EVGATech_LeeM
Most importantly, you should always follow the result that gives you the best performance and experience.
 
For the record, however, from our engineers and Audio Note's engineers, when using the Headphone out it's recommended to actually set the Windows/Main volume to 100%, and then raise the Headphone volume slider from 0% until the audio level is sufficient for your headphones.  When the main volume is at 100%, that's the default volume level for the Software side before being passed to the audio card.  Therefore, lowering the volume is simply making the original signal quieter, which may or may not reduce the dynamic range of the source, and will occur before the DAC processes the audio.  When using the Headphone amp, you're adding power to the headphones to drive the signal properly, but if Windows/Main volume is lower, then you're amping an artificially quieter signal and giving more power than the headphone actually needs.  This can also have the added side-effect of adding more noise to the source because the amp is now working harder to bring the signal level back up to the original level.  Because of these interactions, it's possible that the final outcome may result in a signal that does not actually match the source audio (although we're really only talking about a slight difference).
 
Generally, the last volume control in your signal chain should be what you use to increase/decrease the volume.  Everything that comes before (in this case, just Windows/Main volume) should be set to 100% (or very close to 100%; some opinions vary, so just stating that for the record). 

...
 
Ultimately, the OP's suggestion and my post here both recommend essentially the same tactic, but from different ends.  Whichever way you find better for your own listening, start by setting one to a fixed value and work on the other to adjust the volume level, and then stick with that process so that your listening experience remains consistent.  

For comparison's sake... the PCI HT Omega Claro Halo soundcard that I used prior to the Nu Audio had no fine analog control. It simply had a two position high or low impedance jumper. For my 150 ohm headphones I needed the jumper on high but had to reduce windows volume to 10-16. After years of use and enjoying every minute with it I tried several other soundcards that all had poor soudstages simply because the analog amp was set at a fixed state and all volume adjustment had to be done in windows.

Hear me out... 

The Nu audio out of the box sounded equally as poor as all the rest... I was dismayed and about to box it up... and then I noticed the headphone control. By setting it according to my OP for 150ohm headphones the soundstage instantly went from narrow to wide JUST like my old HT Omega card. Everything sounds much more alive when you run the amp higher and bring the volume back down digitally, this works best on amps with a high SNR ration which the Nu audio absolutely has making it ideal to run this way. This has been my experience on home theater audio as well, Klipsch produced a line of floorstanding speakers a decade back that had amplifiers built into each speaker and run with no amp gain control for you to adjust. They ran the internal amp so "hot" that the hiss could be heard 6-10 feet away when you aren't playing anything. But man did they sound amazing. Your home theater receiver had to be dialed way back to accommodate them but it was so very worth it. This was my first clue on how to best amplify speakers/headphones.

Caveat: You absolutely must have higher impedance headphones for the methodology I described to be noticeably better.  

One test track I highly recommend is the song "Shyer" by London Grammar. In the first 15 seconds there are background voices before the song really gets going. With the volume set according to EVGATech_LeeM's method they sound mostly the same distance away as the vocals in the rest of the song, with the volume set up in the method I described one moves much further back into the soundstage and the other closer to the center in comparison with other elements and main vocal. This expanded soundstage can be detected across a variety of content once you've clued yourself into some exact differences.

But yeah, experiment both ways. Your experience will be based on your own perception and even things like the shape of your ear and amount of hearing loss. I just wanted to share what settings made the Nu Audio go from a poor experience in need of return to a viable replacement for my outdated PCI soundcard. :)

ChaobSiroc
[...]

But yeah, experiment both ways. Your experience will be based on your own perception and even things like the shape of your ear and amount of hearing loss. I just wanted to share what settings made the Nu Audio go from a poor experience in need of return to a viable replacement for my outdated PCI soundcard. :)

Right.  As noted, people need to experiment.  Either suggestion gives people a better methodology to do their own testing to figure out what sounds best to them.  The worst thing is to keep flipping settings around in a random order without any better result; it's kind of like overclocking a graphics card or CPU while changing multiple settings at the same time, and still crashing at the same point in a stress test or benchmark. 
 
For myself, I had a little time to play around with the NU Audio Card with a variety of my own headphones.  In a couple cases, there were sweet spots to have the headphone amp at, whereas others were less sensitive.  However, there's enough power in the headphone amp that I was able to tell when there was a little too much power, even when driving my 600ohm beyer DT 990 Pro's.  The thing to keep in mind is that impedance is only one measure for how hard it is to drive a pair of headphones.  Everyone's experience will vary, but people should remember that over-amping headphones can have an adverse effect on audio quality, as well.

my father has a pair of headphones that might have higher impedance, i remember that they sounded very good (but I was a kid back then). if memory serves me correctly they are Koss (?!)
 
will have to stop by his house to check on them :)

I'm liking this sound card so far, but the one thing I am really not thrilled with is the surround mode. It's hard to explain but it almost seems too precise. The Best way I can think of explaining this is, for example, in minecraft, when I'm hearing things that are to my right, I only hear the audio in my right ear, which is quite distracting, because obviously in real life if you hear something to your right, you hear it mostly in your right ear yes, but you also hear it with your left to a degree. I hate to say it but it almost seems worse than the software the realtek soundblaster card had.

