Another gain DMM thread

[XEnophontos 10+ year member]

Alrighty guys I wanna set my gain right this time around, I dont have a magical ear and I'm afraid I wont be able to tell if theres any clipping. Anyways I know theres a ton of threads, and yes I have looked through them, but thats the problem to many people are saying different things on how to do set your gain right using a DMM.

Such as test tones, 50hz 60hz? 0db -3db?

Another one that's often debated is leaving the sub attached or not?

Thanks guys

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[sacsking916 5,000+ posts]

they are different for different class amps. i know the sub amp will not be tuned the same way or with the same readings as your mids or highs amp will be,.

 

[outsideshot23 10+ year member]

if you cant do it by ear you need an oscope.. and unless you know someone who has tested your amps and got a good idea of the voltage it clips at your going to need an oscope.. play 50 or 60 hz either one.. no subs attached..

 

[Ryan shaw 10+ year member]

play a 40hz tone, plug the DMM to the speaker terminals with subs unattached. then turn the head unit to the maximum volume you will listen to it. with the tone playing, set the dmm to read AC volts and turn the gain knob until you get to your desired voltage.

to determine your desired voltage, multiply the watts rms of your amplifier by the ohms it is running at and take the square root of that final number to determine what voltage to set your gains to.

for example, if you have a 3200wrms amplifier running at 2 ohms, you multiply those to get 6400. then take the square root of that which would be 80. then turn the gain knob until the dmm reads 80 volts.

This isn't the most accurate way to do it, but it's defintely the safest cheapest way. In 99% of systems I believe this will suffice as long as the user is responsible.

 

[MONSONwarrior Premium Member]

play a 40hz tone, plug the DMM to the speaker terminals with subs unattached. then turn the head unit to the maximum volume you will listen to it. with the tone playing, set the dmm to read AC volts and turn the gain knob until you get to your desired voltage.
to determine your desired voltage, multiply the watts rms of your amplifier by the ohms it is running at and take the square root of that final number to determine what voltage to set your gains to.

for example, if you have a 3200wrms amplifier running at 2 ohms, you multiply those to get 6400. then take the square root of that which would be 80. then turn the gain knob until the dmm reads 80 volts.

This isn't the most accurate way to do it, but it's defintely the safest cheapest way. In 99% of systems I believe this will suffice as long as the user is responsible.

50hz //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

 

[2RZ-FE 10+ year member]

I do mine by ear with music. Unless you listen to test tones all day i'd just do it by ear. Test tones, music CD's, and iPod MP3's put out different voltages through your rca's do they not?

 

[MONSONwarrior Premium Member]

I do mine by ear with music. Unless you listen to test tones all day i'd just do it by ear. Test tones, music CD's, and iPod MP3's put out different voltages through your rca's do they not?

They do, so I use my iPod's frequency app to set my gains with my o-scope.

 

[Haunz 10+ year member]

I know theres a ton of threads, and yes I have looked through them, but thats the problem to many people are saying different things on how to do set your gain right using a DMM.

What makes you think this thread will be any different ?

I wanna set my gain right this time around, I dont have a magical ear and I'm afraid I wont be able to tell if theres any clipping.

A DMM can't tell you if your amplifier is clipping //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

 

[MONSONwarrior Premium Member]

A DMM can't tell you if your amplifier is clipping //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

O-scope can //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

the DSO Nano is like 70 bucks shipped and completely worth it if you have the cash to spare.

 

[retrojordans 10+ year member]

The absolute only option is an oscilloscope.

Amazon.com: Velleman 10 MHz Handheld Oscilloscope: Electronics

Simple:

Head unit volume 1-60

Head unit clips @ 50 (with all settings, boosts, etc. FLAT meaning set to 0)

1. Run a tone 50-60hz depending on your application.

2. Turn the head unit volume to 50 with no sub woofer attached (with the bass boost again on 0!).

3. With the O-scope hooked up to the amp adjust the gain until the wave on the screen goes from rounded just barely into the squared shape (volume 50 all settings to 0)

4. Don't play music above head unit volume 45 to be safe.

No need to **** with the bass boost...That's what the amp is for??

