered yours. Thanks for the impedance charts. I used to own Sennheiser HD600s and I've seen impedance charts for them with a huge rise at 80-100 Hz and I just assumed that all dynamic headphones performed similarly. The Denons impedance does remain remarkably flat - comparable to a planar headphone. Impressive. After learning more about amps and output impedance, I was convinced that my Nova was a POS (as a headphone amp) due to its' 30 ohm output impedance - if the designers did that, what else did they do wrong? Well, it sounds extremely similar to my O2 and Violectric (in sighted A/B listening), so now I know why. I'll just have to stick with Denons and planars!
   
  I think anytime you mix science with emotion (which hi-fi certainly is both), you open the door for "snake oil" sellers. Within the first week of the first Model T Ford rolling off the assembly line, I'm sure someone was selling a silver gas cap to ionize the fuel tank and improve combustion!
   
  Someone else mentioned the 6Moons reviews and I think that not only are they indecipherable, but they are also completely meaningless. Anyone who has taken high school level science knows that in order to prove a hypothesis, you have to test with a large sample, have a baseline, and take measurements - OK, maybe that's not exactly what they teach in high school, but you get my meaning. When I read a review that has lots of flowery prose and lists all the high-end esoteric gear used in the listening room, my bull&*%# meter gets pegged.
   
  I thought the "blanket experiment" referenced on NwAvGuy's blog was a particularly good example of how anyone will hear what they want to hear (or expect to hear).
   
  I agree, great discussion here.


----------



## Crazy*Carl

Yeah.  I ordered a $22 ($12 if I get a rebate lol) Asus Xonar DG card with a headphone amp build in.  I will report back with the results later this week.  I assure there will be no placebo effects in my impressions.  I am brutally hard on equipment reviews.


----------



## Naim.F.C

Remember to db match between set ups, otherwise comparisons are pointless. I also find it best to keep a selection of favourite 10 second test segments of music. It's hard to A/B entire songs because each listen you're paying attention to all menner of different things. In a 10 second slot over and over however, comparing specifics is easier.
  
  Quote: 





crazy*carl said:


> Yeah.  I ordered a $22 ($12 if I get a rebate lol) Asus Xonar DG card with a headphone amp build in.  I will report back with the results later this week.  I assure there will be no placebo effects in my impressions.  I am brutally hard on equipment reviews.


----------



## mikeaj

Quote: 





palmfish said:


> Yes, it was your post. I actually only found this discussion yesterday and got through the first 40 pages (phew!) and I remembered yours. Thanks for the impedance charts. I used to own Sennheiser HD600s and I've seen impedance charts for them with a huge rise at 80-100 Hz and I just assumed that all dynamic headphones performed similarly. The Denons impedance does remain remarkably flat - comparable to a planar headphone. Impressive. After learning more about amps and output impedance, I was convinced that my Nova was a POS (as a headphone amp) due to its' 30 ohm output impedance - if the designers did that, what else did they do wrong? Well, it sounds extremely similar to my O2 and Violectric (in sighted A/B listening), so now I know why. I'll just have to stick with Denons and planars!


 
   
  Well for a lot of headphones the 30 ohm output impedance isn't really a significant factor.  Senn HD 600 are what, like 300 ohms to 525 ohms?  With 30 ohms output impedance, you're getting between 90.9% of the signal to the headphones to 94.6% of the signal to the headphones, depending on the impedance the different frequencies.  That's 20*log10(94.6/90.9) = 0.35 dB difference, so who really cares?
   
  I don't think you want to be listening to multi-balanced armature IEMs with crossovers on that, but aside from IEMs, I wouldn't expect huge issues.  Maybe you'll get some bass bloat on some Senn HD 5xx models.  Some people like bass bloat. I wouldn't necessarily think the designers did anything wrong except not care about IEM usage, which is a design decision I guess.  Many IEMs may sound fine; I'd just guess that they're not regular listeners of those where there would be problems.  Higher output impedance is kind of a small crutch in terms of the design, maybe to be able to drive Denons better or not have you accidentally fry some IEMs as easily?
   
  The most flexible solution that more people should adopt, is to have the output impedance switchable.  Some headphones may arguably be designed for that 120 ohms output impedance "standard" from ages back, or something else.


----------



## palmfish

Yes, the 600's also sounded fine (I couldn't tell the difference between the Nova and the O2).
   
  Your explanation with the formula helps me understand it much better, thanks! But I still don't really understand how damping factor and impedance are related. For example, the Sennheisers impedance is much more variable than the Denons, but because they are high impedance, the damping factor is higher, thus there is tight control of the drivers (like rebound damping on a car).
   
  On the other hand, with the Denons the damping factor is very low, but since the impedance is stable, there are no FR anomalies. However, with such a low damping factor, isn't there still less control of the drivers that should (in theory at least) result in bass bloat?


----------



## mikeaj

The damping factor and controlling the movement of the drivers is a separate issue from the frequency response shift.
   
  At a given frequency you have the below because the source output impedance (Z_s) is forming a voltage divider with the load headphone impedance (Z_L), where V_L is the voltage the load gets and V_s is the voltage from the source:

   
  The source output impedance is generally just the same for different frequencies, while the load impedance may change significantly.  For lower Z_s relative to Z_L, you expect the ratio to be relatively constant no matter what Z_L is.  For difference in volume, take 20 * log10 of the ratio of V_L at one frequency compared to V_L at another frequency, assuming V_s is the same for both.
   
  With some IEMs that range from say 10 to 80 ohms impedance and a 30 ohm output impedance source, you're going to have some serious **** going on, as compared to a sub-1 ohm output impedance source.


----------



## Twinster

Not that it would make a big difference but the Peachtree Specification list *<30 *Ohms at the Output Stage. So maybe it's lower than 30.
  
*PreAmp*
Hybrid Tube Design (6922)
6.5V output @ 2.0V input
<30 Ohms at the Output Stage
Class A Output Stage
Switching Relays in the Signal Path
Polypropylene Caps in the Signal Path
   
   
   
  Quote: 





palmfish said:


> I have an O2 (JDS Labs built) and a Violectric V90. Both have output impedance ratings below 1 ohm. My main amp is a Peachtree Nova that I use as a DAC, integrated amp (speakers) and headphone amp.
> 
> Since I have not conducted any blind tests, I won't mention the differences that I (think I) hear, but I do want to mention something that I have noticed that surprised me.
> 
> ...


----------



## palmfish

Quote: 





mikeaj said:


> The damping factor and controlling the movement of the drivers is a separate issue from the frequency response shift.
> 
> At a given frequency you have the below because the source output impedance (Z_s) is forming a voltage divider with the load headphone impedance (Z_L), where V_L is the voltage the load gets and V_s is the voltage from the source:
> 
> ...


 
  I realize this is straying a little off topic, but I think it is pertinent because one of the claims to fame of the O2 (and the design behind it) is that an output impedance of <2 ohms is a performance target.
   
  Mikeaj - I understand the FR shift and how impedance plays a role in that.
   
  But what about controlling the driver "rebound." I thought that was damping factor, which is also related to impedance.
   
  Twinster - I saw that <30 ohm figure on their website too. I actually called Peachtree to discuss this very topic and confirmed it is 30 ohms, so I'm guessing that it is probably 29.9 ohms...
	

	
	
		
		

		
			




   
  Let me reiterate how informative this discussion is. I wish I had this conversation last year when I first started looking at hi-fi headphones and building a system around them. So many people come here seeking advice (myself included) and just get the same old meaningless bull**** hyperbole. I've been going around in circles investing time and money to learning about and experimenting with headphones and accessories. How much time and money and frustration could be saved with a little bit of knowledge upfront?


----------



## LizardKing1

Quote: 





mikeaj said:


> The damping factor and controlling the movement of the drivers is a separate issue from the frequency response shift.
> 
> At a given frequency you have the below because the source output impedance (Z_s) is forming a voltage divider with the load headphone impedance (Z_L), where V_L is the voltage the load gets and V_s is the voltage from the source:
> 
> ...


 

 Thanks, that was the first time I actually understood that, not because I couldn't before, but because it was really straightforward and simple. So basically I can have a FR switch when I swap amps in 2 conditions: either the Z-vs-frequency line isn't flat, making the load voltage change according to the frequency, or with a considerable source Z, that has the same effect. Is this it?


----------



## mikeaj

Quote: 





palmfish said:


> But what about controlling the driver "rebound." I thought that was damping factor, which is also related to impedance.


 
   
  Yeah, damping factor is as you say.  The value is the ratio of load impedance to source impedance.  By the books, higher is supposed to be better, and it should be in general and particularly if the headphones were designed with that in mind.
   
  You can read about some shifts in electrical performance due to different damping factor (recordings of the headphone sound were not taken), here:
http://www.benchmarkmedia.com/discuss/feedback/newsletter/2011/12/2/0-ohm-headphone-amplifier-sonic-advantages-low-impedance-headphone-amp
   
   


lizardking1 said:


> Thanks, that was the first time I actually understood that, not because I couldn't before, but because it was really straightforward and simple. So basically I can have a FR switch when I swap amps in 2 conditions: either the Z-vs-frequency line isn't flat, making the load voltage change according to the frequency, or with a considerable source Z, that has the same effect. Is this it?


 
   
  It may be easier to just look at or play with the numbers yourself.
http://docs.google.com/spreadsheet/ccc?key=0AjhinPmoO8atdE5PRkpkM2hhOGpoNnVqYVAzT083Y2c


----------



## palmfish

According to the Benchmark white paper authors, I should be hearing obvious distortion when powering my D7000s with the Nova due to the low damping factor (which is below zero - no damping or actually exasperating the movement?). I don't hear any anomalies. I even listened to some solo piano music (which they said made the distortion very apparent to their listeners).
   
  I did notice in the attached white paper that the Sony headphones do swing between 60 and 120 ohms across the audible frequency band. Maybe this swing is sufficient to allow the headphones to distort where the Denons do not because the impedance doesn't shift?
   
  The other Benchmark white paper (mentioned in the one you linked) is also interesting in that 2 amps with specifications almost identical to the DAC1 (<1 ohm output impedance) also caused distortion with the Sony headphones while the DAC1 did not. So obviously, something else is going on. Even the white paper authors make no attempt to explain why the 2 competitor amps perform so much worse than the Benchmark amp. Perhaps it isn't damping factor after all and something else is causing the audible and measurable distortion?
   
  Wow, every time I think I'm finally understanding this, more questions come up. Well, I suppose it's safe, based on NwAvGuys comments, to use my O2 as a "Benchmark" (pun intended) for the performance of my other amps.


----------



## mikeaj

No, you can readily see that differences in the design of amplifiers (and components used, to some extent) will impact the performance significantly, even into a purely resistive load that of course has a flat impedance over frequency.  The damping factor isn't at all the only thing by a very long shot.  Reference any number of amp reviews by Voledmort since there are always comparisons, or just dig through something similar on Stereophile or elsewhere.  In the future InnerFidelity will have some amp measurements as well.  e.g. compare FiiO E5 to the O2.  Both are around 0.5 ohms output impedance.
   
  Whether or not those changes are audible is a different matter.  It depends.
   
  Of course Benchmark is going to use language that implies emphasizes changes and is biased to make something a bigger deal than it really is, since they're trying to sell you something.  Read the analysis but draw your own conclusions.  For example, even though in some plots you see second harmonic distortion way up, -70 dB for a 2nd harmonic relative to the fundamental tone is still vanishingly low and probably impossible to hear.  Note that most many headphones have a higher 2nd and 3rd harmonic distortion than that, sometimes significantly so, over a lot of the frequency range.  I think (not sure) for a more resistive load like the Denons, the effect on distortion from the output impedance should be even smaller.
   
  And don't get me wrong:  there's more going on than just THD tests using single tones.  You can look at distortion with test tones as a performance metric, but it's not entirely the whole story. Certainly multi-tone tests and real music would make amplifiers misbehave in slightly different ways than just single-tone THD tests. The argument (challenged by some, though I feel it's without good evidence), is just that the typical benchmarks including some of those two-tone IMD tests, are just good predictors of actual performance with any type of music.  This should particularly hold if the results are very good, since this implies high linearity under whatever kind of operating conditions were tested and thus probably low distortion for any kind of music signal.  There are a lot of different ways you could have 1% deviation in some sense, but anything with 0.001% deviation is just going to be really close to the original.


----------



## palmfish

Quote: 





mikeaj said:


> No, you can readily see that differences in the design of amplifiers (and components used, to some extent) will impact the performance significantly, even into a purely resistive load that of course has a flat impedance over frequency.  The damping factor isn't at all the only thing by a very long shot.  Reference any number of amp reviews by Voledmort since there are always comparisons, or just dig through something similar on Stereophile or elsewhere.  In the future InnerFidelity will have some amp measurements as well.  e.g. compare FiiO E5 to the O2.  Both are around 0.5 ohms output impedance.
> 
> Whether or not those changes are audible is a different matter.  It depends.
> 
> ...


 

 You make some excellent points Mikeaj. It can be really difficult to separate the wheat from the chaff and come out with meaningful information. I'm sure the Benchmark tests were conducted properly, but I agree they have an agenda and there is a lot of room for bias to come into the results (include the stated significance (or lack thereof) of the results). I'm fascinated and frustrated with all of this information all at once, but I suppose it's no different that what I was going through 30 years ago shopping for a new cartridge for my turntable (or maybe, instead of replacing the cartridge, I need those pyramid-shaped, genuine birds eye maple pedestal stands to attenuate the natural harmonic resonance created by the vibrations caused by the wind resistance of the air flowing through the room from the HVAC system in my home).
   
  Some things aren't meant to be clear, no matter how bright a light you shine on them... The thrill of the hobby, I suppose.


----------



## firev1

Quote: 





palmfish said:


> maybe, instead of replacing the cartridge, I need those pyramid-shaped, genuine birds eye maple pedestal stands to attenuate the natural harmonic resonance created by the vibrations caused by the wind resistance of the air flowing through the room from the HVAC system in my home).


 


  As someone who studies wind a lot and I mean A LOT, I tell you today you made the right choice buying that cartridge LOL


----------



## Grev

Got my O2s today, although I have to wait till I'm off work to get to hear it, bummer!


----------



## wje

Quote: 





grev said:


> Got my O2s today, although I have to wait till I'm off work to get to hear it, bummer!


 

 That's what sick leave is for.  Enjoy !!


----------



## Grev

Quote: 





wje said:


> That's what sick leave is for.  Enjoy !!


 


  Thanks! 
   
  So we have very similar setups too, I have the FWJ#9 from Martin and also with Clip+ and O2, which sounds great!  Although I also have ipod touch 64gb with CLAS which sounds very good.   But I'm thinking I need bassier headphones with the O2.


----------



## uelover

Just curious if there is any sonic differences between the portable and desktop version?


----------



## wje

Quote: 





uelover said:


> Just curious if there is any sonic differences between the portable and desktop version?


 

 You've brought up a good question.  Isn't the desktop version supposed to also provide the DAC, too?   I do realize the portable version can be adapted with the DAC by removing the batteries to make space.  However, I would hope that the desktop version would allow for a bit more power --- to drive more difficult orthodymanic headphones.  But, given that the desktop is being created by the same designer, I'm sure there should be minimal if any, sonic differences as that seems to be one of the goals of the objective - to keep the sound as pure as it was received, then to amplify it and pass it on.


----------



## vkvedam

All
   
  If I feed the O2 with a DAC's line out at 2.1 Vrms does it cause the O2 to clip on low gain and volume dial set at 10'O clock position (On batteries)? I have observed it yesterday after having tested with an Arcam rDAC outputting a 2.1Vrms signal in to the O2. Am I doing something wrong? But I could only hear the clipping in high frequency region, to be precise only with one album [Karftwerk - Tour De France Soundtracks] and on tracks 'Prologue' and 'Etape 2'. The recording doesn't have clipping for sure. Is there a way to get around it?
   
  Thanks
  Ven


----------



## uelover

Quote: 





wje said:


> You've brought up a good question.  Isn't the desktop version supposed to also provide the DAC, too?   I do realize the portable version can be adapted with the DAC by removing the batteries to make space.  However, I would hope that the desktop version would allow for a bit more power --- to drive more difficult orthodymanic headphones.  But, given that the desktop is being created by the same designer, I'm sure there should be minimal if any, sonic differences as that seems to be one of the goals of the objective - to keep the sound as pure as it was received, then to amplify it and pass it on.


 

 I read that there are different variant to the desktop version, one that provides a DAC and another that doesn't but will include 1/4inch plug as well as RCA inputs.
   
  I have zero diy skills and since no one is currently selling the ready made desktop version, I ended up ordering the portable version one, compromising with a 1/4inch to 3.5mm adapter plug as well as a 3.5mm to RCA cable.
   
  Hopefully the sonic difference will be minimal and if there is any, it will be due to the adapter plugs that I am using and not the circuitry itself. =)


----------



## uelover

Quote: 





vkvedam said:


> All
> 
> If I feed the O2 with a DAC's line out at 2.1 Vrms does it cause the O2 to clip on low gain and volume dial set at 10'O clock position (On batteries)? I have observed it yesterday after having tested with an Arcam rDAC outputting a 2.1Vrms signal in to the O2. Am I doing something wrong? But I could only hear the clipping in high frequency region, to be precise only with one album [Karftwerk - Tour De France Soundtracks] and on tracks 'Prologue' and 'Etape 2'. The recording doesn't have clipping for sure. Is there a way to get around it?
> 
> ...


 


  Now you have just raised an important point. I am gonna connect the O2 to my desktop DAC which outputs at a fixed line level (not sure what is the Vrms).
   
  Seems like I do need to find out more on how to get rid of any clipping should the situation calls for it.


----------



## stv014

Quote: 





> Originally Posted by *vkvedam* /img/forum/go_quote.gif
> 
> If I feed the O2 with a DAC's line out at 2.1 Vrms does it cause the O2 to clip on low gain and volume dial set at 10'O clock position (On batteries)?


 

 Yes, on batteries, a 2.1 Vrms input can potentially be clipped even with the default 2.5x low gain setting. This is not fixed by reducing the volume, because the clipping occurs in the stage before the volume control. You need to reduce the gain to at most 2x by replacing two resistors, unless you can reduce the output level of your DAC.


----------



## vkvedam

Quote: 





stv014 said:


> Yes, on batteries, a 2.1 Vrms input can potentially be clipped even with the default 2.5x low gain setting. This is not fixed by reducing the volume, because the clipping occurs in the stage before the volume control. You need to reduce the gain to at most 2x by replacing two resistors, unless you can reduce the output level of your DAC.


 


  Thanks for that! Just tested it on AC and it doesn't seem to be clipping. Any specific reason?
   
  Cheers...


----------



## stv014

Quote: 





> Originally Posted by *vkvedam* /img/forum/go_quote.gif
> 
> Thanks for that! Just tested it on AC and it doesn't seem to be clipping. Any specific reason?


 
   
  Simple: when powered from AC, the supply voltage is higher. With batteries, the clipping level is at about 5 Vrms, while AC increases it to about 7.


----------



## vkvedam

Quote: 





stv014 said:


> Simple: when powered from AC, the supply voltage is higher. With batteries, the clipping level is at about 5 Vrms, while AC increases it to about 7.


 


  In that case my line in signal is only about 2.1 V RMS and why is it still clipping?
   
  Thanks...


----------



## palmfish

Quote: 





vkvedam said:


> In that case my line in signal is only about 2.1 V RMS and why is it still clipping?
> 
> Thanks...


 


  Maybe your headphone impedance has something to do with it? A lower impedance headphone would require more current to drive.
   
  OTOH, my Denons are low impedance and my O2 has no trouble driving them on battery or AC. Of course, I've never turned the volume control past 9:00 because it's just too loud.


----------



## uelover

Quote: 





palmfish said:


> Maybe your headphone impedance has something to do with it? A lower impedance headphone would require more current to drive.


 

 Isn't the clipping is due to the input gain being too high? Headphone impedance wouldn't matter since the clipping happened before the output stage.


----------



## stv014

Quote: 





vkvedam said:


> In that case my line in signal is only about 2.1 V RMS and why is it still clipping?


 
   
  Because it is amplified to 5.25 V by the input stage, and that is higher than the 5 V where the distortion starts to rise steeply due to clipping. Also, if the batteries have lower voltage (e.g. not fully charged), then the maximum output voltage without clipping is even less.


----------



## Twinster

I'm currently testing the Desktop version of the O2 that I just finish building with a friend and it sound the same as the portable version. The only differences is the taller case and input/output & volume control mounted on the back/front plate.
   
  I've been listening to the O2 source by a DACport/Foobar with my T1 and I'm very impressed with the combo. I'm still discovering/getting use to the T1 sound (just 1 week) but I'm amazed that the O2 with the 2.5x gain can drive the 600 ohm Beyer to very good quality level. I think the slightly warmish from neutral DACport is just a good match for the O2 and T1 signature.
   

   
  I'm definitely going to look at the upcoming ODA / ODAC combo.  
	

	
	
		
		

		
			




  
  Quote: 





uelover said:


> Just curious if there is any sonic differences between the portable and desktop version?


----------



## Crazy*Carl

Is this the new design from Voldemort, or is it just the same O2 with different mounting locations for everything?


----------



## vkvedam

Quote: 





palmfish said:


> Maybe your headphone impedance has something to do with it? A lower impedance headphone would require more current to drive.
> 
> OTOH, my Denons are low impedance and my O2 has no trouble driving them on battery or AC. Of course, I've never turned the volume control past 9:00 because it's just too loud.


 


  Well I was driving my HE-5LEs which need about 9-10'O clock-ish amplification. For my Denons I don't go past 9'O clock on the dial.


----------



## vkvedam

Quote: 





stv014 said:


> Because it is amplified to 5.25 V by the input stage, and that is higher than the 5 V where the distortion starts to rise steeply due to clipping. Also, if the batteries have lower voltage (e.g. not fully charged), then the maximum output voltage without clipping is even less.


 

 Thanks again. So even if I am on AC and if I use a higher gain it's going to clip in that case because it's only OK up and till 7 Vrms. So I've got to use it in low gain and AC power to avoid any clipping whilst at home at least.


----------



## wje

Quote: 





twinster said:


> I'm currently testing the Desktop version of the O2 that I just finish building with a friend and it sound the same as the portable version. The only differences is the taller case and input/output & volume control mounted on the back/front plate.
> 
> I'm definitely going to look at the upcoming ODA / ODAC combo.


 

 Simon, You're playing with all the fun gear.  I still need to order a black knob from you too.
  
   
  Quote: 





vkvedam said:


> Well I was driving my HE-5LEs which need about 9-10'O clock-ish amplification. For my Denons I don't go past 9'O clock on the dial.


 


 That's essentially where I play my HE-5LEs, too.  Often, I've thought that I should be opting for a better amp for the HE-5LE headphones.  However, it's not all too often that I use the O2 amp with them, as I mostly use the Sansui Vintage receiver to juice 'em.


----------



## stv014

Quote: 





vkvedam said:


> Thanks again. So even if I am on AC and if I use a higher gain it's going to clip in that case because it's only OK up and till 7 Vrms. So I've got to use it in low gain and AC power to avoid any clipping whilst at home at least.


 

 Yes, the default 6.5x high gain mode would clip a 2.1 Vrms input even from AC power.


----------



## mikeaj

Quote: 





crazy*carl said:


> Is this the new design from Voldemort, or is it just the same O2 with different mounting locations for everything?


 

 Most probably the old design with custom mounting locations, since (1) the new design hasn't been released yet and (2) somebody who already has the new design would not be looking at the "upcoming ODA / ODAC combo."
   
   
  I'm starting to wonder if the O2 couldn't have had three gain settings:  high, low, and none.  Are there any kind of through-hole six-pole switches with three settings?  You wouldn't even have to connect two of the poles to anything, since an open circuit is how you get no gain.  It wouldn't require any more resistors than there currently are.  The gain settings are a little more important than for some other amps because of the position of the volume control, so greater flexibility would have been nice.  I mean, two settings is enough for me, but it's less convenient for somebody without extra resistors or a soldering iron, or who don't know what's going on.


----------



## Digital-Pride

Quote: 





vkvedam said:


> Thanks again. So even if I am on AC and if I use a higher gain it's going to clip in that case because it's only OK up and till 7 Vrms. So I've got to use it in low gain and AC power to avoid any clipping whilst at home at least.


 


  To put it in even simpler terms, on AC power the O2 can handle sources up to 2.8 Vrms on low gain, 1.8 Vrms on battery power.  High gain is really more for low powered sources like portable players.


----------



## Grev

Quote: 





mikeaj said:


> Most probably the old design with custom mounting locations, since (1) the new design hasn't been released yet and (2) somebody who already has the new design would not be looking at the "upcoming ODA / ODAC combo."
> 
> 
> I'm starting to wonder if the O2 couldn't have had three gain settings:  high, low, and none.  Are there any kind of through-hole six-pole switches with three settings?  You wouldn't even have to connect two of the poles to anything, since an open circuit is how you get no gain.  It wouldn't require any more resistors than there currently are.  The gain settings are a little more important than for some other amps because of the position of the volume control, so greater flexibility would have been nice.  I mean, two settings is enough for me, but it's less convenient for somebody without extra resistors or a soldering iron, or who don't know what's going on.


 

 I got two O2 units from John at JDSLabs, one with 1x/3x gain and the other at the default 2.5x/6.5x gain, the 1x gain is driving all of my low resistance headphones already from my CLAS, LOD(iDevice) and Clip+.


----------



## vkvedam

An update from my side. Tried using the UE attenuator at the input and it didn't work. So I've got to use it on AC if used with my DAC. Or else change the gain to 1x.


----------



## Crazy*Carl

Can anyone compare the O2 to their computers onboard sound?
   
  I mean take your headphones, plug them into the computer and do some listening.  Then run the PC -> O2 -> headphones and listen and post a comparison.  Thanks!


----------



## Digital-Pride

Quote: 





crazy*carl said:


> Can anyone compare the O2 to their computers onboard sound?
> 
> I mean take your headphones, plug them into the computer and do some listening.  Then run the PC -> O2 -> headphones and listen and post a comparison.  Thanks!


 


  My laptop's headphone out ha lowest noise of all the PCs in my house, so I'll do some extended listening tomorrow and report back on my findings.  Unfortunately I won't able to do any blind testing, but I think I can at least get a tangible sense of any real improvement if there is one.


----------



## Naim.F.C

Comparing PC/Mac > headphone with PC/Mac > O2 > Headphone will yield pretty much exactly the same sound quality. Reason for this is because the PC/Mac's motherboard or soundcard already carries out amplification, so all you'd be doing is amplifying an already pre-amplified sound.
  
  To get a proper real world account of sound quality differences, what you need to be comparing is the PC/Mac's direct headphone jack with a source that bypasses its own amplifier when connected to an amp such as the O2, for example PC/Mac > Headphones vs iPhone/iPod > LOD > O2 > Headphones. Only then could you guage the difference.
   
  Quote: 





crazy*carl said:


> Can anyone compare the O2 to their computers onboard sound?
> 
> I mean take your headphones, plug them into the computer and do some listening.  Then run the PC -> O2 -> headphones and listen and post a comparison.  Thanks!


----------



## MikeW

That's not really true, while most soundcards have an op-amp output stage. It's typically very weak, often times less then 2.0v. And very limited ability to drive headphones, especially difficult to drive ones. So yes, you are "Double amping" the amp still can have a large effect on sound output.
   
  Plug in some HE6 to your sound card and see what happends 
	

	
	
		
		

		
		
	


	



   
  this is why some higher end soundcards have a completely separate jack for headphones, as it's typically a more proper amp for them.


----------



## Naim.F.C

Whilst true, I was referring to bog standard in-built motherboard sound cards which I believe is what Carl uses? Naturally better sound cards will have different levels of performance. For example, on my PC I have an Asus Xonar Essence and it sounds a lot better than headphones straight out of my Macbook Pro, but even then, you have to use one of the other outputs in order to bypass it's own amplification otherwise you essentially get a similar sort of sound despite using a different amp connected to it and still providing further amplification.
   
  On a side note, my Macbook Pro actually sounds worse than the sound straight out of my iPhone 4S! But for reference, when using my Macbook to one of my other amps and then to my headphones, the sound signature itself is almost exactly the same as direct from the Macbook. It's as if the pre-amplified sonics carry through to the amp. Certainly doesn't sound very good. I quite dislike the sound straight out of the Macbook.
   
  Quote: 





mikew said:


> That's not really true, while most soundcards have an op-amp output stage. It's typically very weak, often times less then 2.0v. And very limited ability to drive headphones, especially difficult to drive ones. So yes, you are "Double amping" the amp still can have a large effect on sound output.
> 
> Plug in some HE6 to your sound card and see what happends
> 
> ...


----------



## mikeaj

It's not just volume.  You can easily improve performance by double amping, particularly if the limiting factor is the amplifier and not the D/A behind it.  Here's a few shots from an RMAA run I did a long while back, using 32 ohm headphones at 1V output.  This isn't the first time I posted some of these.
   
    
_IMD SMPTE (7 kHz and 60 Hz test tones), THD (1 kHz test tone), crosstalk_
   
  White lines are double amped (sound card to O2 to headphones/sound card).  Green is single amped (sound card to headphones/sound card).  Note that the measurements are very much limited by the A/D on the cheap sound card.  Still I imagine both the input and output are better than most onboard sound, since those tend to sit on noisy motherboards, not too far from a lot of I/O and CPU and maybe even GPU VRMs.
   
  It's a whole lot easier for an amplifier to drive something like 10 kohms than something like 32 ohms, as you can see above.


----------



## Crazy*Carl

I have listened to Xonar Essence and it sounded the exact same as onboard.  Only difference was it could get my headphones ridiculously loud instead of just insanely loud.
   
  Also, I know from blind testing that amping a HD580 with a powerful headphone amp (10V output) has little or no affect on the sound compared to my PC.  I remain skeptical that the O2 would do any better.  Most people here will dispute that, yet I am the only one to show actual test results.  What does that tell you?  Audio is alot more objective than we make it out to be here, but no one wants to admit that, especially the companies that make all this crap.  Maybe other headphones really do benefit, I don't know.  But I wager to bet that its grossly exaggerated based on what I have read and heard.


----------



## mikeaj

High-impedance headphones like HD 580 are easy loads and should generally do pretty well with anything that has enough volume for it.  I wouldn't be surprised at minimal differences with reasonably competent sources, maybe even differences below audibility.  It's different for lower-impedance headphones, depending.  It's especially true if you have impedance interaction issues and get a significantly different FR because one source has high output impedance.  Aside from that and some other cases, most everybody is probably exaggerating about differences, overemphasizing small details, or just hearing what they want to hear.
   
  Personally, I can say that typical 1V sources are clearly not enough for 100 dB SPL / 1V headphones on classical music, so I got something more powerful.  Also there's less noise when using IEMs.  Aside from that, I wouldn't attest to anything more personally, particularly without first doing the comparisons blind.


----------



## uelover

Quote: 





twinster said:


>


 

 Did you diy those cables yourself? I am still trying to find a RCA-3.5mm cable. Not sure which to get. There are iChord, QED, Oyaide, etc.


----------



## MikeW

Some people are satisfied with a cheap clock radio. You've made your point pretty clear, no need to keep beating a dead horse. Move along please..
  
  Quote: 





crazy*carl said:


> I have listened to Xonar Essence and it sounded the exact same as onboard.  Only difference was it could get my headphones ridiculously loud instead of just insanely loud.
> 
> Also, I know from blind testing that amping a HD580 with a powerful headphone amp (10V output) has little or no affect on the sound compared to my PC.  I remain skeptical that the O2 would do any better.  Most people here will dispute that, yet I am the only one to show actual test results.  What does that tell you?  Audio is alot more objective than we make it out to be here, but no one wants to admit that, especially the companies that make all this crap.  Maybe other headphones really do benefit, I don't know.  But I wager to bet that its grossly exaggerated based on what I have read and heard.


----------



## stv014

Quote: 





crazy*carl said:


> Can anyone compare the O2 to their computers onboard sound?


 
   
  Although this is not exactly what you asked, this thread has some files for blind testing, one of which has been recorded from onboard audio while it was driving headphones at the maximum output level. It is a rather old Realtek chip, though, so it should be easy to tell which one it is out of the 5 files for most, but if there is interest, I will do a similar test with newer "HD" Realtek audio that should perform better.


----------



## Zsubbo

Just finished mine, pretty satisfied with the sound coming out of my grados 
	

	
	
		
		

		
			




   
https://picasaweb.google.com/114049227892902856235/O2?authkey=Gv1sRgCNfli9jH-MX0Rw
  ^Pics of my build.


----------



## Draygonn

mikeaj said:


> The gain settings are a little more important than for some other amps because of the position of the volume control, so greater flexibility would have been nice.  I mean, two settings is enough for me, but it's less convenient for somebody without extra resistors or a soldering iron, or who don't know what's going on.




I would think 2 settings would be fine for most as along as they are the right two. MrSlim included extra resistors with my O2, not sure if the JDSLabs or Epiphany amps include them.


----------



## Crazy*Carl

Quote: 





mikeaj said:


> High-impedance headphones like HD 580 are easy loads and should generally do pretty well with anything that has enough volume for it.  I wouldn't be surprised at minimal differences with reasonably competent sources, maybe even differences below audibility.  It's different for lower-impedance headphones, depending.  It's especially true if you have impedance interaction issues and get a significantly different FR because one source has high output impedance.  Aside from that and some other cases, most everybody is probably exaggerating about differences, overemphasizing small details, or just hearing what they want to hear.
> 
> Personally, I can say that typical 1V sources are clearly not enough for 100 dB SPL / 1V headphones on classical music, so I got something more powerful.  Also there's less noise when using IEMs.  Aside from that, I wouldn't attest to anything more personally, particularly without first doing the comparisons blind.


 

 Best thing I have read at head-fi in a while.
   
  So you got your amp strictly for more volume?


----------



## Twinster

Yes I did this cable myself. It's a silver cable with silver RCA from Cardas.
  
  Quote: 





uelover said:


> Did you diy those cables yourself? I am still trying to find a RCA-3.5mm cable. Not sure which to get. There are iChord, QED, Oyaide, etc.


----------



## Twinster

Hey Carl,
   
  I have done a quick comparison a few months back (Not with the PC on board) between two Centrance products (DACport & DACmini) and one was USB powered only and with the HD-650 and I noticed better impact and control in the lower frequency with the more powerful DACmini. The dynamic was better for sure. I know it's not what you asked for but tough it might add some value. Cheer 
	

	
	
		
		

		
		
	


	



  
  Quote: 





crazy*carl said:


> I have listened to Xonar Essence and it sounded the exact same as onboard.  Only difference was it could get my headphones ridiculously loud instead of just insanely loud.
> 
> Also, I know from blind testing that amping a HD580 with a powerful headphone amp (10V output) has little or no affect on the sound compared to my PC.  I remain skeptical that the O2 would do any better.  Most people here will dispute that, yet I am the only one to show actual test results.  What does that tell you?  Audio is alot more objective than we make it out to be here, but no one wants to admit that, especially the companies that make all this crap.  Maybe other headphones really do benefit, I don't know.  But I wager to bet that its grossly exaggerated based on what I have read and heard.


----------



## Digital-Pride

Quote: 





zsubbo said:


> Just finished mine, pretty satisfied with the sound coming out of my grados
> 
> 
> 
> ...


 


  Excellent work there.  How does the it sound with the Mini-i and how does its amp section compare to the Mini-i's?


----------



## maverickronin

Quote: 





mikeaj said:


> It's not just volume.  You can easily improve performance by double amping, particularly if the limiting factor is the amplifier and not the D/A behind it.  Here's a few shots from an RMAA run I did a long while back, using 32 ohm headphones at 1V output.  This isn't the first time I posted some of these.
> 
> 
> _IMD SMPTE (7 kHz and 60 Hz test tones), THD (1 kHz test tone), crosstalk_
> ...


 

 Awesome post.  I'm bookmarking this for every time I see someone bitching about "double amping".


----------



## mikeaj

Quote: 





crazy*carl said:


> Best thing I have read at head-fi in a while.
> 
> So you got your amp strictly for more volume?


 
   
  I wouldn't say it's the only reason, but the most important one.  Some other reasons are also listed below.
   
  1.  More volume
  2.  Better ability to support headphones or IEMs not yet owned, i.e. have enough power for them, not have background hiss, and not muck up the FR with output impedance interactions
  3.  Better sound quality which I may or may not be able to hear--can't hurt, anyhow
  4.  Support the idea of greater documentation and transparency for consumer audio products
  5.  Getting into a better position for having these kinds of discussions
  6.  An excuse to grab a soldering iron after not having used one in years


----------



## Zsubbo

Thanks, it sounds significantly better in my opinion, it's a lot more dynamic and it's more detailed, also a slightly less colored sound, witch goes nicely with the grados.


----------



## Crazy*Carl

Quote: 





mikeaj said:


> I wouldn't say it's the only reason, but the most important one.  Some other reasons are also listed below.
> 
> 1.  More volume
> 2.  Better ability to support headphones or IEMs not yet owned, i.e. have enough power for them, not have background hiss, and not muck up the FR with output impedance interactions
> ...


 
   
  I like your reasons


----------



## wje

Quote: 





zsubbo said:


> Just finished mine, pretty satisfied with the sound coming out of my grados
> 
> 
> 
> ...


