How to set your car amplifier's gain

Hi, I'm Rodell, and we're going to talk today about setting the gain on our amplifier.

First off, a lot of people make the mistake for thinking the gain is a second volume knob. It's not. I want to say that again: the gain knob is not a second volume knob. What it does is, it actually matches the input stage of our amplifier to the output of whatever source we're using - our aftermarket head unit, a factory radio, or even a line output converter.

Using a voltmeter to set the gain

First, I'm going to show you how to set the gain using a voltmeter, which is the best way, but afterwards I'll show you how to do it by ear using a slightly easier method. All right. To start, we're going to disconnect the speaker outputs from the amplifier. Next, we're going to make sure that everything's turned as low as it can. The gain, the crossovers, any sort of bass boost. So we're good there.

Now if you haven't already, go ahead and download the test tone appropriate for your amplifier. For this Kicker 4-channel, we're going to use a 0dB 1khz test tone that we got from kicker.com. Once you've got that on your source, we're going to go ahead and make sure that our volume is set to about 75%, and let's go ahead and turn our voltmeter on to A/C voltage. All right.

Next we're going to connect our positive and negative voltmeter leads. All right. From there, we're going to play our test tone. And now that we're playing, we are going to adjust the gain – slowly – until we hit, in this case, 16.12 volts. All right. So we've got it set as close to 16.12 as we could without going over, and we didn't just pull that number out of thin air.

What's going on is we got a 65 watts RMS amplifier, and it's connect to 4-ohm speakers. So multiply 65 * 4, take the square root of that, and you got 16.12. You can also just check the specs manual that came with your amplifier; there'll usually be some sort of conversion guide.

From there, you're going to do the same thing for the rear stage: set in the gain again, and disconnect your voltmeter leads, reattach your speaker outputs, and never touch the gain knob again.

Setting the gain by ear

All right, now let's check out how to do this by ear. For a quick and easy setup without a voltmeter, go ahead and leave your speakers connected to the output of the amplifier, and make sure that everything's zeroed out on the gain side.

From there, we're going to turn up our source head unit to about 75%, hit play, and I picked a song that I know pretty well. The idea is that you're hear something that's going to be nice and clean, and you're going to be able to hear if anything changes pretty quickly.

So from there, we are going to turn the gain up slowly. All right. And we're listening, we're listening for any crackling or distortion, and once we start to hear it we're going to back off there, and leave it. We'll do the same thing for the rear stage, and congratulations, you set your gains.

All done!

That's it. You're making sure that you're getting the most out of your amplifier in terms of quality and longevity. If you have any questions about getting more out of your car audio. get in touch with us here at Crutchfield. Take care.