Help Needed - Aftermarket system noise
Thread Starter
Joined: Jan 2004
Posts: 301
Likes: 1
From: San Francisco
Help Needed - Aftermarket system noise I'm completely lost here and would appreciate some help if any of you guys have had this issue before. I just competed installation of a new stereo in my 98SS - I eliminated the Monsoon system and replaced it with a new head unit, 5 channel amp, and component speakers. I tuned the system with a DD1 to make sure the gains are perfectly matched.
Issue:
The moment the car is turned on there is high pitch static in the front speakers (only the fronts). The noise is present at all times, even when the head unit is on mute. As I turn the volume up it will overpower the noise but I can still head an underlying high pitched hum. Almost like a tea kettle sound.
RCA cables are not the issue
There is no issue with the individual channels (1,2,3,4) - I connected a single lead from the RCA's to each channel, it is dead quiet
Channels 3&4 do not have the issue
I confirmed it's not the amp, I can play music from iPad + RCA through all channels without any noise
Now the weird part, when I plug only one RCA into Channel 1, it's fine. The moment I plug the second RCA cable into Channel 2 the noise starts. Any idea what's going on here? All components are new and relatively high end.
Issue:
The moment the car is turned on there is high pitch static in the front speakers (only the fronts). The noise is present at all times, even when the head unit is on mute. As I turn the volume up it will overpower the noise but I can still head an underlying high pitched hum. Almost like a tea kettle sound.
RCA cables are not the issue
There is no issue with the individual channels (1,2,3,4) - I connected a single lead from the RCA's to each channel, it is dead quiet
Channels 3&4 do not have the issue
I confirmed it's not the amp, I can play music from iPad + RCA through all channels without any noise
Now the weird part, when I plug only one RCA into Channel 1, it's fine. The moment I plug the second RCA cable into Channel 2 the noise starts. Any idea what's going on here? All components are new and relatively high end.
TECH Fanatic
Joined: Dec 2017
Posts: 1,468
Likes: 266
From: Bossier City, Louisiana
Something in the wiring of your new stereo is acting as an antenna to pick up electrical system noise. You say this problem only occurs when the "car is turned on".
Turned on to run but no engine running?
Turned on with the engine running?
If with engine running, does the noise change when you blip the throttle?
This should be manageable to fix using standard noise reduction techniques for car stereos. I'm thinking RFI filter kit or perhaps Type 43 or Type 75 split toroids (completely passive) on the offending wire that is acting as the antenna. The engineering discussion on how these work is below:
https://palomar-engineers.com/ferrit...-mix-selection
Mouser Elecgtronics or Digi-Key should also stock these. With the loss of Radio Shack, we must turn to the Internet to find items like these. I really miss Radio Shack . . . . I spent so much allowance money there when I was a kid.
Rick
Turned on to run but no engine running?
Turned on with the engine running?
If with engine running, does the noise change when you blip the throttle?
This should be manageable to fix using standard noise reduction techniques for car stereos. I'm thinking RFI filter kit or perhaps Type 43 or Type 75 split toroids (completely passive) on the offending wire that is acting as the antenna. The engineering discussion on how these work is below:
https://palomar-engineers.com/ferrit...-mix-selection
Mouser Elecgtronics or Digi-Key should also stock these. With the loss of Radio Shack, we must turn to the Internet to find items like these. I really miss Radio Shack . . . . I spent so much allowance money there when I was a kid.
Rick
Sounds like an back feed problem, Try adding a ground to the amp or isolating components. In other words either pull the front speakers so they are not grounded to the chassis and see if the noise goes away or swap front and rear outputs and see if the noise follows to the rear speakers. or try another set of speakers that aren't mounted.
Also check that wires are running close to other electronics like fans and such. It may take a little work but you should be able to narrow down the problem thru process of elimination.
Also check that wires are running close to other electronics like fans and such. It may take a little work but you should be able to narrow down the problem thru process of elimination.
Thread Starter
Joined: Jan 2004
Posts: 301
Likes: 1
From: San Francisco
Thanks Rick!
Some more details:
It is there when turned on to run with no engine running, and the same when the engine is running. There is no change when I blip the throttle. One weird thing I have noticed, the sound changes when I turn the interior light dimmer up and down. Does not go away, just makes a weird feedback sound.
I think you're right about just using a noise filter, but I was really hoping to find the actual problem. What has been throwing me off is that channel 3&4 are fine. And Channel 1 and 2 are independently okay but not okay when both are plugged in. If this was a wiring noise issue wouldn't it affect all channels?
Some more details:
Something in the wiring of your new stereo is acting as an antenna to pick up electrical system noise. You say this problem only occurs when the "car is turned on".
Turned on to run but no engine running?
Turned on with the engine running?
If with engine running, does the noise change when you blip the throttle?
Rick
Turned on to run but no engine running?
Turned on with the engine running?
If with engine running, does the noise change when you blip the throttle?
Rick
I think you're right about just using a noise filter, but I was really hoping to find the actual problem. What has been throwing me off is that channel 3&4 are fine. And Channel 1 and 2 are independently okay but not okay when both are plugged in. If this was a wiring noise issue wouldn't it affect all channels?
Thread Starter
Joined: Jan 2004
Posts: 301
Likes: 1
From: San Francisco
Sounds like an back feed problem, Try adding a ground to the amp or isolating components. In other words either pull the front speakers so they are not grounded to the chassis and see if the noise goes away or swap front and rear outputs and see if the noise follows to the rear speakers. or try another set of speakers that aren't mounted..
