I may be experiencing a similar problem as your not enough current problem ( I have no problem with Hum, however) I experienced this problem with the ZDT Jr I ordered from the latest drop: It worked fine for the first few days and sounded great, then I noticed that the R channel was fading completely out at times for a few seconds and then fading back in. This was using the High Z out. It didn't happen with the Low Z out. I tried different cables and tubes and different DAC's ( EL DAC and Airist R2R) but the problem kept reoccurring with both my headphones - 6xx and Elegia. Drop was great about allowing a return and I'm now awaiting a replacement.