Phil Allison wrote:

snip
** Be very wary of adding +/- DC rail fues to any power amp designed without
them.

Very likely if one or other DC fuse blows or is removed, the amp's output
will swing fully to the rail with its fuse still intact.
snip

One could add overcurrent shutdown circuitry on each rail designed to shut
down the entire supply, or for antique simplicity use 'indicator fuses' which
have a spring-loaded plunger which makes contact with an endstop terminal
when they blow -- the endstop is often connected to a crowbar which blows
main fuses upstream. These are small cartridge fuses with the same form
factor as standard varieties; I had to replace lots of them in old line
printers where they were used in the hammer drivers -- in this
application they did not crowbar but instead were wired to status circuits
that reported the failure.

Regards,

Michael