Fuse type - Audio Note UK 4.1x Balanced

I have an older (pre 2010 I believe) audio note UK 4.1 X balanced DAC. Love it. Anyway it blew a fuse and I need to replace it. There are two fuses accessible from the rear panel, with screw off holders. The one that blew is the 800 milliamp. What I can’t be sure of and cannot find anywhere online is whether it should be a slow blow or a fast blow fuse. When I put fast blow fuses in they trip immediately or after a few listening sessions.

I realize this may be indicative of a different kind of problem but I want to get the fuse right first. I did test my tubes and they don’t have any shorts and I’ll read okay. 

If anyone knows about the fuse requirements, thank you in advance!