 

 Very nice.  At first, that parts pile can seem daunting.  The finished product looks really good though - good solder points, etc.  I think you should contact Twinster for one of those fine, black manly-man aluminum knobs, though.  
	

	
	
		
		

		
		
	


	




   Then, you could call things "done" once you apply your face plate, too.


----------



## Twinster

Sorry but I do not have any Black Alu knobs available. I just promise the last available one to a friend 
	

	
	
		
		

		
		
	


	




.  The other is reserved for the ODA/ODAC.
  
  Quote: 





wje said:


> Very nice.  At first, that parts pile can seem daunting.  The finished product looks really good though - good solder points, etc.  I think you should contact Twinster for one of those fine, black manly-man aluminum knobs, though.
> 
> 
> 
> ...


----------



## Crazy*Carl

Anybody have any guesses on the ODA ODAC time frame.  I am thinking summer, but its just a wild guess.


----------



## Draygonn

crazy*carl said:


> Anybody have any guesses on the ODA ODAC time frame.  I am thinking summer, but its just a wild guess.




I'm guessing next month barring some last second redesign issues.


----------



## Twinster

He might release the info next month (just guessing) but we'll have to wait for the PCB group buy and probably custom plate so I would not expect anything before another 3 months.
  
  Quote: 





draygonn said:


> I'm guessing next month barring some last second redesign issues.


----------



## DarknightDK

I cannot wait for the desktop version of the O2 or any other amp that this designer will make.
   
  I have been doing some serious listening with the O2 paired with my LCD-3s lately and I cannot recommend the O2 enough with the LCD-3. They make for a fantastic pairing. The sound is so good - clean, neutral, dynamic with excellent PRaT and a completely black background. The O2 has enough power to drive the LCD-3 very well with great extension and control. I think the O2 takes things up several notches with the LCD-3.
   
  Compared with the 10SE that I own, I'll say the O2 is a step up from the amplifier section of the 10SE. With the O2 fed with the DAC of the 10SE, there is better sound staging, bass is tighter, punchy and more defined with very good PRaT and a smoothness to the overall presentation. The biggest improvement over the amp of the 10SE is that with the O2, the highs are better extended and defined - with more clarity and extension of the high frequencies. Cymbols sound more metallic and crisp the way they should. With the O2, a veil seems to be lifted and instrument separation and detail coming through to the listener better.
   
  The O2 just makes music so enjoyable. I wouldn't say the sound is overly analytical. It is neutral but at the same time musical. The O2 is really a breakthrough design and I cannot recommend it enough.


----------



## palmfish

Quote: 





darknightdk said:


> I cannot wait for the desktop version of the O2 or any other amp that this designer will make.
> 
> I have been doing some serious listening with the O2 paired with my LCD-3s lately and I cannot recommend the O2 enough with the LCD-3. They make for a fantastic pairing. The sound is so good - clean, neutral, dynamic with excellent PRaT and a completely black background. The O2 has enough power to drive the LCD-3 very well with great extension and control. I think the O2 takes things up several notches with the LCD-3.
> 
> ...


 
   
  A subjective review of the Objective amp! How ironic...


----------



## uelover

palmfish said:


> A subjective review of the Objective amp! How ironic...:wink_face:




I get what you mean. Lol.


----------



## audionewbi

wow this sounds like my kind of amp, finally an amp designed based on objective design. Why isn't this mass produced? The guy must be rich to design what seems on paper a perfect amp and not to want a dollar out of it.


----------



## Naim.F.C

I know Carl is now banned, but if he's reading I thought I'd post this to just tackle a point made about audiophile "descriptions".
   
   
  Such audiophile descriptions are often very accurate, and DarkKnight's was right on the money  At least compared to any smoother or warmer amp such as the ALo Continental, Woo WA2, Violectric V200 etc. The elements he described are common sound attributes of low noise floor but neutral sounding amps.
   
  The main reason for the addition of "tighter bass" is because there is less sub bass cloud or colourisation, so that impression is introduced. Any time you have less sub bass, but the same amount of mid bass, the mid bass will seem a lot tighter and punchier even though it's exactly the same in frequency terms. The clarity, separation of instruments etc, all because of exactly the same reasons. 
   
  If you have an inaudible noise floor, everything else is dependant on the actual frequency of sound. Introduce more bass extension? Lose detail and sound stage. Introduce high extension? Lose sub bass and body, but gain detailing etc etc. It's all about trade off's.
   
  But his description was almost _exactly_ fitting of what one can expect using the O2. Some people need to accept the fact that such descriptions are anything but nonsense, and are actually (often) accurate gauges and descriptors for the audio afflictions introduced as a result of the said equipment.


----------



## Digital-Pride

Now now guys, the whole point of the O2 is so we can relax and just enjoy the music, without worrying about whether or not the headphones are being properly driven.  With its transparency and very low output impedance, just connect a good source to it and let those beautiful notes flow.


----------



## palmfish

Quote: 





naim.f.c said:


> I know Carl is now banned, but if he's reading I thought I'd post this to just tackle a point made about audiophile "descriptions".
> 
> 
> Such audiophile descriptions are often very accurate, and DarkKnight's was right on the money  At least compared to any smoother or warmer amp such as the ALo Continental, Woo WA2, Violectric V200 etc. The elements he described are common sound attributes of low noise floor but neutral sounding amps.
> ...


 

 Why do you think the Violectric V200 is smoother and warmer? Didn't NwAvGuy mention Violectric as one of the companies that builds amps the right way with low output impedance, quality engineering, and meaningful measurements? If you subscribe to NwAvGuy's opinions, any amp that sounds different from the O2 does so because it is introducing something that isn't in the source.


----------



## Naim.F.C

Violectric amps are designed in a similar way, what with impedance having minimal to no affect on SQ etc, but it is wrong to assume all Violectric amps sound alike. The very reason for having different Violectric amps is because they have very subtly different sound signatures.
   
  One way or another, some colour has been introduced here and there to make the sound more engaging, fun etc. The V200 is that product. In this instance, I believe it adds some added colour to sub bass and upper mids based on A/B testing including blind (this would be what you've described as adding something that wasn't on the source). They are very subtle additions, but they exist none-the-less. Additions which have advantages and disadvantages.
   
  From what I've read, the Violectic V100 is the more neutral amp, though without testing it myself I can't know for sure. If true, _that_ would be the one to compare with the O2. 
  
  Quote: 





palmfish said:


> Why do you think the Violectric V200 is smoother and warmer? Didn't NwAvGuy mention Violectric as one of the companies that builds amps the right way with low output impedance, quality engineering, and meaningful measurements? If you subscribe to NwAvGuy's opinions, any amp that sounds different from the O2 does so because it is introducing something that isn't in the source.


----------



## palmfish

Quote: 





naim.f.c said:


> Violectric amps are designed in a similar way, what with impedance having minimal to no affect on SQ etc, but it is wrong to assume all Violectric amps sound alike. The very reason for having different Violectric amps is because they have very subtly different sound signatures.
> 
> One way or another, some colour has been introduced here and there to make the sound more engaging, fun etc. The V200 is that product. In this instance, I believe it adds some added colour to sub bass and upper mids based on A/B testing including blind (this would be what you've described as adding something that wasn't on the source). They are very subtle additions, but they exist none-the-less. Additions which have advantages and disadvantages.
> 
> From what I've read, the Violectic V100 is the more neutral amp, though without testing it myself I can't know for sure. If true, _that_ would be the one to compare with the O2.


 

 I've never heard the V200, so I can only take your word on how it sounds. But I really doubt that Violectric intentionally colored the sound to make it more "fun." The V200, being their top of the line amp, should be more transparent than the lower models, not less.
   
  FWIW, I have the V90 and it sounds identical to the O2 to me.


----------



## Naim.F.C

Fried himself describes the V200 as more "musical" than the V100. What do you believe musical implies? I absolutely think he is referring to a touch of colourisation, and I don't think there's anything inherently wrong with that. I personally think its likely harder to find a great coloured balance than a strictly neutral one.

Adding in colour usually has lots of blow back negatives, in this respect adding sub bass whilst ensuring infractions to detailing are minimal is a task in itself, one that I doubt many could get right. Others follow suit as well. I actually find for example, Amarra (the music player) to also be ever so slightly coloured (sub bass and mids) but only extremely subtly so, as to not detract too far from neutral.



palmfish said:


> I've never heard the V200, so I can only take your word on how it sounds. But I really doubt that Violectric intentionally colored the sound to make it more "fun." The V200, being their top of the line amp, should be more transparent than the lower models, not less.
> 
> FWIW, I have the V90 and it sounds identical to the O2 to me.


----------



## mikeaj

If this is true:
http://www.violectric.de/Pages/en/technical-data.php
   
  then it would seem exceedingly difficult to make those sound audibly different, unless you put in some very sensitive IEMs and are listening for noise levels in an environment with very low ambient noise, and there really is a 2 dB difference in noise levels.  Or I guess if they intentionally make the FR not flat and are playing around with the listed -0.5 dB of wiggle room between 5 Hz and 60 kHz (doubtful).  If you're making a copy of something and the output is stringently defined to be exceedingly close to the original, there's not much way for the output to be distinguished from that of another device that also adheres to those stringent specifications.
   
  However, it _is_ easy and quite necessary to speak the marketing speak, to get sales.


----------



## Twinster

This is good to know that the V90 sound identical to the O2. I was actually thinking of trying theV90 with my T1. Thank you.



palmfish said:


> I've never heard the V200, so I can only take your word on how it sounds. But I really doubt that Violectric intentionally colored the sound to make it more "fun." The V200, being their top of the line amp, should be more transparent than the lower models, not less.
> 
> FWIW, I have the V90 and it sounds identical to the O2 to me.


----------



## palmfish

Quote: 





twinster said:


> This is good to know that the V90 sound identical to the O2. I was actually thinking of trying theV90 with my T1. Thank you.


 

 Keep an eye out in the for sale section then because I think I'm going to sell mine...


----------



## Naim.F.C

Noise floor is pretty much inaudible with the O2 and Vio amps. But with respect to the colourisation on the V200, just read the countless reviews, impressions, comparisons to the other Vio amps etc, the differences are pretty well documented and far from marketing speil. Not talking about the value of amps in general, but I can myself confirm Freid's description.. He mentioned the V200 was a touch more musical and that's exactly what it is.

I will be posting a big thread comparing the V200 and O2 soon, so if you're interested to know specific differences etc, just check out my thread.



mikeaj said:


> If this is true:
> http://www.violectric.de/Pages/en/technical-data.php
> 
> then it would seem exceedingly difficult to make those sound audibly different, unless you put in some very sensitive IEMs and are listening for noise levels in an environment with very low ambient noise, and there really is a 2 dB difference in noise levels.  Or I guess if they intentionally make the FR not flat and are playing around with the listed -0.5 dB of wiggle room between 5 Hz and 60 kHz (doubtful).  If you're making a copy of something and the output is stringently defined to be exceedingly close to the original, there's not much way for the output to be distinguished from that of another device that also adheres to those stringent specifications.
> ...


----------



## mikeaj

Quote: 





naim.f.c said:


> Noise floor is pretty much inaudible with the O2 and Vio amps. But with respect to the colourisation on the V200, just read the countless reviews, impressions, comparisons to the other Vio amps etc, the differences are pretty well documented and far from marketing speil. Not talking about the value of amps in general, but I can myself confirm Freid's description.. He mentioned the V200 was a touch more musical and that's exactly what it is.
> I will be posting a big thread comparing the V200 and O2 soon, so if you're interested to know specific differences etc, just check out my thread.


 

 I don't mean to challenge what you say, but when you say "well documented" and "confirm", is any of it based on the quality of evidence that could be submitted to peer-reviewed academic publications?  A lot of evidence is good, but it's more important for it to be reliable and of quality, particularly in situations where the documentation of one can influence the perceptions of another.  So are there any particularly enlightening posts you could direct me to (I'd be interested in reading), or do they not exist and I should leave the issue alone?  Thanks.


----------



## Naim.F.C

Just go through the official V200 threads. I think there are a few posts just in the last 3 pages comparing the V200 with the other Violectric amps (V181 for example). Several posts ago one user was comparing his V200 with the DAC1 and came to the exact same conclusions as I already had with my own comparisons prior. There's was also some big comparison of different amps by some outlet where the conclusion was to opt for the V100 if you want something more neutral and the V200 if you want something more fun. I don't keep these posts to hand, nor would I seek them out. if you're curious, it's all there. It's not like the official threads are that long, so if you are interested about such things you could always research it yourself.
   
  I understand there is some reluctance to trust the opinions of general users, especially when there is so much hyperbole about. But sometimes, especially when they concern A/B comparisons, users are right on the money.
   
  Past that, I trust my ears and I trust stringent A/B testing. Enough that I would be willing to put down money on being able to blind test differences. At least I could with the O2 vs V200. Are the differences subtle? Sure, but comparing the same segments of the same songs on both, the differences are still noticeable, especially if you know what you're looking for.
  
  If you could get Freid to post frequency graphs and so forth the way NwAvGuy has, I'm sure it'd confirm people's findings.
   
  Quote: 





mikeaj said:


> I don't mean to challenge what you say, but when you say "well documented" and "confirm", is any of it based on the quality of evidence that could be submitted to peer-reviewed academic publications?  A lot of evidence is good, but it's more important for it to be reliable and of quality, particularly in situations where the documentation of one can influence the perceptions of another.  So are there any particularly enlightening posts you could direct me to (I'd be interested in reading), or do they not exist and I should leave the issue alone?  Thanks.


----------



## Bogatyr

Total newb here. Planning on getting Q701's & O2 for desktop use. How would this budget setup work: Xonar DG > O2 > Q701. Anything I should know or consider? Can I use O2 without batteries with AC adapter? Are there other amps I should consider? Do I need a DAC or is Xonar DG fine? Sorry for the blitzkrieg of questions, if anyone could educate me I'd be more than happy to listen


----------



## audionewbi

If you can wait a while the person who has designed the O2 is planning to release a DAC and desktop amp version of the O2 which is better than the O2. 
   
  If you cannot wait ofcourse buying an amp is always is always agood long term purchase. The question is now which one? It comes down to many factors. In my word ofcourse the importance factor is  money. 

 I have my eyes on v-DAC II. I am going to wait for the ODAC but if that is not as good as the O2 I will buy the v-DAC II. 

 Right now I own bresford caiman and fiio E7. I love the Bresford but it is limied to 16/48 over USB, the DAC section is good, but I need to admit it is not wroth $369.
  Quote: 





bogatyr said:


> Total newb here. Planning on getting Q701's & O2 for desktop use. How would this budget setup work: Xonar DG > O2 > Q701. Anything I should know or consider? Can I use O2 without batteries with AC adapter? Are there other amps I should consider? Do I need a DAC or is Xonar DG fine? Sorry for the blitzkrieg of questions, if anyone could educate me I'd be more than happy to listen


----------



## mikeaj

Quote: 





naim.f.c said:


> Past that, I trust my ears and I trust stringent A/B testing. Enough that I would be willing to put down money on being able to blind test differences. At least I could with the O2 vs V200. Are the differences subtle? Sure, but comparing the same segments of the same songs on both, the differences are still noticeable, especially if you know what you're looking for.


 
  Well thanks then, will look through when I get the chance.  Just to be sure, these comparisons are all at least level matched?  I agree that certainly subtle or small differences can be heard (depending on what you mean by "small"), but the main issue and reason for skepticism is that even _zero_ difference can be easily heard as a small difference.
   
   


bogatyr said:


> Total newb here. Planning on getting Q701's & O2 for desktop use. How would this budget setup work: Xonar DG > O2 > Q701. Anything I should know or consider? Can I use O2 without batteries with AC adapter? Are there other amps I should consider? Do I need a DAC or is Xonar DG fine? Sorry for the blitzkrieg of questions, if anyone could educate me I'd be more than happy to listen


 

  It should work fine.  If Asus's listed spec of 1V rms output is correct (they also list 3V p-p which is 1.06V, which would also be okay, but of course one or both figures could be rounded), then even the default high gain of 6.5X will not cause clipping.
  You can run without batteries.  You can also run with batteries and AC adapter, which will charge the batteries while performing as if on AC power, or just on batteries alone.
  There are always other amps to consider, though I wouldn't recommend another one at this price.
  Another DAC may be better than the DG, but the DG is probably fine.  For what little it's worth, loopback RMAA tests run by audio-ignorant computer hardware reviewers uncover no issues that should be audible, for use into an amp.  Of course RMAA can't uncover many potential issues.
   
  edit: the upcoming desktop edition may be more convenient ergonomically, but it's not intended to actually sound any better, except to eliminate the very small turn power on/off transients.  The features are the desktop form factor and more convenient arrangement and array of jacks.


----------



## Naim.F.C

Quote: 





mikeaj said:


> Well thanks then, will look through when I get the chance.  Just to be sure, these comparisons are all at least level matched?  I agree that certainly subtle or small differences can be heard (depending on what you mean by "small"), but the main issue and reason for skepticism is that even _zero_ difference can be easily heard as a small difference.


 

 I can't speak for the other comparisons (I trust one or two of the users enough either way) but yes, all my personal A/B testing is volume matched. Not precisely mind, but I try and do it to within/under a 0.5db difference. And I do agree, zero difference can indeed be heard as some difference. Placebo is one hell of a thing, something I myself have been hit with on occasion.
   
  That's why you have to very strictly A/B. Not entire tracks like some people do either. I personally find 10 second snippets of prominent segments of music compared over and over is best. One's that are very busy with different elements, enough to test all elements of the frequency, or different one's anyway. That and blind testing too.
   
  There's a few different tracks I use now which are quite good for comparisons.
   
  René Aubry - Salento | For bass detail on string resonance, as well as overall detail or transparency.
  Stateless - Matilda (Bonus Track) | For soundstage, detailing and a bit of everything really.
  Andreya Triana - A Town Called Obsolete (Live) | For female vocals and realism.
  Jamie Woon - Lady Luck | Sub Bass and male vocals (few others off his album too).
  The XX - Crystalised | Male and Female vocals (few others off the album too).
  Thom Yorke - Hearing Damage | Sub bass.
  Radiohead (mainly In rainbows) | For soundstage and male vocals.
  Daft Punk - Reconfigured | For mid bass, quite a few sibilant spots also to test high extension.
  Araab Musik - Electronic Dream | Great to test for sibilance and entire range of bass. 
   
  A good mix of the above, lots of others plus some classical too. Check some of them out. You can usually find a good 10 second spot in each track which is perfect to repeat play for more intricate or analytical comparisons.


----------



## sphinxvc

Quote:


darknightdk said:


> I cannot wait for the desktop version of the O2 or any other amp that this designer will make.
> 
> I have been doing some serious listening with the O2 paired with my LCD-3s lately and I cannot recommend the O2 enough with the LCD-3. They make for a fantastic pairing. The sound is so good - clean, neutral, dynamic with excellent PRaT and a completely black background. The O2 has enough power to drive the LCD-3 very well with great extension and control. I think the O2 takes things up several notches with the LCD-3.
> 
> ...


 
   
  I missed this post earlier; totally agree.  The LCD-3, O2 pairing is a surprisingly good one.  And agreed that the 10SE sounds quite good used as a DAC-only.


----------



## Bogatyr

Thanks for the reply. Now I'm curious - if I get O2 and use it as a desktop amp with Xonar DG, what are all the cables I'll need? Also, is there a way to switch between headphones and speakers? I saw these things, is there a way to utilize this and this?
   
  I drew a picture, I do apologize for its crudeness. I'm assuming the green cable is the 3.5mm jack. Is this feasible? Would the sound quality degrade between speakers and headphones? Is there a more efficient way to do this?
   

   
  My current budget is 200-250$, so I guess my options are going for the picture above, getting something like Xonar STX with an amp,
  Getting O2 & and a DAC for around ~100$, Or just wait for the ODAC whenever it is going to come out.


----------



## PurpleAngel

Quote: 





bogatyr said:


> Thanks for the reply. Now I'm curious - if I get O2 and use it as a desktop amp with Xonar DG, what are all the cables I'll need? Also, is there a way to switch between headphones and speakers? I saw these things, is there a way to utilize this and this?
> 
> I drew a picture, I do apologize for its crudeness. I'm assuming the green cable is the 3.5mm jack. Is this feasible? Would the sound quality degrade between speakers and headphones? Is there a more efficient way to do this?
> 
> ...


 
  Plug your speakers in to the back panel of the Xonar DG, hook up the Xonar DG front panel jack to the front headphone jack on your computer case, run a mini stereo jack (3.5mm, 1/8") male to male cable from the front headphone jack to the mini jack input on the O2 (Objective 2), then plug your headphones into the output jack on the O2.
  Don't use the Behringer HA400.


----------



## mikeaj

Just to really reiterate, whatever you do, you want the headphones to be plugged directly into the headphone amplifier.


----------



## Bogatyr

Thanks for replies.


----------



## MikeW

Run a 3.5 mini from soundcard to O2. 
   
  Run a 3.5 mini from O2 to speakers. 
   
  when you want headphones plug headphones into O2, when you want speakers, plug speakers into O2 and use as pre-amp. Now you also get a hardware volume control close at hand, and don't have to use a switch.


----------



## Naim.F.C

Hi guys, was wondering if you could help. My JDS O2 arrived today. John has informed me it is strictly a completely default design and set up as per NwAvGuy's instructions. However, strangely, my Epiphany O2 actually requires more volume to reach the same db (a fair bit more). Anyone know what could be causing this difference? Is there a configuration of the O2 that is even lower gain? Also, would batteries make a difference? I've noticed there are 9V Ni-Mh batteries in the JDS, and 8.4V one's in the Epiphany.
   
  If anyone can chime in I'd appreciate it. I assumed the Epiphany one was also completely default, I guess not? I'm assuming the Epiphany one is set to a lower gain.


----------



## audionewbi

It might be two things:
  1-I know power is important since from what I have read if it was not an important factor he would have just designed the amp based on the USB power, so the 0.6 volt difference might be a reason. If you have a PSU use that, this way you will know if it is battery related or not.
  2-It might be very well a hardware related issue. I know many folks were requesting different gain setting (1x and 3.5x compared to 2.5x and 6.5). Since based on what you wrote that cannot be it since it is based on the originl design my guess is going to be 1, the battery.


----------



## maverickronin

Quote: 





naim.f.c said:


> Hi guys, was wondering if you could help. My JDS O2 arrived today. John has informed me it is strictly a completely default design and set up as per NwAvGuy's instructions. However, strangely, my Epiphany O2 actually requires more volume to reach the same db (a fair bit more). Anyone know what could be causing this difference? Is there a configuration of the O2 that is even lower gain? Also, would batteries make a difference? I've noticed there are 9V Ni-Mh batteries in the JDS, and 8.4V one's in the Epiphany.
> 
> If anyone can chime in I'd appreciate it. I assumed the Epiphany one was also completely default, I guess not? I'm assuming the Epiphany one is set to a lower gain.


 

 NiMh batteries come in multiples of 1.2V since that's how much voltage you get from a single cell and the "9V" battery from JDS is probably just labeled that because of the form factor.  Even if it was an 8 cell 9.6V battery or something that would only change the max input before it clipped on battery power, not the gain.
   
  The likely explanation is that the Epiphany has a lower gain.  If you've got a multimeter you can download a sine wave generator for your computer and test what gains they actually have.


----------



## Naim.F.C

*JDS vs Epiphany*
   
  Hmm, whilst I'll also mention these things in my review, I have to say, I'd personally pay the extra and get the JDS O2. I've heard a lot of people mention they're _exactly_ the same, just get the cheapest. Well, they're _not_.
   

 Aside from the obvious different (silver with JDS branding) front panel of the JDS, there are other things too.
 Different batteries for one.
 The JDS version has slightly thicker panels (front and back) which give it a more weighty and solid feel.
 The JDS holes to the panels, whilst still not perfect, line up better than the Epiphany's.
 The Epiphany O2's volume knob, whilst (imo) better looking, has a slight wiggle to it. I put blu-tac in mine to remove it.
 Lastly, quite an important difference, I noticed that these amps are supposed to be "grounded" with a little wire that connects from the main board to the aluminium housing to reduce humming etc. I noticed the Epiphany O2 does not have this and the JDS does.
 One thing in the Epiphany's favour, it came with a UK AC charger/adaptor. The JDS came with none.
   
  So yes, the Epiphany is lighter and cheaper, but the JDS is better built and follows NwAvGuy's original design closer, well I say closer, I should say strictly, because it doesn't deviate_ at all_ (unless requested). Also, if you order it, I highly recommend buying these feet for it. Without them, it moves around like an ice skater!
   
  http://www.jdslabs.com/item.php?fetchitem=37
   
   
   
  EDIT: Ignore the thing about the pop. I think it might be on the album itself, *Caribou - Swim*, because I get it with the Epiphany one too.


----------



## MikeW

That's strange that Epiphany does not ground it. Are you sure? there's a couple ways to do that, JDS uses the default method, wire to front panel screw, but you can run the wire to the back panel as well. It's pretty easy to do it yourself if nothing else. But a strange ommision on their part. Though, it may not have any real effect on sound quality.


----------



## Naim.F.C

I've checked the front and back and can't see any sign of it. Doesn't have the chip off the corner of the casing near the screw like the JDS either. Not on any of the corners. Whereas on the JDS it's on the front bottom right one. Also, pretty sure it doesn't have any impact on sound quality unless you actually get humming (which I don't think I've ever had). Since based on brief comparisons, after vague volume matching they sound (to my ears) identical. But still, it's an omission that should not exist either way, just in-case.
  
  Quote: 





mikew said:


> That's strange that Epiphany does not ground it. Are you sure? there's a couple ways to do that, JDS uses the default method, wire to front panel screw, but you can run the wire to the back panel as well. It's pretty easy to do it yourself if nothing else. But a strange ommision on their part. Though, it may not have any real effect on sound quality.


----------



## Grev

Quote: 





naim.f.c said:


> Hi guys, was wondering if you could help. My JDS O2 arrived today. John has informed me it is strictly a completely default design and set up as per NwAvGuy's instructions. However, strangely, my Epiphany O2 actually requires more volume to reach the same db (a fair bit more). Anyone know what could be causing this difference? Is there a configuration of the O2 that is even lower gain? Also, would batteries make a difference? I've noticed there are 9V Ni-Mh batteries in the JDS, and 8.4V one's in the Epiphany.
> 
> If anyone can chime in I'd appreciate it. I assumed the Epiphany one was also completely default, I guess not? I'm assuming the Epiphany one is set to a lower gain.


 

 I'm pretty sure it's the gain, I got two O2 units from JDSLabs, one at 1x/3x gain and the other at the default 2.5x/6.5x gain, ready for different headphones.
   
  John also told me the tenergy batteries when charged goes up to 10v too, in which I also have a set of powerex imedion 9v batteries to use too and didn't find much difference.


----------



## Naim.F.C

Have a quick question guys. AC powered, even on low gain with my T1's I'm using like max 9-10 o'clock for volume on the JDS O2, whereas on my Epiphany O2 (I'm guessing it's set to 1x/3x gain) I use around 11-1 o'clock. Am I likely to get more channel imbalance at 10 o'clock and should I get it switched to lower gain settings, or are differences in channel balance likely to be negligible?


----------



## shadow419

At the 9-10 o'clock position the channel imbalance should be gone.  I only have some imbalance when the pot is between 7-8 o'clock area.


----------



## otinkyad

Quote: 





naim.f.c said:


> Have a quick question guys. AC powered, even on low gain with my T1's I'm using like max 9-10 o'clock for volume on the JDS O2, whereas on my Epiphany O2 (I'm guessing it's set to 1x/3x gain) I use around 11-1 o'clock. Am I likely to get more channel imbalance at 10 o'clock and should I get it switched to lower gain settings, or are differences in channel balance likely to be negligible?


 

 I had a JDS O2 with standard gain, the channel imbalance was bothering me at low volumes. JDSLabs recommended replacing with a low gain unit plus a hand selected pot.  I agreed, they did this for me, and I can confirm that channel balance is much better for me.  Of course if you'd like to drive the headphones to high volumes (I prefer low volumes, so I didn't need this) you might not want to go this route.


----------



## Twinster

I beleived that John from JDS include the set of gain resistors and it's very easy to change if you need too.
   
  Mine (build by me) is set to 1x & 3x and on 3x I listen to about 11 o'clock with my T1 so I would guess your JDS O2 has the default 2.5 / 6.5 gain. Again it all depend of the power out of your source.
   
  As for the ground I think it's really important. I build another O2 with the Desktop setup case and a bad ground on the input affected the sound a lot.
  
  Quote: 





naim.f.c said:


> Have a quick question guys. AC powered, even on low gain with my T1's I'm using like max 9-10 o'clock for volume on the JDS O2, whereas on my Epiphany O2 (I'm guessing it's set to 1x/3x gain) I use around 11-1 o'clock. Am I likely to get more channel imbalance at 10 o'clock and should I get it switched to lower gain settings, or are differences in channel balance likely to be negligible?


----------



## Naim.F.C

To save time, John sent me over this little diagram giving me  quick option to change from 2.5x/6.5x to 2.5x/1x if I didn't fancy sending my unit back. I went ahead and did it. Quick, easy and now my gain settings are good at 1x. Never need above 2.5x or close anyway so it's worked out ok. Now the gain button is flush with the power on button during use which is nice. Have to say, never seen any communication or feedback response as efficient and helpful as that from JDS. Hopefully this set up doesn't negatively affect SQ.
   
  On a side note, even with 1x gain on the JDS version, pretty sure it still requires less volume to match the Epiphany at the same point. Maybe the battery _does_ have an affect? Unless it's something else. Hmm..
   

   
   
  Here are some comparison shots with the Epiphany O2.


----------



## Twinster

Maybe the components used by Epiphany supplied in Europe are different or he used compatible alternatives as provided by designer Build Of Material list. If you use the amplifier with the AC adapt or connected the battery shouldn't have any affect.
  
  Quote: 





naim.f.c said:


> To save time, John sent me over this little diagram giving me  quick option to change from 2.5x/6.5x to 2.5x/1x if I didn't fancy sending my unit back. I went ahead and did it. Quick, easy and now my gain settings are good at 1x. Never need above 2.5x or close anyway so it's worked out OK. Now the gain button is flush with the power on button during use which is nice. Have to say, never seen any communication or feedback response as efficient and helpful as that from JDS. Hopefully this set up doesn't negatively affect SQ.
> 
> On a side note, even with 1x gain on the JDS version, pretty sure it still requires less volume to match the Epiphany at the same point. Maybe the battery _does_ have an affect? Unless it's something else. Hmm..
> 
> ...


----------



## mikeaj

Volume just has to do with the gain setting and how much attenuation is being applied via the potentiometer.  Battery has no effect until it starts to clip.
   
  Open up the Epiphany and look at the resistors.  The two ones you took out for the JDSLabs are for the high gain (switch in):  R19 and R23.  One is for left channel, and the other is for right channel.  Look at the two to the left of those, R17 and R21 as well.
   
  Gain is 1 + R16 / R17 for switch out, 1 + R16 / R19 for switch in.  (for the other channel, 1 + R22 / R21 or 1 + R22 / R23).  R16 and R22 are 1500 ohms by the BOM.  To determine what values were used for R19 (R23) and R17 (R21), check the resistor color code:
http://en.wikipedia.org/wiki/Resistor_color_code
   
  With R19 removed, more or less R19 becomes infinite (or at least >>> R16), so the gain becomes unity.
   
  Or alternatively, just measure the outputs.  You could use a multimeter or even do a line out -> line in recording in software like Audacity and then a line out -> amp -> line in recording at 100% potentiometer rotation to determine the gain.  Just don't overload the line in.  Check the relative input levels with and without the amp to see the scaling factor.
   
  Are you checking with the potentiometer turned 100%, all the way clockwise?  There exist different potentiometer tapers, so 12 on one will not correspond to 12 on another, and so on.  Maybe one has 15A taper while other has 3B taper.  Both are listed as options in the BOM:


----------



## otinkyad

Quote: 





naim.f.c said:


> Have to say, never seen any communication or feedback response as efficient and helpful as that from JDS.


 
   
  +1 for this.  I was really impressed with the communication/responsiveness/helpfulness from him.


----------



## Naim.F.C

Ok DIY Detectives. Here are the two boards, top one JDS (2.5x/1x Gain), bottom one Epiphany (Unknown Gain). Can anyone figure out why the Epiphany requires such a good degree more volume, even with the JDS O2 at 1x Gain?
   
   
*JDS O2.*
   

   
   
*Epiphany EPS-O2*
   

   
   
*And for reference, the original default design.*
   

   
  Thanks!


----------



## wje

Quote: 





naim.f.c said:


> Ok DIY Detectives. Here are the two boards, top one JDS (2.5x/1x Gain), bottom one Epiphany (Unknown Gain). Can anyone figure out why the Epiphany requires such a good degree more volume, even with the JDS O2 at 1x Gain?
> 
> 
> *JDS O2.*
> ...


 


  Just below the blue source / input connector - there appears to be different resistors present.  What is the Epiphany running in that area that the JDS Labs is not?  Something looks "different" in that area with those components.


----------



## Naim.F.C

Also, above the three little yellow capacitors(?) on the bottom right, there appears to be a multi coloured resistor on the Reference and Epiphany build, but a brown one on the JDS. Not sure if that makes any difference at all.
  
  Quote: 





wje said:


> Just below the blue source / input connector - there appears to be different resistors present.  What is the Epiphany running in that area that the JDS Labs is not?  Something looks "different" in that area with those components.


----------



## Maxvla

Only other differences I can spot are the red/gray caps and the pair of caps to their bottom right might be different.

The pot itself seems to be different also.


----------



## limpidglitch

Quote: 





maxvla said:


> The pot itself seems to be different also.


 

  
  Different pot, different taper.
  That would be my guess too.


----------



## MikeW

It's either the gain resistors or the POT. 
   
  The afformentioned "resistors below source connector" are the gain resistors. 
   
  the red/grey caps are coupling caps, red being Wima, and the grey or a different type, speced on the more recent BOM, but they make no difference with regard to volume. 
   


> *Volume Control Taper – *The Alps volume controls are available with two different tapers. I have tested both the “3B” taper (used for the measurements in the first article) and the “15A” taper and I prefer the 15A as it’s more “spread out” more below 70% volume. Which you prefer depends on if you’ll be listening more at high volume or low volume settings. At low volume settings (below 70%) the 15A is better. Click the graph for a larger version (graph courtesy Alps). _For most the 15A taper (the default RK09712200MC part in the BOM) is probably the better choice_.


 
   
  This means both Pots can reach the same low and max volume, but do so at a different slope, aka one might get loud faster or slower then the other. So the position of the pot will be different, but overall max loudness will not be effected. 
   
  edit, damn got ninja'ed by limpid


----------



## Naim.F.C

EDIT: Just checked. The Epiphany is using the 15A and the JDS the 3B.
  
  Quote: 





mikew said:


> It's either the gain resistors or the POT.
> 
> The afformentioned "resistors below source connector" are the gain resistors.
> 
> ...


----------



## Naim.F.C

Come to think of it, looking at the diagram posted earlier, the taper is most likely the cause.
   

   
  50% (12 o'clock) rotation on the 15A (Epiphany) is roughly 20% of power on this graph, whereas the 3B (JDS) is at that same level at 30% rotation (10 o'clock). That pretty much perfectly matches up with the volume differences experienced. So I think it is just the taper.
   
  Now would anyone like to explain the difference between the red resistors (wima) and the multi coloured one's?


----------



## vkvedam

Hey Buddy
I've followed your instruction and removed R19 and R23. I don't see any difference with the gain switch now. Did I remove the entire gain from the circuit? It's not an issue as I don't need the gain as of now. 
Ven


----------



## Naim.F.C

Push the gain button in! High gain is now low gain and low gain stays the same (becoming the higher gain). What a mouthful lol.





vkvedam said:


> Hey Buddy
> 
> I've followed your instruction and removed R19 and R23. I don't see any difference with the gain switch now. Did I remove the entire gain from the circuit? It's not an issue as I don't need the gain as of now.
> 
> Ven


----------



## vkvedam

Right, I don't hear any gain even with the gain switch pushed out.


----------



## Naim.F.C

It should be less gain with the switch pushed in. Could you take a photo of the resistors you gave the chop?
   
  Anyway, I've decided I prefer the build and design of the JDS, but prefer the 15A taper (as I listen at very low volumes) on the EPS-O2. I like the fact that the JDS one is more up to date with the latest design revision though.
   
  In-fact, I wonder if JDS do a version with the 15A taper instead of the 3B. I'd imagine this would be especially convenient for those who use mainly IEM's or listen at low levels.
   
  Quote: 





vkvedam said:


> Right, I don't hear any gain even with the gain switch pushed out.


----------



## vkvedam

Would do that tomorrow. Thanks...


----------



## palmfish

naim.f.c said:


> Push the gain button in! High gain is now low gain and low gain stays the same (becoming the higher gain). What a mouthful lol.
> 
> 
> 
> ...




Looking at your photos, I'm thinking about snipping the resistors on the left to get 1/6.5. I think the difference between 1 and 2.5 might be too small to matter. What do you think?


----------



## mikeaj

Yeah both the JDS and Epiphany are using resistors marked with brown black black brown *brown* (100 x 10^1 = 1000 ohms, with 1% tolerance) for a gain of 1 + 1500/1000 = 2.5.
   
