# Setting Gains DMM vs Ear



## 90zcrex (Jan 14, 2016)

How many people use a DMM to set gains?
I've always set the gains on my sub amps by ear by just turning the HU volume to 3/4 of max and turning the amp gain until I hear distortion in the music playing and then backing off until the distortion is gone, 
well on my newest system I decided to set the gains using a DMM as I figure it must be more accurate than just "earing" it. 
Well I used the formula for my amp MRP-M500 which is 500 watts at 2ohm and it comes out to 31.6 Volts output.
So I set HU to 3/4 volume and turn all eq off and levels zeroed in HU, turn the gain up on the amp until I get 31 volts on the output. 
I did the same for my 4 channel which comes out to 14.1V at 4ohm per channel.

Now problem is my sub amp is only at maybe 1/3 of the gain. And is very low in volume compared to my front speakers (not using rear atm), when I say low I mean you can't even barely tell the sub is playing.

I can crank the gain on the sub amp to about 3/4 and get a good balance with the front speakers but the output voltage on the amp goes up to like 46Volts. 
I don't get any distortion in the sub and it plays clean and sounds good all the way to a little under the max volume on the HU with it set like this.

Just wondering if I am doing something wrong or maybe the Alpine wattage is underrated?

Again sorry for the long post and thanks for the help everyone.


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## Weigel21 (Sep 8, 2014)

DMM method is really only good for limiting output of an amplifier IMHO, not setting for maximum clean output. 

To use the DMM method effectively, you'll want to find the HU's maximum clean volume level (as one would want to do whenever setting gains) and then use an attenuated test tone of say -5dB to upwards of -10dB for sub amps. 

honestly, setting gains by ear with the aid of test tones is more accurate and fairly easy, as most can hear 1%THD (when the hum of the tone turns to a buzz at the onset of 2nd and 3rd harmonics).

And I'm going to ASSuME you used a 0dB test tone, which music is NOT recorded at. Very seldom will you get anything recorded in the track at 0dB, major bass peaks. On average, the audio will be attenuated around 10dB or so.


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## Weigel21 (Sep 8, 2014)

What Is Distortion?

Using test tones to set amplifier gain

https://www.youtube.com/watch?v=WhrDqke8BKo

Oh, and with the 4-channel, I bet you used a 1kHz test tone, but is your DMM capable of accurately measuring that frequency? I have a cheap $20 or so DMM that only claims it's accuracy from 50-400hz. Anything above or below that has an unknown level of accuracy.


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## oabeieo (Feb 22, 2015)

Why not set gains to match efficiency of drivers AND most importantly to lower noise. 

If it were me , I love my gains all the way down. And up a tad on the least efficient driver set.


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## 90zcrex (Jan 14, 2016)

I did use a 0db test tone, I used 50hz for the sub and 1khz for the fronts. I just don't understand how it could be that far off. 
I read through SONIC ELECTRONIX and Crutchfields guides before setting with the dmm. 
I set it just as it said in these instructions
How to Adjust Amplifier Gains Using a Digital Multi-Meter | Learning Center | Sonic Electronix

I'll set the gain by ear again with a 50 and 100hz test tone and see what I get.


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## ca90ss (Jul 2, 2005)

The dmm method is a waste of time, set them by ear and be done with it.


As was mentioned earlier, most cheap meters lose accuracy the further you get from 60hz.


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## 90zcrex (Jan 14, 2016)

Nice, that craftsman is the exact one I was using.


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## Weigel21 (Sep 8, 2014)

Yep, as you can see, the model you have is off at higher frequencies and reads lower than the actual voltage. So, you have the 4-channel set as though you used an attenuated tone and the sub amp set with a 0dB tone, which I covered that recordings rarely have. 

Reset your gains by ear with the aid of test tones, then lower gains as needed to blend the system together.


