"Hissing" noise

[UBERS4]

When my Avic D-3 HU is at low volume or off, there is a slight "hissing" noise that seems to emit from either the unit or a speaker. I searched the forum but unlike most people who have had this issue, the noise does NOT get louder when I accelerate. I'm puzzled on what it could be.

 

FYI, I have a 2005 Audi S4.

 

Thanks

[HiFiSi]

If it's coming from the unit, it could be the cooling fan in the back of it.

[JLeach12]

figure out if its the unit or a speaker(s). if its the unit isolate and kill the noise. if its a speaker try adding ground loop isolators regrounding the unit, ditch the factory amp whatever makes it go away

[UBERS4]

If it's coming from the unit, it could be the cooling fan in the back of it.

 

It is the unit, I sourced that. So, if it's the fan, I'm assuming it's normal?

[HiFiSi]

Yeah... you'll be able to hear it with everything else in the car turned off. That's the price you pay for shoving so much electronics in such a small box. It get HOT. So a fan was necessary.

[UBERS4]

Ok, so the issue is still present. We installed ground loop isolators to try to correct it and the noise still seems to be there, it's better (at least I think it is) but there. This problem started happening once the Avic-D3 headunit was installed and I never had the issue with the OEM headunit.

 

Also, the noise DOES seem to get louder when I accelerate, unlike what my initial post says. It is not however coming from the engine.

 

Any help would be much appreciated. My installer is stumped as well. He told me not to worry about paying for anything until we fix the problem.

[HiFiSi]

Wow... 3 months later...

 

So have you determined conclusively whether the sound is coming from the head unit or from the speakers yet? Because from the last post you made, you say the actual head unit was making the noise. Which doesn't have anything to do with a ground loop or engine/alternator interference.

[quickline23]

yea u totally went back on what u said. so its not coming from the unit? do u have a factory amp hooked up at all?

[UBERS4]

I didn't drive the car all winter, hence why the issue hasn't been able to be taken care of until now.

 

Like my recent post said, please disregard the original theory. I have sourced that the sound is not coming from the HU but rather from the speakers. I do have a factory amp and this is why we thought the ground loop isolators (noise filters) might be able to alleviate the problem. The noise is very faint, but enough to hear at low/no volume. It ONLY came about with the installation of the Avic unit. I never had a problem with the OEM unit.

[simi]

Do you have the ipod hookup? If your ipod is hooked up randomly it will make a hissing noise for a few seconds, only wai i know of fixing it is turning the ipod charging off on the d3.

[UBERS4]

Do you have the ipod hookup? If your ipod is hooked up randomly it will make a hissing noise for a few seconds, only wai i know of fixing it is turning the ipod charging off on the d3.

 

Tried it, no difference.

 

The noise does seem to worsen when the headlights are turned on, thus I would have hoped the noise filters would have fixed the issue. Could it be a grounding problem?

[RidinaZ]

i had a problem with grounding in my d3 b/c i blew my fuse. There was a hissing coming from the speakers that got louder when i accelerated.

I had to wrap a piece of bare wire around the a/v inputs and ground that to where i grounded my d3.

 

Ground loop isolators are not good as they are a bandaid for the problem ive read.

[MichaelB]

Ive had the same issue since day one.

Buzzing from speakers. Increases as I step on the gas.

INstaller installed ground loop isolation on both amp outputs but still present.

I installed a ground loop isolator on the head units power lead but no change.

 

Im going to buy new amps for the speakers. Using the factory amp at this time. Crappy GM.

 

One thing I might try 1st however is to disconnect the speed sensor wire.

Im wondering if thats directly effecting it.

 

Anyone have any good recommendations? I have a really old 300Watt Kenwood bridged for my sub. under the back seat. Bose door speakers I will keep so just need a 4 channel Amp.

[HiFiSi]

You might want to do some research before hooking up aftermarket amps to Bose stock speakers... IIRC they might run at an impedance that most amplifiers aren't designed to work at.

[HiFiSi]

I was talking to a guy who worked for Bose about something on another forum a while back... here's a small snippet of the conversation:

 

As for power output, I'm embarrassed that I don't have the exact spec, but it's not much more than 15-20 watts rms per speaker. Unless already familiar with the required math, though, these figures can't really be compared with other aftermarket equipment. BOSE generally uses speakers with an impedence of roughly 1 ohm, compared to the common 4-ohm rating on most widely available components. The BOSE speaker places far less load on the amplifier, allowing lower power output to be used to achieve a given volume level. A BOSE power spec would be rated at the lower impedence, but if connected to a 4-ohm speaker, the actual output would drop significantly. If BOSE speakers are connected to a conventional amp, it'll most likely destroy the speaker AND fry the amp. Most conventional amps can't handle the 1-ohm load. DO NOT TEST THIS THEORY UNLESS YOU HAVE DISPOSABLE COMPONENTS!

 

By the way, for future reference, try to avoid getting a OEM bose system in a car. They're the biggest pieces of junk for how much is charged for them. For a small fraction of the cost you can put together something much, much better.