Hi Jeff and it’s a great question. Lonson is right in that what you have is working great so it’s ok. If, however, you’d like to make a step up in sound quality, then adding a preamp like the BHK is the right thing to do. That is not true for every preamp which is what had me stumped at first, but once I heard a certain level of instrument I was hooked. It turns out that while (obviously) going direct with the DAC is a just fine, the added buffering and isolation of a preamp brings you that much closer to musical truth - and that’s again why you have to be careful that the device is of a certain quality. Place something not up to par inline with the DAC and it’ll actually degrade the sound.
I can certainly speak with some experience on the BHK because my system—like yours—sounds terrific with and without it as fed directly from the DS. With the DS feeding the amps directly there’s a certain flatness to the images that is not apparent until they are rounded by the addition of the preamp. Kind of like moving from slightly two-dimensional cutouts to fully rounded three-dimensional renderings with and without the preamp.
I believe this happens for two reasons: the first is the complete isolation of the DAC when the preamp is inserted, and keeping the DAC’s volume control at 100. The first is somewhat obvious and easy to understand. The latter, not so much. In speaking with Ted Smith about the volume control he/and I are convinced it is bit perfect regardless of where you set it. Yet, I suspect there’s more to the story that hasn’t been sussed out. We know, for example, that small changes in the code make big differences in the sound and I have speculated for some time that keeping the volume at 100 might make a difference, though it’s just an unproven theory.
Hope that helps.