PieSappinMyCake
I'm liking this sound card so far, but the one thing I am really not thrilled with is the surround mode. It's hard to explain but it almost seems too precise. The Best way I can think of explaining this is, for example, in minecraft, when I'm hearing things that are to my right, I only hear the audio in my right ear, which is quite distracting, because obviously in real life if you hear something to your right, you hear it mostly in your right ear yes, but you also hear it with your left to a degree. I hate to say it but it almost seems worse than the software the realtek soundblaster card had.

You can try to also use Windows Sonic or Dolby Atmos for Headphones with the NU Audio virtual surround.  That might alter the processing enough for you that it sounds a little more natural.  

EVGATech_LeeM
Most importantly, you should always follow the result that gives you the best performance and experience.
 
For the record, however, from our engineers and Audio Note's engineers, when using the Headphone out it's recommended to actually set the Windows/Main volume to 100%, and then raise the Headphone volume slider from 0% until the audio level is sufficient for your headphones.  When the main volume is at 100%, that's the default volume level for the Software side before being passed to the audio card.  Therefore, lowering the volume is simply making the original signal quieter, which may or may not reduce the dynamic range of the source, and will occur before the DAC processes the audio.  When using the Headphone amp, you're adding power to the headphones to drive the signal properly, but if Windows/Main volume is lower, then you're amping an artificially quieter signal and giving more power than the headphone actually needs.  This can also have the added side-effect of adding more noise to the source because the amp is now working harder to bring the signal level back up to the original level.  Because of these interactions, it's possible that the final outcome may result in a signal that does not actually match the source audio (although we're really only talking about a slight difference).
 
Generally, the last volume control in your signal chain should be what you use to increase/decrease the volume.  Everything that comes before (in this case, just Windows/Main volume) should be set to 100% (or very close to 100%; some opinions vary, so just stating that for the record). 
 
Examples of some common scenarios.  For simplicity's sake, assume I'm referring to an integrated amp here, and we'll leave the pre-amp/amp discussion for another day:

• Windows/Main (100%) -> NU Audio Card -> (DAC) -> NU Audio Card Headphone Amp (Control Volume Here) -> Headphone Out -> Headphones
• Windows/Main (Control Volume Here) -> NU Audio Card -> (DAC) -> Line Out  -> RCA to 3.5mm / 6.3mm adapter -> Headphones
• Windows/Main (100%) -> NU Audio Card -> (DAC) -> Line Out  -> RCA to 3.5mm / 6.3mm adapter / RCA cables -> Amp (Control Volume Here) -> Headphones
• Windows/Main (100%) -> NU Audio Card -> (DAC) -> Line Out -> Powered Speakers (Control Volume Here)
• Windows/Main (100%) -> NU Audio Card -> (DAC) -> Line Out -> Receiver/Amp (Control Volume Here) -> Passive Speakers 
• Windows/Main (100%) -> NU Audio Card -> (DAC) -> S/PDIF Out -> Powered Speakers / Sound Bar (Control Volume Here) 

• Windows/Main (100%) -> NU Audio Card -> (DAC) -> S/PDIF Out -> TV / Receiver (Control Volume Here) -> Passive Speakers 

Yes, I'm going to take a pass on S/PDIF to TVs with sound bars, since there are too many combinations and TV/sound bar interactions for this sort of post, lol.
 
Now, bear in mind that there's currently no way to change the Headphone volume in the NU Audio Software without Alt-Tabbing out of a program or manually moving it up or down in the NU Audio software, so I can understand that people might want to have some flexibility to raise and lower the Windows volume using hotkeys or through the actual program.  That may require a bit of testing to find the right balance (e.g. set Windows/Main volume between 75-90% and find a good balance with the Headphone volume).  
 
Ultimately, the OP's suggestion and my post here both recommend essentially the same tactic, but from different ends.  Whichever way you find better for your own listening, start by setting one to a fixed value and work on the other to adjust the volume level, and then stick with that process so that your listening experience remains consistent.  

This is amazing information! Thank you!!
 
I am using Beyerdynamic MMX300 which only has an impedence of 32 ohms, but this helped me to dial in the sound. Thank you!

Thanks for your suggestion OP!  Once I used your settings the sound stage opened up.  Much preferred approach compared to the 100% Master Volume advice.

WolfJet

EVGATech_LeeM
Most importantly, you should always follow the result that gives you the best performance and experience.
 
