Hi,
A few days ago i took my 2000 Jetta to have a deler install a MTX Thunder amp and a Sub that I used to have in my previous car. I still haven’t bought a new head unit so I used the original car stereo to feed the amp for now.
Everything seemed to be working fine but yesterday I noticed that whenever the car is turned on and stopped some noise is heard on the speakers and sub, this is most noticeable in the sub that in the rest of the speakers. The symptoms are the following,
- When I press the gas pedal the noise seems to be much less (as long as the engine has enough revs)
- There is no noise at all when the car is turned of and, of curse, the stereo is turned on.
- The same amount of noise is present regardless of the volume setting on the stereo.
I also noticed that, at night, sometimes the car lights lightly blink when the car is stopped. Since I changed the car battery a couple of months ago, I assumed that the entire problem might come from my alternator.
After reading posts regarding noise for about two hours I decided to do some basic testing on my system in order to confirm my thoughts about the alternator being the cause of the problem. This is what I did,
- Checked the cable runs. The power cable is run thru the driver’s side and the input RCAs on the passenger’s side
- Checked the Amp ground. It just has a short length tick cable connected to a bolt that also holds the rear seat belt, it seems to be making good contact with the car’s chassis
- Checked that the remote wire. It was run as a separate blue cable to the amp
- Assuming that the problem could be on the remote wire, disconnected it from the amp and bridged the power terminal to the remote terminal. The problem stayed exactly the same.
- Disconnected the RCA inputs on the AMP. This made the noise to disappear; if these terminals are disconnected I get no noise either if the car is off or on.
- Brought my laptop to the car and connected it to the AMP inputs. In this scenario I don’t get any noise either if the car is off or on
This made me think. If the problem was the alternator inducing noise on the amplifier power feed, I would get noise on the sub whenever the car was turned on regardless if the car stereo or my laptop was feeding the AMP.
My newbie conclusion is that the problem may be related to two possible causes,
1. RCA cables that run from the car stereo to the AMP are somehow damaged (this doesn’t seems very likely, I assume that if this were the case, I would get noise either if the car is off or on.)
2. Bad Alternator inducing noise on the car stereo. This seems more logical, perhaps the power supply in the AMP is better than the one on the car stereo, this may allow it to run fine while the car stereo is having problems. However this assumption does not completely convince me since I was using the same stereo with same alternator before installing the AMP without problems. Perhaps the stereo’s pre amp outputs are more sensitive to noise or something like that…
Well, anyway if somebody has any idea or thought on what can I do to solve this problem it would be greatly appreciated