[skeptic]

  Some amps give some musical color to the music,some headphones do the same thing.
I for one ,try to stay with what the original music,that came off the CD.,
I prefer a neutral SQ.
 
It's all a matter of personnel taste,I let my ears tell me what is good,and what is,not so good.
 

 
I think this is true for all of us really.  The real issue is defining what constitutes neutral SQ and what amp topologies bring us the closest to natural live sound, which almost certainly varies between different listeners who have different sensitivities to different types of distortion components.  
 
The unfortunate part of the o2 revolution on head-fi is that somewhere in the process (probably starting with nwavguy's site), the significance of basic audio spectrum measurements got overstated and vastly oversimplified.  While a lot of aspects of sound were thoughtfully explained on his blog, the use of negative feedback to hit target specs, and the pros and cons of that approach, were not fully disclosed.
 
I only stumbled on this article from Nelson Pass recently, but I think it is must read material for anyone trying to sort through all this information.  In essence, along with supporting measurements, Pass explains how negative feedback in amplifiers like the o2 - decrease total THD, reduce output impedance, and improves other standard audio measurements, but at the cost of adding new complex distortion components/nonlinear distortions, particularly of high order, to the signal that a significant percentage of people find to be more unpleasant and unnatural than certain other types of distortion (e.g. the low order distortions more prevalent in nonfeedback amps).  Pass designs amps that use feedback and amps that do not, so I see this as a purely informative rather than biased account of these design choices.  https://passlabs.com/articles/audio-distortion-and-feedback  
 
Further, as I understand this, it offers a pretty clean and simple explanation for the general bias against opamp based amplifiers.  Opamps can only operate in a linear mode (i.e. in audio amplifiers) when they are fed negative feedback.  So these distortion characteristics are likely to be present in all chip amps.  For some listeners, I suspect these amps do in fact sound better than higher THD discrete or tube designs.  For others, the nonlinear distortions and disproportionate high order distortions will make them sound worse.  

 

[prot]

I think this is true for all of us really.  The real issue is defining what constitutes neutral SQ and what amp topologies bring us the closest to natural live sound, which almost certainly varies between different listeners who have different sensitivities to different types of distortion components.  

The unfortunate part of the o2 revolution on head-fi is that somewhere in the process (probably starting with nwavguy's site), the significance of basic audio spectrum measurements got overstated and vastly oversimplified.  While a lot of aspects of sound were thoughtfully explained on his blog, the use of negative feedback to hit target specs, and the pros and cons of that approach, were not fully disclosed.

I only stumbled on this article from Nelson Pass recently, but I think it is must read material for anyone trying to sort through all this information.  In essence, along with supporting measurements, Pass explains how negative feedback in amplifiers like the o2 - decrease total THD, reduce output impedance, and improves other standard audio measurements, but at the cost of adding new complex distortion components/nonlinear distortions, particularly of high order, to the signal that a significant percentage of people find to be more unpleasant and unnatural than certain other types of distortion (e.g. the low order distortions more prevalent in nonfeedback amps).  Pass designs amps that use feedback and amps that do not, so I see this as a purely informative rather than biased account of these design choices.  [COLOR=405050]https://passlabs.com/articles/audio-distortion-and-feedback[/COLOR]  

Further, as I understand this, it offers a pretty clean and simple explanation for the general bias against opamp based amplifiers.  Opamps can only operate in a linear mode (i.e. in audio amplifiers) when they are fed negative feedback.  So these distortion characteristics are likely to be present in all chip amps.  For some listeners, I suspect these amps do in fact sound better than higher THD discrete or tube designs.  For others, the nonlinear distortions and disproportionate high order distortions will make them sound worse.  

Very interesting link, thank you. I am a fan of the O2 and I do not think it takes anything out of the music or sounds distorted. For me the only issue is that it's kinda harsh/bright and brings the worst out of bright cans.

 

[evillamer]

Audio-gd new dac:
http://www.audio-gd.com/Pro/dac/DAC1911/DAC19EN.htm
 
PCM1704, Single ended, USD$750(first 100 units)

 

[conquerator2]

  Audio-gd new dac:
http://www.audio-gd.com/Pro/dac/DAC1911/DAC19EN.htm
 
PCM1704, Single ended, USD$750(first 100 units)

Yup - http://www.head-fi.org/t/759872/new-audio-gd-dac-19-10th-anniversary-edition#post_11433260

 

[thegunner100]

I've used the O2 amp and the ODAC separately, but never at the same time. The Leckerton UHA-6s mkii (with ADA4627-1A) KILLED the O2 when used with the UERMs, HD600, and HD800s. The odac on the other hand, sounded decent when I had it. It was nice for a portable, but not really good enough for a desktop setup imo. Ever since the Geek Out was released... there's not much reason to get a ODAC unless you can find one for very cheap. The GO 450 is simply better in every way. 
 
If I had to venture a guess, the GO 450 as an amp/dac would probably slaughter the O2/ODAC combo.

 

[tomb]

 

  Some amps give some musical color to the music,some headphones do the same thing.
I for one ,try to stay with what the original music,that came off the CD.,
I prefer a neutral SQ.
 