  The red or white boxes next to the LED are film capacitors between the volume potentiometer and output stage op amps.  As long as they're of the right type (and most probably they are), there's no issue.  As always, there are different parts from different manufacturers that are more or less equivalent for this kind of thing.  One might make the casing red while the other makes the casing white.  Those are the most important and stringently-specified (and tested) capacitors in the whole design, but still, it's not a huge deal.
   
  edit:  by the way...the case is anodized aluminum and the anodized outer layer should be non-conductive, but it still makes me kind of nervous to see the amp placed on top of the case.  Several of those capacitors may still be holding something like 12V, and their leads are below the PCB.  It's not a great idea to short the leads together.
   
   


vkvedam said:


> Right, I don't hear any gain even with the gain switch pushed out.


 
  It's configured with which resistors now?  Take a picture if you have no idea.
   
   


palmfish said:


> Looking at your photos, I'm thinking about snipping the resistors on the left to get 1/6.5. I think the difference between 1 and 2.5 might be too small to matter. What do you think?


 
  1X to 2.5X isn't a huge difference, but It's not trivial either.  That's 8 dB.
   
  Why don't you set it to 2.5X, open a media player with a software volume control listed in dB (e.g. foobar2000) and turn it down 8 dB?  That should tell you what the difference should be.


----------



## Twinster

Looking at the picture and just realized that the gain resistors were not in a socket (as per the picture of the one Voldemort did). So I assume you just cut the resistors that was in place for the 6.5x gain?





naim.f.c said:


> Ok DIY Detectives. Here are the two boards, top one JDS (2.5x/1x Gain), bottom one Epiphany (Unknown Gain). Can anyone figure out why the Epiphany requires such a good degree more volume, even with the JDS O2 at 1x Gain?
> 
> 
> *JDS O2.*
> ...


----------



## Naim.F.C

Honestly speaking, I've never even had to use 2.5x gain, not with the LCD-2's or T1's. I personally think 6.5x is overkill unless you're rocking the HE-6 or something or want to demolish your hearing. Then again I listen at quite low volumes.
   
  Quote: 





palmfish said:


> Looking at your photos, I'm thinking about snipping the resistors on the left to get 1/6.5. I think the difference between 1 and 2.5 might be too small to matter. What do you think?


 
   

  
  That is correct. I snipped the one's off as pictured in the diagram sent by John on the previous page.
   


twinster said:


> Looking at the picture and just realized that the gain resistors were not in a socket (as per the picture of the one Voldemort did). So I assume you just cut the resistors that was in place for the 6.5x gain?


 
   
  I'll take that on board. Didn't realise it was dangerous!
   
   


mikeaj said:


> edit:  by the way...the case is anodized aluminum and the anodized outer layer should be non-conductive, but it still makes me kind of nervous to see the amp placed on top of the case.  Several of those capacitors may still be holding something like 12V, and their leads are below the PCB.  It's not a great idea to short the leads together.


 
   
   
   
  On a side note, I wasn't going to say anything, at the risk of sounding crazy. But is there are chance the differences between the builds could impact SQ at all? Unless it's complete placebo (which it very much could be), I feel like the JDS O2 has a _hair_ more bass. At least it seems to be more of a focus consistently than with the EPS-O2. Probably me going crazy or not volume matching well enough or something lol.


----------



## wullymc

Is anyone using these with Grados?
   
  Does it sound good?
   
  Would really like to hear from someone that has tried both the Little Dot 1+ and also that has tried the O2.
   
   
  Just trying to decide how to amp my Grados.  Right now I have SR60s and hope to procure RS1i next.


----------



## limpidglitch

Quote: 





wullymc said:


> Is anyone using these with Grados?
> 
> Does it sound good?
> 
> ...


 

 Chances are it will sound indistinguishable from your Clip+.


----------



## wje

Quote: 





wullymc said:


> Is anyone using these with Grados?
> 
> Does it sound good?
> 
> ...


 

 I've used the O2 with the Grado / Magnum headphones.  It pairs well with them.  I have not tried the Little Dot.  Also, as a question, why consider the RS1i, when you can get some Magnums for about 350?  Or, spending 550 on used RS1i headphones also puts you in the range for some used orthodynamic headphones such as offerings from HifiMAN.  I used to really love the Grado sound - then, the Magnum sound.  However, after getting hooked on the orthodynamics, it's hard for me to turn back. Then again, some orthodynamic headphones might require a bit more than the O2 to power them right, too.


----------



## idletime1213

I tried the O2 with the RS1i, pretty good combo, you won't be disappointed. I do like the Asgard a bit better for something like the SR325is though, adds a touch more warmth and bottom end and tames the treble a bit.


----------



## Eric_C

Has anyone used the O2 with a JH13? I've tried searching the thread but couldn't find any mention of it.


----------



## limpidglitch

I'll have to agree with wje here, especially the HE500 should be on your list of considerations.
   
  Just see what Tyll says about then here! And they cost practically the same as a set of RS1i.


----------



## Twinster

All it took for a hardcore Grado fan is trying the Fostex T50rp mod and it was history.  now the Hifiman ortho hook you up good.


----------



## wullymc

Thanks guys for your feedback!
   
  Things to think about.  I mostly listen to prog rock that is why I am thinking of sticking with Grado!


----------



## MikeW

Quote: Naim


> Honestly speaking, I've never even had to use 2.5x gain, not with the LCD-2's or T1's. I personally think 6.5x is overkill unless you're rocking the HE-6 or something or want to demolish your hearing. Then again I listen at quite low volumes.


 
   
  no, you can't use more then 2.5x with a dac or 2.0v RMS source. So it would not be useful with HE6 either. The only reason the high gain is needed is for an ipod, or other weak device that only has .05v output. If you ever plan to use it mobile, with a weak source, it's good to keep the high gain around. You may find 1x or 2.5x insuffcient with an ipod.


----------



## Maxvla

Guessing you meant .5v, .05v is pretty weak, heh.


----------



## maverickronin

Quote: 





maxvla said:


> Guessing you meant .5v, .05v is pretty weak, heh.


 

 Some IEMs will get by with just .05V...


----------



## firev1

Quote: 





eric_c said:


> Has anyone used the O2 with a JH13? I've tried searching the thread but couldn't find any mention of it.


 


  My friend seemed happy with it on a JH16, if that helps at all.


----------



## palmfish

The Grado's sound like crap so you need an amp that sounds like crap (but opposite crap) to try and even everything out?


----------



## jseaber

From the photo below, your Epiphany amp's 'low' gain is 1.0x, evident by the absent R17/R21 resistors...
   
  The potentiometer taper no doubt affects attenuation. A 3B taper is the standard volume taper curve. Most of our O2's use the default recommended Alps pot, RK09712200MC, which has a 15A taper. We've been using RK09712200MY's temporarily (Voldemort's 3rd alternative, a 3B taper) while the -MC parts were on backorder.
   
  You guys must be listening at incredibly low volumes! I didn't notice a difference after we switched from 15A to 3B. Granted, we use full size headphones on the test bench; nothing less than 64 ohms. 
  
  Quote: 





twinster said:


> Looking at the picture and just realized that the gain resistors were not in a socket (as per the picture of the one Voldemort did). So I assume you just cut the resistors that was in place for the 6.5x gain?


 

  
  Quote: 





naim.f.c said:


> Ok DIY Detectives. Here are the two boards, top one JDS (2.5x/1x Gain), bottom one Epiphany (Unknown Gain). Can anyone figure out why the Epiphany requires such a good degree more volume, even with the JDS O2 at 1x Gain?
> 
> 
> *JDS O2.*
> ...


----------



## Br777

Quote: 





naim.f.c said:


> Honestly speaking, I've never even had to use 2.5x gain, not with the LCD-2's or T1's. I personally think 6.5x is overkill unless you're rocking the HE-6 or something or want to demolish your hearing. Then again I listen at quite low volumes.


 
   
  yeah, i clipped the gain on my O2, and still never get the volume past 10oclock on low gain with my LCD-2's, and with my ES5 customs, I can barely touch the volume at all before its too loud. 
   
  of course this depends on my source - the above is true when running from my computer, optical to a bifrost dac, and into the O2. 
  When i run a line out from my ipod touch, i get a much larger volume swing due to the ... umm.. lower voltage output?  yeah i think thats it.


----------



## Eric_C

Quote: 





firev1 said:


> My friend seemed happy with it on a JH16, if that helps at all.


 

 It does! Thanks.
   
  [Edit] Oh wait, I forgot to ask: what's his gain setting?


----------



## uelover

Quote: 





br777 said:


> yeah, i clipped the gain on my O2, and still never get the volume past 10oclock on low gain with my LCD-2's, and with my ES5 customs, I can barely touch the volume at all before its too loud.


 

 What is the gain for your O2?


----------



## Br777

low =1
  high = 2.5


----------



## uelover

Quote: 





br777 said:


> low =1
> high = 2.5


 

 So with low gain when paired with Bifrost, you can't really move much with the ES5?


----------



## Br777

i get about a centimeter of play ( i measured)  before most music is either really loud, or too loud.   with an ipod with LOD i might get an extra half centimeter to get to the same volume (roughly)
   
  that said, with the es-5's i listen most often straight from my rockboxed clip+, b/c i cannot tell a difference between it and the setup i mentioned in my previous posts. (aside from a *very *slight hiss from the clip+) 
   
  The es5's dont benefit from an amp IMHO. 
   
  the lcd2's on the other hand sound phenomenal with the O2.


----------



## firev1

Quote: 





eric_c said:


> It does! Thanks.
> 
> [Edit] Oh wait, I forgot to ask: what's his gain setting?


 
  1X will provide plenty of volume for it. 1x FTW, virtually no noise and still plenty of volume for high sensitivity phones


----------



## uelover

Quote: 





br777 said:


> i get about a centimeter of play ( i measured)  before most music is either really loud, or too loud.   with an ipod with LOD i might get an extra half centimeter to get to the same volume (roughly)
> 
> that said, with the es-5's i listen most often straight from my rockboxed clip+, b/c i cannot tell a difference between it and the setup i mentioned in my previous posts. (aside from a *very *slight hiss from the clip+)
> 
> ...


 

 The reason why I use the O2 with my ES5 is not to amp it but to obtain a place to plug my ES5 in. Without the O2, there is no way I could use my ES5 with my desktop rig.
   
  Is there a 0.5 gain option available? Lol.


----------



## Eric_C

Quote: 





firev1 said:


> 1X will provide plenty of volume for it. 1x FTW, virtually no noise and still plenty of volume for high sensitivity phones


 


  Great. Thanks again for the reply.
  -looks at location- Hey, and you're in Singapore too? Gee, what are the odds.


----------



## Draygonn

br777 said:


> the lcd2's on the other hand sound phenomenal with the O2.



Good to hear. I might pick up some LCD-2s to see what all the fuss is about.


----------



## vkvedam

Right. If I remove R17/R21 as well from the board of a JDS labs O2 then what's going to happen? I've already removed R19/R23 and it seems like it has lost the gain functionality with the switch. There's no difference with the switch pushed in or left out. It's not clipping with my 2.1Vrms source even on the batteries now with R19/R23 removed.
   
  Anyone???
   
  Thanks...


----------



## a_recording

Just wanted to repaste some impressions I made in another thread: 
   
   
*Build: *The JDS labs build is very nice. Solid aluminium casing, everything fits together nicely. Again I can say that the 3D renders don't really do it justice, so here's a picture for you to peek at.
   

   
   

   
  My one complaint about the build is that the 3.5mm socket feels a little stiff when inserting a jack, and possibly contributing to this is that the socket move slightly when using them, as if the face plate has a little room for the sockets to wiggle. It's a relatively minor issue though, and honestly what I would expect out of a amp built on a DIY design. The 3.5mm headphone jack I'm very pleased with since I don't have to do any adapter swapping between my phone and this amp. The 3.5mm line in input is a little clunky - I'm using a 3.5mm to RCA adapter to go to my Music Streamer II+. This makes me ardently hope the ODA has a preamp out and RCA line ins.
   
  The whole unit is about the length and width of my wallet and the thickness slightly thicker than a VHS tape. It makes me scared that some people here might not know how thick a video tape is. I can't imagine using this as a pocketable headphone amp, but it seems the right size to toke around with my 11" Macbook Air and rock it out in a library or a park with the battery.
   
*Sound:* This is the real treat. while I am not the biggest believer in amps making a huge difference in sound, I have to say I am pretty darn impressed by this amp. It is very noticeably cleaner then the Schiit Asgard it replaced, the sound being grain free, rich and full of authority. Everything sounds smooth, detailed and clean. What is most striking to me is the sense of authority it has lent to the bass of my lighter cans - the Z1000 sounds nice and liquid on it, with deep bass extension. It is something I suspect I missed since I originally bought them, when I had a Black Cube Linear to demo them on. The AD900 sounds clean and sweet on it as well. I have to say that the lack of grain has made both the Z1000 and the AD900 a lot easier to listen to, compared to when they would have drier, granier treble on the Asgard. Lastly and most happily, my old RE0 which was the start of my Head-fi hobby sounds, well, essentially as good once paired with the O2 as any other high end IEM I've bought since then. 
   
  I don't know enough or have heard enough amps to say whether or not this amp has a particular sound - I am going to take it at face value that the designer of the amp was going for a neutral amp with low distortion and harmonics, and that is what I seem to be hearing. If I had one word for it, it would be: clean. 
   
 Now here's the one troubling note. Yes, the JDS labs O2 has a 2.5x and 6x gain switch. I'm finding that on the high gain setting, there is noticeable distortion. This isn't the high volume kind of distortion, but fluttering noises I'm getting at normal volumes. I'm running off a 14vac adapter. Now, I don't have any high impedance cans to test the O2 with so I don't know if this is an issue that is happening because I'm trying to use high gain with low impedance headphones (I don't know enough about electronics) or because of some fault. Since the amp seems to have more than enough headroom at 2.5x with all my headphones (I'm not even going to 12 o clock on the volume knob on any of my gear) I won't really use the 6x gain mode, but I have sent off an enquiry to JDSLabs about it.
  
 *Edit: *Reviewing the instructions that came with the amp (duh) it seems I may be causing distortion because at 6x gain and the 2v + output of the Music Streamer is overloading the gain stage. Oops!
   
  I was twittering to Mike from Headfonia about the O2, and he pointed out that the JDSLabs O2 he had also had degraded performance on the high gain mode (which is what prompted me to try it), though I do not know if it is quite as bad as what I am hearing. He also pointed out that the Epiphany Acoustics model has a 1x / 2.5x gain switch, and that the 1x gain setting was even better. Again, I can't confirm this, and I don't even know enough about gain to really comment on it - just something to note if you are thinking between the JDS and the Epiphany model. I went with JDSLabs because they are supposedly the more reputable company, but the Epiphany does include a local power adapter for around the same price. All I can say is that on the default 2.5x gain mode I'm more than pleased with the performance. It's dead quiet, even on AC power, with no hum or hissing.  
   
*Overall* for $150 I think anyone with some nice headphones owes it to themselves to give this a go and hear nwavguy's statement with their own ears so to speak. Again, I don't know enough about electronics or amplifiers to say one way or the other whether the technical aspects of his implementation are correct, but I do appreciate his transparency in designing and selling this amp. And I appreciate the amp's own transparency very much. :3


----------



## uelover

Thank you a_recording for this nice and very informative review! Much appreciated =)


----------



## Epiphany Oliver

Just to confirm, the EHP-O2 has 1x and 2.5x gain as standard. As for holes not matching up so well, yes they are ever so slightly out which is something which has been fixed in the second batch, Other than that, the build is standard. Differences in colours of caps etc is just because they are from different manufacturers. For instance, the 2 red caps in the EHP-O2 are Wima.


----------



## khaos974

Quote: 





epiphany oliver said:


> Just to confirm, the EHP-O2 has 1x and 2.5x gain as standard. As for holes not matching up so well, yes they are ever so slightly out which is something which has been fixed in the second batch, Other than that, the build is standard. Differences in colours of caps etc is just because they are from different manufacturers. For instance, the 2 red caps in the EHP-O2 are Wima.


 

 There was a few comments about the grounding of the EHP-O2 a few pages earlier, you may want to clarify a bit.


----------



## Grev

I guess I'm glad I got two O2 units with different gain settings.


----------



## a_recording

Quote: 





uelover said:


> Thank you a_recording for this nice and very informative review! Much appreciated =)


 


  No worries :3 Are you still looking for your perfect closed can?


----------



## uelover

Quote: 





khaos974 said:


> There was a few comments about the grounding of the EHP-O2 a few pages earlier, you may want to clarify a bit.


 

 Yes I will want to know about it as well. It is an important concern.
   
  Quote: 





a_recording said:


> No worries :3 Are you still looking for your perfect closed can?


 

 I have gotten myself a W3000ANV two weeks ago and have ordered Epiphany's O2 two weeks ago as well. Am still waiting for it to be made. Total wait time will exceed a month which is a very long time.


----------



## turokrocks

Good things come to who wait, I had to wait for 6 weeks till i got mine,BEAT THATGood things come to who wait, I had to wait for 6 weeks till i got mine,BEAT THAT


----------



## vkvedam

For all the people in EU. Bear in mind that if your order from JDS Labs like I've done you need to pay the import duty plus the admin charge from the postal services (Royal Mail in my case) which added up to the total. Precisely I got charged £26.00 in excess to the $162 (Shipped) from JDS in the US. I didn't know about Epiphany Oliver at that point or else would have gone for that to avoid the unnecessary customs charge.


----------



## firev1

Quote: 





eric_c said:


> Great. Thanks again for the reply.
> -looks at location- Hey, and you're in Singapore too? Gee, what are the odds.


 

 Coincidence, if you would like, Diyer madcap is selling O2s with JDSlabs style volume knob locally. You can also hit me up a pm if you would like to try out my O2 

  
  Quote: 





vkvedam said:


> Right. If I remove R17/R21 as well from the board of a JDS labs O2 then what's going to happen? I've already removed R19/R23 and it seems like it has lost the gain functionality with the switch. There's no difference with the switch pushed in or left out. It's not clipping with my 2.1Vrms source even on the batteries now with R19/R23 removed.
> 
> Anyone???
> 
> Thanks...


 
   
No idea what happened, I think if you remove R17 R21 you would just have a gain level of 1X you could try installing it again(R19/R23) or install DIP8 sockets so you could try out different gain settings.​


----------



## uelover

JDS Labs will be slightly cheaper for me but I went with Epiphany for the sake of convenience since I also use the UK power adapter. Didn't know the wait would be so long if not I would have gone with JDS and get my own power adapter.


----------



## thehadi

Hi,
   
  Can O2 drive K501 well? I can't find any review with K501.


----------



## vkvedam

I am quite happy with my JDS built O2, it's just the customs charge that I am not happy about. No one has still answered my query about the R17/R21 and R19/R23 from my earlier post. Could anyone please share a thought?
   
  Thanks


----------



## vkvedam

Oops! Just seen that fireV1. Still someone from JDS (Trader) should be able to answer my question.
   
  Thanks...


----------



## mikeaj

Quote: 





vkvedam said:


> I am quite happy with my JDS built O2, it's just the customs charge that I am not happy about. No one has still answered my query about the R17/R21 and R19/R23 from my earlier post. Could anyone please share a thought?
> 
> Thanks


 

 So you removed R19/R23?  If somehow R17/R21 are not connected fully, then you have an open circuit and both will be 1X gain.  Take some close pictures of the board (both sides) to confirm.


----------



## vkvedam

Quote: 





mikeaj said:


> So you removed R19/R23?  If somehow R17/R21 are not connected fully, then you have an open circuit and both will be 1X gain.  Take some close pictures of the board (both sides) to confirm.


 


  Will post some pictures this evening. But your explanation sort of makes sense. It should be 1X with an open circuit and that could be the reason why I don't see the effect of gain switch.


----------



## Eric_C

firev1: Thanks again. Wow, I guess the O2 interest really is a global phenomenon.
   
  Everyone: if you're buying from JDS or Epiphany, do ask about customising the gain settings on your particular unit. I spoke to JDS, and John informed me that he could change the low gain setting if need be.
  Hope that helps you out if you're no DIY-er (like me).


----------



## uelover

Quote: 





eric_c said:


> firev1: Thanks again. Wow, I guess the O2 interest really is a global phenomenon.
> 
> Everyone: if you're buying from JDS or Epiphany, do ask about customising the gain settings on your particular unit. I spoke to JDS, and John informed me that he could change the low gain setting if need be.
> Hope that helps you out if you're no DIY-er (like me).


 


  Could the gain go anything lower than 1X?


----------



## Eric_C

Haha, not that I've heard of. My understanding is that 1x gain is "unity gain", and I haven't heard of anything lower than that.
  A lot of people have also commented that a 1x gain is only really suitable if you're listening at very low levels, so realistically speaking, there probably isn't need for it.


----------



## Naim.F.C

My O2 vs V200 thread is nearly finished now. Got all my photo's done and most of it written up now. Should be posting it soon'ish.


----------



## uelover

Quote: 





eric_c said:


> Haha, not that I've heard of. My understanding is that 1x gain is "unity gain", and I haven't heard of anything lower than that.
> A lot of people have also commented that a 1x gain is only really suitable if you're listening at very low levels, so realistically speaking, there probably isn't need for it.


 

 My DAC lineout is pretty loud and my ES5 is pretty sensitive. So, perhaps, the lower the better will apply in my case =)


----------



## jseaber

No need to e-mail us. There's a "notes" field in the checkout process for...making notes. 
	

	
	
		
		

		
			




  
  Quote: 





eric_c said:


> firev1: Thanks again. Wow, I guess the O2 interest really is a global phenomenon.
> 
> Everyone: if you're buying from JDS or Epiphany, do ask about customising the gain settings on your particular unit. I spoke to JDS, and John informed me that he could change the low gain setting if need be.
> Hope that helps you out if you're no DIY-er (like me).


----------



## firev1

Quote:


uelover said:


> My DAC lineout is pretty loud and my ES5 is pretty sensitive. So, perhaps, the lower the better will apply in my case =)


 
   
  I know what you mean, my DAC output measures 2.4 - 2.6V and I barely use beyond 8-9 o'clock even on 1X on Desktop with my TF10s. 

  
  Quote: 





naim.f.c said:


> My O2 vs V200 thread is nearly finished now. Got all my photo's done and most of it written up now. Should be posting it soon'ish.


 

 Looking forward to it


----------



## mikeaj

For lower gain you could use another O2 as a pre-amp to an O2.  Use the volume control on the first one to attenuate.  Yep.  
	

	
	
		
		

		
		
	


	



   
  Well seriously, this is where some amps with multiple gain settings (including negative) would be useful, and/or multiple stages.  That increases complexity, cost, etc. though.
   
  I've got like 0 + epsilon background in op amp circuits, but the non-inverting amp configuration the O2 uses has gain 1 + R_a / R_b, so you're not going to get lower than 1 with any resistance values.  I'm not sure what kind of configuration would be most suitable for negative gain.  Of course, you could use a resistive divider network somewhere along the line, or equivalently, something like another potentiometer on a second gain/attenuation stage.  Actually, if you put an additional pot before the input stage (that's where the pot is on many audiophile amps, instead of between the input and gain stages like it is here), then you could reduce the input voltage some, which admittedly reduces SNR.
   
  Another thing to consider is a volume attenuator / hiss buster circuit or adapter for the IEMs.  For each channel, put a resistor R_1 in series and another resistor R_2 in parallel with the load.  If R2 << impedance of the IEMs, you get roughly R2 / (R1 + R2) of the voltage you would have gotten, to the IEMs.  Adjust R1 accordingly to be larger than R2, so you get a lot of attenuation.


----------



## maverickronin

Quote: 





thehadi said:


> Can O2 drive K501 well? I can't find any review with K501.


 

 I couldn't say for sure, but I'd imagine it would be ok.  Its great with my K601s and many others like it with K701s.
   
  Quote: 





mikeaj said:


> Another thing to consider is a volume attenuator / hiss buster circuit or adapter for the IEMs.  For each channel, put a resistor R_1 in series and another resistor R_2 in parallel with the load.  If R2 << impedance of the IEMs, you get roughly R2 / (R1 + R2) of the voltage you would have gotten, to the IEMs.  Adjust R1 accordingly to be larger than R2, so you get a lot of attenuation.


 
   
  What does that do to the output impedance the IEMs see?  It really should be as low as possible with BA drivers.
   
  Another option, if you have a good 24 bit DAC, is to lower the volume in software.  The extra bit depth will keep you from losing dynamic range with 16 bit recordings and nothing actually uses enough that you'd all the dynamic range in a 24 bit one.


----------



## mikeaj

Quote: 





maverickronin said:


> What does that do to the output impedance the IEMs see?  It really should be as low as possible with BA drivers.


 
   
  I've never seen or done the analysis for this or any similar situation, and I don't really have the background in feedback theory, but I don't imagine the effect would be great.  The amplifier drives this new, probably more resistive load, rather than the original load, and it has no idea what's going on with the headphone drivers.
   
  Certainly the FR would be mostly unchanged since the voltage is getting scaled mostly constant over frequency.  As for phase, correcting back EMF, etc., I'm not sure.  Do those things really matter that much?


----------



## maverickronin

Quote: 





mikeaj said:


> I've never seen or done the analysis for this or any similar situation, and I don't really have the background in feedback theory, but I don't imagine the effect would be great.  The amplifier drives this new, probably more resistive load, rather than the original load, and it has no idea what's going on with the headphone drivers.
> 
> Certainly the FR would be mostly unchanged since the voltage is getting scaled mostly constant over frequency.  As for phase, correcting back EMF, etc., I'm not sure.  Do those things really matter that much?


 

 That would still raise the output impedance  as measured from the output of the attenuater adapter unless R2 was really small though, right?  With impedance curves like this you want the output impedance to be as low as possible.
   
  Isn't the math the same as this example on the Meier site?  (At the bottom of the page.)
   

   
  Ignore the O2's .5 ohm Z out, let his Ro = R1 and Ra =R2 which makes Ro part of the adapter.  Then the output impedance of the amp + adapter should be (R1*R2)/(R1+R2) or did I mess something up?


----------



## hekeli

Quote: 





a_recording said:


> My one complaint about the build is that the 3.5mm socket feels a little stiff when inserting a jack, and possibly contributing to this is that the socket move slightly when using them, as if the face plate has a little room for the sockets to wiggle. It's a relatively minor issue though, and honestly what I would expect out of a amp built on a DIY design.


 


  I was bothered by the jacks at first too. But I've done a lot of inserting and removing since, and it's better now, not an issue really. JDS even offered to replace the unit, which is nice, but I don't think it would have made a difference. 
   
  Would have no problem paying few bucks more for better jacks though.


----------



## thehadi

Quote: 





maverickronin said:


> I couldn't say for sure, but I'd imagine it would be ok.  Its great with my K601s and many others like it with K701s.


 

  Thank you


----------



## hekeli

Quote: 





vkvedam said:


> For all the people in EU. Bear in mind that if your order from JDS Labs like I've done you need to pay the import duty plus the admin charge from the postal services (Royal Mail in my case) which added up to the total. Precisely I got charged £26.00 in excess to the $162 (Shipped) from JDS in the US. I didn't know about Epiphany Oliver at that point or else would have gone for that to avoid the unnecessary customs charge.


 

  
  It's surprising that there really are people who don't know about customs etc.. even our customs agency has a "guide for dummies" for buying on the net.
   
  Total price to Finland (EU):
   
*Epiphany:* 117 GBP = *183 USD*
*JDS labs:* 160 USD + 37 USD (customs) + 15 USD (power) = *212 USD*
  
  So it would have been a measly 29 USD difference here. Bear in mind that not all packages end up in customs, so you might get lucky. But I happily paid that for the "JDS trust" and better specced power (link) of my own choosing.
   
  Of course there is the chance of needing warranty etc, but from here it's pretty much the same shipping to US or UK. Might just take longer.


----------



## KGee

I just finished by O2 build a few days ago and am impressed with the sound so far, although I'm waiting for my HD650 to arrive.  Hopefully I'll be blown away.
   
  I'm also thinking about clipping/removing R19 and R23 to get 1x gain instead of 6.5x with the gain switch in.  I'm not sure if 1x gain is a good match for HD650 vs. 2.5x gain, but I'm barely at the 10 o'clock volume position on 2.5x gain with my MDR-7506.


----------



## hekeli

Quote: 





kgee said:


> I just finished by O2 build a few days ago and am impressed with the sound so far, although I'm waiting for my HD650 to arrive.  Hopefully I'll be blown away.
> 
> I'm also thinking about clipping/removing R19 and R23 to get 1x gain instead of 6.5x with the gain switch in.  I'm not sure if 1x gain is a good match for HD650 vs. 2.5x gain, but I'm barely at the 10 o'clock volume position on 2.5x gain with my MDR-7506.


 


  As it has been stated, unless you never intent to use low output portable sources, you can't even use the 6.5x gain. I clipped mine by just removing one head of the resistors (pulled with small pliers) and left them hanging in the air. So in theory it should be dead simple to solder them back if needed.


----------



## vkvedam

Here we go!!
   
  !
   

   

   
  Did I do something wrong?


----------



## firev1

Quote: 





vkvedam said:


> Here we go!!
> 
> !


 
  It looks to me that R17 is kind of clipped which may be the source of your gain problems.


----------



## mikeaj

Quote: 





maverickronin said:


> That would still raise the output impedance  as measured from the output of the attenuater adapter unless R2 was really small though, right?  With impedance curves like this you want the output impedance to be as low as possible.
> 
> Isn't the math the same as this example on the Meier site?  (At the bottom of the page.)
> 
> ...


 

 Oh, that looks right then (taking without proof, and without going through it myself).  Generally you do make R2 really small.  With say Ro (R1) = 16 ohms and Ra (R2) = 1 ohm, Ro * Ra / (Ro + Ra) gives you 0.94, not that bad.  Voltage to the headphones would be approximately 1/16th of normal, so 20*log10(1/16) = -24 dB gain.  Those are about reasonable numbers for both output impedance and attenuation, for those multi-balanced armature IEMs that have something like 130 dB SPL / 1V.
   
   
   


firev1 said:


> It looks to me that R17 is kind of clipped which may be the source of your gain problems.


 
   
  That should effect one channel but not both.  Also, R17 looks a little rough but not cut through.  To me, it looks like the PCB trace is damaged, where the resistors were taken out.  Thus the resistor is no longer connected to the circuit where it should be, so you have an open circuit and 1x gain.
   

   
  I've marked it with red arrows.  There's no longer a connection between the spots indicated by the arrows.  The start of the arrow is where the gain resistor is.  It's supposed to be connected to the rest of the PCB trace, but the damage looks like the connection may be broken now.  You could manually solder a couple wires (insulated) between the spots the resistors are and the points where the PCB traces end, at the next solder point on the PCB for the next part.  i.e. bypass the PCB trace and just do that portion point-to-point.


----------



## maverickronin

Quote: 





mikeaj said:


> Oh, that looks right then (taking without proof, and without going through it myself).  Generally you do make R2 really small.  With say Ro (R1) = 16 ohms and Ra (R2) = 1 ohm, Ro * Ra / (Ro + Ra) gives you 0.94, not that bad.  Voltage to the headphones would be approximately 1/16th of normal, so 20*log10(1/16) = -24 dB gain.  Those are about reasonable numbers for both output impedance and attenuation, for those multi-balanced armature IEMs that have something like 130 dB SPL / 1V.


 

 Ok then.  That makes sense.


----------



## a_recording

I'm curious about the whole 1x gain thing, though I am not sure exactly which resistors I'd have to clip.
   
  Another question of mine is though: doesn't 1x gain mean that the amplifier is doing no amplification at all? Or rather, apart from changing the output impedance, could someone with a bit more know how tell me how having a 1x gain would differ from taking the amplifier out of the chain and plugging headphones directly into a source?


----------



## mikeaj

Quote: 





a_recording said:


> I'm curious about the whole 1x gain thing, though I am not sure exactly which resistors I'd have to clip.
> 
> Another question of mine is though: doesn't 1x gain mean that the amplifier is doing no amplification at all? Or rather, apart from changing the output impedance, could someone with a bit more know how tell me how having a 1x gain would differ from taking the amplifier out of the chain and plugging headphones directly into a source?


 

 To make switch out = 1x gain, remove (or just clip one side of) R17 and R21.  To make switch in = 1x gain, remove R19 and R23.  The diagrams are in this thread in the last few pages and of course on the blog.  These four resistors are close to the front side, near the volume knob.
   
  The amplifier's ability to drive headphones is based on the design of the circuit:  the circuit configuration and topology, PCB layout, parts used (and for example, op amps contain complicated circuits inside), and so on.  This will influence the amp's ability to maintain a steady output (i.e. maintaining what was given to the amp: the input) into different headphones, at different volumes, with different input signals.  The source may not have an amplifier with the same kind of electrical characteristics, so the performance may be worse into some different headphones at some different volumes with different input signals, or it may not even have a headphone amplifier at all, so you'd get massive amounts of clipping trying to drive lower-impedance headphones.
   
  Amplification is an analog process, and like all real-world analog systems, it's impossible to have completely ideal input/output relationships.  Some amps are closer or further from the ideal, some intentionally and some not intentionally.
   
  The current is just the voltage provided divided by the impedance.  Some amplifiers start to misbehave more when they're handling more current.  At a given output voltage, the lower the load impedance, the higher the current.  Amplifiers have current, voltage, and/or total power limitations.  Most cheaper headphone chips and definitely most op amps aren't specified for being able to handle that much current.


----------



## vkvedam

Thanks mikeaj. Stupid of me. Should've left it alone, sort of ruined that. But 1x gain seems to be more than sufficient even with my HE-5LEs as it stands. But I would do that wire thing so that I'll have at least 2.5x gain in future for low powered sources.


----------



## a_recording

Quote: 





mikeaj said:


> To make switch out = 1x gain, remove (or just clip one side of) R17 and R21.  To make switch in = 1x gain, remove R19 and R23.  The diagrams are in this thread in the last few pages and of course on the blog.  These four resistors are close to the front side, near the volume knob.
> 
> The amplifier's ability to drive headphones is based on the design of the circuit:  the circuit configuration and topology, PCB layout, parts used (and for example, op amps contain complicated circuits inside), and so on.  This will influence the amp's ability to maintain a steady output (i.e. maintaining what was given to the amp: the input) into different headphones, at different volumes, with different input signals.  The source may not have an amplifier with the same kind of electrical characteristics, so the performance may be worse into some different headphones at some different volumes with different input signals, or it may not even have a headphone amplifier at all, so you'd get massive amounts of clipping trying to drive lower-impedance headphones.
> 
> ...


 

 Thanks for that helpful reply Mike  
   
  I just realised looking closer at the image that all the resistors are labelled. Is there any chance when clipping the resistors and leaving them hanging that they could still move around and make contact? 
   
*Edit*: Okay, I removed those two resistors completely. Keeping them in a safe place. Was very easy - the hardest part was finding a small pair of scissors, and also one of the case screws was stubborn about going back in. Now I have 2.5x / 1x gain, with no distortion running off battery connected to a line level source. Yay!
   
  I have to really commend John from JDSLabs, he has responded to my every email quickly and politely. Now there is a customisation tab on their website that details the different gain options that can be requested upon checkout. Turns out he is reading this thread


----------



## Eric_C

+1 on John's communication. It impressed me back when I got a CMoyBB, and it impresses me again now.
   
  Btw does anyone have a turn-on/off thump with their O2? How does it compare to the Pico Slim, if anyone happens to know?


----------



## maverickronin

Quote: 





eric_c said:


> Btw does anyone have a turn-on/off thump with their O2? How does it compare to the Pico Slim, if anyone happens to know?


 

 There is one, but its not even that loud with my SE530s.  I don't know how it compares to the Pico's.


----------



## pekingduck

Yes there's thump on the O2 but it is a LOT weaker than the Pico's.
   
  Quote: 





eric_c said:


> +1 on John's communication. It impressed me back when I got a CMoyBB, and it impresses me again now.
> 
> Btw does anyone have a turn-on/off thump with their O2? How does it compare to the Pico Slim, if anyone happens to know?


----------



## Eric_C

maverick, pekingduck: Thanks guys, that's music to my ears. Especially you pekingduck--I just auditioned the Slim yesterday and I think that power up transient is unacceptable.


----------



## sonitus mirus

Small thump observed when powering off, but much more tame than my Asgard.  I'd say that this behavior is normal, although it would be appreciated if one of the engineering braniacs stepped in and provided a rational explanation on why this occurs.
   
  I've read that it is a good practice to always lower the volume to the minimum value before shutting off a device or plugging-in/unplugging a pair of headphones.


----------



## Bogatyr

Greetings all. I've posted few days ago in regards to running O2 from Xonar DG and appreciate quick replies.
   
  Forgive my lengthy post however I have a couple of general & O2 oriented questions.
   
  1. I've seen many posts arguing on what is a good dac \ amp pairing for AKG Q701. As I have no idea or knowledge I was curious whether anyone had tried O2 with AKG Q701 cans.
   
  2. Everyone keeps saying I need an amp to drive AKG Q701 well, I'm a total noob and am currently running them on Xonar DG. I use about 25/100 volume in Windows 7 with Xonar DG set to 32-64 Ohm settings. What does it mean to drive Q701's well? I really wouldn't want unpleasantly loud volume levels.
   
