Hi.
Few days ago my DX3 Pro+ arrived so I though I will write a short opinion piece. I won't touch topics of measurements or sound quality etc. - I have no knowledge nor means to do that beside subjective claims (well, it seems to produce sound, so...).
I recently replaced my old M-Audio speakers with KRK Rockit 5 and what I really needed was a sort of glorified volume control device plus ability to plug in my headphones. So I could probably find some cheaper alternative, on the other hand DX3 Pro+ with its good measurements and few additional perks seems like a good option.
I wasn't 100% sold on the look of the device - actually I liked Loxjie D30 a bit better, and if that one had a black variant I imagine I would picked D30. The element I was not sure was this orange display as I planned to place the device in front of me under the computer monitor and I was worried that it will be a bit distracting. But you can switch the display to turn off all the information (besides the input indicator) after 30 seconds which is good enough for me. Other than that the device seems to be a good looking and nicely build one - I don't have much experience here really so take this statement with a grain of salt. The box and packaging is nice, no complaints.
The primary feature that made me select DX3 Pro+ was ability to switch between output modes. There are three - line out, headphones and line-out and headphones both at the same time. It means that I can connect my KRK's (using two RCA - XLR cables - picked up something cheap from some Polish vendor) and my headphones (I have just a pair of Superlux HD668B) and then easily switch using the volume knob or the remote.
The volume knob is of click-clickety type. My wife immediately noticed this trait - I'm not sure if she was in the kitchen, but she came in and expressed her opinion anyway (actually she asked 'Does that thing have to do that?' with her eyebrows raised). I would say the clicks are a bit on the loud side, personally I don't find it annoying or distracting.
As you can find in the manual the volume knob is multi-functional. Besides controlling the volume you can press it once to switch between input sources, and double press to switch between outputs. That was another advantage of this device. For example I also considered some models from JDS but they have the line-out/headphones switch button on the back and it is also used to power off/on - not the best design IMO. Anyway in practice one may find double-press action of the volume knob in DX3 Pro+ a bit hard to execute initially. I have learned that you really need to allow the button to 'de-press'/go back to the initial position before executing the second click/press, otherwise you will likely switch input sources twice. It could be a bit better/easier (its a mechanical thingy primarily I suppose), but after few days I kind of adjusted to it. Anyway, one can also use the remote to switch the outputs. Personally I would prefer to have outputs switcher bound to one click and inputs switcher bound to double click, but that's me I suppose.
I don't have personally much use for coaxial or optical inputs. I tested the Bluetooth input with my phone (Nokia 8/Android) and it seems to work. Although I think I had one or two cases when the connection seems to be established but no sound was produced - I had to fiddle a bit with switching inputs to fix it, or something like that. Also my phone won't connect to DX3 Pro+ automatically - I need to select it each time. I don't care about this feature much (at least for now), maybe there are some settings in Android, dunno. I may try to test it with other phones later - from time to time my phone seems to have problems with talking to my car via Bluetooth so the problem may be on its side.
As mentioned earlier you can switch between line-out, headphones and both. Each mode has a separate volume level maintained which is quite nice. Before, when connecting my headphones to my M-Audio speakers I had to pump-up the volume (and then decrease it before disconnecting headphones again...). The new configuration allows to more control in that regards obviously.
The device is a bit of warm when powered on, but not hot, so I think everything is OK on that front as well.
Below are a few Linux-related comments, as this is what I use on my PC.
Actually after connecting DX3 Pro+ to the PC via USB I got no sound initially. I fiddled a bit with the sound settings, alsamixer etc. but to no avail. I restarted the computer which helped. I had no such problems later so I haven't try to investigate it more.
In the sound settings I have two new output devices: 'Digital Output (S/PDIF) - DX3 Pro+' and 'Analogue Output - DX3 Pro+'. I kind of don't understand that really, I'm not sure if that's how it supposed to be? Switching between them does not seem to make any difference.
PulseEffects seems to work - I don't use it much to be honest, just played a little bit with its PEQ some time ago.
You can configure Pulse Audio to (try to) avoid resampling - I tested several high-res sample audio files and according to info displayed by DX3 Pro+ they weren't resampled.
There is one weirdness related to the list of USB devices. DX3 Pro+ is identified as Bus 001 Device 003: ID 152a:8750 Thesycon Systemsoftware & Consulting GmbH DX3 Pro+
which is kind of strange (Thesycon seems to be some company related to USB audio). Anyway, the real weirdness is that after connecting DX3 Pro+ my mouse, which is normally identified as Bus 001 Device 005: ID 1e7d:2dc2 ROCCAT
now is identified as Bus 001 Device 005: ID 1e7d:2dc2 ROCCAT DX3 Pro+
. On the other hand I'm definitely observing much improved smoothness and accuracy of my mouse - the cursor glides now through the screen with unparalleled accuracy and anything it moves over is blessed with additional sharpness and level of details. Unexpected, but I suppose that's what makes Topping so awesome company!