DMM+ Gains: Accuracy, Concerns and Clipping.

[PollyCranopolis 10+ year member]

I've read members claiming the DMM method of gain adjustment is inaccurate and does little to prevent clipping. I myself have used this method and am ending up turning my gains up VERY high on the amp to reach the desired voltage. Can anyone comment?

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[tRiGgEr 5,000+ posts]

As long as you have your volume about 3/4 of the way up, the sub output turned all the way up, and are using a 0db test tone. You sholdn't have to turn it up too much. Depending on your head units output voltage and your amps input voltage range.

You were told correct. Setting the gains with a DMM will not prevent clipping, and can not be tested to verify. To do this you would need to use an O-scope.

 

[psych0ticnemes1 5,000+ posts]

just be smart... if your sub looks like it is stressing at 3/4 volume, turn it down... if it sounds like poo, try turning it down... as long as you aren't hurting your sub or your ears, 9 times out of 10 you won't be hurting your equipment either.

 

[Ali1 10+ year member]

^ is that a fact?

 

[PollyCranopolis 10+ year member]

Lemme give you a perfect example...

I 'm running my whole system of a RF851x currently, as my sub amp fried.

I'm running 1 4ohm SVC 15' bridged across one half of the amp.

Amp is rated 425x2@4 mono, Sub is 550rms, So i take the lower of the two....

Calculation states 425*4=1700Sqrt=41 volts

I have to turn the gain up almost 85% to hit this voltage with a 0db, 60hz test tone. Thats pretty high don't you think? Would this have anything to do with my cars electrical system output?

 

[PatFitz9 10+ year member]

the location of the gain isn't exactly related to clipping. there isn't a line that if crossed your amp goes into clipping. like, 85% of the travel might be clipping in some cars, and might not be in others. it depends on your preamp voltage, cars electrical, etc. if you have an oscilloscope, that will give you a better idea of clipping. a DMM isn't perfect, but it's a good start. you also could take into account that not all music is going to be a 0dB test tone. so you are most likely putting out a lot less wattage.

 

[PollyCranopolis 10+ year member]

Yeah I get what your saying. I have a 92 Civic. It has a 1.5liter engine and a battery smaller than a box of tissues. The alt isnt very big either. Never had any real problems with dimming, etc, even when I was pulling 160 amps. I can leave it off with the stereo running for over an hour which amazes me. Thinking of getting a H/O alt and Big 3 wiring.

 

[Johnny Drama 5,000+ posts]

Lemme give you a perfect example...
I 'm running my whole system of a RF851x currently, as my sub amp fried.

I'm running 1 4ohm SVC 15' bridged across one half of the amp.

Amp is rated 425x2@4 mono, Sub is 550rms, So i take the lower of the two....

Calculation states 425*4=1700Sqrt=41 volts

I have to turn the gain up almost 85% to hit this voltage with a 0db, 60hz test tone. Thats pretty high don't you think? Would this have anything to do with my cars electrical system output?

What is your head unit? and are any of the filters set on the HU or amp?

 

[xpl0it 10+ year member]

just be smart... if your sub looks like it is stressing at 3/4 volume, turn it down... if it sounds like poo, try turning it down... as long as you aren't hurting your sub or your ears, 9 times out of 10 you won't be hurting your equipment either.

How could I tell if I'm clipping my system? It's already deafening loud.

 

[PollyCranopolis 10+ year member]

Pioneer 880 Prs. I have all the amp xovers/filters turned off. Everything is off at the deck while adjusting gains except for the deck xovers. Wont let me completely turn the xovers off from the deck.

 

[tRiGgEr 5,000+ posts]

even when I was pulling 160 amps.

You were never pulling 160 amps //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

You also should not be using a 60hz test tone. try a 40-45hz test tone.

 

[PollyCranopolis 10+ year member]

I doubt in hindsight my tiny electrical system is capable of that anyway. I'm bout to start re-wiring everything in the car. The wires been in there for a while and some of them have splices and are starting to get dirty. Especially the wires off the battery terminals. Gona get them in with nice and clean connections. Redo the ground for the amp. (It on a screw, on a hole I drilled into the body). Then I'll start to deaden the front doors.

 

[digital mint 10+ year member]

You were never pulling 160 amps //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif
You also should not be using a 60hz test tone. try a 40-45hz test tone.

Big difference between from 50 to 45hz ? i was always told to use 50hz.

 

[psych0ticnemes1 5,000+ posts]

Big difference between from 50 to 45hz ? i was always told to use 50hz.

ditto

 

[DBfan187 5,000+ posts]

most DMM's can read 60Hz the most accurate.