Topping A90 failure issues. Should I try a 3rd A90?

Thanks, sincerely, for everyone's comments.
@atmasphere long story short, I've diagnosed 2 different laptops. I did have a static issue with a new Dell (I think it's their UBS audio -- part of the motherboard -- that's frankly cheap) but an 7 year old Lenovo X1 Carbon works great. I tried 3 different A-B USB cables and 2 of ifi inline jitter devices. No help. But this is different. After a loud static discharge, one channel went out. The volume knob - turning it down or up -- made it worse. I'm 90% sure it's the Topping A90 has a problem. As to an eariler comment from @ audio2design there is no external power supply on these. The A90 & D90 have their own. (Earlier Topping models did have an external power supply). Again, thanks to all. I loved the idea of this set but I think there's a build issue? Who knows. 

@soix valid point but I'm not sure what could contribute to it from my setup. I use it as a standalone setup, the Topping A90 & D90 with the recommended XLR balanced cables. The only inputs are a USB A-B connection to the D90 (DAC, not amp) and power cords into a separate power conditioner/strip.  

Have you used the same balanced cables on both units?

@djones yes. I purchased them from Apos as part of their bundle with the A90 & D90.

But this is different. After a loud static discharge, one channel went out.

Sounds a bit like an opamp failure. And really bad luck, considering how well the unit measures.