Circuit City.....

[kballa422 10+ year member]

We took my friends car up to circuit city yesterday to ask them about some noise the sub was picking up. When the blinker was turned on you could hear it in the sub and there was alwys a low rumbling when the volume was at zero, engine noise.

I thought it might be a bad ground but they said it was good, without checking it, so we asked them to measure the resistance, it said .2ohms so it was good, and then said they dont know what the problem was. One guy tried to say he couldn't hear it, another said it will do that a little, its normal, and then he continues on to say that a capacitor would help out a lot. The next thing he said was the battery could be dying bc one of the batteries main jobs is to filter out noise, besides starting the car.

I just laughed and said ok and we left, lol. just thought i would share this. Also, if anyone wants to make any suggestions to what it could be that would be great, we are checking to see if its the head unit today.

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[psych0ticnemes1 5,000+ posts]

check the ground of the head unit and amp to be sure.

 

[ramos 5,000+ posts]

what kind of head unit , and where is the turn on lead coming from ? //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[kballa422 10+ year member]

Its a Sony head unit, dont know the exact model but i could ask him. What u mean by turn on lead?

I already talked to Snoopdann online and he gave me some advise, he said it prob is a bad internal ground in the head unit and to run some rcas from a walkman to the amp and see if that eliminates the noise, if so, its the head unit. We checked the ground of the amp, .2 ohms. I just thought it was ridiculous what they told us might fix it, i mean a capacitor for noise?

 

[ramos 5,000+ posts]

I have seen some pretty weird sources used for the 12v turn on lead for the amplifier . A local hack shop here was known for tapping the tail lights, which causes a problem very similar to yours //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[lilmaniac2 5,000+ posts]

have to ride the break to get your amp to turn on

awesome

 

[Flipx99 5,000+ posts]

have to ride the break to get your amp to turn on
awesome

You could only boom when at a stop sign...ha ha

 

[kballa422 10+ year member]

luckily he's not having that problem lol

 

[luvinthebass 5,000+ posts]

lol

 

[KaeZoo 10+ year member]

First of all, .2 ohms is not a good rating for a ground connection. You can calculate the voltage drop through a resistance using Ohm's Law, E=I*R. If you have a .2 ohm resistance, then running just 10 amperes of current through it will drop your voltage by 2 volts. To put it another way, if there's a point with .2 ohms resistance in the circuit, it's the same effect as running your power through 200 feet of 10 gauge wire. On the other hand, most DMMs aren't very accurate when measuring very low resistance values, so who knows what the real resistance is.

Second, he was technically correct about the battery playing a major part in filtering noise from the electrical system, but recommending a capacitor to fix a noise problem is completely ridiculous.

Using a walkman to provide a signal to the amplifier will automatically remove a ground loop, since the walkman doesn't share the same ground as the amplifier. So even if you get clear sound with the walkman as a source, it doesn't mean the head unit is the culprit. The way to eliminate the head unit is to substitute another known-good head unit, not a portable player.

I'd try re-grounding the amplifier to another point, and make sure you have a tight, paint-free ground connection. Double-check the head unit ground also. Check your battery connections and make sure they're tight and not corroded. Also check the connection between the chassis and the battery negative post.

 

[.::DuD3::. 10+ year member]

have to ride the break to get your amp to turn on
awesome

lmao that would be awesome.

 

[luvinthebass 5,000+ posts]

^^^ definitely piss some drivers off in rush hour that's for sure, **** em //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[helotaxi 5,000+ posts]

.2 ohms is attrocious. Any ground resistance that you can measure directly is too much honestly. The DMM should show a short or basically 0 ohms when measuring ground. If it doesn't then it isn't really a ground.

 

[thunder9500 10+ year member]

We took my friends car up to circuit city yesterday to ask them about some noise the sub was picking up. When the blinker was turned on you could hear it in the sub and there was alwys a low rumbling when the volume was at zero, engine noise.
I thought it might be a bad ground but they said it was good, without checking it, so we asked them to measure the resistance, it said .2ohms so it was good, and then said they dont know what the problem was. One guy tried to say he couldn't hear it, another said it will do that a little, its normal, and then he continues on to say that a capacitor would help out a lot. The next thing he said was the battery could be dying bc one of the batteries main jobs is to filter out noise, besides starting the car.

I just laughed and said ok and we left, lol. just thought i would share this. Also, if anyone wants to make any suggestions to what it could be that would be great, we are checking to see if its the head unit today.

Don't judge us all by our worst link.

I would of course check the amp ground yourself...then possibly reground the head unit to a better ground. (if your bud's car is a Honda, then they are known for horrible grounds) try grounding both the amp and battery to the frame as well.

If re-grounding the amp and the head unit doesn't solve the problem, I would re run your RCA's. Chances are maybe your rca's are running right in line with the 12 volt wire to the back blinkers and you are picking up some noise there....if moving the RCA's doesnt help, I would try replacing them. Just grab another set and run them outside the car to see if it solves your problem. If it does, then run them properly.

 

[thunder9500 10+ year member]

.2 ohms is attrocious. Any ground resistance that you can measure directly is too much honestly. The DMM should show a short or basically 0 ohms when measuring ground. If it doesn't then it isn't really a ground.

almost all meters have some variance in them. To find one that doesn't is extremely difficult.