[bada bing]

Likely your amp is clipping. It is a well known design trade off of the O2. Either you need a source with less voltage swing or use low gain. The O2 clips from too high an input voltage for the gain used, not from the volume output.

 

[thuNDa]

@escalibur
 
try setting the digital volume lower to 50% or so(either in windows, or in the player), and see if the problem persists.
If no = see post above, if yes = something else is going on.

 

[MrMateoHead]

 

Escalibur -
 
WHAT is the source going in to the O2, and what gain settings does it have? (2.5X or 6.5X) or is it (1X and 3.3X)? Or is it (1X or 2.5X)?
 
IF you are using a 2V source, you are not supposed to use more than a 3X gain. 6.5X is for sources with 1V or less. If you use a source with 2V or more and high gain in excess of 3X, you are most definitely clipping. That would be normal, for mismatching gain / input voltage.

If it is not making bad noises at 2.5X, that is the setting I would use - save high gain for your MP3 player or phone.
 
BTW it can also sometimes be that you are hearing clipping in the recording itself. I haven't listened to Contiuum in awhile, but it sounds the same embedded in the recording as it does on the electronics.
 
My understanding is that the ODAC rev B has slightly higher output volage - 2.1V vs. 2.0V for the original ODAC.

 

[escalibur]

  @escalibur
 
try setting the digital volume lower to 50% or so(either in windows, or in the player), and see if the problem persists.
If no = see post above, if yes = something else is going on.

 
Thanks for the idea. I've tested and no noise at all.
 

  Escalibur -
 
WHAT is the source going in to the O2, and what gain settings does it have? (2.5X or 6.5X) or is it (1X and 3.3X)? Or is it (1X or 2.5X)?
 
IF you are using a 2V source, you are not supposed to use more than a 3X gain. 6.5X is for sources with 1V or less. If you use a source with 2V or more and high gain in excess of 3X, you are most definitely clipping. That would be normal, for mismatching gain / input voltage.

If it is not making bad noises at 2.5X, that is the setting I would use - save high gain for your MP3 player or phone.
 
BTW it can also sometimes be that you are hearing clipping in the recording itself. I haven't listened to Contiuum in awhile, but it sounds the same embedded in the recording as it does on the electronics.
 
My understanding is that the ODAC rev B has slightly higher output volage - 2.1V vs. 2.0V for the original ODAC.

 
 
The source is my motherboard Asus Ranger VII with USB 3.0 (Intel controller). I'm using Windows 10 64bit with disabled all sound enhancements, 24/96k and volume at 100%.
 
For playing music mostly Spotify Premium but that should be good enough in this case.
 
 
Continuum can indeed be tricky for this testing because some songs definitely have some mixed noise or whatever effects in them.

 

[MrMateoHead]

  Thanks for the idea. I've tested and no noise at all.
 
The source is my motherboard Asus Ranger VII with USB 3.0 (Intel controller). I'm using Windows 10 64bit with disabled all sound enhancements, 24/96k and volume at 100%.
 
For playing music mostly Spotify Premium but that should be good enough in this case.
 
Continuum can indeed be tricky for this testing because some songs definitely have some mixed noise or whatever effects in them.

 
Hi there - Contiuum looked "clean" under audacity, even in Mp3, so that can't be the noise you were hearing. Unless the noise is a feature of the music (probably is!), it is coming from something else. Better to see if you can find other recordings that either definitely use static sources (like Hip Hop), or are definitely pristine (like some Jazz or classical recording) to compare results. Just because the file isn't clipped when I look at it (usually from excess compression), doesn't mean that some waveforms in there aren't clipped.
 
Most Motherboards do not, I think, put out more than about 1V, so your source is "weak" in the sense that 2V is the typical standard in the Audio world. That said, the original O2 was designed to be optimized for a 2V source at no more than 2.5X gain. So, with a 2.1V source, anything beyond 2.5X would definitely be enough to clip it, I would think. Anyway you could plug the motherboard straight into the O2 to listen for the noise. My guess is you wouldn't be able to clip the amp, but you might not hear the static either, unless the fidelity of the motherboard was good.
 