  3. If I were to get O2, what would be a good DAC to go with it? Once again I've seem many posts stating X is a good dac Y is a good amp yet X and Y do not pair well together.
   
  4. Which O2 gains would be ideal for Q701 and my preference for not so loud sound levels?
   
  5. My budget is 200-300$, and my Q701's are desktop headphones. I listen to music, play games, and watch movies. What would be the smartest thing to do in my position? ( I understand that debates on audio are completely subjective )

 Get an external DAC & AMP such as HRT Streamer 2 DAC + Objective 2 Amp. Or Fiio E7/10/17 + Fiio E9. Despite once again not knowing whether I need a Dac or Amp in the first place or whether those are good matches for me.
 Keep Xonar DG & continue running Q701 from it as I find volume levels at 1/4th adequate despite not knowing what it means to drive a card well
 Get a sound card such as:
HT | OMEGA Claro Halo 24-bit 192KHz PCI Interface Sound Card w/ a built-in HI-FI Headphone Amplifier
ASUS Xonar Essence STX Virtual 7.1 Channels 24-bit 192KHz PCI Express x1 Interface 124 dB SNR / Headphone AMP Card
 Get a Dac&Amp 2in1 such as NFB-12 or a cheaper solution such as Fiio E10
 Go with something else that I have not yet mentioned.
   
  Once again I apologize for the length and if I went over same questions more than once but after doing hours of research instead of arriving at a conclusion I've only acquired more questions. Thanks in advance, hope to hear suggestions.
   
  Perhaps it is wrong of me to shove my confusion  and worries onto you guys but I honestly don't know where else to turn since I cannot afford frequent purchases such as these nor the ability to try out any equipment in person prior to buying it.


----------



## Eric_C

Quote: 





sonitus mirus said:


> Small thump observed when powering off, but much more tame than my Asgard.  I'd say that this behavior is normal, although it would be appreciated if one of the engineering braniacs stepped in and provided a rational explanation on why this occurs.
> 
> I've read that it is a good practice to always lower the volume to the minimum value before shutting off a device or plugging-in/unplugging a pair of headphones.


 


   
  I would have to say it depends on the amp. The Pico Slim certainly has a power on thump, the loudness of which varied in my testing yesterday, but it always occurred even with the volume at minimum and no music playing from the source. To Justin's credit, the Slim is otherwise fantastic.
   
  Dr Meier's Jazz also exhibited a thump, and I could hear music playing clearly even when the volume knob was at 0. 
  (It was a darned fine amp otherwise, though.)
   
  I guess I've been spoiled by the DIY amp my friend built for me. Desktop tube amp but he somehow got it to have zero on/off thump, no discernible channel imbalance, and relatively clean amplification up to my listenable levels (slight hiss after the tubes warm up).


----------



## mikeaj

re: turn off and turn off transients
   
  It really depends on the design, particularly regarding the power rails.  If there's no sound at all, that's likely due to there being a relay to disconnect the output (and thus the headphones) from the amp while it is powering on or off.  This prevents any signal from reaching the headphones during this period, hence no sounds.  Pretty much, when an amp's turning on or off, three can be some oddities in the power rails.  Capacitors can't charge instantly, some voltage regulators may not regulate all that well with the circuit just half-on, and so on.  All other things equal, larger capacitors store more energy so they take more time to charge.  If a circuit works as intended with full power, it may still do weird things when in the middle of going towards full power.  With huge fluctuations in the power rails going from 0V to whatever, this could cause some spurious noises (click or pop usually) to appear on the output.
   
  When powering off, you can expect similar issues. Capacitors take time to discharge.
   
  With the O2 in particular, the power supply is pretty much a half-wave rectifier for the positive rail and a half-wave rectifier for the negative rail.  So the positive side of the AC input gets changed into the positive DC rail the components use, while the negative side gets changed into the negative DC rail.  With half-wave rectification, you're only using half of the AC cycle: in this case, one side uses one half and the other side uses the other half. The AC input is of course not both positive or negative at the same time, so when you turn it on, one side (positive or negative) will start charging before the other. Hence you can easily expect the power rails to be temporarily imbalanced, leading to weird behavior on the output, before both rails reach steady state and go into regulation.
   
  Some designs like the Asgard may have large caps to charge and overall, the kind of single-ended FET outputs it uses tend to reject a whole lot less power supply weirdness than the kinds of op amps used in the O2.  (at least in normal operation, and I assume while powering on/off as well)
   

 Quote:


bogatyr said:


> 1. I've seen many posts arguing on what is a good dac \ amp pairing for AKG Q701. As I have no idea or knowledge I was curious whether anyone had tried O2 with AKG Q701 cans.
> 
> 2. Everyone keeps saying I need an amp to drive AKG Q701 well, I'm a total noob and am currently running them on Xonar DG. I use about 25/100 volume in Windows 7 with Xonar DG set to 32-64 Ohm settings. What does it mean to drive Q701's well? I really wouldn't want unpleasantly loud volume levels.
> 
> 4. Which O2 gains would be ideal for Q701 and my preference for not so loud sound levels?


 
  {I snipped out some of the less addressable stuff}
   
  Plenty of people have used K701, K601, and I think maybe Q701 (I forget).  It works just fine.  A lot of amp designs will struggle a bit being sufficiently loud with Q701, or actually sounding good while being asked to source that much current.  However, this is completely not the case for you, since at your low volumes, you're not going to be stressing much of anything.  I'd just run the DG, to be honest, unless you think you hear some kind of noise, fuzziness, lack of detail, or something like that.  Save the money for something else.
   
  If you were to get an O2, you would get 1x gain, and the other wouldn't matter because you wouldn't use it.  Say 4x would be okay.  If you did get the O2, I'd just use the DG to feed it unless you think there's something wrong with it.


----------



## Bogatyr

Quote: 





mikeaj said:


> {I snipped out some of the less addressable stuff}
> 
> Plenty of people have used K701, K601, and I think maybe Q701 (I forget).  It works just fine.  A lot of amp designs will struggle a bit being sufficiently loud with Q701, or actually sounding good while being asked to source that much current.  However, this is completely not the case for you, since at your low volumes, you're not going to be stressing much of anything.  I'd just run the DG, to be honest, unless you think you hear some kind of noise, fuzziness, lack of detail, or something like that.  Save the money for something else.
> 
> If you were to get an O2, you would get 1x gain, and the other wouldn't matter because you wouldn't use it.  Say 4x would be okay.  If you did get the O2, I'd just use the DG to feed it unless you think there's something wrong with it.


 

  
  When using the front panel jack or the headphone settings on Xonar DG, there is a distant hiss, I'm assuming due to interference caused by power supply. I honestly don't feel like my current sound card does Q701 justice. Considering how much time I spend near a computer a 200$ invested into audio hardware that will last me for some time to come is money well spent. If I were to save it instead, I'd probably spend it on more headphones or a new video card (currently using gtx 460) but this off topic.
   
  I still don't understand what it means to drive headphones well. Can one drive them well at moderate to low volume? Is there a difference between well driven quiet sound and poorly driven same loudness sound?


----------



## mikeaj

Well then get an O2 and use it through the DG.  If there's still noise (I think a combination of attenuation through the O2 and some of the RF filtering will clean it up, so I don't think it will be necessary), then you can look at some relatively cheap DAC or sound card that has lower noise.  You aren't by any chance using the DG via the front panel connection, right?  edit: sorry, I can't read.  Try the back panel connection.  The cable from the card to the front panel often picks up a lot of stray EMI from noisy computer internals.  By the way, the noise is much more likely to be from stray radiation and so on, maybe all sorts of components dirtying the power in between the power supply and audio card, than the power supply itself.
   
  Yes it's possible for one amp to do better than another, at any volume.  Voldemort's blog has reviews where there are graphs of different headphone amplifiers, showing THD+N vs. output voltage.  This is just one metric, but look at the value at say 0.1V for different amps, at a given load.  There's just usually less of a difference at lower volumes because (1) most headphone amps won't be stressed so badly by such modest power draws and (2) small differences in sound quality are harder to detect when the sound level is lower.  More of the slightly bad crud may just be lost in the noise.


----------



## sonitus mirus

Thanks mikeaj,
   
  Yep, Asgard has a few relatively large electrolytic capacitors that I can see through the cooling grates.  I'm certain these caps explain the 4-5 second wait between flipping the power switch on and the alarmingly loud "bump" I hear 4-5 seconds later in my headphones, even with the volume turned all the way down.  I believe any potential damage or wear on my headphones is significantly less than what I would experience by unplugging my headphones before shutting off my amp every time.  My headphone drivers will probably be able to handle the transients far longer than my amp's connectors will be able to handle frequent insertions and extractions.


----------



## Bogatyr

Back panel of Xonar DG is indeed without noise as long as its set to speakers mode. This solution however creates another problem, switching between headphones and speakers. If I were to get a DAC + Amp I could dedicate them to my headphones and dedicate Xonar DG to speakers, otherwise I'd have to unplug and replug each time I wish to go from one to other. From what I understand splitters aren't all that great.
  Quote: 





mikeaj said:


> Well then get an O2 and use it through the DG.  If there's still noise (I think a combination of attenuation through the O2 and some of the RF filtering will clean it up, so I don't think it will be necessary), then you can look at some relatively cheap DAC or sound card that has lower noise.  You aren't by any chance using the DG via the front panel connection, right?  edit: sorry, I can't read.  Try the back panel connection.  The cable from the card to the front panel often picks up a lot of stray EMI from noisy computer internals.  By the way, the noise is much more likely to be from stray radiation and so on, maybe all sorts of components dirtying the power in between the power supply and audio card, than the power supply itself.
> 
> Yes it's possible for one amp to do better than another, at any volume.  Voldemort's blog has reviews where there are graphs of different headphone amplifiers, showing THD+N vs. output voltage.  This is just one metric, but look at the value at say 0.1V for different amps, at a given load.  There's just usually less of a difference at lower volumes because (1) most headphone amps won't be stressed so badly by such modest power draws and (2) small differences in sound quality are harder to detect when the sound level is lower.  More of the slightly bad crud may just be lost in the noise.


----------



## palmfish

I removed the 6.5X gain resistors tonight (wow, resistors are a lot smaller than I remember them being back when I used to work with electronics) . Now at 1X gain I can turn the volume knob all the way up to 9:00 before it starts getting too loud. I never realized how much gain 2.5X already was. I'm glad I've been keeping up with this discussion and learned about this.


----------



## JRoyen

Auditioned the O2 the other day, and it blew me away. I have been waiting many years for a headphone amp this powerful, revealing, quiet and neutral. Actually got me excited about audio again in the longest time. Now my only decision is whether to wait for the ODA/ODAC, for a neater all-in-one package.


----------



## uelover

Quote: 





jroyen said:


> Auditioned the O2 the other day, and it blew me away. I have been waiting many years for a headphone amp this powerful, revealing, quiet and neutral. Actually got me excited about audio again in the longest time. Now my only decision is whether to wait for the ODA/ODAC, for a neater all-in-one package.


 


  I would think that the O2 is affordable enough for you to keep it even after you have gotten the ODA/ODAC.
   
  Its portability is a plus for traveling use =)


----------



## turokrocks

Quote: 





uelover said:


> I would think that the O2 is affordable enough for you to keep it even after you have gotten the ODA/ODAC.
> 
> Its portability is a plus for traveling use =)


 

 I have a lost twin, who reads my mind!


----------



## a_recording

Quote: 





uelover said:


> I would think that the O2 is affordable enough for you to keep it even after you have gotten the ODA/ODAC.
> 
> Its portability is a plus for traveling use =)


 


  That's my plan exactly. :3 I'm thinking that this: http://www.headstage.com/USB-DAC-Cable/USB-DAC-Cable-with-35mm-Mini-Plug-75cm-30::10134.html?XTCsid=ef7d80bbc2f318d5c52b1a5a010badee would be a wonderful companion for the O2's 3.5mm input and a laptop. I'm a little discouraged when the website hasn't even bothered to update the images with the latest version of the cable though. Anyone got any opinion on these or can suggest a similar alternative?


----------



## turokrocks

I never used my O2 with Batteries, I directly removed the batteries and connected it to my DAC LX,  I think I should see how it sounds.


----------



## shotgunshane

a_recording said:


> That's my plan exactly. :3 I'm thinking that this: http://www.headstage.com/USB-DAC-Cable/USB-DAC-Cable-with-35mm-Mini-Plug-75cm-30::10134.html?XTCsid=ef7d80bbc2f318d5c52b1a5a010badee would be a wonderful companion for the O2's 3.5mm input and a laptop. I'm a little discouraged when the website hasn't even bothered to update the images with the latest version of the cable though. Anyone got any opinion on these or can suggest a similar alternative?




I'm using the dac cable with my O2 and laptop. Works very well. I have the previous version of the cable with the components in the middle.


----------



## wje

I was reading someone's for sale thread on the O2 (possibly in another forum) and they indicated that their O2 amp was properly grounded to the case.  I suspect mine is suffering from a grounding issue because I bumped it with my metal iPod classic and I noticed a slight spark.  Apparently, this was more than just static, but suspect since the PCB was just inserted into the slots on the case and the front / rear covers were put on, the PCB itself isn't, or may not be properly grounded to the case.  Thoughts?  If this should be done, I was wondering at which point would be best to attach my ground wire on PCB and then I'll locate an area on the case to secure it to.
   
  Thanks,


----------



## uelover

Quote: 





turokrocks said:


> I have a lost twin, who reads my mind!


 
   





   
  Quote: 





turokrocks said:


> I never used my O2 with Batteries, I directly removed the batteries and connected it to my DAC LX,  I think I should see how it sounds.


 

 I would think that the batteries, in addition of serving its primary purpose, works also to ensure that the power supply is as clean as possible. Something like the JKenny MK3.


----------



## stv014

Quote: 





> Originally Posted by *uelover* /img/forum/go_quote.gif
> 
> I would think that the batteries, in addition of serving its primary purpose, works also to ensure that the power supply is as clean as possible. Something like the JKenny MK3.


 

 Not really, the power supply voltage (which is regulated) should never drop to such a low level that the amplifier becomes battery powered.


----------



## uelover

Quote: 





stv014 said:


> Not really, the power supply voltage (which is regulated) should never drop to such a low level that the amplifier becomes battery powered.


 
   
  Not sure what you mean really. You mean that amps like the RWA Corvina, SR71B and etc should never have used battery in the first place?
   
  Anyway, arguing about what voltage level is appropriate is not my point. I am just stating the fact that a battery powered amp also helps to ensure that the power is as clean as possible.


----------



## stv014

Quote: 





uelover said:


> Not sure what you mean really. You mean that amps like the RWA Corvina, SR71B and etc should never have used battery in the first place?
> 
> Anyway, arguing about what voltage level is appropriate is not my point. I am just stating the fact that a battery powered amp also helps to ensure that the power is as clean as possible.


 

 I do not know about those other amplifiers, but from the schematics of the O2, it seems the batteries do not really make the power "cleaner" under AC operation. That purpose is served by the capacitors C2 to C10, C17, and C18, as well as the two voltage regulator ICs. The batteries are effectively only in the circuit through the 220 Ohm resistors (R1 and R2), and they are actually being charged, rather than providing any power.


----------



## uelover

Quote: 





stv014 said:


> I do not know about those other amplifiers, but from the schematics of the O2, it seems the batteries do not really make the power "cleaner" under AC operation. That purpose is served by the capacitors C2 to C10, C17, and C18, as well as the two voltage regulator ICs. The batteries are effectively only in the circuit through the 220 Ohm resistors (R1 and R2), and they are actually being charged, rather than providing any power.


 

 I wasn't referring to the O2 when being powered by the AC power, for that will make it no different from ODA.
   
  My comment is on the fact that the availability of battery power (when disconnected from the AC) allows the O2 to benefit from a clean power source.


----------



## mikeaj

If anything, while on AC power, the batteries are a liability rather than helping anything out.  The batteries are not helping out the noise or any part of performance while the amp is plugged into AC.  At no point do the batteries supply any power, if you're plugged into AC power.  Thus they're not smoothing out anything.
   
  This is because, as mentioned earlier, they're just sitting there being charged (indefinitely; at full charge, the amount they're getting charged by is very little so it's not a fire hazard), so they're drawing current that the regulators wouldn't otherwise have to provide.  If you're charging batteries that are dead, you'll pull more power than if the batteries are charged, and it's possible that the regulators could get noticeably hotter because of the extra load of charging the batteries a lot.  I really doubt this would make much of an impact on the power supply performance though, and furthermore the power supply performance doesn't have too much of an impact on this circuit or most ones using these kinds of op amps in these kinds of configurations.
   
  edit: most or at least many battery/AC powered amps should be similar in this regard.  Actually, some may have a charging mechanism for the battery that stops charging them, so it's not any kind of strain on the power supply, slight or not.  Regardless, I mean that most probably aren't being helped at all by the batteries, while running on AC power.
   
  Here's a test, if your amp is working properly (also, I don't recommend this at all unless you have insensitive fullsize headphones that are more tolerant of larger transients):  with headphones plugged in and no music playing, remove the AC power and then plug it back in.  This is effectively switching from +-12V power to +-8V or +-10V or whatever the batteries are, and back.  Well, the change is gradual due to the (small) capacitors taking time to discharge, but still.  Do you hear anything, and if so, how much?  A 2V or more change in power supply rails is much more of a disturbance than you'd normally ever see in normal operation.  This indicates a relatively high tolerance to weirdness on power supply rails, maybe more technically, a high power supply rejection ratio.  On second thought, I'm not sure how long it would take for the power supply caps to discharge, so maybe the switch to battery would be slow and maybe if there were some funny business going on, it would be below audible frequencies?  I don't think so though.


----------



## stv014

Quote:  





> My comment is on the fact that the availability of battery power (when disconnected from the AC) allows the O2 to benefit from a clean power source.


 

 That was not clear from the first post I replied to.  Anyway, the AC powered mode should be clean enough, and using the batteries just reduces the voltage (more risk of clipping). Maybe with some sources it fixes grounding problems, but the noise level of the O2 itself is not affected significantly by using AC vs. battery power (see here and here).


----------



## uelover

Quote: 





stv014 said:


> That was not clear from the first post I replied to.


 
   
  I was talking to turokrocks but you just came in and interrupted us lol (refer to original post below).
   
  For the sake of explicitness, the primary purpose of battery is to provide power on the go whether there is no AC plug.
   
  The secondary purpose is to still be able to provide the cleanest power possible when the AC power is very dirty and one does not wish to invest on power conditioner.
   
  I thought that listing these two points out explicitly are pretty dumb so I shortened my post.
   
  No doubt there are cons of using batteries but I have never said anything that they are all-perfect. I am merely listing out two benefits of using batteries and I am not sure why there are so many attacks on it. 
	

	
	
		
		

		
			




   
   
  EDIT: I would think that the clipping issue due to batteries having lower voltage could be resolved by tweaking the circuitry to accept either batteries with higher voltage or more 9v batteries laid in a way to increase the voltage.
   
  Quote: 





uelover said:


> Quote:
> 
> 
> 
> ...


----------



## mikeaj

Quote: 





uelover said:


> For the sake of explicitness, the primary purpose of battery is to provide power on the go whether there is no AC plug.
> 
> *The secondary purpose is to still be able to provide the cleanest power possible when the AC power is very dirty and one does not wish to invest on power conditioner.*
> 
> I thought that listing these two points out explicitly are pretty dumb so I shortened my post.


 
  (emphasis added, some removed)
   
  The point being made was that the battery does not in any way help to provide clean power when the amp is plugged into the wall, so the bolded second point is inaccurate.  No offense made or attacks intended, just pointing out what I interpreted to be a misconception.
   
  Or are you talking about designs in general using batteries and not the O2?  Still, I would think the vast majority when plugged into AC power, would not be using the batteries to improve the power rail quality in any way.
   
  Some amps have (non-trivially) lower noise and less issues when running on batteries as opposed to AC power, but we're not talking about battery-only operation, right?  Just batteries being in the circuit when plugged into AC power?


----------



## maverickronin

Quote: 





mikeaj said:


> Here's a test, if your amp is working properly (also, I don't recommend this at all unless you have insensitive fullsize headphones that are more tolerant of larger transients):  with headphones plugged in and no music playing, remove the AC power and then plug it back in.  This is effectively switching from +-12V power to +-8V or +-10V or whatever the batteries are, and back.  Well, the change is gradual due to the (small) capacitors taking time to discharge, but still.  Do you hear anything, and if so, how much?  A 2V or more change in power supply rails is much more of a disturbance than you'd normally ever see in normal operation.  This indicates a relatively high tolerance to weirdness on power supply rails, maybe more technically, a high power supply rejection ratio.  On second thought, I'm not sure how long it would take for the power supply caps to discharge, so maybe the switch to battery would be slow and maybe if there were some funny business going on, it would be below audible frequencies?  I don't think so though.


 

 Even with my SE530s, my O2 doesn't make any noise at all when I do that.  I tested that with my orthos first though.  My Yamahas probably wouldn't even mind if you shorted the whole power supply to the drivers for a second or two.


----------



## uelover

Quote: 





mikeaj said:


> (emphasis added, some removed)
> 
> The point being made was that the battery does not in any way help to provide clean power when the amp is plugged into the wall, so the bolded second point is inaccurate.  No offense made or attacks intended, just pointing out what I interpreted to be a misconception.
> 
> ...


 

 I am actually intending to say that when the AC power is very dirty, one can choose not to use the AC power at all and use only the battery.
   
  (i.e., use the AC power to only charge the O2 and when using the O2, completely completely plug off the AC power line and power the O2 via its internal dual 9V batteries)
   
  I am sorry that it was not being made clear but never had I thought that anyone would think that I was implying that the existence of the batteries would clean up the AC power.
   
  I think this is where all the misconception of my original post starts..


----------



## mikeaj

I apologize for the misinterpretation then (no offense ever intended), but there are much weirder claims on head-fi, so maybe I'm conditioned to take everything literally as they come.
   
  Anyhow, as posted earlier, you can look through the results yourself.  There's very little difference in noise levels with AC power as opposed to batteries.  Unplugging seems like a real hassle for the lack of benefits you get.  Even if the AC power were extraordinarily dirty, the filter capacitors + 7812/7912 regulators + op amp PSRR + apparently reasonable grounding/power layout really should take care of it.


----------



## uelover

Quote: 





mikeaj said:


> I apologize for the misinterpretation then (no offense ever intended), but there are much weirder claims on head-fi, so maybe I'm conditioned to take everything literally as they come.
> 
> Anyhow, as posted earlier, you can look through the results yourself.  There's very little difference in noise levels with AC power as opposed to batteries.  Unplugging seems like a real hassle for the lack of benefits you get.  Even if the AC power were extraordinarily dirty, the filter capacitors + 7812/7912 regulators + op amp PSRR + apparently reasonable grounding/power layout really should take care of it.


 

 Yes I know. But I have been at Head-fi for pretty long so please have some little faith in me! 
	

	
	
		
		

		
		
	


	



  I don't like to state the obvious for I risk being demeaning to others. 
   
  Some of the things are a little tricky to discuss so we shall call it an end of the day.


----------



## a_recording

Quote: 





uelover said:


> Yes I know. But I have been at Head-fi for pretty long so please have some little faith in me!
> 
> 
> 
> ...


 
   
  I think what we can all be thankful for is that nwavguy has provided enough data (though it would be nice to see it independently verified) to head off a lot of myths and speculation that might otherwise surround the design. Even though a lot of this information is beyond my knowledge, it is definitely a boon to see it out there where anyone can put the ideas or the results to the test. The next myth I'd like to see tested is: is it really true that the iPhone line out is in fact worse than the headphone out at max-volume, and is it in fact true that the evils of 'double-amping' are a myth and it really depends on a multitude of factors?
   
  Reason why I ask is that I'd like to use my iPhone 4 as a source for the O2 and would love to know if I'm better off using the LOD or the HP out.


----------



## Eric_C

Quote: 





a_recording said:


> The next myth I'd like to see tested is: is it really true that the iPhone line out is in fact worse than the headphone out at max-volume, and is it in fact true that the evils of 'double-amping' are a myth and it really depends on a multitude of factors?
> 
> Reason why I ask is that I'd like to use my iPhone 4 as a source for the O2 and would love to know if I'm better off using the LOD or the HP out.


 

 In terms of real-world usage, I would say it depends on the material you're listening to. The gamers over in MLE's thread note that double amping is sometimes a necessary evil, and not much of an evil at all--a console or PC > MixAmp > Amp > Headphones, because the MixAmp has trouble driving some headphones (even when it comes to volume alone). Game audio is of course, often more compressed than music, but it does go to show that the "no double amping" rule is a generalisation. It's a safe rule to follow, but when it can't be, you might as well test it out and see if you can hear any loss in quality.
   
  On a related point: I've been wondering about the iPhone 4's headphone out. It regularly gets praised, especially for IEMs; if that's the case, has anyone tried replicating its amp section for other sources?
  E.g. iPod Classic > LOD > "iPhone 4 amp"


----------



## mikeaj

I have no idea about this, but I think I've heard that the typical iDevice has a 1V headphone output and 0.5V line output.  This is something that could be confirmed with just a few minutes with a junk $5 multimeter and a 0 dBFS 60 Hz audio file (file can be generated with something like Audacity, for example).
   
  You can think of running through the amp to another amp--double amping--as if the first amp is just another stage in the whole amplifier.  Even though the first amplifier is not exactly optimized for this purpose, it's generally not going to misbehave much when driving another amplifier, which has input impedance like 10k ohms or so rather than something in the 16-600 ohms range like headphones.  (Another amplifier is a lot easier to drive than actual headphones).  Almost always with amplifiers, the output stage driving headphones is the limiting factor.  So double amping is worse, but it's generally not a big deal, particularly if the first amplifier doesn't have strange problems or limitations.  If you want to feed another amplifier, avoid double amping if possible since it's generally a little worse (mostly in theory), but don't worry if that's not possible or if it costs money to avoid doing so.
   
  I made some (very limited) test results pertaining to double amping a while back and reposted about it a week earlier in this thread, in case anybody didn't catch it. I wasn't testing for the same situation we're talking about here though:
   
  http://www.head-fi.org/t/568705/review-nwavguys-o2-diy-amplifier/1080#post_8150435


----------



## upstateguy

Quote: 





wje said:


> I was reading someone's for sale thread on the O2 (possibly in another forum) and they indicated that their O2 amp was properly grounded to the case.  I suspect mine is suffering from a grounding issue because I bumped it with my metal iPod classic and I noticed a slight spark.  Apparently, this was more than just static, but suspect since the PCB was just inserted into the slots on the case and the front / rear covers were put on,* the PCB itself isn't, or may not be properly grounded to the case. * Thoughts?  If this should be done, I was wondering at which point would be best to attach my ground wire on PCB and then I'll locate an area on the case to secure it to.
> 
> Thanks,


 


  I'm curious about this too.  My board is just inserted into the slots in the case.  I don't see any particular grounding wire and I've never seen a spark.
   
  Anybody else have this issue ?  Mav, Willikan, Mike??


----------



## shadow419

I've never had this happen on either of my builds, but I do have the pcb grounded to the case/front panel. Take it for what it's worth.


----------



## maverickronin

I've never seen mine spark like that.  There's a really thin wire running from the input jack (IIRC) to the screw for the front panel as well.
   
  Mine was built by Voldermort though so its probably as perfect as an O2 can be.  He even sent me some printouts of its measurements from his dScope.


----------



## palmfish

Quote: 





maverickronin said:


> I've never seen mine spark like that.  There's a really thin wire running from the input jack (IIRC) to the screw for the front panel as well.
> 
> Mine was built by Voldermort though so its probably as perfect as an O2 can be.  He even sent me some printouts of its measurements from his dScope.


 


  Are you a Death Eater?


----------



## maverickronin

Apparently I am...


----------



## upstateguy

Quote: 





maverickronin said:


> I've never seen mine spark like that.  There's a really thin wire running from the input jack (IIRC) to the screw for the front panel as well.
> 
> Mine was built by Voldermort though so its probably as perfect as an O2 can be.  He even sent me some printouts of its measurements from his dScope.


 

 I'll take a look and see if I have a wire like that......


----------



## MikeW

I built my O2 so the wire is most definitely there  Though, in practice, im not sure it matters that much.


----------



## wje

Quote: 





mikew said:


> I built my O2 so the wire is most definitely there  Though, in practice, im not sure it matters that much.


 

 Actually, it does. If you go back 15 posts or so where I posted my question on how to complete the ground process, I explained that there was an issue with my metal-bodied iPod touching the O2 and seeing sparks.  Not really an ideal situation if you ask me.  Though this does not reflect any bad light on the designer, it does point to the builder who might have skipped a quite important step.


----------



## shadow419

Quote: 





mikew said:


> I built my O2 so the wire is most definitely there  Though, in practice, im not sure it matters that much.


 


  Agree, I'm not seeing the connection of grounding the input jack to the case as a means to eliminate possible hum and spark/static discharge.  It's not like the case is electrified or the metal back of an iPod.  I'd chalk it up to a static discharge, but I could be wrong of course.


----------



## audionewbi

what happened to the O2 vs V200 review, is it up yet?


----------



## jseaber

Great info here. It's worth noting that the O2 is $144 + shipping. So, it's barely $160 USD with a power adapter to those in North America (shipped).
   
  Quote: 





hekeli said:


> It's surprising that there really are people who don't know about customs etc.. even our customs agency has a "guide for dummies" for buying on the net.
> 
> Total price to Finland (EU):
> 
> ...


----------



## MikeW

For reference I spent about 85$ to build mine complete with JDS Labs faceplate/PCB, 16v PSU, shipping, everything, except batteries.
   
  I ordered parts from Mouser, JDS, and I can't remember were i got the enclosure, I was going to get it at Allied, but it came out a few bucks cheaper somewhere else, because of allieds dumb handling fee.


----------



## Naim.F.C

No dude sorry! Haven't had the time! Been hyper busy the last few days sorting out bits and bobs. Hopefully Tues/Wed now.



audionewbi said:


> what happened to the O2 vs V200 review, is it up yet?


----------



## Bogatyr

Can I run O2 without batteries? I'm still searching for a desktop dac\amp. Must the batteries always be in O2 during operation or are they just there for portability? I've did some forum searches and from what I gather they must always be inside even when hooked up to a power source. Can anyone confirm? Thanks!


----------



## audionewbi

you can use without batteries.
   
  Quote: 





bogatyr said:


> Can I run O2 without batteries? I'm still searching for a desktop dac\amp. Must the batteries always be in O2 during operation or are they just there for portability? I've did some forum searches and from what I gather they must always be inside even when hooked up to a power source. Can anyone confirm? Thanks!


----------



## Anaxilus

I have yet to put batteries in mine and LFF doesn't even have the terminals for the 9Vs.


----------



## Eric_C

Kinda curious if anyone has an opinion on O2 vs Stepdance, given that both are supposedly (quite) neutral.


----------



## Anaxilus

Quote: 





eric_c said:


> Kinda curious if anyone has an opinion on O2 vs Stepdance, given that both are supposedly (quite) neutral.


 

 Stepdance 1 is a leaner, brighter more analytical sound IME.  Remember that harmonics and other aspects affect tonality as well so 'neutral' doesn't guarantee things sound the same.  I never got to try it w/ the upgraded batteries so I couldn't comment on power delivery comparisons though I suspect the O2 to be better.  It's dynamics are very linear regardless of where the pot is, more so than any other 'smaller' classed amp I've tried.


----------



## Eric_C

Quote: 





anaxilus said:


> Stepdance 1 is a leaner, brighter more analytical sound IME.  Remember that harmonics and other aspects affect tonality as well so 'neutral' doesn't guarantee things sound the same.  I never got to try it w/ the upgraded batteries so I couldn't comment on power delivery comparisons though I suspect the O2 to be better.  It's dynamics are very linear regardless of where the pot is, more so than any other 'smaller' classed amp I've tried.


 


  It really is mind-boggling that these things can be said of a much, much cheaper, DIY amp. I tried the 2stepdance yesterday and thought it was great; I quite literally cannot imagine how much better the O2 could be, if at all.


----------



## Anaxilus

The 2step is using the same opamp in my Leckerton UHA6S that I actually prefer over the O2 for sheer transparency so I couldn't comment on the 2step not having heard it.  I hear it's a slighter warmer sounding tonality compared to the step1. 
   
  Its best to consider the size and objectives of the two.  The O2 is more headphone oriented and transportable/stationary.  Others are more IEM, easier to drive oriented portable solutions.  Though the Stepdance1 tries to have it both ways so I think that's a fair comparison.


----------



## lukeahale

Is there any reason the ODA version of the amp could not have the option of being built with a variable gain control (as in a pot) instead of just a switch?  I would think that would give it even more versatility, all the way from super sensitive IEMs at 1x, all the way to extremely low sensitivity headphones runing from a low voltage source at the full 12X (though I doubt there are many situations where that much gain would really be necessary in a desktop version. . . not likely to be using an ipod with a desktop amp, but you never know).  With the desktop version it could be on the back of the amp by the inputs and out of the way.  I don't really know how that would affect performance like noise, etc.  I could be totally wrong though....


----------



## firev1

Gain stage requires 2 resistors of equal values in parallel, with pots, this cannot be done unless said pot is hard to install etc.


----------



## stv014

Quote: 





firev1 said:


> Gain stage requires 2 resistors of equal values in parallel, with pots, this cannot be done


 

 It can definitely be done with stereo pots. Of course, it will only be roughly "equal value" with typical potentiometers.


----------



## limpidglitch

Quote: 





lukeahale said:


> Is there any reason the ODA version of the amp could not have the option of being built with a variable gain control (as in a pot) instead of just a switch?  I would think that would give it even more versatility, all the way from super sensitive IEMs at 1x, all the way to extremely low sensitivity headphones runing from a low voltage source at the full 12X (though I doubt there are many situations where that much gain would really be necessary in a desktop version. . . not likely to be using an ipod with a desktop amp, but you never know).  With the desktop version it could be on the back of the amp by the inputs and out of the way.  I don't really know how that would affect performance like noise, etc.  I could be totally wrong though....


 


  I've actually asked him about this before, here is the answer I got:
   
   
  Quote: 





			
				NwAvGuy said:
			
		

> Aksel, Meier has done some interesting things. My personal opinion is he keeps trying to re-invent the wheel when there's no need to. His "virtual ground" arguments, for example, make no sense to me. See my Virtual ground article for lots more about that topic.
> 
> If you're talking about his "portable amp" with the LM6171 output stage. His use of the volume control in the feedback loop is very noise prone. When the pot becomes noisy (dirt/wear on the track/wiper) that "noise" in the pot will cause the amp to briefly go to full volume. The effect will be to make the pot wiper noise massively loud.
> 
> ...


----------



## wje

Through the aid of some posters on this forum and receiving a PM from another member, I was able to get my items sorted out.  After removing the front plate, it was easy to see where the metal wires of "4" of the resistors on the right side were rubbing against the aluminum case.  These were straightened out and then trimmed with one of my smaller side-cutters.
   
  Also, I didn't have the ground wire from the input terminal to my case.  I soldered a ground wire, sanded off a slight amount of the black paint on the inside of the front cover where the screw would mount --- and, where my wire connection would be applied to the case.  The front panel was re-installed and everything was tested.  I'm now back in good shape. 
   
  This is one fine amplifier.


----------



## Digital-Pride

Indeed it is.   I'm glad you got yours back ip and running problem free.


----------



## firev1

So guys, apparently the ODAC article is up, can't wait for the finished product


----------



## audionewbi

May-June is the release date. Cant wait that long, I just order the O amp, cant wait thatlong.


----------



## Eric_C

Quote: 





audionewbi said:


> May-June is the release date. Cant wait that long, I just order the O amp, cant wait thatlong.


 


  Didn't he say the DAC can be placed inside the O2? It just replaces the battery compartment.


----------



## Scog

Quote: 





eric_c said:


> Didn't he say the DAC can be placed inside the O2? It just replaces the battery compartment.


 

  
  Yep. It's held in between the back panel and the spring pressure of the battery terminals, a case slot on one side and a mounting hole on the other that lines up with one on the O2. 3 shielded wires connecting them, and it's done.


----------



## audionewbi

it is not a plug and play, you need a little DIY skills. From what I have read we can order the ODAC with an external case, I might either do that or simply get the ODA+ODAC once they both come out, (from the looks of things it might be end if this year)
  Quote: 





eric_c said:


> Didn't he say the DAC can be placed inside the O2? It just replaces the battery compartment.


----------



## kiteki

So I'm curious, has any experimented with different opamps in this yet?  I heard of someone in Hong-Kong using AD797 or the like.  Thanx.


----------



## Eric_C

audionewbi: Ah, yes that's true. It shouldn't be *too* hard to find someone in your area who could do the job, tho, no?


----------



## palmfish

Quote: 





kiteki said:


> So I'm curious, has any experimented with different opamps in this yet?  I heard of someone in Hong-Kong using AD797 or the like.  Thanx.


 
  Why would anyone do that?


----------



## ringyring

Quote: 





kiteki said:


> So I'm curious, has any experimented with different opamps in this yet?  I heard of someone in Hong-Kong using AD797 or the like.  Thanx.


 


  nwavguy already did all the experimenting, the end result was the O2.  He mentions in his blog that he tried dozens of different opamps and the final build was what brought the best overall performance. You could certainly try different opamps, I just don't see the point of messing with something that was custom built using the best professional equipment.


