I checked the graph once again and compared it with my measurings. This looks most similar to yours:Amplitude has no effect, even at -10dB down in the signal generator I still get the same spectrum of distortions. This is definitely some processing going on.
No biggie though. Since I use the rather excellent ASIO driver of my RME for my VSTi anyway, I just set Foobar to ASIO for peace of mind. This way I get bit-perfect playback (verified) and can still mix in other sounds from other programs if need be. Best of both worlds, I guess.
The difference is close to impossible to hear for me. I put on a track ( a loud one, lots of high frequency content) at my usual 90dB Z-peak listening volume and turned it down by 55dB. I could hear faint high frequencies just at the edge of my perception. There is -0- chance I would ever hear that while actual music is blasting into my ears.
Signals were generated at 48KHz while output was set to 44.1KHz. Signals were 18500Hz and 19000Hz at -6.3dB. If it will be louder, it will be all over the place because of CAudiolimiter. Converting 48KHz source to 44.1 seems to be worse case scenario.
Also when CAudiolimiter is triggerred it looks like this:
So I assume you triggered just the resampling/reclocking filter, but not limiter. I assure you in that case its much worse.