Guido is probably right as usual.
I would like to share my experience with my Esoteric K-01 and I believe it applies to the D-03 too. If you go to settings, and toggle through to "Analog Output" you have a choice of 0dB or +6dB. Try the +6dB and see if this improves things. If not, you are better off with a high quality analog preamp. I have found the +6 dB setting changes the sound. Although you get more gain, but strangely enough, as the volume increases, the sound gets congested or constricted, and the soundstage collapses. So, I got a good analog preamp and everything just falls into place very nicely after that.
Cheers! J.
I would like to share my experience with my Esoteric K-01 and I believe it applies to the D-03 too. If you go to settings, and toggle through to "Analog Output" you have a choice of 0dB or +6dB. Try the +6dB and see if this improves things. If not, you are better off with a high quality analog preamp. I have found the +6 dB setting changes the sound. Although you get more gain, but strangely enough, as the volume increases, the sound gets congested or constricted, and the soundstage collapses. So, I got a good analog preamp and everything just falls into place very nicely after that.
Cheers! J.