----------



## shadow419

Quote: 





palmfish said:


> Why would anyone do that?


 


   


  Quote: 





ringyring said:


> nwavguy already did all the experimenting, the end result was the O2.  He mentions in his blog that he tried dozens of different opamps and the final build was what brought the best overall performance. You could certainly try different opamps, I just don't see the point of messing with something that was custom built using the best professional equipment.


 

  
  Even though nwavguy tried and tested many opamps in designing the O2, there's no reason not to experiment a little for your own curiosity.  The best measuring may not be the best fit for your taste.  I haven't rolled any opamps, but I prefer to just build other diy designs and try those.


----------



## Anaxilus

Quote: 





kiteki said:


> So I'm curious, has any experimented with different opamps in this yet?  I heard of someone in Hong-Kong using AD797 or the like.  Thanx.


 

 Yup.  Purrin and myself tried the LM4562 on the input side and it cleared up some of that JRC congestion bringing the transparency closer to my Leckerton w/ the OPA209s.  I'll be leaving the JRC out.
   
  Quote: 





ringyring said:


> nwavguy already did all the experimenting, the end result was the O2.


 

 No he didn't.  In fact, he left a number of opamps some of us wanted specifically tested off or omitted for whatever reason.  When I saw the list of opamps he tested I just 
	

	
	
		
		

		
			





.
   
  Anyway, the O2 was designed for linear power delivery and that's what it does.  Timbre and tonality are anathema to the very concept of the O2 and it's supporters.  The O2's 'transparency' is also overhyped here IMO.  So yeah, my JRC input opamp is rotting at the bottom of a box somewhere.  Maybe the LM4562 just sounds better because it costs $2 more.


----------



## limpidglitch

Quote: 





ringyring said:


> I just don't see the point of messing with something that was custom built using the best professional equipment.


 


  I see you're new to the community 
   
  The Head-Fi reasoning goes as such: Op-Amps are like tubes, therefore they can be rolled like tubes.
   
  Trying to fight the urge to 'improve' on true and tested designs, is much like trying to prevent the change of the seasons.


----------



## kiteki

Quote: 





> Originally Posted by *palmfish* /img/forum/go_quote.gif
> 
> Why would anyone do that?


 

 Quote: 





> Originally Posted by *ringyring* /img/forum/go_quote.gif
> 
> nwavguy already did all the experimenting


 

 Well uh, for starters, you can win $500.00


----------



## ringyring

Quote: 





anaxilus said:


> Anyway, the O2 was designed for linear power delivery and that's what it does.  Timbre and tonality are anathema to the very concept of the O2 and it's supporters.  The O2's 'transparency' is also overhyped here IMO.  So yeah, my JRC input opamp is rotting at the bottom of a box somewhere.  Maybe the LM4562 just sounds better because it costs $2 more.


 
  Isn't the Leckerton you mentioned previously also made to be highly linear as well? I'm interested to hear (or read I guess) why you prefer it. I'd think the O2's ability to drive a larger number of headphones and the price point would make it a much better option for most. How great is the different between the two? I haven't tried the UHA6 though so I'm not going to pretend like I'm some authority on the subject.


----------



## lukeahale

Quote: 





anaxilus said:


> Yup.  Purrin and myself tried the LM4562 on the input side and it cleared up some of that JRC congestion bringing the transparency closer to my Leckerton w/ the OPA209s.  I'll be leaving the JRC out.
> 
> 
> No he didn't.  In fact, he left a number of opamps some of us wanted specifically tested off or omitted for whatever reason.  When I saw the list of opamps he tested I just
> ...


 

 Perhaps you could make a suggestion that he run some tests with that particular modification to see how it performs on the test bench... He seems pretty happy to take suggestions.  
   
  And as far as testing, I'm sure there are hundreds of op-amps he could have tested as well, both less and more expensive... but being this was already a rather large project all done in his free time, out of his own pocket, I probably would have limited my testing to a handful of opamps as well that fit a certain criteria on the spec sheet, but once his design goals were met, why keep searching further?
   
  None of this is meant to say you are wrong, I just would like it measured because I am more of a numbers/measurements guy personally.  I can say though, if you are correct and there is a big improvement, I can only imagine what that would sound like considering how much I love the sound as it is


----------



## Draygonn

kiteki said:


> Well uh, for starters, you can win $500.00




the $500 goes to charity


----------



## lukeahale

Quote: 





draygonn said:


> the $500 goes to charity


 


  I wonder if he will let you choose the charity?  Perhaps we could choose the OHAAF....Overextended Headphone Addict Assistance Fund


----------



## ringyring

Quote: 





lukeahale said:


> I wonder if he will let you choose the charity?  Perhaps we could choose the OHAAF....Overextended Headphone Addict Assistance Fund


 


  Sounds legit to me


----------



## kiteki

Quote: 





draygonn said:


> Quote:
> 
> 
> 
> ...


 

 So I'll send it to Antarctica, it's still "winning" ;p
   
  I'd just like to see more experimentation and thoughts on the opamp's he's outlined he thinks will sound_ identical._


----------



## firev1

anaxilus said:


> Yup.  Purrin and myself tried the LM4562 on the input side and it cleared up some of that JRC congestion bringing the transparency closer to my Leckerton w/ the OPA209s.  I'll be leaving the JRC out.
> 
> 
> No he didn't.  In fact, he left a number of opamps some of us wanted specifically tested off or omitted for whatever reason.  When I saw the list of opamps he tested I just
> ...


 


  Analixus you and Purrin need to take up the Opamp listening challenge, it would really help the community.


----------



## kiteki

Quote: 





firev1 said:


> Analixus you and Purrin need to take up the Opamp listening challenge, it would really help the community.


 

 It seems what is required is three objective2's, two of them with the same opamp, and one with a different opamp (of your choice..?), and being able to ABX them, i.e. hear any difference at all.
   
  It just seems a little too easy, that's why I'm here asking if anyone has experimented yet.


----------



## Maxvla

It's nice this product is cheap enough to actually consider having 3 of them. Imagine getting 3 Balancing Acts or similar to ABX tube/opamp rolling.


----------



## kiteki

It's nice it's "Designed in USA" and "Assembled in England" too


----------



## palmfish

Quote: 





anaxilus said:


> Yup.  Purrin and myself tried the LM4562 on the input side and it cleared up some of that JRC congestion bringing the transparency closer to my Leckerton w/ the OPA209s.  I'll be leaving the JRC out.
> 
> 
> No he didn't.  In fact, he left a number of opamps some of us wanted specifically tested off or omitted for whatever reason.  When I saw the list of opamps he tested I just
> ...


 
   
   
  I think it's great that you have found a way to make your O2 sound better to you, but I would not agree though that your modification has improved the sound of the O2 and is superior to a spec O2. I think it's deceptive to say that "timbre and tonality are anathema to the concept of the O2 and it's supporters." I think it is more correct to say that coloration, while enjoyed by many audio enthusiasts, is not part of the O2's lexicon. If a straight "wire with gain" is not what you're looking for, then look elsewhere. There are hundreds of amps on the market that deliver all sorts of "timbre and tonality."


----------



## syphen606

Quote: 





kiteki said:


> It's nice it's "Designed in USA" and "Assembled in England" too


 


  Strange, mine was assembled in Canada...


----------



## JamesMcProgger

Quote: 





syphen606 said:


> Strange, mine was assembled in Canada...


 


  fake.


----------



## mikeaj

Quote: 





palmfish said:


> I think it's great that you have found a way to make your O2 sound better to you, but I would not agree though that your modification has improved the sound of the O2 and is superior to a spec O2. I think it's deceptive to say that "timbre and tonality are anathema to the concept of the O2 and it's supporters." I think it is more correct to say that coloration, while enjoyed by many audio enthusiasts, is not part of the O2's lexicon. If a straight "wire with gain" is not what you're looking for, then look elsewhere. There are hundreds of amps on the market that deliver all sorts of "timbre and tonality."


 

 I would say this, but look at the change that was actually being made.  It's just the gain stage op amp, which has some proper compensation in the circuit.  A suitable modern audio op amp is not going to make a significant difference in this application, unless it's a really finnicky model that's not going to be unity gain stable, and you lower the gain all the way to unity gain.  Well, there's some difference in noise levels, as much as about 6 dB or so between models that were tested.  I'd believe that you could tell a difference between those noise levels with some really sensitive IEMs and a really quiet environment.  But good luck hearing the other differences between these parts when you're going to be bottlenecked first by the headphones, the output stage, and your ears.  If you can prove this wrong, please demonstrate this in proper blind testing so you can shut me up for good.
   
  For that matter, JRC4562 was tested, which should be mostly similar to LM4562 unless you really believe in some mystical "JRC congestion."  Yeah, their chip designers decided to add the "congestion circuit" as a part of all of the op amps, maybe even ones that aren't suitable for audio applications?  Or maybe just to add a congestion flavor to those with otherwise suitable audio specs?  /sarcasm


----------



## maverickronin

Quote: 





mikeaj said:


> For that matter, JRC4562 was tested, which should be mostly similar to LM4562 unless you really believe in some mystical "JRC congestion."  Yeah, their chip designers decided to add the "congestion circuit" as a part of all of the op amps, maybe even ones that aren't suitable for audio applications?  Or maybe just to add a congestion flavor to those with otherwise suitable audio specs?  /sarcasm


 

 The JRC congestion circuit is awesome!  I set it up in an inverting configuration and it does wonders for my allergies!


----------



## Anaxilus

I fail to see how an amp that hides source material is transparent and 'wire with gain' but feel free to believe that.  It's a better amp, not best.
   
  As for 3 O2s we haven't done that but if you read back in the thread you'll find picks of our bench w/ 2 O2's and a CMoy we AB'd.
   
  Congestion opamp?  Funny, hilarious.  What do you call the opamps or components in amps performing worse than the O2?  Or is that not a fair analogy against the $100 sacred cow?  I also like the idea that 'it was tested' implies some sort of finality beyond reproach.


----------



## maverickronin

Quote: 





anaxilus said:


> Congestion opamp?  Funny, hilarious.  What do you call the opamps or components in amps performing worse than the O2?  Or is that not a fair analogy against the $100 sacred cow?  I also like the idea that 'it was tested' implies some sort of finality beyond reproach.


 

 The point is that many opamps perform almost almost identically in such an application, not that the O2's gain stage opamp is really the best at anything except the bang for the buck ratio.
   
  If you change the opamp in the gain stage and hear something different the overwhelming probability is that it either messed something up and dramatically changed the measured performance or that you only hear the difference because you know what opamp you're listening to.


----------



## Anaxilus

Quote: 





maverickronin said:


> The point is that many opamps perform almost almost identically in such an application, not that the O2's gain stage opamp is really the best at anything except the bang for the buck ratio.
> 
> If you change the opamp in the gain stage and hear something different the overwhelming probability is that it either messed something up and dramatically changed the measured performance or that you only hear the difference because you know what opamp you're listening to.


 

 Well, it wasn't as dramatic as when we replaced all 3 JRCs w/ the LMs.  That was 'interesting' and definitely sounded wrong.  For whatever reason anyone would like to believe we heard what we heard and believe we heard, what matters to me as the end user is the LM is staying in mine based on better retrieval of source material I'm familiar with.
  __________________________ 
   
  I've made no claim  beyond a subjective experience I've relayed (because Kiteki asked) so feel free to disregard it all as placebo and look elsewhere for those so inclined to do so.


----------



## mikeaj

maverickronin covered it above (thanks).  That the LM4562 does better would not be a surprise; that you can hear the difference, all other things considered, is the extraordinary claim.
   
  These op amps weren't even tested beyond noise and THD+N, which significantly less than the usual battery of tests, so any claims about performance are weaker than typical based just off test data.  Regardless, understanding the system as a whole including the listener, the headphones, and other parts of the circuit, the input stage op amp seems to not be a primary consideration.
   
  By the way, when people have done proper listening tests where 16/44.1 A/D -> D/A loops were placed into full analog or high-res playback chains and nobody could tell when this happened, the A/D -> D/A loop probably had audio op amps like these in the signal path.  (We're ignoring for now the contribution of the actual D/A and A/D processes, which you should probably feel should be a much bigger deal than passing through those op amps.)
   
  On a side note, you could make a funny or plausible argument for NJM/JRC and all sorts of other op amps being so prevalent in mixing boards, recording setups, and the audio chain in general prior to mastering, causing "congestion" in modern recordings.  In reality, that's not the correct cause-and-effect sequence, since the cause generally is more about the dynamic range compression and other details of poor mastering or recording, but that's the angle I would take if I wanted to play devil's advocate.


----------



## Anaxilus

There seems to be a logical leap occurring here.  Saying the O2 sounded less 'congested' by replacing the JRC w/ the LM (noticeable but not immense to making the O2 sound like an HD800) is different than claiming the JRC is a congested opamp.  I only stated the first.  Others are free to go down the other rabbit hole.  Whether changing the input opamp has minimal or no audible difference is another.
   
  The point of our exercise was to see if we could get the O2 to be a little more transparent like my UHA6S w/ 209s.


----------



## maverickronin

Quote: 





anaxilus said:


> Well, it wasn't as dramatic as when we *replaced all 3 JRCs* w/ the LMs.  That was 'interesting' and definitely sounded wrong.  For whatever reason anyone would like to believe we heard what we heard and believe we heard, what matters to me as the end user is the LM is staying in mine based on better retrieval of source material I'm familiar with.
> __________________________
> 
> I've made no claim  beyond a subjective experience I've relayed (because Kiteki asked) so feel free to disregard it all as placebo and look elsewhere for those so inclined to do so.


 

 If you replace the output opamps then all bets are off.  I would not be surprised if it sounded different under those circumstances which is why I specified the gain stage opamp before.
   
  The 4556 are used for the output stage because it has a lot more current capability than any "popular" opamp except the AD8397 which seems to take a fair bit of work to make stable and is prone to blowing itself up when shorted if the power supply gives it enough juice.  Using most anything else will likely increase distortion in to low impedance loads and it might not like being paralleled either.
   
  Voldermort's challenge is just about the gain stage opamps for the reasons I've just outlined.


----------



## mikeaj

Quote: 





anaxilus said:


> There seems to be a logical leap occurring here.  Saying the O2 sounded less 'congested' by replacing the JRC w/ the LM (noticeable but not immense to making the O2 sound like an HD800) is different than claiming the JRC is a congested opamp.  I only stated the first.  Others are free to go down the other rabbit hole.  Whether changing the input opamp has minimal or no audible difference is another.
> 
> The point of our exercise was to see if we could get the O2 to be a little more transparent like my UHA6S w/ 209s.


 

 Okay, I agree about that being something of a logical leap if taken in a vacuum (no side information assumed about the electronics themselves).  Your observations and conclusion can also make a lot of sense if we ignore what we know about electrical theory, psychoacoustics, and psychology.


----------



## Anaxilus

Quote: 





mikeaj said:


> Your observations and conclusion can also make a lot of sense if we ignore what we know about electrical theory, psychoacoustics, and psychology.


 

 Beautiful.  And you thought Nessy and Bigfoot didn't exist either.  Good thing I swapped that opamp so we could unify the paranormal and known verses.  Any other personal commentary you'd like to make based on your empirical certitude of the universe?
   
  I was unaware this wasn't an impressions thread.  Excuse me.


----------



## BobSaysHi

Quote: 





mikeaj said:


> Your observations and conclusion can also make a lot of sense if we ignore what we know about electrical theory, psychoacoustics, and psychology.


 

 I like you.


----------



## mikeaj

Quote: 





anaxilus said:


> Beautiful.  And you thought Nessy and Bigfoot didn't exist either.  Good thing I swapped that opamp so we could unify the paranormal and known verses.  Any other personal commentary you'd like to make based on your empirical certitude of the universe?
> 
> I was unaware this wasn't an impressions thread.  Excuse me.


 

 Impressions are important, which is why it would be great if we could have them substantiated in a more credible fashion.  This is why we're interested if you could prove these findings under properly-controlled listening conditions, which involves removing any potential biases.  It takes somebody with a good ear and who believes there should be a change (I quality for neither of these things, and you quality for both) to try to do that.
   
  In general, an unusual or anomalous impression may warrant further investigation.
   
  By the way, I definitely don't want to discourage experimentation and questioning things in general.  I'm just saying that the body of evidence shows that a different gain stage op amp (out of those that are suitable, with the proper electrical behavior) in this kind of circuit shouldn't contribute, take away, or otherwise change anything regarding the sound.  I think you're much more on the mark trying to modify things that we all know can make a difference like the materials in the headphone construction.  e.g. HD 800 foam / whatever mods.


----------



## maverickronin

Quote: 





anaxilus said:


> Beautiful.  And you thought Nessy and Bigfoot didn't exist either.  Good thing I swapped that opamp so we could unify the paranormal and known verses.  Any other personal commentary you'd like to make based on your empirical certitude of the universe?
> 
> I was unaware this wasn't an impressions thread.  Excuse me.


 

 Well when someone ABXs that kind of thing we'll change our mind just like we'll change out mind when someone drags in a bigfoot carcass or a dead nessie washes up on shore.
   
  In controlled circumstances people never notice the difference between good "consumer" CD players and expensive "audiophile" ones, class AB "pro sound" amps and "audiophile" class A amps, or notice an extra A/D and D/A process inserted into the signal chain.  Considering all that, I find the idea that two opamps which measure to within a few dB of each other on standard nosie and THD tests in a given circuit are audibly different pretty implausible.
   
  Its not impossible, but I don't really think that anyone should give such claims any more consideration that if you had reported bigfoot or something.  Its nothing against you or anyone else here.  I wouldn't even't accept anyone's personal testimony on that sort of thing without some more evidence to back it up.  Hell, even if I thought I saw bigfoot there's not any good reason for me to believe it actually happened.  It might get me curious, I might mount an expedition and ask others who already believe or are curious to help me, but I wouldn't go around telling other people that I know bigfoot exists or that I saw it.  The most I'd say is that I _think_ I saw it.


----------



## Draygonn

inb4 moved to SS


----------



## Sil3nce

Quote: 





bobsayshi said:


> I like you.


 

  
  I like you too babe, you changed your signature?


----------



## Naim.F.C

On a serious note, why hasn't anyone taken him up on his challenge? $500 is a good amount to go to charity.


----------



## maverickronin

I might have tried if I thought I could do it...
   
  On a serious note, such things are often annoying to arrange and I'm sure a lot of people will say that $500 isn't worth all the time it would take.  Some will say that its just a cheap publicity stunt since they "know" than no one will take Voldermort up on his offer.  They might say he should offer more but I think $500 out of his own pocket is plenty.  Its not likely he's going to get cool million from a rich benefactor for his challenge like the JREF got for theirs.
   
  What Voldermort's challenge has that the JREF's doesn't is a penalty to the challenger if they lose.  I think it shows that no one is really that confident about passing the test though you could easily spin it the other way as well and say it shows Voldermort is insecure.  The last I heard from Voldermort no one has contacted him about any of his challenges yet but sooner or later I'm expecting someone to ask Voldermort about what charity he's picked for if he wins and then for people to complain about the charity being a bad choice for some reason.


----------



## Anaxilus

Quote: 





maverickronin said:


> The last I heard from Voldermort no one has contacted him about any of his challenges yet


 

 That's not entirely true and per the parameters of his own guidelines he asked an intermediary be contacted.  But I'm sure that's how he imagines it just like the reimagining of other events he's posted about.


----------



## maverickronin

Quote: 





anaxilus said:


> That's not entirely true and per the parameters of his own guidelines he asked an intermediary be contacted.


 

 On his site it just says that a 3rd party would conduct the tests, probably to keep people of accusing him from cheating.  Do you know something I don't?


----------



## mikeaj

Regardless of what we think happened specifically (hard to say unless you're involved yourself), it should be fairly clear that nobody has been very insistent and serious about taking the challenge, and gotten to the stage of planning everything out and finalizing the details.  Otherwise, we would have heard about specific test procedures and test dates, or something along those lines.
   
  An issue is lack of open communication, because people would prefer to set up and discuss things on head-fi, and he's banned here.  Has anybody ever opened up a thread about this, even on head-fi?  (I'm certainly not aware of every single thread, so I could have easily missed something.)  If you're really interested in setting something up, you would probably do it on another forum where he can actually respond, though.


----------



## Draygonn

V's comment about setting up a challege:

_start a thread on diyAudio or ABI, someone let me know it's there, and I'll gladly respond in an open public forum to any blind challenge requests._




draygonn said:


> inb4 moved to SS


----------



## kiteki

Before anyone actually takes up the official challenge, I'd imagine they would first start by rolling an opamp in their O2, feeling like they can hear a difference.
   
  Then, they'd acquire another O2, with a different opamp in each, and directly compare them (same source with a splitter), seeing if they can identify which unit is which.
   
  Then they'd start posting in a thread like this saying "AD797 is clearly identifiable, 10/10", or the like.


----------



## upstateguy

Quote: 





maverickronin said:


> I might have tried if I thought I could do it...


 

  +1

  
  Quote: 





kiteki said:


> Before anyone actually takes up the official challenge, I'd imagine they would first start by rolling an opamp in their O2, feeling like they can hear a difference.
> 
> Then, they'd acquire another O2, with a different opamp in each, and directly compare them (same source with a splitter), seeing if they can identify which unit is which.
> 
> Then they'd start posting in a thread like this saying "AD797 is clearly identifiable, 10/10", or the like.


 

 It's pretty good just as it is, but I think you will degrade performance by interchanging components if you don't measure carefully.


----------



## kiteki

Yes, when someone hears a difference with OPA627, AD797, AD8620 etc. it's thanks to "degraded performance", clearly... that is what I'm hearing, 'OK'.


----------



## Head Injury

Quote: 





kiteki said:


> Yes, when someone hears a difference with OPA627, AD797, AD8620 etc. it's thanks to "degraded performance", clearly... that is what I'm hearing, 'OK'.


 

 Yes, it is. The opamps in this amp were chosen because they had the best performance in the circuit of all the ones tested. If you roll opamps, the changes you hear are due to degraded performance or placebo, until you prove otherwise with measurements. You should really assume this about _any_ amp, because it's nice to think the engineers knew what they were doing.


----------



## frenchbat

For the record, V's challenge is :
   
  1. DBT
   
  2. Meant to test a different amp, that measure sufficiently well. It's never been about a different op-amp in the O2. 
   
  Just my 2 cents ...


----------



## kiteki

Quote: 





head injury said:


> Yes, it is. The opamps in this amp were chosen because they had the best performance in the circuit of all the ones tested. If you roll opamps, the changes you hear are due to degraded performance or placebo, until you prove otherwise with measurements. You should really assume this about _any_ amp, because it's nice to think the engineers knew what they were doing.


 

 As already stated, he didn't measure or listen to particular opamps.
   
  If an engineer builds a merry go round and paints the horses, it doesn't mean he used the best paint, especially if he never even saw or tested that paint.


----------



## Head Injury

Quote: 





kiteki said:


> As already stated, he didn't measure or listen to particular opamps.


 

 NwAvGuy didn't? He has an entire article about them and why he used the ones he used.


----------



## frenchbat

Ahemm ...
   
  You might want to go and read the article about the Op Amp Measurements before saying he didn't measure particular op-amps. Here's the list :
   

 *NJM2068*
 *NE5532*
 *OPA2134*
 *OPA2227*
 *OPA2277*
 *LM4562*
 *TL072*
   
  Quote: 





kiteki said:


> As already stated, he didn't measure or listen to particular opamps.


 
   
  EDIT : Head Injury was faster than me, but I put on the list ...


----------



## mikeaj

Quote: 





head injury said:


> Yes, it is. The opamps in this amp were chosen because they had the best performance in the circuit of all the ones tested. If you roll opamps, the changes you hear are due to degraded performance or placebo, until you prove otherwise with measurements. You should really assume this about _any_ amp, because it's nice to think the engineers knew what they were doing.


 

 IMHO this is kind of a stretch, or you need to be more careful about the wording.  If you consider battery operation power consumption and cost, the chosen gain stage NJM2068 was easily the best of those tested.  If you consider just power consumption and performance, NJM2068 was the best.  Going by raw performance, OPA2227 did better, and some alternatives had lower distortion but higher noise.  But this is based just on just a few tests, which are not particularly conclusive.  It may be premature to declare a winner based on just that data, if you're looking at just performance and ignoring the power consumption.
   
  The point is that aside from the outdated TL027, everything did really well, to the point that differences are quite boring and marginal--other than potentially noise levels, which could be relevant if you're using very sensitive IEMs in some very quiet listening environment.  There's not much motivation to look harder at alternatives or investigate the performance more carefully when a relatively cursory overview already finds something sufficiently good that's cheap.
   
  There are definitely parts with higher performance, even for audio purposes and even for a gain stage.  However, with that circuit and PCB and other surrounding parts, you might not be able to reach the potential of those expensive op amps.  (This is aside from whether or not those improvements in the gain stage would be audible, which seems highly unlikely for reasons previously discussed.)


----------



## upstateguy

Quote: 





kiteki said:


> Yes, when someone hears a difference with OPA627, AD797, AD8620 etc. it's thanks to "degraded performance", clearly... that is what I'm hearing, 'OK'.


 


  The audio DiffMaker is perfect for testing differences between opamps.  If you can hear a difference the diffMaker program will isolate it for you.
   
  Ti Kan did a manual null for me between the OPA637 and the AD8610 in an M^3.  The difference was at -45dB and probably due to doing it manually.
   
  So the real challenge is to post some diffMaker recordings of these differences so we can all evaluate it.


----------



## Naim.F.C

If he measured it to be a near perfect neutral response with a flat curve and inaudible noise, I very much doubt it'd make a difference even if superior opamps were used. You can't really fix something that has nothing there to be fixed. Unless of course it could bring less noise than already inaudible noise or something unnecessary like that. 
  
  Quote: 





kiteki said:


> As already stated, he didn't measure or listen to particular opamps.
> 
> If an engineer builds a merry go round and paints the horses, it doesn't mean he used the best paint, especially if he never even saw or tested that paint.


 

  
  EDIT: Also, why has this been moved to Sound Science? Lol. Surely it belongs in the Headphone Amps section? Scientific or technical discussions about amps are only natural in amp threads.


----------



## mikeaj

Quote: 





naim.f.c said:


> EDIT: Also, why has this been moved to Sound Science? Lol. Surely it belongs in the Headphone Amps section? Scientific or technical discussions about amps are only natural in amp threads.


 

 This is not that uncommon.  Once the number of "contentious" posts surpasses a certain threshold,_ the powers that be _relegate the discussion to the ghetto of head-fi:  Sound Science.  There it may continue to fester without disturbing the ordinary netizens.  Draygonn totally called it. 
   
  One interpretation is that such arguments about blind testing, measurements and listening impressions, etc. are old and stale, and nobody ever comes to an agreement, so it's kind of annoying and pointless to see happen again.  It's cleaning the garbage to move the discussion elsewhere.  The other interpretation is that such discussions give rise to thinking that would not be favorable to head-fi's many sponsors, some of which rely on some amount of misinformation or false hype to generate sales.  e.g. If you take the view that most well-designed solid-state amps aiming for accuracy (and accomplishing that) should sound the same, then you're less likely to purchase new solid-state amps, even ones that are very good.  Also, for various reasons, _the powers that be_ aren't exactly fans of V.
   
  Those responsible for the move maybe think they have reasoning more along the lines of the first interpretation, while V would be convinced it's clearly the second.  I would think that both are factors, but of course I can't know for sure.


----------



## kiteki

Quote: 





head injury said:


> NwAvGuy didn't? He has an entire article about them and why he used the ones he used.


----------



## Head Injury

Don't try to derail with pony images, now. The latest episode was about being assertive, and I'm putting my hoof down.


----------



## uelover

Unsubscribed.


----------



## kiteki

Quote: 





head injury said:


> Don't try to derail with pony images, now. The latest episode was about being assertive, and I'm putting my hoof down.


 

 You can put your hoofs down. =]
   
  In post #1345, I am only at stage 1.
   
   
  Quote: 





mikeaj said:


> There are definitely parts with higher performance, even for audio purposes and even for a gain stage.  However, with that circuit and PCB and other surrounding parts, you might not be able to reach the potential of those expensive op amps.


 

 Sure, but before we put it in the stable of most transparent hi-end amplifier ever necessary, there should at least be some experimentation, at least in my view.  There are electrical engineers which think opamps sound different for reasons beyond their dScope.

  
  Quote: 





upstateguy said:


> The audio DiffMaker is perfect for testing differences between opamps.  If you can hear a difference the diffMaker program will isolate it for you.
> 
> Ti Kan did a manual null for me between the OPA637 and the AD8610 in an M^3.  The difference was at -45dB and probably due to doing it manually.
> 
> So the real challenge is to post some _diffMaker recordings of these differences so we can all evaluate it._


 

 That's interesting, but then we are listening to the sound of recordings with opamps, that is why I don't see the examples of "100 opamps in a studio recording" or the Meyer & Moran ADC/DAC CD duplicates as perfectly valid.


----------



## mikeaj

Quote: 





kiteki said:


> Sure, but before we put it in the stable of most transparent hi-end amplifier ever necessary, there should at least be some experimentation, at least in my view.  There are electrical engineers which think opamps sound different for reasons beyond their dScope.


 
   
  Considering all that I don't know, and the level of education and thinking of plenty of electrical engineering graduates, I must say that some electrical engineers thinking _anything _is not much of a surprise to me.  It doesn't particularly signify much, all things considered.  And a lot of times for audio you hear from audio engineers, who may have a much different background.
   
  But I'm always down for more experimentation.  Who's up?

  
   


kiteki said:


> That's interesting, but then we are listening to the sound of recordings with opamps, that is why I don't see the examples of "100 opamps in a studio recording" or the Meyer & Moran ADC/DAC CD duplicates as perfectly valid.


 
   
  Maybe I'm just being really dense, but I don't quite follow what you're saying here.  When you say "sound of recordings with opamps" are you talking about op amps in our playback chain or in the studio recording/mastering chain?  What does this have to do with a null test?
   
  At least for the O2 and these gain stage op amps, for a single tone test, we'd be looking at a difference in the 0.001% (-100 dB) range or so, or a little lower.  For real music, which has multiple tones, or an IMD test, you would probably expect a little more differentiation, but not like an order of magnitude, which would still be vanishingly small.


----------



## kiteki

Quote:


> Originally Posted by *mikeaj* /img/forum/go_quote.gif
> 
> Maybe I'm just being really dense, but I don't quite follow what you're saying here. When you say "sound of recordings with opamps" are you talking about _*op amps in our playback chain *_or in the _*studio recording/mastering chain?*_ What does this have to do with a null test?


 

 Yeah I mean the two above are different.

 When upstateguy said _"recordings of these differences so we can all evaluate it." _ It looked like he meant listening to the latter, using the former.
   
   
  Quote: 





mikeaj said:


> But I'm always down for more experimentation. Who's up?


 

 That's more like it, I think I'll start with NE5532 versus OPA2134 (since they have been tested), if I can't hear any difference at all, then move on to something like NE5532 versus OPA627, still no difference?  Then I'd find that quite interesting and most likely quit, with some satisfaction of the result.


----------



## mikeaj

Why would you suspect that op amps in the playback system would be different than those in the studio?  These are often some of the exact same models, used in similar circuits for similar purposes.  I can't think of what the distinction would be.


----------



## Willakan

There are engineers that believe lots of things. None of these things have ever been produced under controlled conditions. I wonder why.
   
  Also, how did this end up in Sound Science? Kinda ironic, surely, moving a thread that is turning to the subject of opamp rolling into Sound *Science...*
  Also, where's the V200 vs O2 review?


----------



## kiteki

Quote: 





mikeaj said:


> Why would you suspect that op amps in the playback system would be different than those in the studio?  These are often some of the exact same models, used in similar circuits for similar purposes.  I can't think of what the distinction would be.


 

 If opamps have a certain sound-quality or performance inherent to them, or even a type of signature, then that will be inherent to all music played through them, from all studios and decades.
   
  How am I supposed to listen to the performance of X opamp in X studio using X opamp?


----------



## Battou62

Quote: 





draygonn said:


> inb4 moved to SS


 
  What is really impressive about this clairvoyant post is that it was post number 1337


----------



## Willakan

Move had already happened by then, unfortunately.
  I think that people are reading too much into opamp rolling. Opamp rolling works on two principles:
   
  1) That you know better than the designer/designer cut corners of some sort.
  2) That audible differences will result even when neither opamp is seriously upset (Oscillation doesn't sound too great apparently...)
   
  I can't see either of these statements holding true, the latter never being true IMHO if you are using a half-decent audio opamp and implementing it properly.


----------



## thehadi

Hello guys,
   
  I received my JDS Labs O2. I am using it with K501 and NuForce uDAC. I hear some distortion. Is it because of DAC or amp?


----------



## stv014

Quote:  





> I received my JDS Labs O2. I am using it with K501 and NuForce uDAC. I hear some distortion. Is it because of DAC or amp?


 

 Try using the lower gain setting, if you are not already doing so. Also, the NuForce uDAC(2) is not very good in terms of distortion, and it cannot output a full scale signal without clipping. In this particular aspect, even a decent onboard audio chip is better.


----------



## thehadi

Quote: 





stv014 said:


> Try using the lower gain setting, if you are not already doing so. Also, the NuForce uDAC(2) is not very good in terms of distortion, and it cannot output a full scale signal without clipping. In this particular aspect, even a decent onboard audio chip is better.


 


 Thanks for quick reply stv,
   
  When i try low gain (x2,5), i think it's not enough for K501. And uDAC is first generation. uDAC(1).


----------



## Willakan

The uDAC actually clips from its line outputs (yup, Nuforce are that incompetent) so that could be what you're hearing.
  2.5X gain is plenty anyhow, looking at the sensitivity of your headphones. 6X gain is designed to be used with MP3 players and other devices with low voltage outputs and will result in clipping when used with a higher-voltage source. This is by design.


----------



## thehadi

Thanks for reply. I think it's time to go from uDAC to another toy. Waiting my DX100 and new ODAC.


----------



## kiteki

Quote:


> Originally Posted by *Willakan* /img/forum/go_quote.gif
> 
> I think that people are reading too much into opamp rolling. Opamp rolling works on two principles:
> 
> 1) That you know better than the designer/designer cut corners of some sort.


 
   
  I'm pretty sure modding the Fostex T50RP works on this principle, yes?  In the case of the O2 corners were cut from a price perspective, if not, it'd be 'spec'd out' with AD8620, or the like...
   
  ﻿﻿Quote: 





> Originally Posted by *Willakan* /img/forum/go_quote.gif
> There are engineers that believe lots of things. None of these things have ever been produced under controlled conditions. I wonder why.


 
   
  First you experiment, then you believe, then you test, then you look for hard data.
   
  Most people stop at 2, or start at 4...
   
  I came to this thread to check on 1...


----------



## Head Injury

Quote: 





kiteki said:


> I'm pretty sure modding the Fostex T50RP works on this principle, yes?  In the case of the O2 corners were cut from a price perspective, if not, it'd be 'spec'd out' with AD8620, or the like...


 

 The T50RP was a good driver by a company that makes good OEM drivers, slapped into the first enclosure they could think of. It was never intended to be a reference design, they probably didn't even think about how good the driver was. It wouldn't be worth their R&D cost to research a good design and sell it for more.
   
  The Objective2 is an amp designed exclusively for measured performance, and has had a considerable amount of R&D put into it to make sure it performs as well as it can for its design and cost.
   
  Amps work with relatively simple electrical signals. Headphones work with complex sound waves and reflections, and are considerably more unpredictable. With an amp, you can compare opamp specs and measurements to see which works best with the design, and even less optimal designs will have fairly benign audible effects. With headphones, there are a nearly infinite number of tweaks that can be made to alter the sound waves to a very audible degree. Reportedly, the HD800 has been improved with a strip of t-shirt, and the LCD-3 improved with a piece of toilet paper.
   
  See the difference?


----------



## kiteki

I see the difference.
   
  Most studios just buy the Fostex T40RP and leave it at that, ftr.


----------



## derbigpr

Just a quick question so I wont have to read trough 90 pages... is this O2 really that good if I just want a powerful amp to amplify whats coming from the DAC with colorations, but with lots of authority and power? Would it be an improvement over the Little Dot Mk5 for AKG Q701's?


----------



## mikeaj

Quote: 





derbigpr said:


> Just a quick question so I wont have to read trough 90 pages... is this O2 really that good if I just want a powerful amp to amplify whats coming from the DAC with colorations, but with lots of authority and power? Would it be an improvement over the Little Dot Mk5 for AKG Q701's?


 
   
  Yes, but maybe or maybe not by a significant or even audible amount.  If you go by the spec listed for the Little Dot Mk5, it claims 0.05% THD+N into 300 ohms at 100mW (5.48V rms) with the standard 1 kHz test tone.  Assuming that the O2 does similarly with 300 ohms as it does with 150 ohms and 600 ohms (a very reasonable assumption, considering the performance into 150 ohms and 600 ohms is very similar), it gets about 0.001% THD+N with the same test.  It depends on the design, but most amplifiers will have a harder time putting the same amount of power into a lower impedance like the ~60 ohms of the Q701, so the distortion could well be significantly higher than 0.05% just for THD+N when driving the Q701.  With real music, distortion is higher than for just a 1 kHz test tone, because of intermodulation products and so on.
   