 

[Haunz 10+ year member]

The absolute only option is an oscilloscope.

He could also use a distortion analyzer //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

(more useful IMO)

 

[Kangaroux 5,000+ posts]

The absolute only option is an oscilloscope.
Amazon.com: Velleman 10 MHz Handheld Oscilloscope: Electronics

Simple:

Head unit volume 1-60

Head unit clips @ 50 (with all settings, boosts, etc. FLAT meaning set to 0)

1. Run a tone 50-60hz depending on your application.

2. Turn the head unit volume to 50 with no sub woofer attached (with the bass boost again on 0!).

3. With the O-scope hooked up to the amp adjust the gain until the wave on the screen goes from rounded just barely into the squared shape (volume 50 all settings to 0)

4. Don't play music above head unit volume 45 to be safe.

No need to **** with the bass boost...That's what the amp is for??

leaving the subs attached accounts for imp. rise //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

 

[akheathen Premium Member]

lol, there was a recent thread where a couple of us tested the theories. i pretty much simulated a real-world experience on my bench, though i did not have an o-scope. also, i want to add, that if you set an amp to play just under clipping like that, and you put an actual load on it, the setting will be way beyond clipping. the safest way is to set it like the jl manuals say, but you can miss out on a lot of power, depending on box rise. first thing to think about, is not to turn it up past the power you can supply. once you drop below 13v with the car running, don't go any higher, always keep that in mind, as peak spikes, like drum/bass hits will momentarily drag it even lower. keep the bass on the hu at 0, though the sub can be mid range, which gives you your adjust-ability when listening to it. about the tones, 50hz+ is going to have a higher voltage than lower tones, which is why you use them. 0db means it is not quieted. -3 is just because it has a higher sq for other tuning uses. usually, you can spot when an amp starts to clip by the indicator light(s) dimming. a little can be normal, and so is more than a little on the cheaper amps with little displays, or flashy dress-up lights, but the on led will always tell-tale rail sag. if you are turning the volume up and get near higher volumes, adn you hear the sound change, but not gain, you are clipping (you have to be by the speaker, not in the driver seat)

 

[akheathen Premium Member]

... oh, and i also have to add, as i mentioned in the other thread, that there are some self-sensing load amps, like jl, jbl crown, and a few others from different makes that you do, in fact, set un-loaded, as per manufacturer specified.....

 

[retrojordans 10+ year member]

lol, there was a recent thread where a couple of us tested the theories. i pretty much simulated a real-world experience on my bench, though i did not have an o-scope. also, i want to add, that if you set an amp to play just under clipping like that, and you put an actual load on it, the setting will be way beyond clipping. the safest way is to set it like the jl manuals say, but you can miss out on a lot of power, depending on box rise. first thing to think about, is not to turn it up past the power you can supply. once you drop below 13v with the car running, don't go any higher, always keep that in mind, as peak spikes, like drum/bass hits will momentarily drag it even lower. keep the bass on the hu at 0, though the sub can be mid range, which gives you your adjust-ability when listening to it. about the tones, 50hz+ is going to have a higher voltage than lower tones, which is why you use them. 0db means it is not quieted. -3 is just because it has a higher sq for other tuning uses. usually, you can spot when an amp starts to clip by the indicator light(s) dimming. a little can be normal, and so is more than a little on the cheaper amps with little displays, or flashy dress-up lights, but the on led will always tell-tale rail sag. if you are turning the volume up and get near higher volumes, adn you hear the sound change, but not gain, you are clipping (you have to be by the speaker, not in the driver seat)

Setting the sub amp on 60hz will ensure it won't clip where it will primarily be playing 30-50 hz..Furthermore you set the amp with the head unit's bass level on 0 so on certain recordings you can either go down as low as -8 on some units and sometimes as high as +8...When you venture away from the bass level on which you set the amp you will be relying on your ear to fine tune it.

If you set it to clip @ volume 50 @ 60hz and don't turn it up past volume 45 and it will never play 60hz that is not that close that's actually really safe seeing as that we run what 1 - 2 ohm loads direct from the sub tops?