If you don't have a preamp, it cannot degrade the sound.
Listen to a DAC direct to amp at low volume and then listen to the same DAC via a preamp like the Benchmark LA4. There are some expensive DACs that are similar to the LA4 level of volume, such as the Lumin X1 with Leedh volume control. All DACs I have owned in the moderate price range were not good direct to amp at low volume.