It depends on how good the volume control on your preamp or integrated amp is. Basically you want to set the volume of the less accurate preamp as high as possible (90% of maximum for example) and use the better preamp to make the fine adjustment. If both are equally good, set both to around 0db (mid-point). It is easier to test your preamp at low volume. Set DAC-9 to near maximum volume and try it out with your integrated amp. Does the music sound well detailed at very low volume? Do the opposite and compare again.