My new car radio "hisses" -- why?

Factual Questions
1

Okay, so actually it’s my wife’s stereo, in her Pathfinder. I bought her a new CD/receiver for her birthday.

I’ve noticed that when playing CDs (and, to a lesser extent, listening to the radio) on this newfangled thing, there’s an audible “hiss” under the music. That didn’t happen on the factory-installed CD/receiver that used to be in there.

I didn’t buy new speakers when I got the CD/receiver; the old receiver was broken, and needed to be replaced. Could it be that I’m kinda-sorta forced to buy new speakers now, to eliminate the hiss? Or is it some wrong connection or spliced wiring in the new CD/receiver that’s causing the hiss?

The hiss isn’t terribly noticeable, and I can live with it. But it’s annoying to spend money on a new CD/receiver and hear the hiss, when it wasn’t there on the old CD/receiver.

2

Ah, the wonderful problem of “noise.” This is probably the most difficult thing to diagnose in the realm of car stereos, and potentially the most frustrating and labor- and cost-intensive as well.

OK, now that I’ve scared you, it could one of several things.

Potential problem: Your new stereo is higher-powered than the old one, thus amplifying engine noise, alternator noise, random noise, to a high enough volume that it is now audible, where it wasn’t before. Pray this is not your problem if this noise really annoys you.
Solution: Long process involving things like Dynamat, stripping car to frame, and long, expensive hours as installers crawl over your car adding insulation to wires.

Potential problem: Stereo got hooked up wrong, or at least sloppily. Bad connections can cause noise.
Solution: Take it back to the installer and make the bums fix it.

Potential problem: Crappy replacement stereo.
Solution: Buy a better replacement product.

Potential problem: Factory stereos are somewhat designed for the car. There may be some insulation designed into it just because this car is the way it is.
Solution: Try a different brand of stereo.

Potential problem: Treble too high.
Solution: Duh.

If, as you rev the engine, the sound gets higher-pitched and eventually goes away (because you can’t hear it anymore), it’s noise from the engine compartment. If not, it could be the stereo. Another way to change the equation is to feed your head unit through an outboard amp, and see if that helps.

I’m sure that there are others things it could be, and others will come along to…wait a second. You’re just using this as a justification to your wife so you can buy new speakers, aren’t you? :slight_smile:

3

Noise certainly is the most insidious difficulty in the world of car stereo. I’ve been trying off and on for over 7 years to rid the noise from the system in my truck.

From your description, I assume your system is a basic head-unit and four factory speakers. New speakers won’t eliminate the hiss. I’m quite sure the noise is coming from the CD player, and you’ll have to determine if that particular make/model is just noisy, or if there’s something amiss in the way it was hooked up.

I would guess it’s probably a ground loop, meaning the black wire from the head-unit isn’t connected to a “good enough” ground spot. Try grounding the head-unit to another place, preferably some solid, bare metal that is connected to the chassis or frame of the car. Installers often put it on the easiest piece of metal to get to, only to find out later that they chose some structural component of the dashboard that is totally (electrically) isolated from the rest of the car.

4

The ground loop is a good call. Another trick I’ve heard of is to put a suitable (big 100 micro-farad) capacitor across the power and ground lines going to the radio/cd player. This should filter out the buzz while still letting normal direct-current electricity flow to the radio/cd player.
-Ben

5

I’ve heard of several people that had snakes get up under the dash board. Usually quite a job getting them out.

6

An easy way to see if it’s the CD player is to simply take the line out from a portable CD player into the tape player (CD line out to tape player adapter 20.00 at Circuit City) and see if hiss is same as before. If not onboard CD player is culprit. If yes problem is in amp section or wiring.

7

An easy way to see if it’s the CD player is to simply take the line out from a portable CD player into the tape player (CD line out to tape player adapter 20.00 at Circuit City) and see if hiss is same as before. If not onboard CD player is culprit. If yes problem is in amp section or wiring.

8

If the “hiss” you describe is present when the engine is running but NOT when it’s off, it’s RF noise from the vehicle’s electronics. If the “hiss” is there all the time it’s probably the grounding as several people have already pointed out, or the unit itself. Listen to the same unit in a store and see if the noise is present, if it is, get a different stereo.

There are inexpensive RF filters you can buy to cancel a lot of the RF noise. Buy them where the Ham Radio guys shop, or go to Radio Shaft.

Good luck!!

Oh, yeah, you REALLY have to get new speakers for that.

( copy/paste the above to show to wife)

b.

9

When I replaced the head unit in my car with a CD player, it hissed. I got returned it and got one that wasn’t defective.

Try that first… then if there’s still problems, try something new. Also, replacing the speakers will do nothing except make the hiss clearer

10

Thanks for all the input, folks. This will come as a shock to many of you, but I have no interest in buying new speakers for the wife’s vehicle. I’m a tightwad.

The hiss doesn’t bother the wife, so I guess I’ll just leave things as they are. My suspicion is that the unit wasn’t installed properly, and it’s likely grounded incorrectly. The hiss doesn’t changes as the engine shifts gears.

kniz, I’ll ask my wife to check for snakes. Good tip.