I tried to make it work : a simple 4CM with my Diezel VH-4 (deadly silent by itself or using AXE FX III in 4CM or Strymon pedals in its FX loop).
With QC I got very loud hum!
So I bought and tested the 4 CM with Palmer galvanic isolators putting them in various points of the signal path and the hum has transformed in big hiss.
I’ve changed the cables brand and points of current of the adapter and the amp power cable, optimized the levels etc etc …nothing… the hum /hiss remains…
Connected again a TimeLine and a BigSky in the FX loop: et voilà…the amp turned deadly silent again
@Ringo hello, i also have the same problem and i reported it to the neural! with the 4cm connection I have an exaggerated hum noise and if I put a galvanic isolator the noise becomes a hiss that looks like a tornado
it’s doubtful that your issue is power related but ensure that you are using the correct voltage/amps to power the QC and worst case, feel free to send an email to support@neuraldsp.com so that they can log the issue and hopefully provide resolution.