RichieC

Has anyone had any probs with interference through their amp??

Ive got a 4ch Kenwood in my MY93 and its horrendous with the engine running.

Its what I would descibe as a coil type buzz which changes pitch with revs but turning up the volume on the head unit doesn't increase it.

Could it be:
1) Bad Earth, should be OK but noise goes when you unplug the RCAs at the amp end?

2) Bad routing of RCAs? Ive run them down the passenger side (amp is under front seat) and power leads are down the drivers side, around the back of the handbrake and under the seat. There is no improvement if the RCAs are pulled out and away from the power leads.

Alternatively has anyone looked into suppression with the scoob engine (nightmare I would expect??)

Thanks in advance

Richie

AlexM

RichieC,

I'd like to know if you find a solution - I am suffering from exactly the same problem. It is also significantly louder at some times than others..... very strange!.

Rgds,

Alex

RichieC

P***es you right off doesnt it !!

Spoils an otherwise good system.

R

[This message has been edited by RichieC (edited 30-06-2000).]

Mike Tuckwood

It's called MEMIC. <I>(amongst other things)</I>.
You can get a suppressor fitted onto the back of the alternator, try any specialist ICE dealer.

Mike.

RichieC

Cheers Mike, do these suppresors work well?

Any idea about cost?

Cheers

Richie

kryten

Haven't put my kit in yet, but from experience of this in other cars:

are all components grounded at the same point? If not, try it!

What happens if you unplug the RCAs from the amp: is it still there?

What happens if you unplug the RCAs from the head unit: still there?

What happens if you feed the output of a personal stereo into the amp: still there?

Are any of the battery terminals loose? Is the ground from the battery to the chassis good?

RichieC

Wo, too many questions

erm....ok

are all components grounded at the same point? THE AMP IS EARTHED AT THE SEAT BELT MOUNTING POINT

What happens if you unplug the RCAs from the amp: is it still there? YES

What happens if you unplug the RCAs from the head unit: still there? DUNNO, WILL TRY

What happens if you feed the output of a personal stereo into the amp: still there? WILL TRY

Are any of the battery terminals loose? Is the ground from the battery to the chassis good? DUNNO, HOW CAN I CHECK IT??


Cheers M8 Ill try running a direct earth off the battery, any good?

If I disconnect the RCAs at the amp and it goes, does that not mean the problem is with the RCAs??

Cheers

Richie

kryten

Can you clarify something, you said:

>What happens if you unplug the RCAs from the amp: is it still there? YES

but then:

>If I disconnect the RCAs at the amp and it goes, does that not mean the problem is with the RCAs??

Which is it?

Try checking out the Electrical section at

RichieC

OK When I unplug the RCAs at the amp end, the noise disappears.

But does this not indicate that it must be them which is causing the problem (ie routed too clos to power)?

Or not?

Cheers again Ill check the link

RIchie

Lee

No No No NO NO NO NO !!

Do *not* fit any suppressors to the head unit, RCA leads or AMPS.

When I originally fitted mine I had this problem. All the ICE specialists I spoke to said that with the head/RCA/Amp setup you shouldnt get it.

In the end it was fixed simply by checking the RCA connections at the head unit end (I have 3 leads and space is er.."tight" !)

I run the power from battery down the passenger side..a distribution block for power and ground. The ground is bolted onto the chassis in the boot. Ideally the head unit would be grounded there too but that is too much aggro.

The RCA's are down the drivers side into the boot.

My speaker leads back up the car are on both sides.

RichieC

Hmmm so might be better off fitting the amp in the boot. Incidently the RCAs are coiled up under the front seat as theyre too long, might be inductiong loads of nasties, although noise still present when I pull them out straight.

Its been mentioned from a mate that it could be the earth loop in the head unit?

Any way of proving/disproving?

Cheers

Richie

kryten

There are two possibles:

a) Your RCAs are picking up the noise directly
b) You have a 'gound loop' - which normally means your grounding points aren't too hot.

To check a) get some other RCA leads and route them from the head unit directly to the amp to see if it goes away (you are using decent quality shielded RCAs, I assume?)

For b) you'll really need a voltmeter. Measure the voltage at the battery, then across the head unit, then across the amp - all while the system is on. Any voltage drop across one of them means you have a problem with earthing (assuming your power/earth cables aren't bell wire!).

You can also measure the resistance (ohms) from the negative terminal of the amp to the battery's negative (with the system OFF) - it should be almost zero.

Mike Tuckwood

Suppressor at the Alternator will clean up a 'dirty power signal' from the Alternator to the amp.

It could be anything, Head unit, amp, cables routing, termination. Eliminate them one by one.


Mike.

RichieC

Thanks Adam, I need to sit down and sort it.

Cheers

Richie

RichieC

Cheers Mike, will do.

Have you still got those RCAs, if so what length are they?

Cheers Rich

Adam M

Listen to Lee he is right.

Run power and rca down opposite sides of the car.

More importantly don't let the power cable cross the engine bay. Send it down the same side as the battery ie the near side. Routing near the alternator is hazardous to the smoothness of the dc.

Try to run speaker cable down the middle and then branch out to the doors behind the dash.

It is alright to cross power and earth but don't run then parallel at al if you can avoid it. Due to the nature of the field changing in the power cable, it will induce a current in the signal cable which distorts the true signal as it is only line level.

Fitting a signal booster such as a phoenix gold pro line driver will help but it is better to erase the noise rather than cover it up.

This is only done by cable re routing.

You could also try resoldering suspect rca plugs. Check all earths with a voltmeter too.

I would bet money on the problem being due to cable routing.
Good luck.

ps. do not buy a surpressor, they tend to be crap.

kryten

Browsing the other day and saw this site:

chiark

If the noise doesn't get louder when you turn the volume up, could it be coming in after the amp has done its work?

I had *exactly* this problem that was driving me mad. The problem was that the passive crossover was picking up electrical noise. It was behind the driver's kick panel, and moving it 8 inches across towards the middle of the car sorted the problem. There is something *very* noisy in that area.

Don't go near noise supressors. You need to remove the cause of it, not treat the symptoms. No matter what, it will be a cable problem.

Back a few years ago I also had the same with an RCA lead that decided to play silly devils. I guess that soldering the terminals again, as has already been suggested, would have fixed it.

Good luck!

RichieC

Come to mention it, occassionally the amp goes quiet and seems to drop its amplification, Ie if you waggle the RCAs into the phonos it comes back on. Ive opened it up and they appear to be sealed phono sockets, anybody know how to resolder them?

This could well be a snag as its obviously a dodgy connection. Theres no reason for me to suspect the RCAs themselves as theyre brand new Fosgate ones, plus the noise was there with the old RCAs.

Bit of a puzzler.............

strong

This is probably of no interest in this case since the replies mention alternator buzz but my radio recently starting buzzing in time with engine revs.

Took it to local audio shop (Top Banana in Fleet - good blokes) they pulled off each of the HT leads and found one connector was dirty (others were quite shiny), gave it a clean and the buzz has disappeared.

RichieC

Hmmm sounds like there might be something in that.

I remember when I first got my car one of the plug caps was leaking the spark, ie the nasty bakelite had broken down and split slightly. The outcome was the spark was being blown out at full boost.

I wonder if one of the others is breaking down and allowing said spark to leak??

Any thoughts?