  100mW is actually a typical power input to a Q701 to play loudly, so that's not that much of a stretch.  Into a load like that, O2 should get between 0.001 and 0.002% THD+N...for what that's worth.  THD+N for a 1kHz input is just one benchmark out of many, so it's not particularly indicative of total performance, especially since the number alone doesn't tell you about whether the distortion is 3rd order harmonics, 2nd order, or what else.  Many more tests are on the designer's blog for the O2, if you want to look yourself.
   
  They don't list the output impedance for the Little Dot, but based on the listed output power at different loads, it would seem like it's probably not negligible.  That would slightly alter the frequency response of those headphones and contribute to additional distortion when driving headphones as opposed to test resistors on the lab bench.  Still, we have a very incomplete picture of the type of distortion and the overall performance characteristics of the Little Dot, so it's hard to say if these issues would actually be audibly worse and whether the O2 would actually be a real upgrade for those headphones.  By the books, the specs indicate lower performance for the Little Dot, but the "how much" and "how" are not clear.


----------



## derbigpr

Quote: 





mikeaj said:


> Yes, but maybe or maybe not by a significant or even audible amount.  If you go by the spec listed for the Little Dot Mk5, it claims 0.05% THD+N into 300 ohms at 100mW (5.48V rms) with the standard 1 kHz test tone.  Assuming that the O2 does similarly with 300 ohms as it does with 150 ohms and 600 ohms (a very reasonable assumption, considering the performance into 150 ohms and 600 ohms is very similar), it gets about 0.001% THD+N with the same test.  It depends on the design, but most amplifiers will have a harder time putting the same amount of power into a lower impedance like the ~60 ohms of the Q701, so the distortion could well be significantly higher than 0.05% just for THD+N when driving the Q701.  With real music, distortion is higher than for just a 1 kHz test tone, because of intermodulation products and so on.
> 
> 100mW is actually a typical power input to a Q701 to play loudly, so that's not that much of a stretch.  Into a load like that, O2 should get between 0.001 and 0.002% THD+N...for what that's worth.  THD+N for a 1kHz input is just one benchmark out of many, so it's not particularly indicative of total performance, especially since the number alone doesn't tell you about whether the distortion is 3rd order harmonics, 2nd order, or what else.  Many more tests are on the designer's blog for the O2, if you want to look yourself.
> 
> They don't list the output impedance for the Little Dot, but based on the listed output power at different loads, it would seem like it's probably not negligible.  That would slightly alter the frequency response of those headphones and contribute to additional distortion when driving headphones as opposed to test resistors on the lab bench.  Still, we have a very incomplete picture of the type of distortion and the overall performance characteristics of the Little Dot, so it's hard to say if these issues would actually be audibly worse and whether the O2 would actually be a real upgrade for those headphones.  By the books, the specs indicate lower performance for the Little Dot, but the "how much" and "how" are not clear.


 


  Yes, it appears that by specs O2 should do better. The biggest reason why I want a new amp for Q701's is I feel Little Dot doesn't work well with low impedance cans. It actually has high output impedance, not sure how much, nobody knows, but the fact is, Little Dot ships it with a little impedance adapter for low impedance headphones. I don't have that adapter since I bought mine second hand, but it says something.  It just sounds overly bright and thin, changes the sound that comes out of my sound card drastically.


----------



## khaos974

Are we forbidden to mention that blog or simply forbidden to link to it?


----------



## syphen606

Quote: 





khaos974 said:


> Are we forbidden to mention that blog or simply forbidden to link to it?


 


  Not sure as I wasn't around during the whole banning thing, but one thing I will say is that as wide-spread as the O2 is becoming.. internet censorship of mentioning his name is cheesy and goofy. Like looking at some back water countries internet censorship policies.
   
   
  I don't see what everyones problem is with the O2, as some here don't seem happy with it.  It drives my HD650's beautifully and sounds great. I'm happy with it in its stock configuration and don't feel the need to move on. I'm very happy with what I put together with my own hands for the price I did.


----------



## palmfish

Well, I am about to come full circle with my audio setup.
   
  I started with a pair of HD600's for quiet-time listening, and found they didn't pair well with my 80's vintage Carver receiver. This led me on a search for a more headphone friendly solution. I ended up with a Peachtree Nova, which I love thanks to it's built-in DAC and great analog and digital switching capabilities.
   
  I lived with this nice setup for a few months but I was never quite happy with the HD600's - they were so balanced I never found anything I liked better, but I was always bothered that they were a little on the bass light side of things for my preference. Then a month ago, I discovered the Denon AH-D7000 and everything changed. They sounded fantastic to me, but I started worrying that with their low impedance, they weren't a good match for the Nova (30 ohm output impedance). This is about the time I discovered the O2, so out of curiosity, I bought one and a Violectric V90 to see if a low output impedance amp would be a better match for the Denons (even though I couldn't detect any problems with the Nova, which sounded great).
   
  What I found is that all three amps sounded extremely similar to each other. I came to the conclusion that, because the Denons have very stable impedance across the audible frequency range, they are not picky about amplifier output impedance. With this conclusion on my mind, I decided to see how my Carver receiver sounds with the Denons. I hauled the Carver home from work today (I have been using it in my office system) and hooked it up. Well, what do you know? It sounds terrific with the Denons - I really can't tell it apart from the Nova or the O2. Maybe with extreme eye squinting and A/B switching I could spot some tiny differences, but my primary conclusion is that the Denons are just really amp friendly and I really don't need any special gear for them.
   
  The bonus for me with the Carver receiver is that it has Tone Controls. With all the other setups I've sampled and owned, there were always some albums that weren't mixed "neutrally" and sounded poor to me. Some old rock albums that sound thick and muddy or 80's CD's that sound too "U" shaped. For 80% of my collection, everything was great, but with that other 20%, there was nothing I could do so I just avoided listening to them.
   
  So I've come full circle - back to my beloved Carver. I'm going to keep the O2 because it's just really cool and I like it - I'm sure I'll find a use for it. I've already sold the Violectric because I don't need it, and now I think I'm going to sell the Peachtree Nova too - I'm going to Europe this summer so the extra money will be helpful. I will be in the market for an inexpensive DAC to replace the Nova's DAC, but even if I spend $300 or $400, I'll still come out ahead.
   
  Sorry if this wasn't interesting to you, but I had to let it out somewhere. I thought this was a good place because it was NwAvGuy's blog that educated me about output impedance and the O2 which got me to experimenting. Thanks for reading!


----------



## zzffnn

@ thehadi,
   
  You may want to fully charge O2 first. My JDS O2 revealed distortion upon arrival, which went away completely after charging overnight.
  
  Quote: 





thehadi said:


> Hello guys,
> 
> I received my JDS Labs O2. I am using it with K501 and NuForce uDAC. I hear some distortion. Is it because of DAC or amp?


----------



## thehadi

Quote: 





zzffnn said:


> @ thehadi,
> 
> You may want to fully charge O2 first. My JDS O2 revealed distortion upon arrival, which went away completely after charging overnight.


 


 I will try it, thank you zzffnn. I will try it with DX100 after i get it and with ODAC when it's on the market.


----------



## Maxvla

syphen606 said:


> Not sure as I wasn't around during the whole banning thing, but one thing I will say is that as wide-spread as the O2 is becoming.. internet censorship of mentioning his name is cheesy and goofy. Like looking at some back water countries internet censorship policies.




It had to do with his posting saying to the effect of 'Hey I have this information you just have to see, click the link and see it on my blog' which uses Head-fi to generate traffic for him and make him money from said traffic. That's just not something you do. If he had simply posted his information here he probably wouldn't have been banned at all. A lot of his negative comments about various products spread around Head-fi are still here unedited, so it wasn't that.

The rule about not talking about banned members is common courtesy. He can't defend himself against comments posted, so we don't allow those comments to be posted. It's not about censoring, it's about giving respect to someone who didn't give us respect.

And in that spirit, lets let it die and continue on.


----------



## frenchbat

As much as I understand the no-linking-to-increase-oneself's-blog-traffic part, AFAIK there's not a single ad on his blog. So I fail to see how one can make money without ads. Go see for yourself, not even google ads.
   
  Why this need of making him a vile and interested person ? I just can't, for the life of me, understand that. The same thing is popping out every now and then, when talking about the design he simply gave everyone. The funniest part of all is that while he has been banned, Head-fi sponsors are now making money though head-fi with his design.
  
  Quote: 





maxvla said:


> It had to do with his posting saying to the effect of 'Hey I have this information you just have to see, click the link and see it on my blog' which uses Head-fi to generate traffic for him and make him money from said traffic. That's just not something you do. If he had simply posted his information here he probably wouldn't have been banned at all. A lot of his negative comments about various products spread around Head-fi are still here unedited, so it wasn't that.
> The rule about not talking about banned members is common courtesy. He can't defend himself against comments posted, so we don't allow those comments to be posted. It's not about censoring, it's about giving respect to someone who didn't give us respect.
> And in that spirit, lets let it die and continue on.


----------



## mikeaj

As always, there's (at least) two sides to every story...but saying that he makes money from generating traffic is a complete falsehood, unless you believe something like he has some shady under-the-tables profit from Epiphany or JDSLabs or maybe whichever companies he (the bench equipment really) gives good product reviews for.  Some say he's after profit in some non-monetary sense.  Choose the conspiracy theory of your liking.  The linking seems to be a website policy though, but arguably it seems to be "selectively" enforced.
   
  Some people don't have time to repost lengthy (and with him it's generally going to be _lengthy_) explanations all the time, so the convenient thing would be to link the information directly.  Is it considered respect to knowingly leave people in the dark?  Of course, depending on your perspective and beliefs--which may or may not be founded in reality--you could call it proselytizing.
   
   
   


thehadi said:


> I will try it, thank you zzffnn. I will try it with DX100 after i get it and with ODAC when it's on the market.


 

  By the way, charging the batteries will only help if it's clipping the gain stage (which it might be), and only if you're actually running it off the batteries.  Clipping happens if the battery voltage is too low and the source and gain are too high; however, it's a somewhat narrow range of values where the combination of source and gain will clip the amp when on low batteries, but the combination will not clip the amp on high batteries.


----------



## frenchbat

Of course there are 2 sides, and Voldemort himself isn't without his own quirks. I had a few words with him and he's a very opinionated guy which might fail to see the point you're trying to make. But saying he has a big mouth is one thing, and saying he's fooling everyone is another. 
   
  Oh well, the success of the O2 will bring whomever wants to read the blog straight there by a simple google search I guess. At least it seems like using his name is now tolerated, and that's already a sufficient indication.


----------



## Maxvla

Since you can't help but discuss it...

Whether he gained money from it or not isn't the point, really. You show up on a popular site and blatantly try to pull their traffic, you will be removed. It's really plain to see. It has nothing to do with Head-fi or NwAvGuy. If this happened on some other forum with someone else they would respond the same way.

The 'don't have time to post twice' excuse doesn't work either. How long does it take to copy/paste something of any length? A few seconds? Someone acting in this manner is already making the post to link to his/her site. They've already copied and pasted their link. Instead of the link it could be the message.

If I had a message that was for the public good and nobody would be harmed in any way by saying it I still couldn't just drive up to my local TV station and expect air time on their hard earned network. On a public forum, though this is allowed. Take it a step further and instead of your message being played on the TV station, you demand that their TV station say 'This is channel 5, there is an excellent message on channel 6, watch their channel, not ours'. This is what people who spam links to blogs are demanding the right to do.

The whole 'staff thinks he's a vile person' I don't believe is true. There was a policy breach, I'm sure he was warned a few times, then banned as a matter of course. Because he didn't want to play by the rules here, and with his message of returning to real fidelity and not taking any benefit, I believe many members misunderstood and became angry scapegoating the staff to console themselves. It has continued to fester all this time.

Now please drop it or take it to pms. I've already talked about it more than I should, but I'm tired of this attitude tainting this design, the designer, and our staff. I fully support the designer and intend to buy an ODA or ODAC when they are available. It think it's refreshing, but the way it was done could have been better.


----------



## frenchbat

It's not that I can't help but discuss it, but you can't just say the guy is actually making money out of something, thus creating the image of a biased person, and say "now let's stop talking about it". If you had left it at the no-external link policy, I probably wouldn't have posted anything.
   
  Now I'll quietly go back to the shadow, where I'm usually staying.


----------



## Maxvla

I actually haven't looked at his blog much and assumed there were ads or some form of monetary compensation for the traffic, but that being false doesn't make it right. I apologize that I didn't look into it clearly enough and stated incorrect information.


----------



## Shike

His banning had nothing to do with blog spam, and that was out of Jude's mouth http://www.head-fi.org/t/562736/what-causes-this-amp-related/120#post_7619633
   
  This also doesn't include his side of the events though.
   
  Now that that's out of the way, let's drop it alright?  Next time don't speculate on subjects you don't know, and more importantly don't derail the topic at hand.


----------



## jude

> Originally Posted by *jude* /img/forum/go_quote.gif
> 
> 
> 
> ...


----------



## zzffnn

Guys, let us calm down and just talk about the amplifier and its sound. Discussing more about those sensitive "political" topics will only get this thread locked.


----------



## wje

Quote: 





zzffnn said:


> Guys, let us calm down and just talk about the amplifier and its sound. Discussing more about those sensitive "political" topics will only get this thread locked.


 

 Agreed.  I received a nicely-build O2 amplifier from JDS Labs on Saturday.  Prior to that time, I had been using an O2 amp build by another individual that, essentially, had problems all along.  These various issues added up to the point where I contacted the builder and was able to return the amp and get the JDS offering.  Just a short bit ago, I picked up a HifiMAN EF-2A tube amp.  While I love how the O2 provides a clean signal, I'm also interested in testing some amps that might potentially color the sound slightly.  In the case of the HifiMAN amp, it also has a built-in DAC where Burr-Brown chips were used.  This hobby gets bigger as the days go by.


----------



## mikeaj

Quote: 





wje said:


> Agreed.  I received a nicely-build O2 amplifier from JDS Labs on Saturday.  Prior to that time, I had been using an O2 amp build by another individual that, essentially, had problems all along.  These various issues added up to the point where I contacted the builder and was able to return the amp and get the JDS offering.  Just a short bit ago, I picked up a HifiMAN EF-2A tube amp.  While I love how the O2 provides a clean signal, I'm also interested in testing some amps that might potentially color the sound slightly.  In the case of the HifiMAN amp, it also has a built-in DAC where Burr-Brown chips were used.  This hobby gets bigger as the days go by.


 
   
  Just out of curiosity, what were the issues with the build?  (unless you earlier mentioned who the builder is and don't want to slander his/her name with more details)  I know it's a fairly easy build, but several things can go wrong, and JDSLabs even said they had issues figuring out all the tricks to get the yield rates high.


----------



## wje

Quote: 





mikeaj said:


> Just out of curiosity, what were the issues with the build?  (unless you earlier mentioned who the builder is and don't want to slander his/her name with more details)  I know it's a fairly easy build, but several things can go wrong, and JDSLabs even said they had issues figuring out all the tricks to get the yield rates high.


 

 The following issues were encountered in under a 4-month period of time:
   

 My Triad power supply died within the two-month mark.
 My metal case would emit a spark when my metal iPod housing came in contact with it.  (There was not ground established from the input jack to the case screw.)
 The amp started to get quite warm and distort.  It turns out one of the two power regulators had not been fully seated prior to soldering in place, so it sat up a bit over 1/4".  This meant that 1/4" of the metal tab, that works to absorb head from the chip was not capable of proper functionality.
 The 4 resistors just behind the input jack were not trimmed close enough to the circuit board -- meaning that they had enough length and enough of a slight bend to come in contact with the internal rail of the case.
 One of my 9V rechargeable batteries started to blister and malform a bit from its original shape - suggesting that possible the power regulators not operating correctly, could have been oversupplying a voltage to the batteries during the charging state.
   
  I understand that issues can happen.  Nothing we ban can be 100% perfect.  However, I do expect some level of reliability and being that the number of issues kept mounting, I needed to contact the seller so this could be resolved.


----------



## Willakan

Quote: 





wje said:


> The following issues were encountered in under a 4-month period of time:
> 
> 
> My Triad power supply died within the two-month mark.
> ...


 


  Point 2 would not be caused by failing to ground the amplifier to the case. The only reason grounding is recommended is because otherwise you get hum when you use it with sources with a high output impedance AFAIK. The sparks likely came from some resistors touching the screw rail (as you mentioned happened also.)
   
  As regards point 3, was the regulator's metal tab actually touching the case?
   
  This wasn't one of the 2 big builders, was it? Seems like a pretty impressive list of errors...for the batteries to be damaged something would have to be seriously wrong IMHO: would have thought stuff like that would be caught in build testing.


----------



## wje

Quote: 





willakan said:


> Point 2 would not be caused by failing to ground the amplifier to the case. The only reason grounding is recommended is because otherwise you get hum when you use it with sources with a high output impedance AFAIK. The sparks likely came from some resistors touching the screw rail (as you mentioned happened also.)
> 
> *As regards point 3, was the regulator's metal tab actually touching the case?*
> 
> *This wasn't one of the 2 big builders, was it?* Seems like a pretty impressive list of errors...for the batteries to be damaged something would have to be seriously wrong IMHO: would have thought stuff like that would be caught in build testing.


 

 To answer the items in bold:
   
  1) The regulator tab wasn't touching the case.  It had just been snipped in half so that it was the same height as the correctly mounted reglator right next to it.
   
  2) It wasn't one of the big builders at all.  I believe it was just an individual who built a few here and there to earn a few extra bucks. 
   
  My purchase was made on this amp before JDS Labs had released their offering.  If that had been the case, I would have easily gone with JDS, spent about $15.00 more and not had these hassles.


----------



## 2000impreza

Quote: 





wje said:


> The following issues were encountered in under a 4-month period of time:
> 
> 
> My Triad power supply died within the two-month mark.
> ...


 



 Sounds like first time builder mistakes. Can't go wrong with a JDS labs built O2. I recently ordered one from JDS labs as well along with a extra PCB and front plate. Could not decide to build one myself or go pre-assembled so I did both.


----------



## wje

Quote: 





2000impreza said:


> Sounds like first time builder mistakes. Can't go wrong with a JDS labs built O2. I recently ordered one from JDS labs as well along with a extra PCB and front plate. Could not decide to build one myself or go pre-assembled so I did both.


 

 My JDS Labs version is lovely.  Then, this past weekend when I learned the builder of my first O2 was providing a full refund, I went a bit nuts.  I found a builder (with an electrical engineer background) to build the amp (board and components) and I also ordered a bamboo front panel for an extra $3.00.  I'll put everything into the proper case from Allied, which is already in waiting as well as 2 power supplies that I ordered, to have a spare on hand.


----------



## silversurfer616

As I have an O2 from JDSLabs I am not really interested in all the technical details and specs everybody is going on about.Would like to read a bit more about how the amp sounds like.
  Considering that the designer said it doesn't need" burning in" I am slightly underwhelmed by this amp(but then again I only have it running for ca.30 hours and maybe a little burning in does help).Even my Little Dot MK III was better but maybe I am just a "tube"guy!
  Music has clarity,separation and a good soundstage but for me it is not engaging,not warm enough,not enough ambiance....too clinical!
  I must be a "tube"guy!


----------



## mikeaj

Quote: 





silversurfer616 said:


> As I have an O2 from JDSLabs I am not really interested in all the technical details and specs everybody is going on about.Would like to read a bit more about how the amp sounds like.
> Considering that the designer said it doesn't need" burning in" I am slightly underwhelmed by this amp(but then again I only have it running for ca.30 hours and maybe a little burning in does help).Even my Little Dot MK III was better but maybe I am just a "tube"guy!
> Music has clarity,separation and a good soundstage but for me it is not engaging,not warm enough,not enough ambiance....too clinical!
> I must be a "tube"guy!


 

 No, the sound doesn't change from any burn in.  Unless you no longer have the Little Dot MK III, there's nothing preventing you from going back to using that, so maybe that's for the best.  You can also try running the output of the Little Dot to the O2 and plugging the headphones into the O2:  if some of the "character" of the Little Dot's sound is from  the stages prior to the output rather than just peculiarities dealing with driving low impedance loads, this could be another option to try as well.  So-called double-amping is not really an actual issue, so don't let that stop you.
   
  edit: by "output" of the Little Dot, I was talking about the headphone output, not the RCA jacks out back, though that's also a possibility.  Are the RCA jack outputs just an input passthrough (in this case, going through the RCA would not do anything), or are they amplified with the pre-gain or otherwise run through part of the amp?


----------



## Shike

I saw in another thread the MKIII Is tube only (not hybrid) with a higher output impedance.  If this is true both amps will sound different as the MKIII will effect frequency response of the headphones.


----------



## palmfish

Quote: 





shike said:


> I saw in another thread the MKIII Is tube only (not hybrid) with a higher output impedance.  If this is true both amps will sound different as the MKIII will effect frequency response of the headphones.


 

 The Grados have very steady impedance across the frequency band. They might not be significantly affected by a high output impedance.


----------



## Head Injury

Quote: 





palmfish said:


> The Grados have very steady impedance across the frequency band. They might not be significantly affected by a high output impedance.


 

 That depends on the output impedance. If it's 75 ohms, for example, there will be a 1.6 dB increase in the mid-bass, which would definitely be audible.


----------



## palmfish

Audible, but subtle. Many listeners might consider it an improvement.


----------



## Shike

Quote: 





palmfish said:


> The Grados have very steady impedance across the frequency band. They might not be significantly affected by a high output impedance.


 


  Is he only using Grado's?


----------



## Head Injury

Quote: 





palmfish said:


> Audible, but subtle. With the SR325, many listeners might consider it an improvement.


 

 No one said he'd have to dislike it. It's still coloration. And 1.6 dB increase in such a critical part of the audible spectrum isn't going to be all that subtle. I wouldn't want anything over 1 dB to be safe.


----------



## palmfish

LOL!
   
  I just realized he never said what kind of headphones he's using. I was confusing him with someone in another thread.
   
  I hope he doesn't have Sennheiser HD5XX's. They have a huge impedance bump at 80-100 Hz.


----------



## wje

I love the O2 amp.  However, last evening, I had been using my HifiMAN EF-2A for about an hour and getting acclimated to the sound - with my Fostex T50RPs.  I then took the headphones up to bed, so I could go to sleep.  I noticed quite a difference in the sound signature.  Considering the O2 is an amp designed to not color the sound (as is the intent of most amps), I realized that some color can be good.  In that case, the HifiMAN had me quite impressed for a hybrid.  I need to run it this weekend with my HifiMAN headphones and see how it compares to the O2.  I still won't pull my O2 amps from use, though.  They do a great job, too.


----------



## otinkyad

Has there been a comparison of O2 to Violectric V200?  I've seen some comments where both are mentioned, and some discussion that someone was going to do a comparison (Naim.F.C...?) but haven't been able to find an actual comparison.  Sorry if I've overlooked a review somewhere, I did search a fair amount.


----------



## lukeahale

I see no reason this should be in the Sound Science forum whatsoever.  There was a short discussion that if taken by itself might be, but other than that, I see very little difference in this thread than any other amp review thread. Does 1% of "sound science" override 99% of headphone amp review discussion?. . . not trying to cause a fuss, just not understanding the logic.


----------



## everlong

How does the T50rp(with simple mod) pair with the O2? Will it lack in power for the T50rp?


----------



## mikeaj

Quote: 





everlong said:


> How does the T50rp(with simple mod) pair with the O2? Will it lack in power for the T50rp?


 

 It should get something like 5-6V cleanly into something with about 50 ohms impedance.  That should be way plenty of power even with plenty of mods.  IIRC maverickronin (or who else was it?) has some modded T50RP and the O2, so maybe you can ask him.


----------



## wje

Quote: 





everlong said:


> How does the T50rp(with simple mod) pair with the O2? Will it lack in power for the T50rp?


 

 I'm using my T50RPs (modified) with the O2 amp - as well as some other amps, too.  However, the O2 pairs really well with the Fostex headphones after modifications (which tend to make the T50RP less efficient than when stock).


----------



## upstateguy

Quote: 





wje said:


> I love the O2 amp.  However, last evening, I had been using my HifiMAN EF-2A for about an hour and getting acclimated to the sound - with my Fostex T50RPs.  I then took the headphones up to bed, so I could go to sleep.  I noticed quite a difference in the sound signature.  Considering the O2 is an amp designed to not color the sound (as is the intent of most amps), I realized that some color can be good.  In that case, the HifiMAN had me quite impressed for a hybrid.  I need to run it this weekend with my HifiMAN headphones and see how it compares to the O2.  I still won't pull my O2 amps from use, though.  They do a great job, too.


 


  Here's an experiment for you.
   
  See how closely you can EQ your O2 to the sound signature of your EF-2A.


----------



## wje

Quote: 





upstateguy said:


> Here's an experiment for you.
> 
> See how closely you can EQ your O2 to the sound signature of your EF-2A.


 

 That's a good idea.  I'm assuming that you mean using the EQ on the iTunes side to set the EQ into the song, or set one of the EQ defaults and save it to the player and see I can change the sound more like the O2.  I'm capable of doing that, but for the moment, I'm just appreciating the differences between the two - as I think they are good at complimenting each other.  I also have the C&C BK portable amp that I could try again, too.  It would be interesting to see / hear how it compares in the mix with the O2 and EF-2A amps.  The C&C amp does have some adjustments that can be applied on the amp itself - a bass boost, and a spatial adjustment, where you can use the switch to slightly open up the sound stage of your music a bit.
   
  It's all fun, though.


----------



## maverickronin

Quote: 





everlong said:


> How does the T50rp(with simple mod) pair with the O2? Will it lack in power for the T50rp?


 

 It should be fine.  My source and gain configuration currently give a maximum of 5Vrms and even with ReplayGain and some EQ the O2 still has plenty of headroom.
   
  When watching movies with a 5.1 to binaural DSP I turn the LFE channel up a ton to try and make up for the fact that I can't use a sub or speaker system and can sometimes crank the O2's volume to the max that way but with normal music I never come close to doing that.


----------



## upstateguy

Quote: 





wje said:


> That's a good idea.  I'm assuming that you mean using the EQ on the iTunes side to set the EQ into the song, or set one of the EQ defaults and save it to the player and see I can change the sound more like the O2.  I'm capable of doing that, but for the moment, I'm just appreciating the differences between the two - as I think they are good at complimenting each other.  I also have the C&C BK portable amp that I could try again, too.  It would be interesting to see / hear how it compares in the mix with the O2 and EF-2A amps.  The C&C amp does have some adjustments that can be applied on the amp itself - a bass boost, and a spatial adjustment, where you can use the switch to slightly open up the sound stage of your music a bit.
> 
> It's all fun, though.


 
   

 Actually I was thinking you would be using the EQ on something like foobar and adjusting the O2 until it approximated  the sound signature of your EF-2A.
   
  I doubt you could successfully adjust any of the other amps to sound like an O2 because they lack the transparency and resolution.


----------



## Satellite_6

With stock tubes the EF2A is rather bright and distorted. . . a solid state amp should sound noticeably clearer.


----------



## Zsubbo

I had both, (the O2 and the EF2A), the O2 is noticeably better, they are not in the same league IMO, but you can start tube rolling, and can find out, if it's your thing or not. (BTW, some cheap Chinese amp from eBay, like the Indeed or the Bravo would be better for this IMO)


----------



## wje

Quote: 





upstateguy said:


> Actually I was thinking you would be using the EQ on something like foobar and adjusting the O2 until it approximated  the sound signature of your EF-2A.
> 
> I doubt you could successfully adjust any of the other amps to sound like an O2 because they lack the transparency and resolution.


 
   
  Ahh, I see.  Yes, that would be a good option.  Though, I don't think too highly of the built-in DAC on the EF-2A.  It will really take quite a bit of EQ work to get it corrected.

  
  Quote: 





satellite_6 said:


> With stock tubes the EF2A is rather bright and distorted. . . a solid state amp should sound noticeably clearer.


 

 I'm assuming I'm running the stock tubes, or so it was indicated to me by the seller.  I haven't found the EF-2A to be bright at all.  I used to be a big fan of the Grado house sound, so I do realize when I'm listening to something with a lot of detail -- above and beyond the natural detail of the O2 amp.  I haven't pushed the EF-2A to the point where my ears could detect distortion - then again, by the time it reached that level, it might be too late to prevent damage.
  
   
  Quote:


zsubbo said:


> I had both, (the O2 and the EF2A), the O2 is noticeably better, they are not in the same league IMO, but you can start tube rolling, and can find out, if it's your thing or not. (BTW, some cheap Chinese amp from eBay, like the Indeed or the Bravo would be better for this IMO)


 

 I think it depends on a lot of variables.  The EF-2A can be found at some pretty great prices that can be a bit less than the O2 amplifier itself.  It also depends on one's listening desires.  Some may prefer the tube sound over the solid state sound of the O2. 
   
  I'm not here trying to defend the EF-2A because I own one, but rather, point out my personal experiences with it by purchasing one that was used and has some time logged on it.  Also, I feel my observations are also objective regarding the Objective2 amplifier, because I own (2) of them.  So, I have no reason to be hatin' on the O2.


----------



## essencez

Objective2 is a very special amp. I am currently awaiting the adapter to see if it'll dominate my long time favourite portable, RSA P-51 Mustang. Sure the O2 isn't as portable but the fact it can run on batteries alone is a huge plus. Mainly the reason why I got it.
   
  Using it with diyMod LOD + DT48e showed even on a 1x gain setting the amp packs a lot of punch for its size. I am testing with so far, uncharged version of the amp straight from JDS Labs too. Hopefully within the next few months the Objective DAC gets released and meets the high expectations set by the O2 amp. And google Android developers can finally fix the lack of support for native audio DAC devices. Then HiFi portable setups won't be monopolized by Apple and the limited amount of digital out devices.


----------



## gkanai

Hi everyone,
   
  I'm based in Japan (100 V, 50 Hz / 60 Hz) and am interested in an O2.
   
  I asked Voldemort what power adapter I should get and he said:
   
  Quote: 





> If you can find a 120 VAC to 18 VAC adapter you can use an adapter plug and run it on 100 volts and you will get 15 VAC output. Even a 16 VAC will work OK like the ones in the parts list.


 
   
  I want to be sure I get what I need. Can someone help me identify exactly which Mouser part number is the one I want? Thank you in advance!


----------



## sonitus mirus

In Japan, you need an adapter plug so the US power adapter can get juice from the wall.  
   
  Something like this will suffice:
   
http://www.amazon.com/Adapter-America-Japan-Grounded-Polarized/dp/B001FDC72A
   
  You can then use an AC adapter from Mouser (model number 412-218054) that will output 18VAC with .5A with a nominal input voltage of 120VAC.
   
http://www.mouser.com/ProductDetail/Xicon/412-218054/?qs=DSkiUaeR7Kd3FFc9bqoJoQ%3d%3d
   
  With 100VAC, you should get 15VAC output and just over 400 mA, right in the wheelhouse for the O2.
   
  Any similar adapter will work, just be sure the output of the adapter is AC and not DC.  DC output is much more common, and it would be easy to make the mistake.
   
(Edit: removed poor suggestion)


----------



## mikeaj

I would advise against a 24VAC (from 120V input nominal) adapter, since on a 100V line that's nominally 20VAC with probably a little more on a low load considering the high wattage rating.  That's just unnecessarily high and will produce more excess heat in the regulators.
   
  Any kind of 16-18VAC (from 120V input nominal) is preferred I would say.  The Xicon above or even the WAU16-400 Triad should be okay:
http://www.mouser.com/ProductDetail/Triad-Magnetics/WAU16-400/?qs=IW9Tsl75qsVPD8fyORcCjg%3d%3d


----------



## sonitus mirus

Thanks for the correction about the 24VAC adapter.  I removed this from my previous reply.


----------



## mikeaj

Well actually on second thought I checked the docs and he says up to 22VAC unloaded is okay, so maybe that was a little bit of an overreaction.  It's possible that 20VAC nominal could be over 22VAC unloaded though, and regardless that still is a bit unnecessarily high.  Personally in the US I use the WAU12-200 which is just 12VAC nominal (close to 13.5VAC unloaded), but I don't have any particularly insensitive low-impedance headphones that would require higher power draw.


----------



## darren700

i was wondering where this thread disappeared too... guess it was getting to much attention for the amp forum.


----------



## gkanai

Thanks for the guidance on the power adapters for Japan.

 One further question: I'm going to pick up the rechargeable NiMH 9V batteries for using the O2 on the road. Do I need to get the chargers for those batteries separately? (I'm assuming that the O2 doesn't charge the batteries via USB or via the power adapter?)


----------



## pekingduck

The O2 DOES charge the batteries so you don't need a separate one 
	

	
	
		
		

		
			




  
  Quote: 





gkanai said:


> Thanks for the guidance on the power adapters for Japan.
> 
> One further question: I'm going to pick up the rechargeable NiMH 9V batteries for using the O2 on the road. Do I need to get the chargers for those batteries separately? (I'm assuming that the O2 doesn't charge the batteries via USB or via the power adapter?)


----------



## gkanai

Quote: 





pekingduck said:


> The O2 DOES charge the batteries so you don't need a separate one


 


  Awesome! Thanks for the info.


----------



## 129207

Why is this in the sound science forum? C'mon people, even without the whole Voldemort drama, this is just an amp review thread! Let it rest already and accept the O2 as part of the Head-Fi community. Make amps, not war and whatnot.


----------



## darren700

negakinu said:


> Why is this in the sound science forum? C'mon people, even without the whole Voldemort drama, this is just an amp review thread! Let it rest already and accept the O2 as part of the Head-Fi community. Make amps, not war and whatnot.




this!


----------



## zzffnn

My gut feeling is that this thread was moved to Sound Science forum to minimize its "fame". This thread was/is clearly active enough to be listed as Most Active Thread on Headfi's home page, but it has never been there.
  
 To be fair though, there has been quite a lot of technical talk here in this thread, which is hard to understand for anyone without some good Electronic Engineering training. In that sense, this thread is not purely a review thread. Although it is weird to see it in Sound Science as well.
  
 The designer of this amp might be a bit too aggressive in his comment towards some Headfi sponsors, even thought some of his comment seems to be blatantly honest or based on data. Headfi moderators do not like him, which is understandable. Let us face it, if each and every Headfi sponsor is "attacked" and retracts sponsorship, we will not have such a thriving online community that we have today.
  
 We need those sponsors. Just let newbies or people who doe not care about measurement support those "technically inferior" gear. Sometimes "technically inferior" gears may sound good actually.
  

  
 Quote: 





darren700 said:


> i was wondering where this thread disappeared too... guess it was getting to much attention for the amp forum.




  
 Quote: 





negakinu said:


> Why is this in the sound science forum? C'mon people, even without the whole Voldemort drama, this is just an amp review thread! Let it rest already and accept the O2 as part of the Head-Fi community. Make amps, not war and whatnot.


----------



## mikeaj

I think there have been quite a few newbies who have gotten the amp from JDSLabs, Epiphany, or through DIY (by themselves or by somebody else).
   
  Maybe the upcoming ODA (desktop version) will be even more popular, since it will have a few more conveniences like better jacks placements and more options there, and I think more gain options.  Some people were a bit confused by the gain / clipping amounts for the O2, though it's really not that complicated if you can find the information.  It should still be relatively small and transportable, though not usable on batteries.


----------



## zzffnn

I really want more people to hear this lovely O2 amp. It plays very well with LCD2s, Dt880/600, and my IEMs (Westone ES3Xs). Transportable size and full size performance. It is hard to beat at $150. 
Edit to correct grammar errors.


----------



## upstateguy

post removed by request


----------



## mikeaj

Nevermind, original post wasn't so relevant in hindsight.


----------



## zzffnn

Let us get back to the REVIEW of O2 amp.
  
 Edit:
  
 I was just saying that this O2 amp review thread fits better in the Amp forum..........


----------



## upstateguy

Why doesn't someone start another* NwAvGuy's O2 DIY Amplifier* thread in the amp forum, so we can pick up where we left off


----------



## zzffnn

I used to own both Objective2 amp and Hifiman HM-801 (stock discrete amp card) at the same time. I did some careful comparison. I eventually sold the HM801 and now live happily with O2. Please read on and see why.
   
        Comparing HM801 vs iPhone 3GS -> O2 amp:
   
        1) From LCD-2 r1s
My ears prefer the O2 rig slightly. HM801 sounds more veiled and lacks transparency, although its large soundstage is appreciated. I do prefer slightly warm and laid-back sound in general, however HM801 with LCD2 r1s are too warm / laid-back for most of my music listening. The O2 rig provides more realism, dynamic contrast and resolution, although the perceived soundstage depth is slightly less.
   
         2) From Westone ES3Xs
My ears CLEARLY prefer the O2 rig. With HM801 (and in comparison with O2 rig), bass sounded loose, treble was too laid-back and transparency is lacking. Even though HM801 is more portable, I still found myself turning more to the O2 rig.
   
         3) From DT880/600ohms
I slightly prefer HM801, which added warmth to DT880s. DT880s are slightly bright to my ears, so they welcome the warmth added by HM801 to bass and mid range, along with slight reduction in treble. I can understand it if a detail freak would prefer O2 with DT880s though, because everything there is crystal clear and bass is fast and tight along with good impact.  
   
