I had my DX3 Pro for about 4 months before it put itself into standby mode and refused to come out of it. Now amount of input switching, power-cycling, factory-resetting, or anything else would get the device to come out of its coma.
However, my first assumption was that there might be something wrong with the cheap power-supply that it shipped with. So, I grabbed a much higher output rated supply from my closet and tried that before assuming the DX3 Pro was toast forever.
It worked!!! ... ... Sort of.
The DX3 Pro would come out of standby reliably using a stronger power-supply. But, now I had a new issue. Anytime an input was active, I would hear a loud distorted buzzing coming through the headphones. This noise wasn't only when audio was playing, nor was it influenced at all by volume controls. The noise stayed the same volume no matter what. If I switched to an inactive/unused input, then the noise would stop.
Oddly enough, I was able to get the noise to go away if I unplugged and re-plugged my headphones into the front of the DX3 Pro some inconsistent amount of times. However, as soon as the DX3 Pro was power cycled or put in and out of standby mode, the noise would come back, and I'd have to do the headphone jack dance again to try to get it to go away. While it was nice to have a remedy of sorts, it was inconsistent, and it seemed to work less consistently after each attempt.
Given the fact that I could make the problem go away temporarily by screwing with connecting things to the headphone jack, I began to wonder if the problem was isolated to just the headphone output paths in the DX3 Pro. So, I bought an Atom Amp to hook up to the DX3 Pro to try to use it as just a DAC. I figured it'd either work and I'd have a solid DAC with an improvement to my amp setup, or it wouldn't and I'd be half-way to having a replacement setup (just needing to buy a dedicated DAC and figure out what to do about the defunkt DX3 Pro I have laying around).
At first I thought this worked. I hooked everything up, and it didn't seem like the buzz/hum/noise was making its way to the DX3 Pro's Line-Out and into the Atom Amp, but I was wrong. I tempted fate and did a power cycle on the DX3 Pro. The noise was now making its way into the Atom Amp too. At this point, no amount of fiddling with the plugging things into the DX3 Pro's headphone jack appears to get me to a half-working setup, and now the buzz/hum/noise is a constant. I then tried yet another power supply, and that had no impact whatsoever. The noise persists, so I've just removed the DX3 Pro from my setup, I'm trying to sort out what to do to replace it.
I don't have much in the way of capacity to analyze the DX3 Pro meaningfully to track down what went wrong with it, but I wanted to layout my saga with the thing here in case it triggers any thoughts for the experts around here as to what's going wrong with these units.