It's all a matter of personnel taste,I let my ears tell me what is good,and what is,not so good.
 

 
I think this is true for all of us really.  The real issue is defining what constitutes neutral SQ and what amp topologies bring us the closest to natural live sound, which almost certainly varies between different listeners who have different sensitivities to different types of distortion components.  
 
The unfortunate part of the o2 revolution on head-fi is that somewhere in the process (probably starting with nwavguy's site), the significance of basic audio spectrum measurements got overstated and vastly oversimplified.  While a lot of aspects of sound were thoughtfully explained on his blog, the use of negative feedback to hit target specs, and the pros and cons of that approach, were not fully disclosed.
 
I only stumbled on this article from Nelson Pass recently, but I think it is must read material for anyone trying to sort through all this information.  In essence, along with supporting measurements, Pass explains how negative feedback in amplifiers like the o2 - decrease total THD, reduce output impedance, and improves other standard audio measurements, but at the cost of adding new complex distortion components/nonlinear distortions, particularly of high order, to the signal that a significant percentage of people find to be more unpleasant and unnatural than certain other types of distortion (e.g. the low order distortions more prevalent in nonfeedback amps).  Pass designs amps that use feedback and amps that do not, so I see this as a purely informative rather than biased account of these design choices.  https://passlabs.com/articles/audio-distortion-and-feedback  
 
Further, as I understand this, it offers a pretty clean and simple explanation for the general bias against opamp based amplifiers.  Opamps can only operate in a linear mode (i.e. in audio amplifiers) when they are fed negative feedback.  So these distortion characteristics are likely to be present in all chip amps.  For some listeners, I suspect these amps do in fact sound better than higher THD discrete or tube designs.  For others, the nonlinear distortions and disproportionate high order distortions will make them sound worse.  

 
Interesting ...
 
This isn't about chip-based amps, but still pertinent.  I have direct experience in measuring two tube amps with almost identical circuitry, except for the localized tube circuit and tube types. One measured almost a magnitude less in distortion (as in 0.034% vs. 0.198%), yet the higher distortion amp sounded better in all aspects with all headphones tested.  IMD was similar difference - 0.040% vs. 0.319%.  Noise, crosstalk, dynamic range were all within a couple of dB of each other.   It wasn't really that close in listening, though.  As if, "What's wrong this amp?  It measures better, but sounds worse."
 
Both of these amps had zero feedback, so there's still more to measuring - or a lack of understanding of what those measurements show, rather.

 

[Liu Junyuan]

  I've used the O2 amp and the ODAC separately, but never at the same time. The Leckerton UHA-6s mkii (with ADA4627-1A) KILLED the O2 when used with the UERMs, HD600, and HD800s. The odac on the other hand, sounded decent when I had it. It was nice for a portable, but not really good enough for a desktop setup imo. Ever since the Geek Out was released... there's not much reason to get a ODAC unless you can find one for very cheap. The GO 450 is simply better in every way. 
 
If I had to venture a guess, the GO 450 as an amp/dac would probably slaughter the O2/ODAC combo.

Bill P. suggested I look at the Leckerton. How does it drive orthos? Looking at the specs (which I know isn't everything), it would seem to not have adequate current. Is that what you use the Magni for?  Thanks~

 

[purrin]

On O2/ODAC:
 
ODAC is OK sounding if fed good USB.
 
O2 is pretty craptastic in the overall scheme of things:
 

• O2 adds crap that isn't there. Errors of commission. The bit of stridency. Rolling the voltage gain op-amp can warm up the sound, but that stridency is always there. Also, there is a bit of veil to the sound compared to better amps (of which I can name many many of them).
• O2 subtracts a lot of stuff that is there, especially microdynamics, small changes in volume, granularity. Microdetail which is smothered by the veiled. Compared to good stuff, the O2 sounds flat and boring.

 
The O2 at $99 is a good price for what it is, but let's not believe it's a great or even good sounding amp. It's a $99 amp that sounds like a $49 amp. It is somewhat fair to call it an uncolored neutral sounding amp, but something uncolored and neutral sounding can just as well suck. An HD600 out of a Torpedo or Valhalla2 destroys in O2 in terms of conveying realism. As someone above said, O2 takes emotions away from music. And no, neither of those tube amps are colored, bloomy, warm, tubey, if the the right tubes are used.
 
In the end, the comparison needs to be relative to other equipment. People who think the O2 is "good" or "transparent" sounding haven't heard anything better or don't have a chain (headphones or source) able to take advantage of a superior amp. People who think O2 is competitive with superior amps are suffering from serious serious confirmation bias because of select measurements (which don't measure the right thing.) Yes, confirmation bias works both ways. This is why I listen to headphones before I take measurements.
 
The O2 is a fairy cheap amp that sounds like a fairly cheap amp. No more, no less.

 

[wahsmoh]

  On O2/ODAC:
 
ODAC is OK sounding if fed good USB.
 
