Since you have bitstreaming set to ON for DSD files, that means JRiver doesn't touch the data when sending it to your DAC. It just sends it with no modifications. So, that means JRiver can't change the volume of those files. It's bitstreaming them! That's why the volume control shows 0. It's disabled because of the bitstreaming.
I have no idea if what you're hearing is a consequence of the recording, your DAC, or something else. But you *might* try turning bistreaming off. Then set up the Output Format section in DSP Studio to convert DSD to PCM. To do so, just set everything from 352,800 Hz and up to a rate that your DAC can handle. For example, on my DAC, it's maximum supported PCM rate is 192,000 Hz. So I set 352,800 and up to be converted to 192,000. That's how I listen to DSD because my DAC doesn't support DSD.
Why would I suggest this if your DAC *does* support DSD? Because some people say that nice some nice sounding DACs that happen to support DSD, do a better job with PCM and you get better sound quality by converting to PCM first. I don't know if it's true, but it's probably worth testing. It's just a few clicks of the mouse.
Good luck,
Brian.