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## 90zcrex (Jan 14, 2016)

Cool I'll redo it by ear and see how it turns out thanks


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## rafaelf.donis (Jan 20, 2016)

nice information


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## Dmsodaro (Apr 6, 2021)

90zcrex said:


> How many people use a DMM to set gains?
> I've always set the gains on my sub amps by ear by just turning the HU volume to 3/4 of max and turning the amp gain until I hear distortion in the music playing and then backing off until the distortion is gone,
> well on my newest system I decided to set the gains using a DMM as I figure it must be more accurate than just "earing" it.
> Well I used the formula for my amp MRP-M500 which is 500 watts at 2ohm and it comes out to 31.6 Volts output.
> ...


I am going through the same thing right now. I’m so glad I found this


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## Weigel21 (Sep 8, 2014)

There are numerous ways to find your HU's maximum clean volume level and set your gain.

By ear/sight using test tones.






Using a speaker with a capacitor.






Using a piezo buzzer.






Making your own DIY distortion detector that Rockford posted a pdf file on how to make YEARS ago.



rockford distortion detector - Google Search








Cheap O-Scope you can buy for like $40-$80.







Keep in mind that unless you use an attenuated test tone, you're leaving a lot of power off the table. I'd recommend -3dB or -5dB.


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## HCWLSU101 (Apr 30, 2009)

So based off this information sub amp should be set with an attenuated tone say -5db and mids and tweeters at 0db?


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## Weigel21 (Sep 8, 2014)

Tweeters definitely 0dB, then backed off to blend with mids. 

Mids could be set with -3dB or maybe -5dB, as you'll want to not leave a whole lot of power off the table. 

Subs -5dB to upwards of -10dB, as you can't hear distortion vas easily in lows. This will also allow for much more dynamic output from the sub stage. 

However, you can take some of the music you listen to and run it through audacity to see what the average recording level is and what the recording level of peak bass hits are, if you're looking to squeeze our all the power you can. 

Remember though that for roughly 3dB in increased output, you're asking for double the power. So it's not like a you'll really notice the difference in feeding your subs say 70% of their rated power vs 100%.


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## mrexcitement (Jan 23, 2019)

For me personally I would never ever set them by ear , I would never be sure it's correct doing it by ear , I always do it with an oscilloscope as you can clearly see what is going on and allow yourself some headroom if wanted , I could never do that by ear.

Or a clipping indicator would do the same job but the oscilloscope is the best way for sure and what I always use. 

I set my levels with -5db test tones for mid/upper frequencies and -10db for the Subwoofer.


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## Weigel21 (Sep 8, 2014)

There's no set in stone correct method. 

O-Scope is good, but remember, not all have the greatest resolution to see if the wave has an irregularity. Not to mention, even if you set it for a perfect -5dB or -10dB sine wave, that's not what you're playing later. Music is dynamic. There are many occasions where notes are recorded at stronger reference levels than those. So in the end, you either set gain for clip free output and lackluster performance, or you set with gain overlap and enjoy more dynamic range, be get occasional soft/ moderate clipping. 

Years ago, back when I bought a cheap pocket O-Scope, I found that, at least for me, I could hear when the tone changed upon 2nd and 3rd harmonics at the same time the O-Scope showed the smooth wave breaking up. 

As time goes, hearing degrades, so I don't know for sure if I can still detect distortion at the same time as an O-Scope. I'll have to do some testing and find out.


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## mrexcitement (Jan 23, 2019)

Each to there own , but for me this is the only way to do it correctly and the resolution is a non issue as I have a high quality digital storage oscilloscope ( I'm an electronics tech )


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## Weigel21 (Sep 8, 2014)

Yep, everyone has their own preferences, nothing wrong with that, so long as one isn't ruining equipment left and right.


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## sfarisminhas (Apr 4, 2019)

I've never done it by ear. I have used a DMM an oscope and a DD1. For me the most accurate and reliable one has been the DD1. I faced an issue that I highlighted elsewhere on the forum with regards to having a DSP in the gain train. I know the DD1 isn't cheap, but I have found it to be reliable. Use a 0db to find max headunit volume, then use -5db and -10db for setting the gains. Light turns red if there is distortion, just back down and light goes off, your done.


