I've always known that the power supplies to the Blackstar pedals can tend towards causing a fair bit of hum.
Anyway, I was moving my HTdist's PSU around again trying to find the "point of least hum" in comparison to the rest of my pedalboard after yet another jiggle round of the board. Just by chance I did something different I haven't done before ..... I turned the power supply upside down. And Voila, the hum virtually disappears. Big result !!
Just something that might work for you, or might not. But it's worth a try.