O2 is pretty craptastic in the overall scheme of things:
 

• O2 adds crap that isn't there. Errors of commission. The bit of stridency. Rolling the voltage gain op-amp can warm up the sound, but that stridency is always there. Also, there is a bit of veil to the sound compared to better amps (of which I can name many many of them).
• O2 subtracts a lot of stuff that is there, especially microdynamics, small changes in volume, granularity. Microdetail which is smothered by the veiled. Compared to good stuff, the O2 sounds flat and boring.

 
The O2 at $99 is a good price for what it is, but let's not believe it's a great or even good sounding amp. It's a $99 amp that sounds like a $49 amp. It is somewhat fair to call it an uncolored neutral sounding amp, but something uncolored and neutral sounding can just as well suck. An HD600 out of a Torpedo or Valhalla2 destroys in O2 in terms of conveying realism. As someone above said, O2 takes emotions away from music. And no, neither of those tube amps are colored, bloomy, warm, tubey, if the the right tubes are used.
 
In the end, the comparison needs to be relative to other equipment. People who think the O2 is "good" or "transparent" sounding haven't heard anything better or don't have a chain (headphones or source) able to take advantage of a superior amp. People who think O2 is competitive with superior amps are suffering from serious serious confirmation bias because of select measurements (which don't measure the right thing.) Yes, confirmation bias works both ways. This is why I listen to headphones before I take measurements.
 
The O2 is a fairy cheap amp that sounds like a fairly cheap amp. No more, no less.

It uses op amps.. that is just like a no-no for anything I plan on listening to

 

[estreeter]

Let's cut nwavguy some slack - I never considered him a 'genius', but I admire the fact that he had the guts to make his fledgling designs public. He might not be in the same class as someone like Bruno Putzeys, but they both gave their critics something to chew on, and a lot of it must taste like humble pie. I vividly recall a forum post from a know-it-all DIYer who read Putzey's white paper and declared that it would never even get to the working prototype stage - funny how those guys never come back to accept defeat. 
 
http://spectrum.ieee.org/geek-life/profiles/nwavguy-the-audio-genius-who-vanished
 
http://www.digitalaudioreview.net/2014/09/nad-masters-series-m22-hypex-ncore-for-the-rest-of-us/

 

[tomb]

  Let's cut nwavguy some slack - I never considered him a 'genius', but I admire the fact that he had the guts to make his fledgling designs public. He might not be in the same class as someone like Bruno Putzeys, but they both gave their critics something to chew on, and a lot of it must taste like humble pie. I vividly recall a forum post from a know-it-all DIYer who read Putzey's white paper and declared that it would never even get to the working prototype stage - funny how those guys never come back to accept defeat. 
 
http://spectrum.ieee.org/geek-life/profiles/nwavguy-the-audio-genius-who-vanished
 
http://www.digitalaudioreview.net/2014/09/nad-masters-series-m22-hypex-ncore-for-the-rest-of-us/

 
I think most of us object to the way he went about it.*  He first made his name by taking that DScope his employer let him borrow (my conjecture, admittedly) and tried to fault a number of other products - including DIY-ones.  At least in the case of one particular DIY product, he wasn't even measuring it properly.  As for the rest, it's a bit like picking daisies.  Anyone with experience in the audio industry knows that measurements are often exaggerated.  It was easy to find a few such products, burn them publically, and then make a name for himself.  It also exploited the large numbers of noobs who have blinding faith in measurements.  (It takes some life experience to realize that not everything is so easily quantifiable.)
 
It looks like he at least updated his domain registration again - on 3/10/2015.  Maybe he's planning a comeback when he retires from his present employer.  Or perhaps he's been saving his money to purchase his own DScope (more conjecture again).
 
* There is a long tradition of building reputation by creating good designs or offering great products.  It's not as easy to gain a reputation this way, but better in the long run.

 

[thegunner100]

  Bill P. suggested I look at the Leckerton. How does it drive orthos? Looking at the specs (which I know isn't everything), it would seem to not have adequate current. Is that what you use the Magni for?  Thanks~

Getting a little offtopic, but yes. The leckerton is simply okay for orthos, nothing outstanding. It helps to have it left on stock gain settings for orthos but was otherwise just fine with the paradox slants and he-560s. It might help to use the AD8620 for orthos since that will output more power.
 
If you want a cheap amp for orthos, Magni 2 uber is probably the way to go. 

 

[justsven]

Owning an ODAC and a Vali, wondering if it is worthy to upgrade or side-grade to Modi 2 U.

 

[OJNeg]

Originally Posted by tomb /img/forum/go_quote.gif
 
It looks like he at least updated his domain registration again - on 3/10/2015.  Maybe he's planning a comeback when he retires from his present employer.  Or perhaps he's been saving his money to purchase his own DScope (more conjecture again).
 

 
More likely an auto-renew

 

[Hansotek]

Owning an ODAC and a Vali, wondering if it is worthy to upgrade or side-grade to Modi 2 U.

You should upgrade your ODAC with a Schiit Wyrd instead. IMO, this combo catupults ODAC several spots up the rankings. Honestly, it sounds at least as good as, if not better than the AMB Gamma 2.