During my time with the DSPeaker X4 it never produced any spurious noises or misbehaved in any way. I do know one other user who has had significant issues with the X4. However, the manufacturer has been very helpful and has fixed or replaced the unit quickly and smoothly at no cost to the owner (other than perhaps shipping--not sure about that). He loves the unit and has been using it for several years.
In my time with the X4 I only used it in digital in/digital out mode, so I have no opinion on its capability as a preamp.
My current speakers, the Sanders 10e, come with the dbx VENU360 EQ/crossover/time alignment device so, as with my prior Dutch & Dutch 8c, I don't need the DSPeaker unit.
Anyone looking for an EQ/room correction/crossover/time alignment device for up to a three-way configuration (the X4 only handles mains and subs and I don't think it does time alignment) should consider the dbx unit. It only costs $1,000, seems to be transparent (the Sanders 10e using it are the most transparent-to-source speakers I've owned), and the automatic EQ set up is even easier and faster than the X4. The available crossovers are also more flexible than on the X4. Being a pro-audio device, it has a lot of "features" that audiophiles will not want to use. However, all unwanted functions can be turned off or otherwise bypassed. There is a nifty app which runs the machine from a mobile device (I use an iPad) which makes set up and tweaking from the listening position a total breeze. Much more information about this unit can be found in my Sanders 10e thread, for example, this post:
https://www.whatsbestforum.com/thre...ybrid-electrostatic-speaker.34273/post-779557