For the record, however, from our engineers and Audio Note's engineers, when using the Headphone out it's recommended to actually set the Windows/Main volume to 100%, and then raise the Headphone volume slider from 0% until the audio level is sufficient for your headphones.  When the main volume is at 100%, that's the default volume level for the Software side before being passed to the audio card.  Therefore, lowering the volume is simply making the original signal quieter, which may or may not reduce the dynamic range of the source, and will occur before the DAC processes the audio.  When using the Headphone amp, you're adding power to the headphones to drive the signal properly, but if Windows/Main volume is lower, then you're amping an artificially quieter signal and giving more power than the headphone actually needs.  This can also have the added side-effect of adding more noise to the source because the amp is now working harder to bring the signal level back up to the original level.  Because of these interactions, it's possible that the final outcome may result in a signal that does not actually match the source audio (although we're really only talking about a slight difference).
 
Generally, the last volume control in your signal chain should be what you use to increase/decrease the volume.  Everything that comes before (in this case, just Windows/Main volume) should be set to 100% (or very close to 100%; some opinions vary, so just stating that for the record). 
 
Examples of some common scenarios.  For simplicity's sake, assume I'm referring to an integrated amp here, and we'll leave the pre-amp/amp discussion for another day:

• Windows/Main (100%) -> NU Audio Card -> (DAC) -> NU Audio Card Headphone Amp (Control Volume Here) -> Headphone Out -> Headphones
• Windows/Main (Control Volume Here) -> NU Audio Card -> (DAC) -> Line Out  -> RCA to 3.5mm / 6.3mm adapter -> Headphones
• Windows/Main (100%) -> NU Audio Card -> (DAC) -> Line Out  -> RCA to 3.5mm / 6.3mm adapter / RCA cables -> Amp (Control Volume Here) -> Headphones
• Windows/Main (100%) -> NU Audio Card -> (DAC) -> Line Out -> Powered Speakers (Control Volume Here)
• Windows/Main (100%) -> NU Audio Card -> (DAC) -> Line Out -> Receiver/Amp (Control Volume Here) -> Passive Speakers 
• Windows/Main (100%) -> NU Audio Card -> (DAC) -> S/PDIF Out -> Powered Speakers / Sound Bar (Control Volume Here) 

• Windows/Main (100%) -> NU Audio Card -> (DAC) -> S/PDIF Out -> TV / Receiver (Control Volume Here) -> Passive Speakers 

Yes, I'm going to take a pass on S/PDIF to TVs with sound bars, since there are too many combinations and TV/sound bar interactions for this sort of post, lol.
 
Now, bear in mind that there's currently no way to change the Headphone volume in the NU Audio Software without Alt-Tabbing out of a program or manually moving it up or down in the NU Audio software, so I can understand that people might want to have some flexibility to raise and lower the Windows volume using hotkeys or through the actual program.  That may require a bit of testing to find the right balance (e.g. set Windows/Main volume between 75-90% and find a good balance with the Headphone volume).  
 
Ultimately, the OP's suggestion and my post here both recommend essentially the same tactic, but from different ends.  Whichever way you find better for your own listening, start by setting one to a fixed value and work on the other to adjust the volume level, and then stick with that process so that your listening experience remains consistent.  

This is amazing information! Thank you!!
 
I am using Beyerdynamic MMX300 which only has an impedence of 32 ohms, but this helped me to dial in the sound. Thank you!

+1 thanks! Great post. 
 
Got a question passing sound to a second PC. Is it possible to pass sound to a second PC (without sound card) with the NU Audio? And if it is what would be the best way to avoid quality/latency issues (if any)?

I am using Corsair G933 with connecting by cable to Headphone exit and I am getting in trouble to config it.
 
When I match both sides, I do not get loud and clear volume. For example I did 60;50. Can someone explain better how it works? Volume in windows are 100%.
 

 
The G933 has
20 Hz- 20 KHz Speaker Response
Technical SpecificationsHeadphone

Driver: 1.6 in (40 mm)

Frequency response: 20 Hz - 20 KHz

Impedance: 39 Ohms (passive), 5k Ohms (active)

Sensitivity: 107dB SPL/mW 

HE4THEN
 
Got a question passing sound to a second PC. Is it possible to pass sound to a second PC (without sound card) with the NU Audio? And if it is what would be the best way to avoid quality/latency issues (if any)?

There's a couple ways you can do this.  I'm assuming that the second PC will have a Line-In port (preferable to a Mic-In, if possible, but the Mic-In would have to do if not).  I would run the Line-Out (RCA) through the RCA to 3.5mm adapter and send that into the second PC.  Not much more to it than that.
 
To keep quality/latency down, I'd make sure that all of the device drivers are installed, use the minimal amount of bloatware, and test for good recording software (Some may perform better than others for your application).  Moreover, I'd also make sure you've turned off any enhancements, including mic boost, echo cancellation, noise reduction, etc.  Of course, once you've tested the incoming audio you can make adjustments to any sort of mixing and enhancements so that it ultimately sounds the way you want it to.