byrdman454

I recently installed a new head unit (Pioneer AVIC 2din). I am using the same speakers as before and the same amp. The only other change I made was installed a battery cut off switch inline. As I turn the key on, I get a high pitched squeal through the speakers. When I turn the HVAC fan on, I get feedback through the speakers. As the engine cooling fans kick on, I also get feedback. Does anyone know why I am getting this now versus before I had nothing? Would the battery cutoff switch mess with the ground? Did something happen to my amp? Would the new head unit have an impact? Any ideas would be appreciated.

Thanks

danglerb

Feedback is when a microphone or some input gets a signal from the output of the amp, and the signal feeds back to the input. What you have is just noise, likely from the positive side of the input power. Different head units have different levels of resistance to noise, or something may have changed between the head unit and Plus side of the battery (poor or weak connection).

I'd look over the connections between the amp and battery, and if that doesn't help between the head unit and the battery.

auzivision

Sounds like a ground look problem, need to use isolators to emilniate ground float between head unit and amp.

http://www.google.com/products?hl=en...ed=0CDEQrQQwAA

Alan

Where is the battery switch? how did you install it? tell me you haven't ever turned it off when the car was running... (you may have blown an alternator diode - which makes things noisy...)

Do you have the suppressor connected in series with the permanent or switched power? (you may need both or to swap it...) where does the permanent power to the head unit come from? Where is the amp located & how is it powered? do the amp and the head unit share the exact same ground (ideally they do).

Are your preamp-outs fully shielded?

Alan

byrdman454

The battery switch is in the back behind the tool cover. One terminal on the cutoff switch is mounted to a bracket which hooks to the original ground. The other terminal on the cutoff switch has a short ground wire hooked to the original flat ground wire (needed more length).

I just got the car running, so no I have not used the cutoff switch to shut the car off.

The permanent power for the head unit uses the same as the original head unit or at least the same as my last aftermarket head unit (which I did not have any problems with). I did not rewire this.

I have 2 amps, one for a sub and the other for speakers. They are both located in the spare tire well. Each amp is wired directly to the battery for hot and to the original ground location (with one side of the cutoff switch) for ground. The head unit is grounded up front like the original or last aftermarket. I did not rewire this either.

I bought a new set of Monster RCAs which feed both amps from the head unit. I can unplug these and still get the squeal through the speakers, so I assumed this was not the problem.

What suppressor are you referring to? I am not familiar with this...

steven storch

a ground loop isolator can be used (any radio shack has them @ ~18.00 each...you'll need two). These will, however, remove some sound quality.

Better to not use the factory ground (bwn wire) but run your own to the car chassis (not just any bolt you find). Make sure there is clean metal to metal contact and that should eliminate the whine coming from the speakers.

Storch
1985 928S

byrdman454

Just saw this review on Amazon for the PAC SNI-1 thanks to Kurt's link above. This sounds like it could be a similar issue. This reviewers AVIC is the previous version of mine. I am also using the rear preamp RCAs and the sub preamp RCAs. I will unhook the Sub RCAs and see if I still get feedback through the other speakers after work today.

This review is from: PAC SNI1 Noise Isolator (Automotive)
I have a pioner avic f90bt hooked up to a crunch 5 channel amp, When I hooked up the front and rear pre amp rca cables everything was fine, soon as I hooked up the sub pre amp rca cables I was getting noise through the front and rear speakers without the engine running, and it only got worse with the engine running, I ordered this product along with a power feed noise filter, the pac filter showed up first,I hooked it up and no more noise, didnt even need the other filter

Randy V

Why two? Where are they installed?

byrdman454

I bought these noise isolators and put them inline on the RCAs from the head unit to both amps (bought 2 isolators). The noise is gone from my sub, but there is still noise through my other amp. When hooking it up direct without the isolator, the noise is VERY loud, almost like a siren. When I hook it up through the isolator, it cuts down the noise quite a bit, but I am getting noise through the speakers which changes depending on what is powered in the car. It seems to change pitch or get louder when the engine fans come on. Anyone else have any ideas. Do you think this amp is defective?

Alan

What you have done so far helps eliminate noise coupled from the signal inputs due to different grounding points (and relative noise between them)

Noise is also coupled into the head unit directly from noise on its supplies - you should ensure you have an inductive noise supresssor in series with both the permanent and switched supplies to the head unit. You should have one supressor from the stock install - it is likely still on the switched line - add another one on the unswitched line.

More complex supressors have more features - but its likely a suitably sized inductor is all you need.

A damaged alternator (burned out diode) will create a lot more electrical noise. If it just got worse without any audio component changes I'd suspect that cause (your indicated running voltage would drop under load in this case).

Alan

byrdman454

Another update. I re-read the directions to the filters and found that they are directional. I had them hooked up backwards back at the amp. I have them now in the correct direction straight out of the head unit. All of the noise is gone now without the car running and the stereo on (I was having some noise before). I still have noise coming through the speakers with the car running. It is mainly a clicking noise at idle.

Alan, what does the stock noise suppressor look like and where is it located? I have no idea on that one. Where should I buy another one? Do you have a recommendation from Radio Shack or something?

I am now going to try running a temp ground wire from the head unit back to where the amps are grounded to see if this helps.

byrdman454

I found the problem, just not sure why it is a problem. I unplugged my new fancy Monster Auto RCA from the mid-range amp (the one producing noise) and plugged in an old cheapo RCA cable and all the noise is gone. WTF? Defective cable or is it routed next to something it shouldn't be. Not sure. This is very depressing. Any way to test the Monster cable?

Maleficio

Don't buy Monster anymore. Get your money back. Monster is an evil corporation anyway. They loike to bully small companies with lawsuit threats for using the word "monster" somewhere in their business name, small companies don't have the funds for a powerful legal team, so they fold, and change their name.

Monster chooses to build cabling with intentionally cheap terminals. They figure they'll save money by cutting corners with the connectors. Termination of cabling is of the utmost imortance for signal purity and product longevity.

byrdman454

Well, I spoke too soon. Turns out the troublesome amp had blown a fuse and was not functioning during that last test with the new RCAs. Back to square one...

Still have the noise with engine running...

danglerb

Noise isolators are cheap transformers and filters, I wouldn't put one in my audio chain, except as a very last resort when time didn't permit a better solution.

Seems to me you need to have somebody that knows auto electrics to go over your install and fix whatever is screwed up.