how do I select amperage of a fuse?

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Well this depends on how much power you have the amp set up for and what it'll draw at idle. Generally, you should pick a value that will blow the fuse under a serious condition but also that will facilitate the start-up and then idle currents of the unit.

Lets say you have an amplifier that draws an inrush current of 6amps for a few milliseconds and then idles at an amp or so. At full power output it draws say 3amps. If you use a slow-blow fuse, you can use maybe 4 or 5 amp fuse. The inrush will exceed the current of the fuse, but being a slow-blow, the inrush will be too fast to blow it. However, if the amplifier shorts out, it will run long enough to kill the slowblow.

In a tube amplifier, you don't really want a slow-blow unless it's a really big amp.

In your case, find out even a ballpark value for the amps maximum current draw and use a fuse just above that. I believe there are some mathematical formulae you can use so we'll see if somebody more knowledgeable about fuses comes with ideas.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.