Blackstar doesn't supply schematics. I made some sketches of the HT-5 based on photos of the PC boards. They are unfinished because I couldn't interprete everything from the photos I had available. Some component values are missing because they were impossible or too uncertain to read and I had no photos of the (solder side of) rear PC board housing the speaker jacks and the FX loop driver circuit. Until I either get more photos or the actual amp these will stay as is.
Anyway, I think you should be able to work from these.