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## Weigel21 (Sep 8, 2014)

sfarisminhas said:


> I've never done it by ear. I have used a DMM an oscope and a DD1. For me the most accurate and reliable one has been the DD1. I faced an issue that I highlighted elsewhere on the forum with regards to having a DSP in the gain train. I know the DD1 isn't cheap, but I have found it to be reliable. Use a 0db to find max headunit volume, then use -5db and -10db for setting the gains. Light turns red if there is distortion, just back down and light goes off, your done.


The DD-1 is the one tool I've never used to set gain. I've tried pretty much every other method I have found. I'd like to get a DD-1 and compare all the different ways to set gain head to head to see if there is a clear winner or which methods are best to avoid. Sadly, I just can't justify $190 just to (most likely) prove the DD-1 isn't any better and in such, is vastly over priced as a one trick pony.


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## sfarisminhas (Apr 4, 2019)

I get what you mean. I think I simply wanted something that was quick, reliable and convenient. The other option to avoid scopes, DMM's and DD1's is something like the JL RD amps or the Rockford Fosgate ones that have those indicators built into them. Have you seen any of the D'Amore engineering videos? Pretty thorough.


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## Gill (Sep 26, 2007)

Oscilloscope with dummy load or with out? I tried without dummy load, then found out variances. Did by ears, blew off MD102 tweeters, still sticking with ears, lessons learnt.


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## Weigel21 (Sep 8, 2014)

sfarisminhas said:


> I get what you mean. I think I simply wanted something that was quick, reliable and convenient. The other option to avoid scopes, DMM's and DD1's is something like the JL RD amps or the Rockford Fosgate ones that have those indicators built into them. Have you seen any of the D'Amore engineering videos? Pretty thorough.


Nope, never seen any of them. 

I did buy an AMM-1 though, but none of the other tools. 

Yeah, I have a few JBL amifiers with the "easy gain" setting feature. Not sure how they compare to using any of the other gain setting methods, but once again, it'd be interesting to find out. I know I've seen videos of JBL and Rockford amplifier's being set with their gain setting lights and then set with a DD-1 afterwards for comparison. 

Another option are amplifiers with clipping indicators. They are becoming more and more common. My last amplifier I bought was a JP8 that has a clip light on the remote knob, along with voltage/temp display.


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## Weigel21 (Sep 8, 2014)

Gill said:


> Oscilloscope with dummy load or with out? I tried without dummy load, then found out variances. Did by ears, blew off MD102 tweeters, still sticking with ears, lessons learnt.


Yep, loaded and unloaded I feel make a difference. The DD-1 is meant to set the gain with the amp unloaded. I'm thinking there is something to account for this in its design, but maybe not. 

I could watch videos and read up on things all day, but honestly, Is just prefer to find out for myself. That day may come. Though I'd need to buy a few things first.


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## sfarisminhas (Apr 4, 2019)

Weigel21 said:


> Nope, never seen any of them.
> 
> I did buy an AMM-1 though, but none of the other tools.
> 
> ...


My Five channel Rockford Fosgate has the bass knob with the clip indicator. I have mounted it in the centre console. Great idea, you can at least see the clipping if it happens.


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## Weigel21 (Sep 8, 2014)

How close is the clip light to your DD-1?

Video I seen of the JP8 I bought, shows the clip light to pretty much be spot on with the AD-1 that was being used to test it's power output.


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## sfarisminhas (Apr 4, 2019)

The clip light comes on at the same time on both the amp and the dd-1 for me. There is one thing that I wish the dd-1 would take into consideration is that there should be a 5000hz and 200hz detect signal to take into account tuning for tweeters and midbass drivers. Maybe there is a reason why specifically 40hz and 1000hz are being used?


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## Weigel21 (Sep 8, 2014)

Never understood why those two are the ones chosen, but they are the two that have been used and recommended to use for years, long before the DD-1 was made. 

I've been told the DD-1 will detect distortion regardless of what you're playing, there's just no detect indicator if it's not those two frequencies. Can't confirm such though, but you could since you own one.


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