Well, I guess I'll go for D50s + Atom (still half price of DX7 PRO), as before I was thinking on more expensive DX7 PRO, but I don't need all those bells and whistles.
Of course, I plan to mod, by changing the OPAMPs, antenna, and more.
Now for some "problems" with the unit, this is due to some factors:
- The bluetooth antenna they supply is pretty bad/crap;
- Coaxial (SPDIF) seems not to work;
- Use a good USB cable.
As for bluetooth, just buy a good WiFi antenna, BT works between 2.4GHz until 2.48GHz (2.4835 to be exact) frequency.
Interference may be at fault too. Don't forget BT works well up to 10m (no walls, etc), after that depends on your antenna + environment + transmitter.
If it "lags"/losses signal (aka connection strength), is due to those things above. LDAC is still the best BT protocol (as of 2019).
Now for coaxial. The cable NEEDS to have 75Ω (ohms) of impedance, also, it should never be over 10m (less is better) !
In general a good quality Composite Video RCA cable will do. That's it.