Amp electrical wiring ?? Help me :)

1055 Views 6 Replies 4 Participants Last post by duckymcse, Jul 9, 2009

duckymcse

Discussion Starter · Jul 8, 2009

I’m currently using the Alpine MRPF450 which rated 70W RMS 4-channel amp in my car.
I wonder if I can take this amp out and replace it with the Alpine PDX4.150 which rated at 150W RMS 4-channel amp using the same electrical wiring cable which I use for the MRPF450?
Or do I have to get an electrical cable for the amp which rated up to 150W RMS?
I notice the amp electrical wire had a capacitor near the car battery. What that capacitor used for anyway?

I’m a noob when it come to car audio installation. If someone can help me on this, I am greatly appreciated.

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sqshoestring

· #2 · Jul 9, 2009 (Edited)

Odds are you don't have to because IIRC the PDX is ICEpower, it is class D full range and will be more efficient and take less power at same output. Like a third less. I'd guess you need 8ga minimum without looking it up. The cap might help dimming lights or might not.

Sorry I got busy....The wire needs to be sized for the total RMS wattage of the amp times its efficiency, times the length of the wire. A large enough wire will not drop the voltage at max output over 0.5v is the standard way to figure it. A little smaller wire may drop more at max, a much smaller wire will drop a lot and can overheat. If you never max it out it is not as important.

Go here http://www.bcae1.com/ and scroll the right down to #16 "wire", scroll down (or better to read it) and the charts/calculators will tell you what wire you need for any amp.

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B_Rich

· #3 · Jul 9, 2009

Well, regardless if the Alpine draws 1/3 less current, you should still look up the current draw vs. wire gague on a chart.

Kinda like this one

That should tell you if you need to upgrade your wire.

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duckymcse

Discussion Starter · #4 · Jul 9, 2009 (Edited)

Please correct my calculation and see if it is right or not.
The PDX4.150 is 150W RMS per channel.
I will be using 4 channel.
So, 150 x 4 = 600W
Than, 600 x 2 = 1200W
1200/13.8 = 86.9A

I looks at my cable and it label 8 gauge.
I think the cable length is about 10-12ft long.
Based on the chart, is that mean my 8 gauge is good enough for the PDX4.150?

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sqshoestring

· #5 · Jul 9, 2009

8ga might work it is right on the line if its 150x4=600rms, I'd not worry if you are not going to beat it hard. You can check the voltage at it, then at the battery and see if it drops more than .5v under max power. Or you can put larger/add more wire if you want. The amp will only draw that kind of power right at the limit, and much less than half that at half volume.

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89grand

· #6 · Jul 9, 2009

Keep in mind too, that amp will never be outputting 600 watts either. I'd say the 8 gauge is more than sufficient.

In fact, I think npdang ran one with 12 gauge.

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duckymcse

Discussion Starter · #7 · Jul 9, 2009

I think 8 gauge will do it for me. The most I crank up the amp gain is probably only 1/2 way. On my current MRPF450, I only crank up the gain half way anyway.

Thanks everyone for the help.

sqshoestring said:
8ga might work it is right on the line if its 150x4=600rms, I'd not worry if you are not going to beat it hard. You can check the voltage at it, then at the battery and see if it drops more than .5v under max power. Or you can put larger/add more wire if you want. The amp will only draw that kind of power right at the limit, and much less than half that at half volume.

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