Thanks once again Avionic. I looked at the path diagram and it looks like the only difference is that tape in comes in further down the path (after the selector and before the main preamp). Until I learn how to clean the input selector switch I'll run the DAC in through the tape inputs. I need to find a primer on cleaning the switches, etc. Selector, volume and loudness are all a bit dirty.
BTW, the sound quality from this DAC (Audioengine D1) is excellent. The maker says that the unit needs to burn in for 40-50 hours (I've done about 8 so far) but I've been listening to Duke Ellington at the Newport Jazz Festival and it sounds great.
Thanks.