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Total ampage allowed by the fuses. Example a amp with 2x20 amp fuses is a 40amp amplifier and will give a maximum output of about 480 watts rms.

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the fuses must be above a the maximum current draw of the amplifier

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Total ampage allowed by the fuses. Example a amp with 2x20 amp fuses is a 40amp amplifier and will give a maximum output of about 480 watts rms.

I'm no amp expert, but this sounds like complete hogwash to me.

Fuses are meant to prevent a fire if the power wires get accidentally grounded. So although the fuses must be above a the maximum current draw of the amplifier, I don't think that translates directly into the amount of sound output you get at the speakers. Those fuses could be almost any value above the max current draw.

Can anyone who actually is an amp expert definitively confirm or deny the "fuse rating indicates amp performance" theory?

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said by the fuse rule i said the MAXIMUM output of the amp would be the total fuse rating multiplied by about 12 volts,

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Also fuses are not only made for preventing fire if the power cables earth

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maximum output of about 480 watts rms.

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Right, and I'm saying that the amp's maximum output is probably a lot less than the fuse rating. Stated another way, the fuse is most likely rated for a much higher amount of current than the amp can draw. That's on purpose, so that the fuse doesn't blow accidentally.

I'm just saying that, at best, looking at a fuse is a highly inaccurate way to determine the capabilities of the device that the fuse protects.

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You wrote it once, and quoted it again. It's the "rms" that makes no sense. In your theory, as soon as your current draw hits 480 watts peak, the fuses will blow. That's not the same as 480 watts RMS.

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And don't be so snippy.

--Dan.

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Also fuses are not only made for preventing fire if the power cables earth, i am not going to explain all the reasons for fuses as there are so many, but all i can say is that by that statement you are showing you naivety.

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inputed

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consider adopting a less aggressive tone

In his defense, I did cop a pretty serious attitude with my first response. So I deserved to get one in reply.

He's also got a point in that... if his real-world experience shows that the fuse rating is a good indicator, then it's possible that he's found a good quick "approximation" way of looking at it. Since I don't have a big list of all the amplifiers' fuse ratings compared to their actual RMS output values, I actually don't have any way of knowing if what he's saying is true.

I'm still not convinced, but I'll concede that what he's saying is possible.

Still sounds goofy to me though, like determining a car's top speed by looking at the highest number printed on the speedometer.

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...Also just because i have not posted much on THIS site doesnt mean that i dont know anything.

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All: i think what i put in my previous post pretty much finilised the conversation,

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and i dont know why people are still posting about wether they agree or not with the theory on a "i just disagree, and cannot be bothered to actually see if it works or not" basis.

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And no its not as inaccurate as you would think because of the electrical systems in cars, the voltage is pretty much constant with little variation. Because of this the fuses are resonably accurate, and also manufacturers use as small as fuses as they think they can get away with because saving 1 cent on a fuse for each amp when they make ten of thousands of amps each year is a lot of money.

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...Also just because i have not posted much on THIS site doesnt mean that i dont know anything.

Yeah, but what little you have posted doesn't prove that you know anything either.

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All: i think what i put in my previous post pretty much finilised the conversation,

LOL. I haven't even started in the conversation yet and you're telling me I'm done? Who do you think you are?

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and i dont know why people are still posting about wether they agree or not with the theory on a "i just disagree, and cannot be bothered to actually see if it works or not" basis.

Because your theory is _CRAP_.

The only thing that you can tell about an amp from the fuse rating is how much current will flow before the fuse blows. And yes, occassionally this can be useful. For instance, when you see that a wonderfully spec'd chinese amp claiming 1000W output only has a 20A fuse, you know that the most use that you're going to get from the specification sheet is if you use it to wipe your arse. But that still doesn't tell you anything about the amp itself. You don't know what (if any) margin has been allocated before the fuse blows.

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And no its not as inaccurate as you would think because of the electrical systems in cars, the voltage is pretty much constant with little variation. Because of this the fuses are resonably accurate, and also manufacturers use as small as fuses as they think they can get away with because saving 1 cent on a fuse for each amp when they make ten of thousands of amps each year is a lot of money.

No, the voltage at the battery is anything but 'pretty much constant with little variation'. A car's electrical system is inherently very dirty. That is why alternator whine and ground loop noise are such big issues. But moving on from this consider the following two facts;

1.) Car audio manufacturers are well aware that people look at fuse ratings to debunk over-rated specifications and are not above abusing this, especially considering;
2.) It doesn't matter if I want 1A, 2A, 3A, 5A, 7.5A, 10A, 15A, 20A, 25A, 30A or 40A fuses. They all cost $0.195 in 10k quantities.

A better indicator is weight. You cannot build a powerful car amplifier without a decent PSU. Decent PSUs need decent heatsinks or they rapidly become dead PSUs. Decent heatsinks aren't light. Furthermore, a class AB design amp (which most are) requires heatsinking because it is inherently inefficient. The more powerful the amp, the bigger and heavier the heatsink required.

Even this is flawed though - some manufacturers make amps that you could fry your breakfast on, whilst other manufacturers' amps barely get warm. And a class D amplifier doesn't play by the same efficiency rules either. (You won't see a pure class B amp, and you're very unlikely to be using a class A amp).

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Grow up, get a wider view, and read my last two posts, i wont say it again.

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I say to all of you, try the theory, if you believe it to be incorrect please PM me with your research that disagrees with it and i will read it, if i find that the theory works less then i think is reasonably useable i will be prepared to eat my own words and appoligise to all of you, but if you provide the disagreeable research be prepared to also have me provide examples of the theory working to you, and if we both agree that my research out weighs yours then i will also expect a post under this topic that says the theory works

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Also weight? Firstly i will say that although i havent researched this i cannot say it isnt possible but i personally think it isnt probable. To me its like saying that a heavier car must have a bigger engine and so be quicker then lighter cars.

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40 amp fuse with a 12 volt current

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40 amp fuse and 12 volt power

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In the "theory" i always use fuse ampage multiplied by 12 volts as the output to the theory is usually a very similar figure to the manufacturers rms rating at 14.4volts.

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the internet seems to be full of people who hear a interesting theory and instantly say that its BS, when they cant be bothered to actually spend the time to try out the theory, and lets face it they have the ability to find out wether or not it true using nothing but their mouse, fore finger and google.

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Maybe I should have some how rigged it up to my radiator and cooled it?

C'mon. You KNOW you want to have a liquid-cooled amp.

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PS RMS is an acronym for "root mean squared", where the exact output of the amplifier is recorded across a range of inputed signals and then there square root is applied to the results, then the mean average is taken and that mean average is then squared.

Err, the other way around, I am affraid: first square, then mean, then root. That way you avoid those pesky complex numbers.

Actually, in the context of amplifiers, it is continuous power calculated from measuring RMS voltage while driving resistive load with harmonic (sinusoidal) signal (for prescribed time with prescribed maximal distortion etc). You could measure peak voltage as well (as long as you know the shape of the signal), but the life is easier with the voltmeter that gives RMS (or effective) voltage.

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The footprint and the digital input seem to make it a good fit for an empeg with one of Stu's sound cards, no?
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