# Setting Gains for 4 Channel Amp



## alan412 (Sep 7, 2009)

I was curious as to how you guys set your gains on your amps that power your components. I know it is ideal to use an o-scope but i don't have one and i cant get my hands on one. I do have a pretty nice digital multimeter though. i know how to calculate the voltage that the gain should be set at but what test tone should i use? I was thinking 1khz... Should i use 0db, -3 db or what? im not too sure on the proper way of doing this.


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## SoundChaser (Apr 3, 2009)

Amp gains at minimum and head unit at ¾ volume. Play some well recorded music that you’re familiar with. Turn the gain on your amp up until the music doesn’t sound quite right. Be it clipping from the amp or distortion from the speakers. That’s it, your done, leave it there.

Down the road if you find yourself turning the volume on your head unit to almost max on a lot of music, turn the gains up higher. If you see that your going less than half volume before **** doesn’t sound quite right, turn your gains down a bit. 


http://www.diymobileaudio.com/forum/diy-mobile-audio-sq-forum/70672-just-reset-my-gains-2.html


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## 89grand (Nov 23, 2006)

DO NOT use a multimeter and test tones, that's the worst way to do it. Just set them by ear like mentioned above.

What I do is take one of my lower recorded CD's and I set the gains to achieve maximum undistorted out from the amps with the volume control almost, but not quite at maximum. 

In other words, if the head unit has a volume control that goes to 35, I set it up so that on the low recorded CD is just starts to distort at around 33. That ensures that I will always have enough range in the volume control for maximum volume without distortion.

I use the lowest recorded CD's because setting the gains with a loud CD will result in not having enough volume control on the lower recorded ones.


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## alan412 (Sep 7, 2009)

89grand said:


> DO NOT use a mulitmeter. Just set them by ear like mentioned above.
> 
> What I do is take one of my lower recorded CD's and I set the gains to achieve maximum undistorted out from the amps with the volume control almost, but not quite at maximum.
> 
> ...



I'm just worried about sending my speakers a clipped signal... why do you advise me to not use a DMM?


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## 89grand (Nov 23, 2006)

alan412 said:


> I'm just worried about sending my speakers a clipped signal... why do you advise me to not use a DMM?


A little clipping never hurt anybody for one thing. Number 2 using a DMM will result in a lot less power out of the amp, it's not an accurate way of determining clipping at all. First off, you really don't know at what point the amp clips so you are using their advertised power output to determine what voltage you are trying for. What if for example the amp is rated for 100 watts per channel, but actually starts clipping at 85 watts? What if it doesn't clip until 130 watts per channel? Most people won't even notice a little clipping during loud peaks, but the system will be much louder overall than if you were to set the amps to limit any clipping.

Also, test tones played at levels up to clipping will result in you posting a new topic something like "what new speakers do you recommend" to replace my blown ones.


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## alan412 (Sep 7, 2009)

89grand said:


> A little clipping never hurt anybody for one thing. Number 2 using a DMM will result in a lot less power out of the amp, it's not an accurate way of determining clipping at all. First off, you really don't know at what point the amp clips so you are using their advertised power output to determine what voltage you are trying for. What if for example the amp is rated for 100 watts per channel, but actually starts clipping at 85 watts? What if it doesn't clip until 130 watts per channel? Most people won't even notice a little clipping during loud peaks, but the system will be much louder overall than if you were to set the amps to limit any clipping.
> 
> Also, test tones played at levels up to clipping will result in you posting a new topic something like "what new speakers do you recommend" to replace my blown ones.


LOL at that last part.

My speakers are rated at 60 watts rms, my amp is rated at 150 wrms x 2 channels. So i figured i take 60 watts x 4 ohms = 240 take the square root and you get 15.49 volts. Is that not a good way to set your gains? 

I just need to know what test tone is best for this method.


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## 89grand (Nov 23, 2006)

I guess you don't like my advice...but anyway, I'll say it again, DO NOT use a DMM and TEST TONES. I just explained why not too. We listen to music, not test tones, so use music to set the gains.

