Opened JDS Labs' C5D page and read: "super fine volume control to handle sensitive headphones and IEMs". Don't know anything about it though, but thought it a bit funny in contrast to what you write. Looks like a very interesting DAC/AMP combo.
Got my C5D, and I really like the sound. I like it because it's very clear and transparent. Lots of treble though. Since I'm a big fan of ODAC/O2 which JDS sells, and communicated with jseaber(JDS Labs) on here, and he assured me the testing procedure of the portable DAC/Amp went through the same spirit as the ODAC/O2, trying to get the same outcomes or better. So, I trusted and got it today, and so far it's sounding real nice. I recommend it, as I like clear transparent sounds.
I wish I could have tried the 334 out of the C5D.
Here is the link to the product thread
Edit: read my posts that follow after to get a more whole assessment. It doesn't sound as well as I initially thought.
Edited by SilverEars - 3/22/14 at 5:47am