USB cables either work, or they don’t. Analog cables, like unbalanced RCA, add more resistive and reactive loads as they get longer, thus slowly degrading the signal as length increases. Use your 15’ USB cable.
Long unbalanced RCA or long USB cable?
In my listening room it's not feasible to put my computer, which I stream from, close to the audio rack. So what's the best option, 15 foot USB to the DAC in audio rack or short USB at computer with 15 foot unbalanced RCA cables to the preamp? Or am I just over thinking it. Presently I'm running a fifteen foot USB to the DAC which is placed with all the other components. I'm getting no dropouts but there is so much talk about long USB cables not being good for sound I'm not sure which way to go.