Don't worry about getting exactly 60 watts out of the amp. Either adjust the gains until it's loud enough, or until the amp starts to distort. Many people here use amps rated at several times the speakers ratings. Proper crossover settings are a must when doing this, but still you don't have to try a limit the amp to 60 watts. With music, the amp will rarely go above 60 watts anyway no matter how high you set the gains, but during loud peaks you'll have that extra power when you want it.


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## alan412 (Sep 7, 2009)

89grand said:


> I guess you don't like my advice...but anyway, I'll say it again, DO NOT use a DMM and TEST TONES. I just explained why not too. We listen to music, not test tones, so use music to set the gains.
> 
> Don't worry about getting exactly 60 watts out of the amp. Either adjust the gains until it's loud enough, or until the amps start to distort. Many people here use amps rated at several times the speakers ratings. Proper crossover settings are a must when doing this, but still you don't have to try a limit the amp to 60 watts. With music, the amp will rarely go above 60 watts anyway no matter how high you set the gains, but during loud peaks you'll have that extra power when you want it.


Ok, i'm understanding more of what you are saying now. So when using my ears to set the gains should I just play any type of music i want? 

edit: i just re read your above post... maybe you could recommend me some good cds to set my gains with.

thanks for your help too


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## 89grand (Nov 23, 2006)

alan412 said:


> Ok, i'm understanding more of what you are saying now. So when using my ears to set the gains should I just play any type of music i want?
> 
> edit: i just re read your above post... maybe you could recommend me some good cds to set my gains with.
> 
> thanks for your help too



Yeah, but I prefer well recorded music as it's much easier to hear distortion. I prefer to use great recordings like Sade, Susan Vega stuff like that for instance over any sort of hip hop stuff, but it really doesn't matter all that much I guess. I already have those CD's so I use them, you don't have to go out and get them in order to do this.

You can use whatever you normally listen to really, but again some music like hip hop is a lot harder to use because it mostly just has bass beats and vocals.


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## JoeDirte (Sep 21, 2009)

These might help you. Some very well recorded music on these discs to test with.

http://www.diymobileaudio.com/forum...15-all-6-focal-demo-discs-ready-download.html


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## 89grand (Nov 23, 2006)

The thing with gains is it's not that big of a deal, don't sweat it. It get a lot more tricky when you are matching the gains and a sub amp, a mid range amp and a tweeter amp in an all active system, but even that isn't too much of an issue. You mainly are just setting the head units volume control sensitivity really. I mean if your head units volume goes to 35, you don't want to have maximum volume at 12 on the deck, and you don't want to go all the way to 35 and still not have enough volume.

It's not your fault, too many people make it seem like setting s gains is a much bigger deal than it is, then people just starting out read this BS and think it's true when it isn't.


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## kvndoom (Nov 13, 2009)

alan412 said:


> Ok, i'm understanding more of what you are saying now. So when using my ears to set the gains should I just play any type of music i want?
> 
> edit: i just re read your above post... maybe you could recommend me some good cds to set my gains with.
> 
> thanks for your help too


Good CD's to set it to would be the music you listen to most often.

I have tried a few times to set with the DMM and tones, and never liked it. For the hell of it, I did so again earlier this week.

My car's HU volume maxes out at *63*, which is ridiculous. Mazda changed that for the 2008-09 models for some reason.... they used to max in the 30's, I think at 36. Still, I set the gains at 47 volume for reference. It sounded like crap. I would be well into the 50's on volume before it reached a suitable level. Often I was past 60 and it still wasn't as loud as the way I had it before.

The other downfall was that I was getting audible distortion from the HU with the volume that high, and the amp wasn't even close to putting out full power. So I was weakly amplifying a distorted signal. Double fail.

Setting by ear, based on a deck volume setting that doesn't distort, is the way to go.


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## 89grand (Nov 23, 2006)

^^^^See, that's exactly what I was talking about. Setting the gains with a DMM and test tones will lead to your 150 watt amp sounding like a 20 watt amp. You'll lose a lot of the amps actual potential.


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## alan412 (Sep 7, 2009)

I'll give it a shot and try setting the gains by ear.

Thanks for all the help


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