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Need help adjusting amp gain


babumazda3

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Guys,

I am trying to adjust the amp gain using multimeter. My amp makes 750W RMS x1 at 1 ohm. The subwoofer is internally wired to create 1 ohm. According to what i read, i need to turn the gain knob till i read around 27V {square root (750x1)} in the multimeter.

So, i unplugged the speaker wire, connected the leads of the multimeter and started turning the knob while playing 50Hz test tone. Even when the amp gain is turned all the way, i'm only reading 7 or 8 V AC.

Any idea why i can't get it to 27V. I haven't done the big 3 upgrades. Running on stock alternator.

Please help.

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get a DD-1...or check out the tool map and hit someone up to borrow! so much easier!

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The problem with using a DMM is it can't tell you if you are putting out a clipped signal. For that you need either a DD-1 like hoit suggested or a o-scope.

That being said, you have other problems. You should be able to get a lot more than 7 or 8 volts out. That's only 50-65 watts. I'm guessing you aren't getting enough signal voltage into your amp. Is your head unit turned up to at least 3/4 full volume? What kind of head unit do you have?

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do u guys think this has anything to do with not having the big 3 upgrade. like the amplifier not getting enough juice from battery. i'm using 4 gauge for both power and ground

Nope, since you had a speaker wire unplugged while you were testing your amp wasn't actually pushing any watts out so there was very little current flowing through the power wires. You could have had it wired up on 16 gauge wire and it wouldn't have made a difference.

Now that being said, doing your big 3 will be beneficial once you get everything figured out.

So here is what I would test next. Unplug your RCAs at your amp and test the voltage your HU is putting into them using the same process you used before. I'm curious what your HU is putting out for voltage. Let us know what the results are.

"Nothing prevents people from knowing the truth more than the belief they already know it."
"Making bass is easy, making music is the hard part."

Builds:

U7qkMTL.jpg  LgPgE9w.jpg  Od2G3u1.jpg  xMyLoO1.jpg  9pAlXUK.jpg

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One of the problems with the DMM method is that you need to know exactly when the HU distorts in order to know where to set the gain to. You can't effectively do that with the DMM

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do u guys think this has anything to do with not having the big 3 upgrade. like the amplifier not getting enough juice from battery. i'm using 4 gauge for both power and ground

Nope, since you had a speaker wire unplugged while you were testing your amp wasn't actually pushing any watts out so there was very little current flowing through the power wires. You could have had it wired up on 16 gauge wire and it wouldn't have made a difference.

Now that being said, doing your big 3 will be beneficial once you get everything figured out.

So here is what I would test next. Unplug your RCAs at your amp and test the voltage your HU is putting into them using the same process you used before. I'm curious what your HU is putting out for voltage. Let us know what the results are.

I'll do this and report this back.

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  • 3 weeks later...

do u guys think this has anything to do with not having the big 3 upgrade. like the amplifier not getting enough juice from battery. i'm using 4 gauge for both power and ground

Nope, since you had a speaker wire unplugged while you were testing your amp wasn't actually pushing any watts out so there was very little current flowing through the power wires. You could have had it wired up on 16 gauge wire and it wouldn't have made a difference.

Now that being said, doing your big 3 will be beneficial once you get everything figured out.

So here is what I would test next. Unplug your RCAs at your amp and test the voltage your HU is putting into them using the same process you used before. I'm curious what your HU is putting out for voltage. Let us know what the results are.

Sorry for the delay in getting back. I carried out the measurement using the DMM at ac voltage setting by unplugging RCA going into sub amp. The reading i received was just around .2V. This was with the sub setting turned all the way high in the head unit. Does this explain the problem i'm facing?

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That would probably be the issue with not getting the desired output. As to what is causing that, that's what you need to figure out. thats a stock HU? Are you using a LOC or does it have stock RCA outputs?

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