[LizardKing1]

I installed WASAPI on my laptop (Windows 7) a while back and through the crappy speakers there was a very obvious difference. So today I thought about checking out if it would make a difference with my headphones. I am using a Fiio E7 as a USB DAC/amp and the Shure SRH750. WASAPI made a clear difference from my desktop computer for the better, everything was more refined, better instrument separation, more detail. 
 
But I remember having read somewhere on Head-Fi that USB DACs didn't benefit from WASAPI since they already bypass all the Windows sound filters, and also that the Windows 7 sound was much better than the previous versions' (my desktop computer runs XP). So I assumed that maybe the improvement I have seen is just the Windows 7 sound and not WASAPI. I turned WASAPI off during playback, and I think I noticed a difference. I think the sound got a bit less refined and warmer, like it's veiled. I could be imagining it, the difference is small. And it still sounds better than on XP.
 
Now, another thing is that with this setup I find some distortion on some tracks. I don't think they are the best mastering piece of work so I thought maybe the track is just bad, and whatever improved the sound, be it WASAPI or Windows 7, just exposed those flaws more.
 
So the short version is this: WASAPI on Windows 7 makes music sound better than on XP, is this WASAPI or Windows 7, considering I'm using a USB DAC? Second, can WASAPI create distortion, or instead it, or Windows 7, is just exposing the distortion that already existed on the track? Thank you for helping.

 

[MaciekN]

USB DACs have nothing to do with windows "sound filters", only their drivers can if they support ASIO or something. It is the driver that can bypass system sound mixer, and wasapi does just that. It is a step up from XP where you had to install third party drivers to bypass the kmixer like ASIO or Kernel Streaming. Now, about the distortion, it may be due to any EQs turned on. WASAPI does not introduce any kind of distortion, it is just a build in route for sound related software to communicate directly with hardware.
 
Maybe the difference between OS' is because you used Direct Sound on XP, native xp sound drivers that pass the sound data through kmixer.

 

[LizardKing1]

I don't have any VSTs turned on on Foobar, and since nothing else could affect it (that's the point of WASAPI 

) it's not due to any EQ. I think the distortion might be from those songs only, it's only in a vocal part of an electronica song and I'm used to those sounding bad with vocal samples.
 
So as you say WASAPI is definitely making a change, wether I can perceive it or not? Good to know. As for the difference between XP and 7, like I said even with WASAPI off it's obvious. So on Windows 7 sound doesn't go through any system sound mixer? 

 

[Elysian]

All Windows sound goes through the Windows Kernel Mixer.  You must use WASAPI, ASIO, or kernel streaming to bypass the kernel mixer.
 
The USB connection on your DAC has absolutely nothing to do with the way Windows outputs your music's digital signal through its kernel mixer.

 

[LizardKing1]

Right, too bad on XP Kernel insists in barely playing anything and ASIO simply doesn't work...
But then I would assume the Windows 7 mixer must be much better than the XP's mixer, right?

 

[Elysian]

Kernel streaming in XP is super buggy.  I used to BSOD all the time using kernel streaming through Foobar.  It might've been my Creative drivers at the time, but I heard a fair number of complaints.
 
I'm not sure what differences there are between the Windows 7 and XP mixer, honestly.  Hydrogenaudio is probably a much better community for that kind of question, as they know computer music far better than any other audiophile community out there.
 
Most people don't notice much difference going between DirectSound and WASAPI.  I wouldn't stress out too much over it, and would just use whatever's stable.  Even at HA, they say that the majority of users will notice no difference between DS and WASAPI, which is a testament to the placebo effect among audiophiles.

 

[Roller]

DirectSound in Vista and 7 is quite decent because the KMixer issue is significantly alleviated from its trash condition on XP. Technically speaking, as long as audio drivers are working along without applying any sort of processing to sound, DirectSound (again, on Vista and 7, not XP)should sound virtually indistinguishable from WASAPI as long as all audio changes are done after the computer is done putting out sound.