'Attacking' sound quality of the Denon DCD 680?

Hi guys
i am new to this forum, absolute beginner in electronic skills but experienced in HiFi.
few days ago i got Denon DCD 680 for almost nothing.
it is built like tank, mechanism is ok, laser reads in second....but sound is poor, enhanced trebles, the whole 'picture' is too agressive and atacking

some people says it is the analogue part of its output and recommended Pass D1 instead the original one.
what do you think of that? is there any thread of this subject, perhaps with picture of PCB, list of parts...?
@oshifis...hi neighbor lol
well yes i have sony d1000 *the old one with HD inside too* and that one is singing very sweet
on the other hand Denon played harsh through Denon pma 920 and through Rotel 840bx2 too so i guess it must be the 680?
any suggestions, tweaking it or to use it as transport only and build separate DAC (terrifying idea for me lol)?
I have no direct experience, but the datasheet says it is a 1-bit DAC. This type is very sensitive to master clock jitter. Perhaps you could upgrade it with a low-jitter clock, but I am not sure it is worth the effort. It could turn out that you also need to upgrade the power supply, the analog output, replace capacitors, etc. At the end it could be more economical to find a Philips/Marantz CD player with multibit DAC second hand.