But I've confused myself - you are using the O2 / ODAC rev B correct? If that is the case the Motherboard Audio outputs aren't relevant since the ODAC rev B is handling the audio feed.

 

[escalibur]

   
Hi there - Contiuum looked "clean" under audacity, even in Mp3, so that can't be the noise you were hearing. Unless the noise is a feature of the music (probably is!), it is coming from something else. Better to see if you can find other recordings that either definitely use static sources (like Hip Hop), or are definitely pristine (like some Jazz or classical recording) to compare results. Just because the file isn't clipped when I look at it (usually from excess compression), doesn't mean that some waveforms in there aren't clipped.
 
Most Motherboards do not, I think, put out more than about 1V, so your source is "weak" in the sense that 2V is the typical standard in the Audio world. That said, the original O2 was designed to be optimized for a 2V source at no more than 2.5X gain. So, with a 2.1V source, anything beyond 2.5X would definitely be enough to clip it, I would think. Anyway you could plug the motherboard straight into the O2 to listen for the noise. My guess is you wouldn't be able to clip the amp, but you might not hear the static either, unless the fidelity of the motherboard was good.
 
But I've confused myself - you are using the O2 / ODAC rev B correct? If that is the case the Motherboard Audio outputs aren't relevant since the ODAC rev B is handling the audio feed.

 
 
Thanks for the analysis. Yes I'm using RevB and it is plugged straight into my MB to USB 3.0 port. Intel's controller which should be the best if not the best available in my case. I'm using Windows 10 native USB drivers because I'm not sure are there any better versions even available.
 
I will try to find some hip hop music to test this even more. So far John Mayer's and Carrie Underwood's songs definitely caused some noise on my cans. :/
 
I will test even with this song. It has some quite 'scary' bass tracks.
 

 

[MrMateoHead]

   
 
Thanks for the analysis. Yes I'm using RevB and it is plugged straight into my MB to USB 3.0 port. Intel's controller which should be the best if not the best available in my case. I'm using Windows 10 native USB drivers because I'm not sure are there any better versions even available.
 
I will try to find some hip hop music to test this even more. So far John Mayer's and Carrie Underwood's songs definitely caused some noise on my cans. :/
 
I will test even with this song. It has some quite 'scary' bass tracks.

 
OK that helps. Frankly, I think you are clipping the O2 by running 2.1V into it + High Gain. Any reason you feel the need to run your headphones that way? FYI 9 O'Clock is a tad low on the dial - running lower gain, you avoid clipping + can definitely get out of possible channel imbalance territory on the volume dial.
 
In short use low gain!

 

[WilliamLeonhart]

 

I would concur with the others that this is caused by clipping. Had it on my old Mayflower O2 ODAC. It's a very lousy decision to build into the product something that you (should) know would cause trouble. So yes it's a "feature" that will result a bug.
Can you specify what make is your O2 ODAC and what is the hi-low gain setting (2.5x/6.5x?) I think the O2 would clip at around 3.5x when driving demanding cans. IMO none of the O2 builds I tried could drive the HD650/HD600 effectively. My first one is only 1x/3x and on hi-gain the volume was not adequate.

 

[castleofargh]

 

 

I would concur with the others that this is caused by clipping. Had it on my old Mayflower O2 ODAC. It's a very lousy decision to build into the product something that you (should) know would cause trouble. So yes it's a "feature" that will result a bug.
Can you specify what make is your O2 ODAC and what is the hi-low gain setting (2.5x/6.5x?) I think the O2 would clip at around 3.5x when driving demanding cans. IMO none of the O2 builds I tried could drive the HD650/HD600 effectively. My first one is only 1x/3x and on hi-gain the volume was not adequate.

