Dac+ standard exhausting/tiring to listing at

 Hi
I have a Dac+ standard board that I am not super excited about - Yes the sound is well detailed incomparable with my computers Audio output but one annoying thing is that I kind of gets an exhausting/tiring feeling in my ears when listing to it ! and its gets like that immediately when I start listing to music.

I had a oscilloscope on it playing a sound file with a 1KHz sinus sampled at 48K - and l I could see some peaks around the sample frequency when doing FFT but  beside from that nothing to see - think the 48KHz signal was down with -60-70dBV if I remember correct and I guess that's fine, i would have to check again to be sure.

had the DAC+ for little longer than a year but haven't been used it much but now i am looking in to build the RSP2 together with an old home-made B&O ice-power Power amp as an streaming amplifier so its kind of a petty

any idea if there could be something wrong with the module ? and if there's a way to measure it or if it just my ears + my girlfriends ears not liking the sound

I tried playing with different speaks and Amps  the listing tiring is the same.