@Shelley:
Sporting the JH13s at my desk this morning, using the HeadRoom Desktop Amp/DAC (Home Modules) and HeadRoom Desktop Power Supply. I have tried them out with no music, with a few different types of music, and with Luis's "TOTAL SILENCE" track from something he did awhile back.
With no music playing, at low gain it is pretty much dead silent all the way up the volume range, but after 12 o'clock there is a little "presence" of background that is very faint. At medium gain, it is pretty similar, but the low background starts at 11 and is not above background level most of the way although it is noticeable. At high gain, it starts about 11 o'clock again and is "louder" above 12 than either of the other settings. All in all, very impressive noise floor and there is no point at which I would call it "hissing" because it is a passive sound, if that makes any sense.
With music on, there is no untoward sound to my ears at any gain setting. I listened to quiet pieces and noisy one, and did not get any kind of hiss or noise floor in quiet passages or in between tracks. Unless it is in the recording, that is, because recordings that have a lot of noise come through loud and clear just like anything with these cans. At low volumes there is no hiss or noise floor on any gain setting. I have them playing now and it sounds very sweet and noise-free at low volume (7/8 o'clock on medium).
The TOTAL SILENCE track is just that and I cranked it up all the way with very similar results to the no music playing info above.
All in all, a good match and something that would make a great transportable setup for hotels/road trips/etc.