 I measure about 0.2Vrms at the output of my O2 right now and that's fine for me while I use replay gain on my music. that gets me at close to 80db more or less at 1khz on my hd650. I get digital peaks around -10/-12db for most songs from replay gain with my settings(not all songs obviously, but it's often in that ballpark for digital peaks with my settings). I know that I'm not a loud listener, when it's late and quiet at night I'm around 50-60db loud and I enjoy that. still, with replay gain, I can get close to 100db with my music on gain 1 and the pot maxed out on the hd650. that's loud for me, I would need to be drunk and screaming the song out of my lungs to justify louder personally. but then again if I was drunk I probably wouldn't care to piss off the neighbors with my speakers instead of using my headphone.

and gain 3X is close to +10db added to whatever I just talked about up until now, that's about twice as loud.
so my hypothesis for your volume not being adequate with the 3X gain, is that your computer never was at maxed output for some reason, or that you might want to start worrying about your ears. I would expect most people to be very fine with gain 1 on the hd650.

 

[WilliamLeonhart]

I never measured mine so I can't know for sure, but I can be sure that my computer was at max volume (why would I touch the volume there?) and it wasn't just me that could not get enough volume from the o2+odac driving hd600/hd650. Gave it to a few friends that own the Senns and they all said the same. So it could be that I remember the wrong gain level on that one O2 (it was diy). But even with some O2 that could give enough volume, the sound was disappointing, in comparison to the Lovely Cube for example. The sound has every trace of bad synergy, like bass that don't have oomph or trebels that is very dull. Not to say that the o2 odac is bad because I stick with them for years before moving onto the $500 price range this last winter, but I think it's not the omnipotent amp/dac that people would want to believe. Anyway now I do have another diy O2 with upgraded opamps to try, but I have not laid my hands on another hd600 yet

 

[dukefx]

Almost every HD600 reviewer complains about the lack of (sub)bass and sluggish speed. Of course there isn't much oomph. Don't blame the amp for that. As far as I know the HD600s are fairly easy to drive. Anything providing more juice than a standard onboard soundcard should do the trick.

 

[escalibur]

  Any reason you feel the need to run your headphones that way? 

 
Mostly out of curiousity is this 'normal' behaviour of my ODAC and HD650s or not. I can live with low gain setting just fine. I don't go over 12 almost at any point. Sometimes when I hear some crazy good song I might give them a shot at 1-2 or too but I couldn't stand that loudness for any longer.

 

[MrMateoHead]

  Mostly out of curiousity is this 'normal' behaviour of my ODAC and HD650s or not. I can live with low gain setting just fine. I don't go over 12 almost at any point. Sometimes when I hear some crazy good song I might give them a shot at 1-2 or too but I couldn't stand that loudness for any longer.

I see!

 
Playing around is certainly a good way to learn. I find that my O2 at 2.5X is TOO MUCH for my more sensitive headphones (I can barely stand 9 O'Clock). My much less efficient HE-400s live around 9-1 O'Clock depending on song, mood, and so on.
 
That said, I haven't yet had the nerve to chop the gain down to 1.0X / 2.5X, which would probably be a lot better for a wide range of very efficient / moderately efficient headphones.
 
Anyway - in the future don't intentionally clip your amps! You risk damage to them or your speakers. Enjoy the O2, it is a great little amp.

 

[Nachash]

You risk damage to them or your speakers.

Worse, your ears

 

[WilliamLeonhart]

Almost every HD600 reviewer complains about the lack of (sub)bass and sluggish speed. Of course there isn't much oomph. Don't blame the amp for that. As far as I know the HD600s are fairly easy to drive. Anything providing more juice than a standard onboard soundcard should do the trick.

nah. I can hear the difference between a well amped HD600 and a not-so-well amped HD600. Just because you have enough volume doesn't mean the cans are being driven to their full potential. After all there's a reason people pay a few hundred bucks to buy an amp for headphones like the ad2000 or the grado ps1000