Can't blow fuse.

[pensacol 10+ year member]

Well here's my problem. I've been wondering this for a while. I got an MB Quart RAA2400, supposed to do 800 watts bridged at 4 ohms. I'm running it at 4 ohms bridged. This amp has 3 - 30 amp fuses on it. I am running a 60 amp in the inline from the battery (nobody around here carried anything higher, but I guess it doesn't matter anyways). My question is if this amp is doing 800 watts it should pull more than 60 amps right? Thinking along the lines of somewhere about 65% EFF, give or take a few. The fuse has never blown. Set the gains with a DMM, running 4 AWG both ways. Why is it doing this, or are MB Quarts underratted, and it's not doing no where near 800 watts?

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[ultimate157 5,000+ posts]

You'll never see 800w on music. Only way you'll see that kind of power is with 0db sine waves.

 

[pensacol 10+ year member]

Tried that to. Mostly what I listen to is stuff like Bass Mekanics, where the bass drops low for periods of time, and I have also tried 0 db test tones. I tried them when I installed the subs. Went from 10hz to 50hz, full blast.

 

[bass_lover1 10+ year member]

Because often fuses only blow on a dead short, or something that well exceeds the amperage rating.

You might have a 60amp fuse, but it could take 100 amps for it to actually heat up enough to pop.

 

[luvinthebass 5,000+ posts]

yup

 

[thejoker989 10+ year member]

Because often fuses only blow on a dead short, or something that well exceeds the amperage rating.
You might have a 60amp fuse, but it could take 100 amps for it to actually heat up enough to pop.

Fuse Opening Time:

A fuse does not blow when the current reaches its rated current. It is designed to pass its rated current without opening. A fuse will take varying times to blow under different conditions. A fuse will pass significantly more than its rated current for a very short time. It may take 10 minutes or more to blow a fuse at 25% over its rated current. The table below is an example of the specifications for a slow blow fuse. You can see that a 20 amp fuse may pass 40 amps of current for as long as 5 minutes before blowing although it probably wouldn't take a full 5 minutes to blow. The times for other fuses will be slightly different.

%of amp rating Opening time

110% 4 hours minimum

135% 1 hour maximum

200% 5 minutes maximum

-bcae1.com

 

[thegreatestpenn 5,000+ posts]

^ good explanation. Yes fuses are very durable and can handle alot of current for short bursts. I've run a 1200wrms amp with a 40A fuse unclipped and 50A with some clipping with no problems. It doesn't mean my amp is underrated (we used an O-scope, the power was there), it just means the fuse is doing its job. that inline fuse is to protect the wiring anyways. As long as wire isn't melting you are alright

 

[pensacol 10+ year member]

Cool, thanks for the explanation. You learn something new everyday!