# What size fuse do I need?



## Kaya9508 (Dec 10, 2019)

I have a Power Acoustik RZR1-2500D monoblock amp. What size fuses should I put in the amp


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## gijoe (Mar 25, 2008)

Fuse for the wire, not the amp. What AWG are you using, and how long is the run?


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## Holmz (Jul 12, 2017)

Kaya9508 said:


> I have a Power Acoustik RZR1-2500D monoblock amp. What size fuses should I put in the amp


Is there no amperage spec on the amplifier?


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## syc0path (Jan 23, 2013)

gijoe said:


> Fuse for the wire, not the amp. What AWG are you using, and how long is the run?


That would be true if he's adding a fuse for the power wire. But he said "in the amp", suggesting that he's looking to replace the amp's internal fuse. And if he doesn't know the amperage, that suggests the previous fuse is missing.

Anyway, Google is a wonderful thing. A simple search indicates that the amp uses a 40A fuse. Seems a little small for a "2500W" amp Obviously it's way overrated!


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## Holmz (Jul 12, 2017)

syc0path said:


> That would be true if he's adding a fuse for the power wire. But he said "in the amp", suggesting that he's looking to replace the amp's internal fuse. And if he doesn't know the amperage, that suggests the previous fuse is missing.
> 
> Anyway, Google is a wonderful thing. A simple search indicates that the amp uses a 40A fuse. Seems a little small for a "2500W" amp Obviously it's way overrated!


A 40A fuse suggests tat it draws less than 40A, which sort of answers questions on what size alternated that 2500W amp requires.


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## gijoe (Mar 25, 2008)

syc0path said:


> That would be true if he's adding a fuse for the power wire. But he said "in the amp", suggesting that he's looking to replace the amp's internal fuse. And if he doesn't know the amperage, that suggests the previous fuse is missing.
> 
> Anyway, Google is a wonderful thing. A simple search indicates that the amp uses a 40A fuse. Seems a little small for a "2500W" amp Obviously it's way overrated!


Yeah, if he's missing the fuses on the amp, you're right. 

The amp is only rated for 650 watts at 2 ohms so it won't need a big fuse.


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## F150Man (Apr 14, 2017)

Where did you find that spec ? 650w @ 2 ohms would draw more than 40a. My 500w @ 2 ohms Alpine has 60a of fusing.


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## gijoe (Mar 25, 2008)

F150Man said:


> Where did you find that spec ? 650w @ 2 ohms would draw more than 40a. My 500w @ 2 ohms Alpine has 60a of fusing.


Found this on the internets.


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## F150Man (Apr 14, 2017)

OK. See if it shows the fuses on any photos or it lists the amperage requirement.


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## Shadow_419 (Aug 1, 2018)

2 x 25 amp according to the review


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## F150Man (Apr 14, 2017)

Ya, well, I'm assuming an output of around 450w RMS @ 2 ohms if it is a class D.


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## Holmz (Jul 12, 2017)

gijoe said:


> Found this on the internets.


Nice.

I am wondering what is the "max power" and "RMS power" definitions are in that amp manufacturer's context?


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## 04quadcab (Dec 31, 2017)

Assumptions:

The stated specs are accurate (650 W RMS)
13.8 volts
The amp is 60% efficient
You will draw almost 80 amperes of current.

But, we know that it has 50 amperes of fusing, so my assumptions are wrong. Perhaps you have 80% efficiency and 14.4 volts? That will draw 57 amperes of current. More than likely the amp is only good for 400 watts. After making that prediction I am going to watch the video posted above.

Edit: From the video posted above: 631 RMS certified. Must be more efficient than I thought.


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## hankhowdy1 (Jul 21, 2016)

04quadcab said:


> Assumptions:
> 
> The stated specs are accurate (650 W RMS)
> 13.8 volts
> ...


Are class D amps 80% efficient and A/B 60%?


Sent from my iPhone using Tapatalk


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## F150Man (Apr 14, 2017)

I have always read 80% for class D and 60% for class AB, but this morning I am seeing 95% for class D.


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## Holmz (Jul 12, 2017)

hankhowdy1 said:


> Are class D amps 80% efficient and A/B 60%?


Most amps have the lowest efficiency at the lowest output, so for instance a Class-A may draw 100w at zero volume... aka "quiescent current (power) draw".

Class-AB have a much lower quiescent draw.

What the efficiency is flat out I am not sure... but a lot of people do not run their equipment flat out.


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## F150Man (Apr 14, 2017)

OK well they all draw amperage and output watts so ...


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## Holmz (Jul 12, 2017)

F150Man said:


> OK well they all draw amperage and output watts so ...


(So) he should probably use the fuse that manufacturer recommends inside the amp, ignoring any sidetracking math lessons about efficiency.

Or do you mean how do we find out what the efficiency of an amplifier is?

The only solid way I know how to do the later is by measuring RMS current going into the amp, but those clamp amperage meters are not in everyone's tool kit and they are not cheap.


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## 04quadcab (Dec 31, 2017)

hankhowdy1 said:


> Are class D amps 80% efficient and A/B 60%?
> 
> 
> Sent from my iPhone using Tapatalk


It is going to vary by amp manufacturer. Willision Audio Labs on YouTube will put a clamp on the power wire and calculate efficiency on MOST of the amplifers that he tests. The highest I have ever seen was 80% on an audio control amplifier. A lot of the cheap brands are not terrible efficient.


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## sqshoestring (Jun 19, 2007)

Most amps you have to run a tone full bore to use the full amp rating. Though I know some amps used to run tons of fuses for looks. I have a 100A 5ga kit running 1kw with 2 class D and use a 50 or 60A fuse at the battery and never had an issue. But I don't listen to bass tones at full volume, maybe dubstep has been run on there loud though. But only a 500w on the subs. I don't get any voltage drop at the amps. If you want a treat put a clamp on meter on your power wire and see what you get. It is very low until you get to high volumes or crank bass tones.


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## georgenavarro737 (5 mo ago)

gijoe said:


> Fuse for the wire, not the amp. What AWG are you using, and how long is the run?


Iam not using it right now I just want to see if it works to my battery first & I don't want to blow it out


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