        4) MarkL damped Creative Aurvana Live or V-MODA V80
Not too much difference really. I can live with either rig happily. 
   
       So in summary, HM801 does not worth $400 more for me (I would rather put that extra $400 into desktop rig). Neither rig sounds as good as my AMB Gamma2 coupled with Beta22 and neither rig is truly portable. As a transportable rig, O2 amp attached to iPhone 3GS or Sansa Clip is slightly larger in size than HM801, but offer similar or better performance for much less money. 
   
       Note: All impressions herein were obtained with volume matched to average of 82 db (except for Westone ES3Xs, wherein I volume-matched by ear).


----------



## peanuthead

Did you just volunteer? 
  
  Quote: 





upstateguy said:


> Why doesn't someone start another* NwAvGuy's O2 DIY Amplifier* thread in the amp forum, so we can pick up where we left off


----------



## upstateguy

Quote: 





zzffnn said:


> Neither rig sounds as good as my AMB Gamma2 coupled with Beta22 and neither rig is truly portable.


 


  I would like to hear more about that comparison.


----------



## zzffnn

@ upstateguy
   
      I am not sure comparing AMB Beta22 with Objective2 is fair, in view of the difference in size, part cost/quality and power supply.  However, since you asked for it, here it is.
   
     Overall Beta22 provides better musical immersion, soundstage depth (O2 is more upfront in presentation) and dynamic contrast.  
   
      In bass region, Beta22 hits noticeably harder and deeper than O2. Speed, tightness, and resolution is about on par.
   
      In mid region, they are on par. Music may sound slightly closer to you with O2, which maybe a good thing if you want a more forwarded presentation (in comparison sense, as neither is overly forward).
   
      In treble region, Beta22 sounds noticeably more laid-back (but still clear/clean enough for my ears). O2 let you hear treble more closely when you are analyzing or monitoring. When using some bright headphones such as DT880s or K701s, I would prefer Beta22 over O2. If you have some music that sounds aggressive and trebly, Beta22 may work better. If your music sounds too distant for you to start with, I would suggest using O2.   
   
     To my ears, Beta22 is worth the difference in cost. If I do not need portability, I would always use Beta22. My Beta22 is a simple 2 board built with a separated Sigma22, but they weight 10lb+ easily.
   
       I bought AND KEPT O2 because:
   
      1) O2 does not sound far less than my previous AMB M3 (based on memory only, sorry can not offer impression between O2 vs M3. But based on side-by-side comparison, my ears did prefer Beta22 over M3 overall and especially in terms of soundstage, musical immersion and refinement);
   
      2) O2 is transportable (i.e., fits in my jean pocket) and drives LCD-2s sufficiently when I need a clean portable amp around my house. O2 is cheap but good enough to be my secondary rig outside of my man cave (which has Beta22).
   
      3) O2 can be used as a battery-powered pre-amp that is free of noise (e.g., no ground loop), if you do not mind using adapters. O2 drives my FirstWatt F2 clone beautifully without any noise. By contrast, I had to have my M3 modified to work as a pre-amp (M3's stock gain 11X and ground loop caused noise).


----------



## stv014

Quote: 





zzffnn said:


> 1) O2 does not sound far less than my previous AMB M3


 

 It should not be worse in theory than the Mini3, quite the opposite in fact.


----------



## zzffnn

I did Not mean Mini3. No one here use M3 to represent Mini3.
  I was just too lazy to type MMM or M^3. I meant M^3 with Sigma11. Not Mini3 with some batteries.


----------



## 2000impreza

Quote: 





zzffnn said:


> @ upstateguy
> 
> I am not sure comparing AMB Beta22 with Objective2 is fair, in view of the difference in size, part cost/quality and power supply.  However, since you asked for it, here it is.
> 
> ...


 



 Interesting comparison between the Objective 2 against the Beta22 and the bit on the M3 at the end. I have been considering putting together a M3 to see how it stacks up against the Objective 2. The Beta 22 seems like quite a step up from the Objective 2. I would imagine the future up coming desktop version of the O2(ODA) would better compete against it.


----------



## zzffnn

@ 200impreza,
   
  I suggest that you build both M3 and O2 and decide for yourself.
   
  M3 may sound better than O2. I just can not remember it as I did not have O2 and M3 side by side.  When I had M3 and Beta22 side by side, M3 did not impress me enough sonically for me to keep it. Utility wise, M3 is the same as Beta22 (not portable).
   
  While O2 can not compete with Beta22 in sonic performance either, its portability attracts me enough to keep it.
   
  I do not know if ODA would be better if its power supply section is not improved further.


----------



## mikeaj

With this design, as has been established earlier (I'm skipping the details here), an improvement in the power supply shouldn't make a difference in the sound.
   
  That said, ODA should have a different power supply scheme, so the power supply performance could be improved.  Actually, a different PCB and layout probably could potentially improve performance more than a change of power supply, and the ODA will have that as well.  Maybe the hotter components will be moved away from the electrolytic capacitors, which could improve their lifespan from maybe a decade or two, to more decades.  Anyway, the key point is that _the designer doesn't even expect the ODA to sound different than the O2_, unless I've misinterpreted things, so I wouldn't hold off on the ODA expecting it to be much better from a sound quality point of view.  I don't expect all listeners to agree though, so it'll be interesting to see what peoples' impressions are.
   
  The more interesting thing is the ODAC I think.  And that fits into the O2 default enclosure if you remove the batteries, as well as the ODA, but of course it can be used as a standalone DAC too.  Anybody planning to get an ODAC?  (I probably won't.)  Are you willing to give up on the batteries?  I rarely make use of the battery operation, but maybe others use it much more.  I guess the ODAC will need its own thread when the time comes.


----------



## zzffnn

I guess I would wait for a portable O2 with an integrated ODAC that takes USB, optical and coaxial inputs (in other words, something better than Fiio E17). The current ODAC takes USB only. The designer is surely right in that more people use computer as source, thus a good USB dac would be more helpful.
   
  However, there are also people (like me) who wants coaxial and optical dacs to work with CD players, Squeezebox and PS3. The benefit of being portable is that you may only need one for your entire house (as opposed to multiple rigs for multiple rooms). Desktop rigs surely sound better than portables;  however when you have a good desktop rig already, you may not want to spend that much more for a 2nd or 3rd rig.


----------



## Draygonn

mikeaj said:


> The more interesting thing is the ODAC I think.  And that fits into the O2 default enclosure if you remove the batteries, as well as the ODA, but of course it can be used as a standalone DAC too.  Anybody planning to get an ODAC?  (I probably won't.)  Are you willing to give up on the batteries?  I rarely make use of the battery operation, but maybe others use it much more.  I guess the ODAC will need its own thread when the time comes.




I'm planning on getting an ODAC for my secondary rig, placing it inside the Crack's enclosure. I haven't used the O2's batteries yet but I'll try out the O2/Thunderpants combo on my next cross country flight.


----------



## upstateguy

Quote: 





zzffnn said:


> @ upstateguy
> 
> I am not sure comparing AMB Beta22 with Objective2 is fair, in view of the difference in size, part cost/quality and power supply.  However, since you asked for it, here it is.
> 
> ...


 

 Sounds to me like your B22 is coloring the sound a bit, boosting the bass and depressing the treble.  My O2 sounds like a less powerful GS-1 while my M^3 sounds like a less powerful beta. 
   
  Both the O2 and the GS-1 have a greater transparency more resolution than the M^3, which interestingly, colors the sound in the same way your beta does.
   
  I haven't compared the GS-1 with a beta in a while but when I did, I felt the GS-1 was cleaner and more transparent and the Beta more powerful and capable of higher volumes.


----------



## 129207

Quote: 





upstateguy said:


> Sounds to me like your B22 is coloring the sound a bit, boosting the bass and depressing the treble.  My O2 sounds like a less powerful GS-1 while my M^3 sounds like a less powerful beta.
> 
> Both the O2 and the GS-1 have a greater transparency more resolution than the M^3, which interestingly, colors the sound in the same way your beta does.
> 
> I haven't compared the GS-1 with a beta in a while but when I did, I felt the GS-1 was cleaner and more transparent and the Beta more powerful and capable of higher volumes.


 

 Obtained an O2 through a great friend of mine and he's shipping it to me as we speak. It's the JDS Labs build. Can't wait to get my grubby paws on it and dirty fingerprints all over it.


----------



## zzffnn

[size=10.0pt]@ upstateguy[/size]
 [size=10.0pt]Your sound description may be absolutely right if it is in relative terms. Some times it is really hard to say what is neutrality as opposed to coloration. [/size]  [size=10.0pt]I guess it is more of a preference thing. One person’s definition of “coloration” may be another person’s “neutrality”, just like [/size][size=11.0pt]one person’s “greater transparency / more resolution” may be another person’s “brightness[/size] [size=11.0pt]coloration”.[/size]  [size=10.0pt]I am quite sure GS-1 and Beta22 will reveal similarly impressive measurements (e.g., frequency response and slew rate, ect). Still, one individual may prefer Beta22 because of 100 factors, 50 of which may not applied to another individual. [/size]


----------



## Satellite_6

Quote: 





zzffnn said:


> [size=10.0pt]@ upstateguy[/size]
> [size=10.0pt]Your sound description may be absolutely right if it is in relative terms. Some times it is really hard to say what is neutrality as opposed to coloration. [/size]  [size=10.0pt]I guess it is more of a preference thing. One person’s definition of “coloration” may be another person’s “neutrality”, just like [/size][size=11.0pt]one person’s “greater transparency / more resolution” may be another person’s “brightness[/size] [size=11.0pt]coloration”.[/size]


 

 You could just look a FR graph and figure out who's right. . .


----------



## mikeaj

I can appreciate different preferences and perceptions of what the sound is, but for a quick sanity check, figuring out the frequency response would be very easy and doesn't require any expensive equipment.  Something like "boosted bass" doesn't leave much other room for interpretation, so that can be readily confirmed or denied.
   
  You can test output voltages with a decent multimeter using 0 dBFS (or any level) test tones and record the result.  If the result is different at different frequencies and your multimeter can actually measure voltages correctly across the audio frequency range, then the FR is not flat.
   
  If it's a 2-channel amp, then you could just use RMAA loopback through the amp.  A 3-channel Beta22 or M^3 wouldn't appreciate the active ground being shorted to the sound card line in ground though.  Most people probably don't have an interface with a floating ground input.


----------



## zzffnn

@ Satellite_6,
   
  ^ No offence, but have you compared the FR between O2 vs. Gs-1 vs. M^3 vs. Beta22? I bet you 5 bucks that all 4 amps produce ruler flat FR from 20 Hz-20k Hz.
   
  My 2cents:
   
  1) flat frequency response alone may not mean neutrality to ears. An amp with rule flat FR may not sound neutral to ears (that flat FR amp may sound edgy / bright or warm / musical), because of distortion, slew rate, sound decay or circuit design.
   
  2) FR graph is not music. Let your own ears judge and do not just rely graphs alone. Your individual preference is likely determined by 100s of graphs, which no one can predict.
   
  3) We are reviewing an amp here to help future / potential buyer, so it is probably irrelevant to argue what is neutrality or if neutrality is always preferred. It would be up to an individual's preference eventually (e.g., Some people may be sensitive to treble while some love treble).
   
  4) To be helpful in providing an impression, I suggest that we compare sound of amps in relative terms, e.g.,  "amp X has more perceived treble presence than amp Y".


----------



## palmfish

Quote: 





zzffnn said:


> @ Satellite_6,
> 
> ^ No offence, but have you compared the FR between O2 vs. Gs-1 vs. M^3 vs. Beta22? I bet you 5 bucks that all 4 amps produce ruler flat FR from 20 Hz-20k Hz.
> 
> ...


 

 Amp performance is influenced by the load it's driving too. A "neutral amp" may sound warm driving a low impedance headphone that has a mid-bass region impedance hump.
   
  Personally, I never understood the attempt to find "synergy" between an amp and headphone. Why do I read so many comments about folks who have a bright and crisp headphone and then they try to warm it up with an OTL amp and EQ?
   
  If your amp is neutral with low output impedance, then you're free to choose a headphone that sounds right to you out of the box. This is why I like the O2 so much


----------



## mikeaj

Quote: 





zzffnn said:


> ^ No offence, but have you compared the FR between O2 vs. Gs-1 vs. M^3 vs. Beta22? I bet you 5 bucks that all 4 amps produce ruler flat FR from 20 Hz-20k Hz.


 
   
  I think that's the point being made.  And I think all of these have fairly low output impedance, so it's not going to depend on the headphones too.
   
  The next questions are then about if those listening impressions are consistent, and _why_ people may hear one to have more or less bass, treble, or whatever presence or quantity or whatever (some aspect of the performance characteristics other than FR, or imagined?).  If there's a difference and if we understand why, then we can subjectively review the amps more accurately and give better amp recommendations in the future, taking this into mind.
   
   
  There's a distinction between "sound neutral" and "neutral" that's been discussed previously of course, but I'd emphasize that you can't listen to amps without transducers and I'd agree that different people have different ideas of what sounds right, so "sounds neutral" is a lot more difficult to define.  I think it's better for everybody to converge on the same reference points and terminology, so subjective reviews are more consistent between different people (of course it'll never be close to exact) and thus useful.  Defining what's most mathematically neutral as the reference point, would be the natural way for a number of reasons.


----------



## maverickronin

Quote: 





palmfish said:


> Personally, I never understood the attempt to find "synergy" between an amp and headphone. Why do I read so many comments about folks who have a bright and crisp headphone and then they try to warm it up with an OTL amp and EQ?
> 
> If your amp is neutral with low output impedance, then you're free to choose a headphone that sounds right to you out of the box. This is why I like the O2 so much


 

 EQ is a pretty useful tool.  I wouldn't dismiss so quickly.
   
  From a practical and economic point of view I think the best way to find "your sound" is to start with the headphones.  They have more affect on the final sound then all the rest of your hardware combined.  In theory the DAC and amp are just as important but in practice the variation between different models of DACs or amps is almost always miniscule as compared to the differences between of headphones so excepting models that require unusual amps like 'stats or the K1000 and HE-6 always pick the headphones first.  Even if you have an unlimited budget there are only so many models of headphones to choose from so finding one that's perfect for you out of the box requires a lot of luck and you might need more tweaking.
   
  Next I'd try modding the headphone since the mods will "follow" the headphone and affect its sound from any source.  Depending on your skill, confidence, and budget (not many people will want to try and mod expensive flagships) you might not be able to get satisfactory results.  I think its still worth mentioning for those with an adventurous streak.
   
  The next step is software EQs and DSPs but they aren't a panacea either.  Even if your computer is your only source they don't "follow" everything perfectly as they're usually set up in a single program and not "system wide" affecting everything you might play.  Despite that limitation I place them here because they're usually free or pretty cheap.  You can spend thousands on name brand professional mastering VST plugins if you want to though.
   
  After that I'd try hardware filters, EQs, or DSP boxes.  They can be used with more sources than a purely software solution but often they're more expensive and aren't as customizable so I place them after the software types.  Example of these such as crossfeed circuits and tone controls seem to be the most common and accepted of these sorts of tweaks among the head-fi community.  The Smyth Realiser is now making a strong case for hardware DSPs as well but its price keeps it a niche within a niche.  Hardware EQ boxes seem nearly unheard of on here though.
   
  Only after all that would I consider looking for "synergy" between a headphone and an amp or DAC.  Clean and neutral components take many variables out of equation and give you a blank slate to create your desired sound.  As the Objective2 shows they can be a lot cheaper as well.  Even after factoring in a large budget for professional VST plugins or hardware DSP boxes you'll likely save as compared to something like a TOTL tube amp plus a tube rolling budget.
   
  Of course your preferences might actually lead you towards a "synergistic" DAC or ampin the end even if you try all the other steps I listed.  No off the shelf product I know of will replicate the sound of a specific amp and unless you're Bob Carver you probably aren't going to be able to do it yourself either.  There are other factors besides the just the sound that some may consider as well.  Besides practical features I think tube amps just look amazingly cool.  It's only the fact that making one which sounds as clean as the O2 would be monstrously expensive that keeps me from using one instead.
   
  In the end what you like is what you like (assuming it's actually real and not just in your head anyway) and there's nothing wrong with that.  I just think that from a cost perspective jumping to a new amp or DAC to change the sound usually be at the bottom of the list of things to try.  There are plenty of people here who don't have to worry about that sort of thing and can pretty much buy whatever they like.  If you know what you're getting into then go right ahead.
   
  What I hate is when newbies are given the impression that you have to spend big bucks on a DAC and amp for a good headphone to sound better than a cheap one.  The endless, "oh its your amp/DAC no wonder you think audiophile headphone X sucks" sort of comments around here convince people to spend money on things they don't need or want.  Even if their DAC or amp really does suck that's probably still not why they don't like headphone X.  The sort of differences most people in this hobby care about are tiny on an absolute scale.  They get blown out of proportion on here and some people keep spending money on upgrades waiting for a revelation that never comes.  For the most part plugging a new pair of good headphones straight in your iPod is the biggest revelation you're going to get.  If someone doesn't think that's worth the money then they sure aren't going to think the smaller improvement a better amp may bring will be worth it either.
   
  This wandered quite a bit, and most of it isn't really even directed at palmfish, who I quoted, but I felt like a rant today for some reason...


----------



## Satellite_6

Quote: 





zzffnn said:


> @ Satellite_6,
> 
> ^ No offence, but have you compared the FR between O2 vs. Gs-1 vs. M^3 vs. Beta22? I bet you 5 bucks that all 4 amps produce ruler flat FR from 20 Hz-20k Hz.
> 
> ...


 

 Meaning they should probably probably all sound the same in terms of neutrality. I'm not sure how distortion and circuit design can affect neutrality if the FR is flat. I can't see how listening to the same music at the same volume with the same headphones through an amp with the same flat FR is going to result in different neutrality. I think my preferences are going to remain with headphones and not listening to amps. We could compare in relative terms through subjective impressions (with conflicting opinions all over the place no doubt) or we could figure out through measurement which amps change the sound and which do not, or if they should all sound the same. Sorry, I'm just talking hypothetically and being argumentative, so I'll stop now anyway.


----------



## zzffnn

I can see that we all agree on certain things, although not all things.
   
  I agree that headphones (transducers) tend to affect sound more than amps. Of course, we should try to compare amps using the same headphones, if possible.
   
  I am not sure you can compare sounds of amps by comparing measurements alone; I am not saying that measurements are not important, I meant that you should also take a good listen because measurements do not always tell the full story. I bet that you would not be able to compare amps very well, If you just compare FR graphs. Case in point here is that all the 4 amps mentioned above should be dead neutral / flat according to FR, but ears tend to believe M3/Beta22 sounds slightly warmer than O2/GS-1.
   
  I guess neutrality according to Satellite_6 should be always measured by machine. I was mainly talking to Upstateguy, because his neutrality is apparently based on ears not scope.
   
  Example for distortion affecting neutrality (perhaps I should say PERCEIVED neutrality here):
  one example is that odd-order distortion may impart some PERCEIVED brightness to sound, even though an amp that produces the odd-order distortion reveals ruler flat FR; in this case ears may think that said odd-order-distortion-producing amp is bright instead of neutral. Conversely, even-order distortion may be perceived as warmth by ears. 
   
  Examples for circuit design affecting neutrality:
  The MOSFET in M^3 is usually consider to be warm sounding. Another example is that OPA627s / 637s in M^3 are usually considered warmer or more laid-back sounding that AD8610s (which some considered as cold/bright) or AD843s in otherwise the exact same circuit of M^3.   I heard OPA627s vs AD843s in M^3 and have to agree that OPA627s sounded warmer and more laid-back.

  
   
  Quote: 





satellite_6 said:


> Meaning they should probably probably all sound the same in terms of neutrality. I'm not sure how distortion and circuit design can affect neutrality if the FR is flat. I can't see how listening to the same music at the same volume with the same headphones through an amp with the same flat FR is going to result in different neutrality. I think my preferences are going to remain with headphones and not listening to amps. We could compare in relative terms through subjective impressions (with conflicting opinions all over the place no doubt) or we could figure out through measurement which amps change the sound and which do not, or if they should all sound the same. Sorry, I'm just talking hypothetically and being argumentative, so I'll stop now anyway.


----------



## palmfish

Quote: 





maverickronin said:


> EQ is a pretty useful tool.  I wouldn't dismiss so quickly.


 


  I wasn't dismissing EQ and never said it wasn't useful.
   
  What I said was that EQ should not be thought of as a band-aid for "fixing" headphones that you don't like.
   
  If you don't like bright, sibilant sound, don't buy a pair of Grados and hope you'll find a "warm" amp to tame the treble. Just buy headphones that aren't sibilant.


----------



## thehadi

Hello all,
   
  I bought JDS Labs O2 and i would like to buy HD800. For a while i will use iBasso DX100 as a source. May be in a few months i will buy a proper DAC.
   
  How is O2 with Senn HD800? Should i look another amp or O2 is well with it?
   
  Thanks


----------



## Maxvla

I'd like to know as well. Considering a HD800 and will get the objective amp + dac when it's released, primarily for my UERM.


----------



## upstateguy

Quote: 





zzffnn said:


> *The MOSFET in M^3 is usually consider to be warm sounding. Another example is that OPA627s / 637s in M^3 are usually considered warmer or more laid-back sounding that AD8610s (which some considered as cold/bright).... *


 

 Grasshopper, you couldn't be more incorrect.
   
  If you were to ask Ti Kan, he would tell you that 637/627s sound exactly the same as 8610s in an M^3.
   
  In fact, more than a few years ago, I sent him WAVs of the 637/627s and the 8610s so he could hear the differences himself.  He nulled them with audacity and sent me back the difference which was at -45dB (instead of complete silence),  because he had to invert and line up the wave forms by eye.
   
  Now what?


----------



## zzffnn

I guess if you don't think HD800s are too bright and like them to start with, then O2 amp may suit you.

Please take my comment with a grain of salt. I prefer slightly warm and laid back sound (I am sensitive to treble). I do not like HD800s to start with, so I would prefer HD800s on OTL tube amp to obtain warm coloration. If I have to go with solid state amp, I would prefer M3 with OPA627s or Beta22 over Objective2 or GS-1; in other words, I prefer "treble polite" amp with HD800s.


----------



## zzffnn

Upstateguy,

Firstly I am not Grasshopper.

Secondly, if you want to discuss opamp rolling with M^3, I invite you to continue on the thread for M^3. Not here.

Thirdly, opa637 requires different gain value than opa627. Are you sure your WAC files are volume matched to start with (gain value affects volume).

Fourthly, I would like to know how Ti Kan proved that those two opamps "sound the same". Please continue with me on PM if you care. Let us not go off topic.


----------



## Draygonn

thehadi said:


> How is O2 with Senn HD800? Should i look another amp or O2 is well with it?




I enjoy my 02 with the HD800s. The E9 lacked soundstage and detail with the HD800s. The O2 seems to do everything right. It sounds a little thin compared to the WA2 for obvious reasons but I don't have an expensive SS amp for comparisons. Too bad we didn't get Naim's O2 vs V200 comparison.


----------



## palmfish

In keeping with the "sound science" theme...
   
  http://www.engadget.com/2008/03/03/audiophiles-cant-tell-the-difference-between-monster-cable-and/


----------



## thehadi

Quote: 





draygonn said:


> I enjoy my 02 with the HD800s. The E9 lacked soundstage and detail with the HD800s. The O2 seems to do everything right. It sounds a little thin compared to the WA2 for obvious reasons but I don't have an expensive SS amp for comparisons. Too bad we didn't get Naim's O2 vs V200 comparison.


 


  Thanks for reply. I hope i can see more answers about HD800s with O2


----------



## calist3r

I plan to add an O2 in my audio chain for my LCD-2 and feed it with the Xonar, will I hear any difference?
   
  From what I have read, the Xonar STX can provide sufficient power to most of the headphones out there but it's not completely flat as it still has a tint of warmness. Some reviews even describe the sound as tube-like.
   
  I don't know if it's true or not but I do hear that "warmness".
   
  I expect the O2 to have less "warmness" than the Xonar STX because the added warmness makes my LCD-2 Rev.2 sounds a bit darker than I would like.
   
  Will the neutral amp like an O2 brighten my LCD-2 Rev.2, compared to the Xonar?
   
  I don't want to turn my LCD-2 into Grado or anything but I want to make sure that It sounds like it supposed to, without extra colouration from an amp.
   
  Also, more impressions from users who are using LCD2-Rev.2 with the O2 would be much appreciated.


----------



## jmwreck

I've got nothing to say, but I'll post a pictures instead 
   

   
*compared to *
   

   
*=*


----------



## Llloyd

Quote: 





jmwreck said:


> I've got nothing to say, but I'll post a pictures instead


 


  lol what a beefy portable setup. looks great


----------



## upstateguy

Quote: 





palmfish said:


> In keeping with the "sound science" theme...
> 
> http://www.engadget.com/2008/03/03/audiophiles-cant-tell-the-difference-between-monster-cable-and/


 


  Based on the premise that you can always fool enough of the people, enough of the time, to make doing this profitable.....


----------



## palmfish

Quote: 





jmwreck said:


> I've got nothing to say, but I'll post a pictures instead
> 
> 
> 
> *compared to *


----------



## 129207

Quote: 





calist3r said:


> I plan to add an O2 in my audio chain for my LCD-2 and feed it with the Xonar, will I hear any difference?
> 
> From what I have read, the Xonar STX can provide sufficient power to most of the headphones out there but it's not completely flat as it still has a tint of warmness. Some reviews even describe the sound as tube-like.
> 
> ...


 
   
  Adding an O2 to that chain will just amp the Xonar's signature. If you don't like the "warmness" (whatever that may be) just use an equalizer to adjust the sound to your liking.


----------



## stv014

Quote: 





negakinu said:


> Adding an O2 to that chain will just amp the Xonar's signature.


 

 Not necessarily, maybe the "signature" comes from the amplifier (TPA6120) or its high output impedance. Although the opinions on how the STX sounds seem to be conflicting, other people say that it is overly bright, or even has "ear shredding" treble. I wonder how much of it is real. In any case, the DAC does have some treble roll-off, but it is not very significant:


----------



## mikeaj

If it's real, maybe the conflicting reports come from the behavior being different in different peoples' systems, what with different configurations and positioning of other add-in cards (particularly video cards) and the CPU power circuitry, and so on?


----------



## estreeter

My EHP-O2 seems to be giving me a good window to my sources, but both have dedicated line-outs. I prefer my other portables with some of my music, but thats more a reflection on my sources and the recordings themselves than a criticism of the Objective2. I think its good that many who banged on endlessly about the importance of accuracy and neutrality finally got what was coming to them !


----------



## jmwreck

Quote:


----------



## shorke

Would getting a more powerful AC adapter than the WAU200 or whatever the one JDSLabs comes with actually give my O2 more power or would it just charge the batteries faster? Would it make an audible difference is the main question I guess. Also, is there anyway that I could bypass double amping with my soundcard if the only line outs are digital coaxial and optical?


----------



## palmfish

Quote: 





shorke said:


> Would getting a more powerful AC adapter than the WAU200 or whatever the one JDSLabs comes with actually give my O2 more power or would it just charge the batteries faster? Would it make an audible difference is the main question I guess. Also, is there anyway that I could bypass double amping with my soundcard if the only line outs are digital coaxial and optical?


 

 No and no. No. No.


----------



## shorke

Alright, thanks. That ODAC is looking better all the time then, I hope it turns out to be good.
  
  Quote: 





palmfish said:


> No and no. No. No.


----------



## palmfish

Quote: 





shorke said:


> Alright, thanks. That ODAC is looking better all the time then, I hope it turns out to be good.


 


  The ODAC will be USB only. Knowing the source, I'm sure it will be good. 
	

	
	
		
		

		
			





  I assume your card has USB?
   
  You could also get a DAC with Coax and/or Optical inputs. There are a number of good affordable ones.


----------



## shorke

No, I meant for just completely bypassing the card all together. If the ODAC is higher quality than my soundcard (no double amping which will lead to less distortion and the DAC will probably be a lot nicer), I will just slide it inside my O2 and use that hooked up via a rear usb port on my pc. Unless I have misunderstood how external DACs and amps work.
   
  My card uses the AK4396VF DAC so I'm sure the ODAC will be an improvement in many ways.


----------



## stv014

Quote: 





mikeaj said:


> If it's real, maybe the conflicting reports come from the behavior being different in different peoples' systems, what with different configurations and positioning of other add-in cards (particularly video cards) and the CPU power circuitry, and so on?


 

 Maybe, although I would expect those factors to affect mainly the SNR, rather than the frequency response.


----------



## everlong

The O2 is a bang-for-the-buck amp, but what is a bang-for-the-buck usb dac to be used with the amp?
  Fiio, behringer, ...?


----------



## 129207

Quote: 





everlong said:


> The O2 is a bang-for-the-buck amp, but what is a bang-for-the-buck usb dac to be used with the amp?
> Fiio, behringer, ...?


 


  Just wait for the ODAC.


----------



## palmfish

Quote: 





shorke said:


> No, I meant for just completely bypassing the card all together. If the ODAC is higher quality than my soundcard (no double amping which will lead to less distortion and the DAC will probably be a lot nicer), I will just slide it inside my O2 and use that hooked up via a rear usb port on my pc. Unless I have misunderstood how external DACs and amps work.
> 
> My card uses the AK4396VF DAC so I'm sure the ODAC will be an improvement in many ways.


 


  Yes, you're right. Sorry, I misunderstood what you meant before.
   
  You can plug an outboard DAC (like the ODAC) into the USB port and bypass your internal soundcard.
   
  On the other hand, AKM makes some fine DAC chips and the AK4396 has been used in some very "high-end" gear. As long as the card is well designed, I would think it should perform as well as the ODAC. Double amping isn't nearly the problem that many people claim. As long as you're not driving the card into clipping (it may clip at 100% volume, and it may not - every card is different), there is no harm in driving the O2 direct from the cards headphone jack.
   
  Or you could use the onboard DAC but bypass the amp stage by using a Coax or TOSLINK cable to an outboard DAC.
   
  You have several options that really come down to subjective sound quality (for what that's worth) and money. If you are at all interested in the O2 and ODAC, you should read more of NwAvGuy's articles and discover more about what he thinks about DAC's, amps, subjective vs. objective, double amping, etc. It may help you decide what to do.


----------



## joe_cool

Quote: 





palmfish said:


> Or you could use the onboard DAC but bypass the amp stage by using a Coax or TOSLINK cable to an outboard DAC.


 
   
  I think this is so incorrect I'm not even going to argue the point. Do "you all" really know anything about audio?


----------



## 129207

Quote: 





joe_cool said:


> I think this is so incorrect I'm not even going to argue the point. Do "you all" really know anything about audio?


 

  
  No. But I'm still a headphoneus supremus. Hear me roar! USE THE ONBOARD DAC TO BYPASS THE ONBOARD AMP TO TOSLINK TO COAX TO EXTERNAL TRIPLE BYPASS.


----------



## palmfish

Quote: 





joe_cool said:


> I think this is so incorrect I'm not even going to argue the point. Do "you all" really know anything about audio?


 
   
  No need to get your panties in a bunch...  I wrote that at like 3 in the morning, OK? Yes, it is incorrect - My apologies. Obviously coax and optical outs bypass the card entirely (or at least the DAC and onboard amp).
   
  May I suggest that in the future, if you have something constructive to contribute, then please do. Otherwise, at the very least, conduct yourself like a grown up and treat others the way you yourself would like to be treated.


----------



## joe_cool

Quote: 





palmfish said:


> No need to get your panties in a bunch...  I wrote that at like 3 in the morning, OK? Yes, it is incorrect - My apologies. Obviously coax and optical outs bypass the card entirely (or at least the DAC and onboard amp).
> 
> May I suggest that in the future, if you have something constructive to contribute, then please do. Otherwise, at the very least, conduct yourself like a grown up and treat others the way you yourself would like to be treated.


 

 My comment led to a helpful correction on your part. And I I didn't insult your choice of undergarments. Please conduct yourself with civility.


----------



## joe_cool

Quote: 





negakinu said:


> No. But I'm still a headphoneus supremus. Hear me roar! USE THE ONBOARD DAC TO BYPASS THE ONBOARD AMP TO TOSLINK TO COAX TO EXTERNAL TRIPLE BYPASS.


 


  I actually liked this response!


----------



## palmfish

Quote: 





joe_cool said:


> My comment led to a helpful correction on your part. And I I didn't insult your choice of undergarments. Please conduct yourself with civility.


 


  So being disrespectful to others is OK if it is for the betterment of the discussion. Great attitude Snoopy.


----------



## oyster

Can i use a 13v ac-ac transformer with the O2?
  Will it do any damage to the amp?
  If 13v is usable would a 16/18v supply make any difference for good?
   
  I am unable to find 14-20 VAC, 13v is the best i could manage. Hence the questions.
  Thanks much.


----------



## mikeaj

Quote: 





stv014 said:


> Maybe, although I would expect those factors to affect mainly the SNR, rather than the frequency response.


 

 Yeah true, interference and noise should be affecting SNR and non-harmonic distortion artifacts, not really FR.
   
   




oyster said:


> Can i use a 13v ac-ac transformer with the O2?
> Will it do any damage to the amp?
> If 13v is usable would a 16/18v supply make any difference for good?
> 
> ...


 

  Check the current rating as well, though likely it's at least 200 mA or so and thus okay.
   
  It may be okay.  If you have a multimeter to measure the voltage unloaded, then that should tell you.  The voltage you measure without the adapter plugged into the amp (so unloaded) should be about 13.5V AC or so.  In fact the "default" AC adapter recommended, the WAU12-200 (which I and many others use), is rated for 12V nominal but is more around 13.5V unloaded, so your 13V adapter may be okay.  It depends also on what exactly the voltage is you're getting from the wall.  Note that the transformer output voltage drops, the more power you pull from it.
   
  If the rating is too low, then under sustained heavy power consumption, the voltage out of the transformer to the 12V regulators may drop close enough to 12V that the regulators get cranky and start to misbehave, meaning that the power supply rails have more noise on them, degrading the performance a little bit.  Heavy power consumption pretty much means bench testing max output into low impedances--this probably won't happen in practice unless you're listening really load on a planar magnetic headphone while charging batteries (which are depleted) simultaneously.  If not under sustained heavy power consumption, a suitable adapter on the "low" side is just as good, maybe even preferred since there will be less waste heat generated by the regulators.


----------



## 129207

Quote: 





palmfish said:


> So being disrespectful to others is OK if it is for the betterment of the discussion. Great attitude Snoopy.


 


  I agree with this, Collateral damage is unavoidable. Everything for the cause man. All the way, no prisoners. Snoopy's not here to make friends. Madness? THIS! IS! HEAD-FI!


----------



## oyster

Quote: 





mikeaj said:


> Check the current rating as well, though likely it's at least 200 mA or so and thus okay.
> 
> It may be okay.  If you have a multimeter to measure the voltage unloaded, then that should tell you.  The voltage you measure without the adapter plugged into the amp (so unloaded) should be about 13.5V AC or so.  In fact the "default" AC adapter recommended, the WAU12-200 (which I and many others use), is rated for 12V nominal but is more around 13.5V unloaded, so your 13V adapter may be okay.  It depends also on what exactly the voltage is you're getting from the wall.  Note that the transformer output voltage drops, the more power you pull from it.
> 
> If the rating is too low, then under sustained heavy power consumption, the voltage out of the transformer to the 12V regulators may drop close enough to 12V that the regulators get cranky and start to misbehave, meaning that the power supply rails have more noise on them, degrading the performance a little bit.  Heavy power consumption pretty much means bench testing max output into low impedances--this probably won't happen in practice unless you're listening really load on a planar magnetic headphone while charging batteries (which are depleted) simultaneously.  If not under sustained heavy power consumption, a suitable adapter on the "low" side is just as good, maybe even preferred since there will be less waste heat generated by the regulators.


 

 Many thanks for the response. Although i could not understand most of it......am a big zero in electronics 
   
  The wall output is 240V. Just measured the unloaded output of the adapter, it's 13.05V. Should be ok then...right?
  Also, would you still suggest getting a >14V supply for a better performance.....maybe more volume output?


----------



## mikeaj

Quote: 





oyster said:


> Many thanks for the response. Although i could not understand most of it......am a big zero in electronics
> 
> The wall output is 240V. Just measured the unloaded output of the adapter, it's 13.05V. Should be ok then...right?
> Also, would you still suggest getting a >14V supply for a better performance.....maybe more volume output?


 
   
  13.05V is too low for it to work (apparently), but it practice it might be okay with some headphones maybe?  I'm not that familiar with how those regulators behave, and I didn't check the data sheet.  How much current is the adapter rated for?  There should be a number given like 0.5A or 200 mA or something like that.
   
  This is a situation where more (voltage) past a certain point is not better, but you're definitely under that point.
   
