Kudos to Ted Smith and must agree with his advice to use the DS DAC without a preamplifier. If you have not tried the feeding the output of the DS directly into an amplifier, it may be worth trying. Per the owner’s manual, I eliminated my preamplifier and was highly pleased with the resulting advance in sound quality. As Ted suggested, I am using an XLR cable costing less than $100. As well I am using the iTunes/BitPerfect combination. Wow, much thanks for the advice!
As an update to the above, I went back to using my preamplifier. Previously, I cut out my preamplifier because my inexpensive XLR provided some benefits over using my preamp with RCA cables. Recently, I got a very good XLR from High Fidelity Cables and the transparency helped me to hear what was missing without the preamp in the system. To get the preamp back in the system, I used a Cardas XLR/RCA adapter.
The setup with the preamp provided a much more resolving, tonally balanced and in-depth listening experience.
Bottom-line: this hobby is about tinkering so do try different things with your equipment!