BSS Audio DPR-504 Owner's Manual - Manual (Page 7)

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Note: For USA and Canadian users, the replacement fuse must be of an
identical UL rated type fuse for continued compliance with safety standards.
It is very unlikely that fuses will blow during normal use, but if replaced fuses
continue to blow, then the internal transient suppressors may have become
damaged. If this case, you should refer to section 8.1 for the replacement
procedure.