  The text from the article is this:
  Quote: 





> *AC Wall Transformer* – There has been some confusion over the wall transformer and it’s a critical component. Most wall transformers put out DC but _the O2’s power supply requires at least 13.5 volts *AC*_. The ideal transformer would be rated at 14 - 16 VAC and 400 mA or higher. In North America the Triad WAU12-200 from Mouser is rated at 12 volts but is really about 13.5 VAC with no load, and on normal 120 volt line voltage works fine for anything but full power sine wave testing or driving rare low impedance power hungry cans. _If your line voltage is below 117 VAC  or 235 VAC, and/or you plan to drive difficult low impedance headpones (i.e. HiFiMan planars), I would suggest a 14+ VAC transformer at 400+ mA._ The best Mouser transformers are the WAU16-400, 412-218054 or WAU16-1000 CUI. But those are more expensive than the WAU12-200. The WAU20-200 also works for higher impedance headphones. At least some European 230 volt input 12 VAC output transformers only measure around 11.5 to 12 volts on normal line voltage and won’t work (especially if designed for halogen lights). You can also change the power jack to a 5.5mm x 2.5mm version if needed to match the plug of different wall transformers.


----------



## oyster

Quote: 





mikeaj said:


> 13.05V is too low for it to work (apparently), but it practice it might be okay with some headphones maybe?  I'm not that familiar with how those regulators behave, and I didn't check the data sheet.  How much current is the adapter rated for?  There should be a number given like 0.5A or 200 mA or something like that.
> 
> This is a situation where more (voltage) past a certain point is not better, but you're definitely under that point.
> 
> The text from the article is this:


 

 The current is rated at 1A. I am using the amp with 150ohm, 92db Yamaha HP50A . The source is HP out from my mp3 players Clip+/touch 3g/Nokia X5. While at low gain i think i definitely need quite more volume.


----------



## darren700

Cant wait for the ODA to come out... so anxious


----------



## Lil' Knight

Spent a couple of hours last weekend building the amp. Pairing with another low budget DAC (Grub) now. I'm getting some pretty nice tunes, excellent value for the money, considering how much they cost ($35 + $35).

However, comparing the O2 with the B22 would be a real joke to me. It's one heck of a fine sounding amp, but by no way on the level of the B22. In the most optimistic way, I'd say it can stand against the M3 pretty well. I also don't think I prefer the O2 than another DIY amp, the Minimax ($250). Still, for $35, I can't ask more.


----------



## LizardKing1

I think the big question was, if all the levels of distortion and frequency coloring on the O2 are below audibility, and the ones on the Beta22 are even lower, then there's no way these 2 amps could be distinguishable. Kind of like if you have have a sphere with 1 micron diameter and another one with 0.0001 micron diameter, in terms of sight it's irrelevant which one is smaller because you can't see any. Why is the O2 not "on level" with the Beta22 in terms of sound? Besides the voltage output, I assume they should be exactly the same to us, and so very much comparable.


----------



## 129207

Quote: 





lizardking1 said:


> Why is the O2 not "on level" with the Beta22 in terms of sound?


 

 Because actually admitting this after you spent $1K+ on a B22 would implode the universe itself.


----------



## Lil' Knight

negakinu said:


> Because actually admitting this after you spent $1K+ on a B22 would implode the universe itself.



Not worth spending time replying to post like this... :rolleyes: How much experience do you have with the B22? :rolleyes:


----------



## 129207

Quote: 





lil' knight said:


> Not worth spending time replying to post like this...
> 
> 
> 
> ...


 


  I am not here to rain on your parade or question the way_ your_ ears work. Your opinion is as valid as mine. I just like seeing the universe implode once in a while.


----------



## Llloyd

this thread has certainly died down since it moved sections, which is quite unfortunate


----------



## zzffnn

I am sorry if my following comment offends anyone. And my comment herein is not aimed at anyone specifically. But let us provide HELPFUL impression in this thread.

if you have actually listened to O2 and Beta22 or Amp XYZ side by side, indicate such like Lil Knight did. If you have not and are speculating, please also indicate that so others can take your comment with caution. 

Please note that some are simply providing subjective preference here. You can not predict preferrence without listening to equipments. More perceived transparency may not always be preferred by human ears.


----------



## maverickronin

Quote: 





llloyd said:


> this thread has certainly died down since it moved sections, which is quite unfortunate


 

 "Mission Accomplished"


----------



## ProjectDenz

Quote: 





maverickronin said:


> "Mission Accomplished"


----------



## LizardKing1

Quote: 





zzffnn said:


> I am sorry if my following comment offends anyone. And my comment herein is not aimed at anyone specifically. But let us provide HELPFUL impression in this thread.
> if you have actually listened to O2 and Beta22 or Amp XYZ side by side, indicate such like Lil Knight did. If you have not and are speculating, please also indicate that so others can take your comment with caution.
> Please note that some are simply providing subjective preference here. You can not predict preferrence without listening to equipments. More perceived transparency may not always be preferred by human ears.


 

 You're right. I never listened to the Beta22. It's just one of those times where I don't see how it could help. I never listened to music using a 650$ Audioquest USB cable either, but I have no reason so assume it will be different from a Monoprice 2$ USB cable. People have every right to have a subjective opinion, and objective assumptions, and have these two fields contradict one another.


----------



## zzffnn

Quote: 





lizardking1 said:


> You're right. I never listened to the Beta22. It's just one of those times where I don't see how it could help. I never listened to music using a 650$ Audioquest USB cable either, but I have no reason so assume it will be different from a Monoprice 2$ USB cable. People have every right to have a subjective opinion, and objective assumptions, and have these two fields contradict one another.


 

   
  Quote: 





lizardking1 said:


> I think the big question was, if all the levels of distortion and frequency coloring on the O2 are below audibility, and the ones on the Beta22 are even lower, then there's no way these 2 amps could be distinguishable. Kind of like if you have have a sphere with 1 micron diameter and another one with 0.0001 micron diameter, in terms of sight it's irrelevant which one is smaller because you can't see any. Why is the O2 not "on level" with the Beta22 in terms of sound? Besides the voltage output, I assume they should be exactly the same to us, and so very much comparable.


 
   
  I think your "objective assumption" over-simplify reality too much, such that it does not make sense. You can not compare 2 amps based on "distortion and frequency coloring" alone. Your assumption of different voltage output is moot as well, because a person can easily adjust volume, gain and/or input to matched levels.
   
  You listen to equipments with your ears too, correct? If you base your "objective assumption" on 3 data points and in reality there are 100 unknown data points, then your assumption would not work. In this case, a real word listening would provide a summary of those 103 data points. No doubt that listening is subjective, but when it is from actual owners, it will be helpful, especially when you know that owner X has the same preference as yourself. 

 Cable vs. cable is different than amp vs. amp. I myself do not believe in cable either (I did compare pure silver cable vs monoprice cable and found no difference).


----------



## mikeaj

Quote: 





zzffnn said:


> I think your "objective assumption" over-simplify reality too much, such that it does not make sense. You can not compare 2 amps based on "distortion and frequency coloring" alone. Your assumption of different voltage output is moot as well, because a person can easily adjust volume, gain and/or input to matched levels.
> 
> You listen to equipments with your ears too, correct? If you base your "objective assumption" on 3 data points and in reality there are 100 unknown data points, then your assumption would not work. In this case, a real word listening would provide a summary of those 103 data points. No doubt that listening is subjective, but when it is from actual owners, it will be helpful, especially when you know that owner X has the same preference as yourself.


 
   
  Okay, so these headphone amplifiers are real-world systems and thus not 100% textbook LTI systems.  We can even quantify how "off" it is by looking at symptoms like THD given a certain input signal, load, and output level.  The less "off" it is in various senses, the more we expect the behavior to be like the ideal "wire with gain" or whatever you want to call it.  If you hypothetically had two different "wire with gain" then they should sound identical, right?  The signal being sent to the headphones would be exactly the same for either.  So if we had two "wire with gain plus no more than a really small disturbance like 0.00000001% added in" then surely those would sound the same too.
   
  One question is then about the level of disturbance that is still so small it can't be detected.  Intuitively this seems like this should depend on the listener, the kind of music, the listening volume, the headphones, the type of disturbance (for example, 2nd order harmonics are of course much harder to detect than something else), and more.  There's probably not a one-size-fits-all perfectly exact answer, but some studies have established some kind of safe estimates, with a lower estimate of the threshold being safer.
   
  The other question is about how indicative the typical audio benchmarks are of real-world performance with music into headphones.  Usually bench tests are with resistive loads using combinations of test tones.  With a fairly low-output-impedance amp that's stable, performance into non-resistive loads like headphones should be pretty close to the performance into resistive loads.  Music is just a combination of tones, but it will in general contain more of them at once than you'll see in a typical IMD test.  Anyway, keep in mind again that the more ideal the response is, the less distortion we should expect of all different kinds.  The THD and IMD tests can be thought of as some kind of predictors of behavior.  If the values are high, then it's hard to say. If the values are low, then we probably expect performance to follow the ideal fairly tightly.  Has anybody ever seen an amp that performs really well at IMD CCIF and SMPTE into different loads and output levels, have high distortion with any other kind of input signal?  It doesn't seem likely that this should happen.
   
   
  Also a trip down to InnerFidelity will show that the difference between headphone drivers (left and right side), not to mention sonic differences from slight differences in headphone positioning, are all way way higher in terms of FR and THD and so on, than between headphone amps that are considered to be probably sufficiently close to "wire with gain."
   
  edit: on a side note, I'm waiting for headphone reviews where they go into the night and day differences between the left and right earcups.
   
  "When paired with my überAmp, the velvety midrange of the left earcup is unmatched, such as when retrieving the low-level details of Lilliputian feet scampering about in the morning dew.  But when combined with the authority of the right earcup in resolving every dynamic, the result I feel is a sound stage that is engaging with some music, yet muddled with certain passages.  Rather than placing you in the second or third row, you are unceremoniously dumped in the second-and-a-half row, hardly a comfortable experience."


----------



## LizardKing1

zzffnn I wasn't implying 3 variables are enough to describe an amp's behavior. "distortion" isn't even a point, it's a category of points I think. What I mean is if we assume/know that we know, and are able to measure, every one of the variables that an amp introduces to sound, I think it's ok to assume that 2 amps with all variables below the audibility treshold (regardless of one having these values much lower than the other) will indeed sound the same. And from there we cross a line into assuming that all subjective impressions that contradict this theory come from imagination, and not actual amplifier characteristics. So do we know and are we able to measure every variation an amp is capable of producing in an audio signal? Because if so, and all of these check well below this limit for both the O2 and the B22, I don't see why it's not ok to say they are equal in sound, let alone compare them.


----------



## zzffnn

Quote: 





lizardking1 said:


> zzffnn I wasn't implying 3 variables are enough to describe an amp's behavior. "distortion" isn't even a point, it's a category of points I think. What I mean is if we assume/know that we know, and are able to measure, every one of the variables that an amp introduces to sound, I think it's ok to assume that 2 amps with all variables below the audibility treshold (regardless of one having these values much lower than the other) will indeed sound the same. And from there we cross a line into assuming that all subjective impressions that contradict this theory come from imagination, and not actual amplifier characteristics. So do we know and are we able to measure every variation an amp is capable of producing in an audio signal? Because if so, and all of these check well below this limit for both the O2 and the B22, I don't see why it's not ok to say they are equal in sound, let alone compare them.


 
   
  I somewhat agree with your statement above. Although you are assuming lot of things there. I would love to know whether or not we can measure EVERY variation of an amp and how they affect human perception of amp performance. However, I would have a hard time to believe someone's statement unless that person has a doctoral degree in Audio Engineering with concentration in amplifier design.


----------



## fishski13

Quote: 





negakinu said:


> Because actually admitting this after you spent $1K+ on a B22 would implode the universe itself.


 

 i see a lot of numbers thrown around for the price of a B22.  if you throw it in a stock Par-Metal chassis with a similar aesthetic as the O2, and stick with an inexpensive pot, a DIYer can build a 2 channel for around $500.  builders often spend the extra cash for a stepped attenuator or more expensive pot and other chassis hardware.  you could easily spend the $80 cost of an O2 on a pair of feet and a volume knob alone.


----------



## zzffnn

Quote: 





mikeaj said:


> Okay, so these headphone amplifiers are real-world systems and thus not 100% textbook LTI systems.  We can even quantify how "off" it is by looking at symptoms like THD given a certain input signal, load, and output level.  The less "off" it is in various senses, the more we expect the behavior to be like the ideal "wire with gain" or whatever you want to call it.  If you hypothetically had two different "wire with gain" then they should sound identical, right?  The signal being sent to the headphones would be exactly the same for either.  So if we had two "wire with gain plus no more than a really small disturbance like 0.00000001% added in" then surely those would sound the same too.
> 
> * snipped *
> 
> ...


 

 @ mikeaj,
   
  I was talking about human preference, while you are talking about signal transparency. We are not talking about about the exact same thing. I was saying that you should hear 2 amps side by side to determine your preference. Signal transparency =/= preference.
   
  It is debatable whether all variations shown on Innerfidelity are truly audible. Headphone positioning, for example, affects high frequency range wherein not much music is present. We are talking about limited variation there, not purposely introduced variation such as headphone pad change (e.g., from very thin pad to very thick pads) or using tube amplifier.
   
  In the realm of audiophile headphones, left vs. right driver should not differ that much (< 3db) to affect music enjoyment (as long as the headphones in question are produced by well-established companies).
   
  What you stated under "edit" is a dramatization, I take that you were trying to be funny? There are indeed reviews like that on Headfi, but nobody would take that seriously. Respectable reviewers would not dramatize small variations in that way. I respect a good review as much as machine measurements.


----------



## mikeaj

Quote: 





zzffnn said:


> Although you are assuming lot of things there. I would love to know whether or not we can measure EVERY variation of an amp and how they affect human perception of amp performance.


 
   
  Well it should be pretty clear that you can measure the output of the amp with extremely high accuracy, in response to any kind of input you want (where the input signal has very high accuracy as well, compared to what you're intending to send as the input).  This includes running music through the amp and measuring how it handles that, when loaded by whatever headphones you want.  However, there are an infinite number of possible inputs you could be looking at.  If you were looking at a nonlinear system with a very odd response, it might be difficult to get a decent model of the system with a relatively limited number of measurements.  With a very close to linear system, it becomes pretty easy.  If it were completely linear and time invariant, all we would have to do is measure the impulse response (or equivalently the frequency / phase response) and then we'd know the output for any possible input.
   
  How that affects human perception of amp performance can be measured too.  Ideally you want to measure every human's perception, but that takes a lot of time.  But again, we do know that extremely small differences are imperceptible and can be shown not to have any impact on perception, at least for the average listener as well as highly-trained and exceptional listeners of different kinds.
   
   

 Quote: 





zzffnn said:


> @ mikeaj,
> 
> I was talking about human preference, while you are talking about signal transparency. We are not talking about about the exact same thing. I was saying that you should hear 2 amps side by side to determine your preference. Signal transparency =/= preference.
> 
> It is debatable whether all variations shown on Innerfidelity are truly audible. Headphone positioning, for example, affects high frequency range wherein not much music is present. We are talking about limited variation there, not purposely introduced variation such as headphone pad change (e.g., from very thin pad to very thick pads) or using tube amplifier.


 
   
  the point is:  to have a preference based on the sound signature, there has to be a perceptible difference in sound.
   
  We're talking about amplifiers that should have no perceptible difference in sound.  Two different 0.5% THD (for a given load, output level, etc.) amplifiers could sound way different.  Two different 0.000001% THD amplifiers should sound the same, and thus there would be no way to have a different preference for one opposed to another, based on how it actually sounds.
   
  The argument is that, if you think the comparatively HUGE differences between headphone drivers are insignificant (in the grand scheme of things, they are kind of small), what about the differences between "sufficiently good" amplifiers, which can be orders of magnitude less?


----------



## zzffnn

Quote: 





fishski13 said:


> i see a lot of numbers thrown around for the price of a B22.  if you throw it in a stock Par-Metal chassis with a similar aesthetic as the O2, and stick with an inexpensive pot, a DIYer can build a 2 channel for around $500.  builders often spend the extra cash for a stepped attenuator or more expensive pot and other chassis hardware.  you could easily spend the $80 cost of an O2 on a pair of feet and a volume knob alone.


 

 Exactly. Some people are assuming things without building equipments or listening them.
   
  My Beta22 is a budget build 2 channel that costs around $550. My JDS O2 costs $150. If I can save $400 by selling Beta22, I would have after hearing them side by side. I did sell my M^3 without regret, because O2 is good enough as a replacement (this replacement saved me $150-200 and kept me happy).
   
  I enjoy both O2 and Beta22 in different ways, although I prefer Beta22 if I can sit down with LCD2s.


----------



## zzffnn

Quote: 





mikeaj said:


> Well it should be pretty clear that you can measure the output of the amp with extremely high accuracy, in response to any kind of input you want (where the input signal has very high accuracy as well, compared to what you're intending to send as the input).  .........
> 
> How that affects human perception of amp performance can be measured too.  Ideally you want to measure every human's perception, but that takes a lot of time.  But again, we do know that extremely small differences are imperceptible and can be shown not to have any impact on perception, at least for the average listener as well as highly-trained and exceptional listeners of different kinds.
> 
> ...


 

*>>>>> Comment: Is this "perceptible difference in sound"* *by machine or by human? *Again, for a human to perceive a sound difference, he/she should at least have 2 amps side by side to compare/"perceive", correct? Or is this "human perception of sound" predicted by machine again?
   
  Re "We're talking about amplifiers that should have no perceptible difference in sound".
  The key word here is "should", have you compare O2 vs Beta22 in reality? And, are you aware that at least 3 actual owners in this thread (who has both O2 and Beta22) perceived some sonic difference? 
   
  Of course, people here are free to make their own judgement with machine prediction vs. actual owner "perception" of an amp's sound.


----------



## upstateguy

Quote: 





zzffnn said:


> ....  And, are you aware that at least 3 actual owners in this thread (who has both O2 and Beta22) perceived some sonic difference? .....


 

 I wonder if someone could itemize these differences so we could have a look at them in one place?


----------



## zzffnn

^ mikeaj's point is that there should not be any sonic difference,
  because both Beta22 and O2 are both designed to be flat/neutral/with extremely low distortion.
   
  I respectfully disagree and I think there is sonic difference between O2 and Beta22, based on my own ears, not based on machine prediction. I was arguing that we should listen with ears and look at specifications at the same time. We should not tell people "those 2 amps will sound the same" based on spec alone.
   
  @ upstateguy,
  You are welcome to go back in this thread and itemize those sonic differences, if you like to. Then we can ask mikeaj to provide an explanation on each item.
  As an example, I heard larger soundstage from Beta22 (compared to O2) with LCD2s, even when I matched volume by decibel (Edit: both were fed by AMB Gamma2). I would love to hear mikeaj's comment on that.


----------



## xnor

How about using a simple null difference testing setup with both the O2 and b22? 
   
  (Carver claims to have achieved a *-70 dB* (0.032%) null in his challenge and the stereophile listeners *gave up* after two days because they *couldn't hear a difference*.)
  (btw: "In the twenty or so years that have elapsed since the emergence of the Subjectivist Tendency, no hitherto unsuspected parameters of audio quality have emerged." - Douglas Self)


----------



## Nebby

I don't believe a Beta22 has been tested/measured in the same rig as an Objective2 yet, so making any argument based on the assumption that they should be audibly identical is rather moot. There simply isn't enough information to really make any sort of objective decision on the differences between the amps.


----------



## upstateguy

Quote: 





xnor said:


> *How about using a simple null difference testing setup with both the O2 and b22? *
> 
> (Carver claims to have achieved a *-70 dB* (0.032%) null in his challenge and the stereophile listeners *gave up* after two days because they *couldn't hear a difference*.)
> (btw: "In the twenty or so years that have elapsed since the emergence of the Subjectivist Tendency, no hitherto unsuspected parameters of audio quality have emerged." - Douglas Self)


 


  
  Quote: 





zzffnn said:


> ^ mikeaj's point is that there should not be any sonic difference,
> because both Beta22 and O2 are both designed to be flat/neutral/with extremely low distortion.
> 
> I respectfully disagree and I think there is sonic difference between O2 and Beta22, based on my own ears, not based on machine prediction. I was arguing that we should listen with ears and look at specifications at the same time. We should not tell people "those 2 amps will sound the same" based on spec alone.
> ...


 

 Wondering what your testing protocol was?


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## stv014

Quote:  





> As an example, I heard larger soundstage from Beta22 (compared to O2) with LCD2s, even when I matched volume by decibel


 

 For correct level matching, you need to measure the voltage on the headphones playing a test tone, and match it within at most 0.1 dB or 1%. Setting the volume by ear is not enough.
  Was you comparison sighted, by the way ?


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## 129207

My O2 on top of his equally awesome bigger brother.


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## zzffnn

Quote: 





stv014 said:


> For correct level matching, you need to measure the voltage on the headphones playing a test tone, and match it within at most 0.1 dB or 1%. Setting the volume by ear is not enough.
> Was you comparison sighted, by the way ?


 
  My comparison was not volume matched by ear. It was done by a sound pressure meter with headphones(LCD2s) cup fully enclosed around the meter. I actually gave O2 around 1-2db more than Beta22, because I wanted O2 to win my ears over and save my money. It did not.
   
  My comparison was sight by my wife, dogs and kids..... Seriously though, are you saying all audio impressions have to be done in your objective way? How many existing Headfi reviews were conducted that way (how many even bothered to use a db meter like I did)? So any review that was not done that way can not provide any useful information?
   
  Ok, I give up. People, if you believe these people who have not even heard both Beta22 and O2 side by side, go ahead.
   
  Search "beta 22" within this thread, and you will see that most if not all actual owners of Beta22 perceived a difference between Beta22 and O2. Feel free to not believe an actual owner's impression and believe those who SPECULATE based on specs and graphs. I hope you will enjoy your music more that way. And by the way, give your review in a subjective scientific manner or it is wrong.


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## LizardKing1

Of course your input is valuable, since you actually own both of the amps being discussed. And of course you taking the time to use an SPL meter helps. No, it's not absolutely required to make a double-blind test or volume matching in every review, but then you have to decide how much you want people to credit your experience. If you have nothing to prove, just do a sighted listening to both amps matched by ear. If you want to convince someone, certain precautions of objectivity should be taken.
   
  I didn't understand, so you yourself did not see which of the amps you were using? If you did this on a few trials and the B22 'won' with something like 75% or above, then it's obviously worth considering that there's some noticeable difference between the 2 that hasn't been measured. As for not owning the amp, no one's trying to argue that the input from someone who never heard them is as valuable as someone who owns both. But the Laws of Physics did not bend to either of these amps, so it's safe to make some assumptions, one of them being that there should be no distinguishable sound between these 2 _if_ every variable has been accurately measured for both.
   
  That's what my earlier USB cable analogy meant: I have never heard the Audioquest Diamond USB cable. Someone who owns it claims it improves the mids, or whatever, and says that since I have not heard it I can't comment on that. Well unless somehow the USB protocol evolved on that particular cable, I can assume that it's impossible for the mids to be any different. On this case for example, you mentioned how the soundstage changed. As far as I know soundstage depends on the driver material, width, placement/angle, material the cups, air flow. Don't quote me on this, but I believe the only way for an amp to 'create' soundstage would be to have some sort of bleed from one channel into the other, along with some frequency change, and not only would this be very much measurable, the chances of this happening by chance are minimal.


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## zzffnn

Lizardking,

I was not trying to convince anyone, except myself. Only my ear preference matters to myself.

I disclosed that review condition because I was asked, so I provided that to be helpful.

Like I said, you are assuming lots of things there. I see no reason to discuss further in this manner so feel free to assume further. Your cable analogy is not relevant.

What you described in amp creating soundstage by bleeding is a crossfeed circuit, which will actually decrease soundstage width by reducing channel separation and blending.


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## mikeaj

Quote: 





lizardking1 said:


> That's what my earlier USB cable analogy meant: I have never heard the Audioquest Diamond USB cable. Someone who owns it claims it improves the mids, or whatever, and says that since I have not heard it I can't comment on that. Well unless somehow the USB protocol evolved on that particular cable, I can assume that it's impossible for the mids to be any different. On this case for example, you mentioned how the soundstage changed. As far as I know soundstage depends on the driver material, width, placement/angle, material the cups, air flow. Don't quote me on this, but I believe the only way for an amp to 'create' soundstage would be to have some sort of bleed from one channel into the other, along with some frequency change, and not only would this be very much measurable, the chances of this happening by chance are minimal.


 
   
  If there's a nontrivial phase shift in the audible frequency range, then that should impact the soundstage.  I wouldn't necessarily count out any differences in frequency response, distortion, or something else as causing shifts in perception of anything, though.  With "good enough" amps, all the factors should be covered though.
   
   




zzffnn said:


> My comparison was not volume matched by ear. It was done by a sound pressure meter with headphones(LCD2s) cup fully enclosed around the meter. I actually gave O2 around 1-2db more than Beta22, because I wanted O2 to win my ears over and save my money. It did not.
> 
> My comparison was sight by my wife, dogs and kids..... Seriously though, are you saying all audio impressions have to be done in your objective way? How many existing Headfi reviews were conducted that way (how many even bothered to use a db meter like I did)? So any review that was not done that way can not provide any useful information?


 
   
   
   
  By changing the overall level you also could be changing the perception of the FR because of equal-loudness contours and so on, or something else.  Louder is usually perceived as better, but it's not an absolute truth.
   
  Most head-fi reviews done in the typical fashion, even about parts that aren't headphones, can have useful comments about build quality, aesthetics, functionality, features, ports, price, noise levels (if noticeable), and so on.  Most things relating to sound quality I would consider unreliable at best, given the circumstances.  For example, see differences in blind versus sighted listening here:
http://seanolive.blogspot.com/2009/04/dishonesty-of-sighted-audio-product.html
   
  The idea that small differences in sound / color / force / whatever are not perceptible to humans, is not that controversial, I would think.  As mentioned earlier, reference the Carver challenge with regards to differences between amps, or maybe some formal studies.  In audio land as well as many others, results tend to shift greatly when there are bedsheets or paper bags involved.  Human ears and brains are amazing compared to current technology at a lot of tasks, but let's not get too ahead of ourselves.


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## zzffnn

Guys, see the reason why this review thread is in Sound Science? 

I found that electrical engineers here have amazing abilities to take the fun out of music listening with their objective methodology of comparison.

If most of the sound description here at Headfi is not to be believed, then why do we gather here? Built features of a product can be easily seen on photo or spec. Without subjective sound description, do we come to Headfi to conduct scientific experiments to treat cancer or what?


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## upstateguy

@*zzffnn*
  
  Since you have both amps, are able to match the volumes and hear differences, would it be so hard for you to do a null test?
   
  Everyone is afraid to use the Audio DiffMaker.  All you need is a cable from the output of the amp to the input of your computer.
   
  It is not absolutely conclusive but it would help a lot if someone who had both amps did it.
   
  Even if you don't want to use the DiffMaker, make some Audacity files and post them.  There are a lot of people here who can use them to eyeball a null test.
   
*I also wanted to ask you what the volume and gain level you had the O2 set to for your comparison?*


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## zzffnn

Volume matched to 80 db. 2.5x on O2 and 2x on beta22.

I do not have time for another test, as I have done one to convince myself. I do not care to convince anyone else. And yes, I am afraid of doing that computer test. I guess by saying that I can get a break from these "objective test"? If so, then yes.


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## upstateguy

Quote: 





zzffnn said:


> Volume matched to 80 db. 2.5x on O2 and 2x on beta22.
> I do not have time for another test, as I have done one to convince myself. I do not care to convince anyone else. And yes, I am afraid of doing that computer test. I guess by saying that I can get a break from these "objective test"? If so, then yes.


 


  it is unclear what position the O2 volume was set at?  Is 2.5 the low gain setting?


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## mikeaj

Quote: 





zzffnn said:


> Guys, see the reason why this review thread is in Sound Science?
> I found that electrical engineers here have amazing abilities to take the fun out of music listening with their objective methodology of comparison.
> If most of the sound description here at Headfi is not to be believed, then why do we gather here? Built features of a product can be easily seen on photo or spec. Without subjective sound description, do we come to Headfi to conduct scientific experiments to treat cancer or what?


 

 Music is an art.  I've played in many musical groups like orchestras for years (not professionally), and I know plenty of professional musicians.  IMHO audio reproduction has a lot more to do with science and engineering, though I would say there's a bit of craftsmanship and sometimes more finesse rather than hard numbers, with regards to headphone/loudspeaker design, maybe room treatment and loudspeaker placement, and some other aspects.  This is about understanding amplifiers, so we can compare them and hopefully get to enjoy the music, rather than think about the gear (non-transducers gear), which tends to make less difference than most probably expect.  I'm not sure why that would have anything to do with taking fun away, unless maybe you're talking about the fun of reading gear reviews or playing around with new gear?
   
  I'd say you're downplaying the value in some other aspects of gear reviews on head-fi, for revealing things like trends of manufacturing defects, headphone jacks that are too loose or tight, how hot some stuff gets, turn on/off transients and other irregularities, and so on, that you wouldn't see from pictures.  Manufacturer descriptions of features are often incomplete as to how they work exactly.  Also, a lot of manufacturers offer little in the way of specs.  That's again, not to mention the headphone / IEMs reviews, which I think is the primary resource of interest.
   
   
   




upstateguy said:


> it is unclear what position the O2 volume was set at?  Is 2.5 the low gain setting?


 

  Does this really matter that much?  It's not like O2 performance is much different on different gain settings or volume levels.  80 dB is kind of low too, for comparison purposes, assuming it was taken with a 0 dBFS tone for normalization purposes.  If it was some kind of eyeball-the-meter with music playing, as an average, then that's better than nothing but probably not very accurate.  Anyhow, an "I don't care" or "don't bother me" kind of response seems perfectly fine and reasonable to me, so I (we?) can let this go since you're not interested, and whoever wants can have the last word.


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## bellsprout

Quote: 





zzffnn said:


> I found that electrical engineers here have amazing abilities to take the fun out of music listening with their objective methodology of comparison.


 

 heavens forbid there being electrical engineers. the headamp world would be so much better without them.
   
  in the meantime ill buy a car without a speedo. as long as it has a bodykit and a loud engine i'll think its fast and nobody can tell me otherwise


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## Shike

Quote: 





zzffnn said:


> *I was not trying to convince anyone, except myself.*


 

 You shouldn't be trying to convince anyone, including yourself.  Using such a mindset, and purposely setting either amp hotter than the other makes your "findings" questionable at best.
   
  I don't understand your shock and indignation for someone calling you on this.  Your test was no better than any other sighted test, and should be seen as such.


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## zzffnn

^ Please go and buy said car and post some impression With photos here. I have no doubt that car would be super fast.

Note I said engineers HERE in this thread. Not all engineers. Some are good at explaining science better than others, and some are good at designing real audio products. Some can only offer assumptions based on theory and confuse people.


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## zzffnn

shike said:


> You shouldn't be trying to convince anyone, including yourself.  Using such a mindset, and purposely setting either amp hotter than the other makes your "findings" questionable at best.
> 
> I don't understand your shock and indignation for someone calling you on this.  Your test was no better than any other sighted test, and should be seen as such.




Please do not tell me what I should do or should not do with my gears and ears. I gave O2 advantage in volume because I wanted to favor O2 such that I can get rid of beta22 and save some money. I could be wrong in doing that, but I still could not favor O2 in view of the volume advantage it had.

I did not say that my test is better than any other test. I do not care if you see it better or not.


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## bellsprout

Quote: 





zzffnn said:


> Note I said engineers HERE in this thread. Not all engineers. Some are good at explaining science better than others, and some are good at designing real audio products. Some can only offer assumptions based on theory and confuse people.


 
  like your test? 
   
  edit: sorry didn't see the "based on theory" part


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## zzffnn

@ shike,

Why should I feel bad? Because my test is poor in your eyes? I find it amusing that you think it that way.

My test is not bad. Please be respectful and don't be personal.

My test was aimed at telling which amp is subjectively better, blindly, even when amp x is a little louder. I did not even pay attendtion to tell which amp is louder or which is beta22. I said a little louder because 3db is perceived as significantly louder, while the 1-2 db more i gave to O2 in average may not even be audible. Variation can easily be 1-2 db.

I challenge you to do a better test between beta22 and O2 and offer some objectively better results. Otherwise you are not provide any useful information here, other than personal attack and BS. You have to build a beta22 though. No, I will not loan you mine.


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## Shike

Quote: 





zzffnn said:


> @ shike,
> Why should I feel bad? Because my test is poor in your eyes? I find it amusing that you think it that way.


 
   
  What credible industry would accept your test as sufficient?  List.
   


> My test is not bad. Please be respectful and don't be personal.


 
   
  What objective did it actually accomplish?  Did it remove any potential for bias at all?  How was it different from hooking up two amps amps at random out of box and plug between the two of them?
   
  If it didn't accomplish any of these, how was it a "good" test.  Explain.
   


> My test was aimed at telling which amp is subjectively better, blindly, even when amp x is a little louder.


 
   
  There's no point in blind testing if it's identifiable due to lack of controls now is there?  Equally a blind test isn't setup for quantifiable difference, just whether one can hear them.
   


> did not even pay attendtion to tell which amp is louder or which is beta22.


 
   
  So you admit that you didn't even pay attention to testing in your own test?  Why should we take it seriously at all then?   The idea of a test is there's some degree of control, which you admit you've gone out of your way to eliminate from the beginning.
   


> I said a little louder because 3db is perceived as significantly louder, while the 1-2 db more i gave to O2 in average may not even be audible.


 
   
  1dB is seen as audible, so 2dB isn't going to be surprising to be audible at all. Equally your method of measuring loudness is too imprecise, the differences could have easily been larger based on the SPL meter and frequency used - assuming you used a test frequency.
   


> Background noise can easily have a variation of 1-2 db.


 
   
  I'm not even going to bother with this till the other flaws of your test are handled.
   


> I challenge you to do a better test between beta22 and O2 and offer some objectively better results. Otherwise you are not provide any useful information here, other than personal attack. You have to build a beta22 though. No, I will not loan you mine.


 
   
  I have level matched, and DBT'd, a Beta22 (and a M3, a Benchmark, and a handful of others).  I'm not the one claiming to hear a difference am I?  I realize I could be biased against hearing a difference, and as such it's the responsibility of those claiming to hear a difference to provide evidence if they want to be taken seriously.  Starting a thread saying "hey, I don't hear a difference" is only going to garner tin ear insults or others that say there shouldn't be a difference anyway.


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## zzffnn

^ Provide some neutral 3rd party proof that you have done what you said in your last paragraph. Nobody would believe that you even listened to a beta22 once without that proof. Let alone your comparison. You did not even specify how you did you test, so your test is "bad".

Also I was not trying to do a objective test by your definition. Again, i care less of what you think, as I did not do the test to make you happy. I did it to make myself happy. I provided the test info because someone asked me to specify; I do not care if anyone else is convinced or not.

People heard you and me already and they will take information that they consider as useful. I do not see that our debate will produce anything more useful than what have been stated. Take it to PM if you care to.


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## mikeaj

Shike, thanks for not being mad, but did I ever apologize for contributing to probably getting this thread kicked to the ghetto (SS)?  My bad, sorry, but I think by this point what's done is done.
   
   



zzffnn said:


> ^ Please go and buy said car and post some impression With photos here. I have no doubt that car would be super fast.
> Note I said engineers HERE in this thread. Not all engineers. Some are good at explaining science better than others, and some are good at designing real audio products. Some can only offer assumptions based on theory and confuse people.


 
  I'm pretty sure I'm not overreaching in thinking this is mostly directed at me, so...
   
  I know my writing sucks, but I don't understand where the confusion is coming from.  Are you suggesting that there's purposeful obfuscation to confuse people, or incompetence?  Could you honestly identify which assumptions you think are based on theory?  I don't recall any other than those based on systems theory and linearity, but were there any inaccurate assumptions or leaps of faith made?  Is the theory wrong, being misapplied, being misunderstood, or what else?  Anybody else feel free to respond here.
   
  I never read these pages until just now (and a quick skim reveals they're not amazing, but the intros are useful), but if anybody wants a quick primer or refresher, these might be relevant:
http://www.libinst.com/distortion_isolation_in_the_time.htm
http://en.wikipedia.org/wiki/Total_harmonic_distortion
   
  If your own tests satisfy you, that's what matters most, and I mean that sincerely.  What matters most for enjoyment is probably to like the gear you own, no matter what the reason.  I don't think we need to go down the route of HydrogenAudio regarding requirements to back up every claim, but if anybody sticks something out, there's just some motivation to examine and integrate those claims with what we know.  No offense.


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## Shike

@mikeaj,
   
  Seriously it's not a problem.  I expected this ending up here when I first posted the review, and was honestly surprised it stayed out of here as long as it did.
  
  Quote: 





zzffnn said:


> ^ Provide some neutral 3rd party proof that you have done what you said in your last paragraph. Nobody would believe that you even listened to a beta22 once without that proof. Let alone your comparison.


 
   
  Can you do the same beyond a reasonable doubt?  I'm sorry, but with the internet to some extent you're either going to believe me or not.  I'm not going to harass friends to join Head-Fi, jump through hoops, or give out personal information just to appease you.  Regardless, I will ask you don't imply negative connotations of a persons character that may be construed as defamation, and furthermore do not derail this thread any longer with such attempts.
   
  The only reason I'm responding to this is I see it as a public attack on my character, and as such deserved to be addressed.


----------



## Shike

So, how many people are interested in dropping an ODAC in the O2?  I'm starting to debate it more, but still hanging fire at this point in time.  Nw had a good April Fool's joke regarding it, but hope we get to see some more real news on it soon.


----------

