How important is fuse ratings on amps?

[CarAudioNewbie9 10+ year member]

I know it isn't the only factor, but how important is the fuse rating on amps? More specifically for class A/B amps. I know that class D amps are more efficient. But I see "2006 cea compliant" A/B amps that claim 600 RMS with only 40 amps of fusing and so on. I then see class D amps claiming 2000 RMS with only 140 amps and so on. I know "2006 cea compliant" doesn't mean much to the real car audio enthusiast, but it pisses me off when I see "2006 cea compliant" Kenwood amps claiming way more RMS watts then their fuse rating suggests. What are some good signs as to telling what the real RMS of amps are?

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[kr15 5,000+ posts]

What are some good signs as to telling what the real RMS of amps are

experience

 

[supermaxx123 10+ year member]

I know it isn't the only factor, but how important is the fuse rating on amps? More specifically for class A/B amps. I know that class D amps are more efficient. But I see "2006 cea compliant" A/B amps that claim 600 RMS with only 40 amps of fusing and so on. I then see class D amps claiming 2000 RMS with only 140 amps and so on. I know "2006 cea compliant" doesn't mean much to the real car audio enthusiast, but it pisses me off when I see "2006 cea compliant" Kenwood amps claiming way more RMS watts then their fuse rating suggests. What are some good signs as to telling what the real RMS of amps are?

most fuses will handle more than they are rated, maybe even double their rating. 600rms with 40 amp fuse? which amp?

 

[n2audio 5,000+ posts]

They'll give you a rough estimate of actual power. I only use them as an estimate when I KNOW I'm dealing with an over-rated amp. For anything decent quality the ratings should be much more accurate.

I know for some amps to produce rated power on a bench the fuses have to replaced with shorting bars because continuous power tests require a lot more long term current than any music will and such tests will blow the fuses. In cases like that the fuses are a form of protection and will blow at the first moment the circuitry is at risk of being damaged.

I'm sure there are other amps with the fuses sized in a way that will cause them only to blow to protect the amp from catastrophic failure.

That is the biggest reason IMO, you can't just assume an amp is over-rated if its fuses are less than it seems they should be. Just as you don't know for sure an amp will DO rated power because the fuses seem large enough.

But generally speaking I think fuse size x10 does get you in the ballpark.

 

[keep_hope_alive Premium Member]

i use the following:

fuse size x 12.5V x efficiency

for estimating usable RMS power. i assume 60% for Class A/B and 80% for Class D or the new hybrid designs.

a fuse has a time/current curve that characterizes it's behavior. how much over current it can accept depends on the amount of time.

 

[deez283 10+ year member]

experience

Yup..