I sometimes used a USB extension cord, both for strain relief and as an inexpensive way to reach the cabling to my stereo. I couldn't hear any difference between having the USB extension in and out of the signal chain. But I could hear differences between the internal DAC and the Dragonfly, and differences using Audirvana to buffer the music files and change the upsampling from 24/96 to 24/88.2 on redbook-based lossless iTunes files.
Like I said, the Dragonfly is a cool little item and extremely well made. It's particularly great at driving bigger headphones with improved dynamics and clarity. For my purposes the money was better spent at this time on Audirvana s/w feeding a real tube linestage.
If I did a lot of traveling with my laptop, I would get the Dragonfly to drive the Sennheiser 580s, or the Grado SR60s for that matter. Since my system is mostly home-based, if I try an asynchronous USB DAC again it will probably be the Musical Fidelity V-DAC MkII with Pangea power supply. My personal opinion is that voltage abundance and stability is the achilles heel of in-line USB DACs. After all, if the Pangea PS improves the sound of the V-DAC, how could an inline USB DAC compete with the miniscule voltage in USB?
Speaking of which, I think half the reason my new tube linestage sounds so smooth and organic is that the transformer is *enormous*. Too tall, in fact, to fit on my equipment rack.
