so you call Z-Reviews someone with little expierience? Yes the amp is weaker, but im pretty sure that YOU don't hear any compression! As said early: Technically thats close to impossible to achieve on the dac side. You know that we have 16bit or 24bit on this dac, depends on what you want, so you have 96dB dnr, reduced to 72db cause you don't want to use the bottom 20dB, so overall your music has 72db possible dnr, a really good recorded orchestra has a dnr of around 80db, which also doesn't look at the 20dB, so we have 96db max, and 80dB max, thats around 65,536 volume steps we could reproduce. btw, the orchestra with 80dB is already a stretch!
So dynamic compression is bound to never happen on the dac side! I found some measurements on the dnr of this device in overall, it's around 76dB which still wouldn't lead to compression. A other thing is, did you use the DSP? So EQ and so on, or did you use the HD Mode(DSP getting ignored)?
BTW hearing a different DAC is possible, though not as clear as you make it up to be.