AC hot wire to fuse or switch first?

gyrene · 22nd January 2012, 10:00 PM

I have been building my amps with the hot AC wire going to a fuse first and then to the switch.
I have seen schematics going either way.
Any preferences and why?

! · 22nd January 2012, 10:18 PM

Yes going to the fuse first is better. You want any amp fault including the switch to cut off power from anything downstream. Suppose a wire to the switch broke off, I know it's not likely but you don't want live ac in the case just because your fuse wasn't before the switch.

Fuse should ALWAYS come before the switch. If there is a legit reason to put a fuse elsewhere it should be in addition to a fuse right after the mains AC gets into the chassis.

gyrene · 22nd January 2012, 11:10 PM

O.K. thanks for the reply

kevinkr · 23rd January 2012, 12:20 AM

Quote:

Originally Posted by !

<snip>
Fuse should ALWAYS come before the switch. If there is a legit reason to put a fuse elsewhere it should be in addition to a fuse right after the mains AC gets into the chassis.

Big

Also I have run into more than one instance where power switch insulation failed and the switch shorted to chassis.
If the chassis is effectively grounded the fuse will blow which is safer than relying on a distant circuit breaker or fuse.

22nd January 2012, 10:00 PM	#1
gyrene diyAudio Member Join Date: Oct 2009	AC hot wire to fuse or switch first? I have been building my amps with the hot AC wire going to a fuse first and then to the switch. I have seen schematics going either way. Any preferences and why?

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22nd January 2012, 10:18 PM	#2
! diyAudio Member Join Date: Jun 2005 Location: Midwest	Yes going to the fuse first is better. You want any amp fault including the switch to cut off power from anything downstream. Suppose a wire to the switch broke off, I know it's not likely but you don't want live ac in the case just because your fuse wasn't before the switch. Fuse should ALWAYS come before the switch. If there is a legit reason to put a fuse elsewhere it should be in addition to a fuse right after the mains AC gets into the chassis.

22nd January 2012, 11:10 PM	#3
gyrene diyAudio Member Join Date: Oct 2009	O.K. thanks for the reply

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