What @atmasphere writes is very much what is causing your change in sound character. Loading at the phono stage and not at the cartridge is what you should be looking for. Also what phono cable are you using and do you know its capacitance? A very low cap cable should be what you use along with a higher resistive setting at the phono stage (like 1000 ohms) then you allow the cantilever to move freely in the groove, rather than a low resistive setting might stiffen the cantilever and make the cart work more.
If I load my Delos at 100 ohms the sound is closed, restrictive and bland, I load at 475 ohms and the sound becomes very dynamic and very high resolution.
If I load my Delos at 100 ohms the sound is closed, restrictive and bland, I load at 475 ohms and the sound becomes very dynamic and very high resolution.