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[paul36uk1]

hi all,i had some muppet fit a blapunkt amp and new rear speakers in my car,the amp gives off alot of interference noise,he fited a rca noise filter (pc8 101) but it hasnt made any difference,he wants to try another filter that goes to the alternator,just asking around to see if any of you clever chaps have any ideas? the head unit is a ncdc 2013

cheers

[Dave DND]

I`d put money on the fault being an insufficient earth to the amplifier. 99.9% of the vehicles we see for interference faults come down to a poor earth supply.

Aftermarket suppressors went out of the window with Cortina`s !!

The fact that you use the word "Muppet" confirm my suspicions about this being an installation issue, and the Omega is not generally a noisy car, so it should be fairly simple to rectify.

[Marks DTM Calib]

How did he connect the balanced speaker outputs (BTL amp operation) from the ncdc2013 to an RCA input to an amp!

I dont suppose there is any series cap or transformer being employed?

[paul36uk1]

to be honest i have no idea how these things work or what you are supposed to do,i just get a lot of interference from anything electrical ie indicators,interior door lights and a buzzin from the engine,its driving me mad,i need to get it sorted quick

cheers

[Marks DTM Calib]

To connect the NCDC2013 outputs to the amp via an RCA they will need to be potted down to a lower voltage level and only one half of the feed should be connected (assuming the amp has internal 0V bias resistors and the inout stage is capacitively coupled).

If you ground the other wire you are shorting the source out which might cause some very starnge affects.

[paul36uk1]

is it easy to solve this problem? or is it just a case of checking that the amp is properly earthed?

[Dave DND]

I think you need to take it to your local Car Audio specialist to have a quick look at - trying to diagnose this install may be impossible via an online forum.

[paul36uk1]

the amp and speakers were fitted in a "so called" car audio shop,the bloke is just trying to fob me off by saying i need these noise filters etc,he has already tried 2 out of 3 and neither of them solved the problem,hes now saying that i need a pc4 50 connected to the alternator but said he doesnt know how to fit it,like i said im dealing with a muppet

[Marks DTM Calib]

the amp and speakers were fitted in a "so called" car audio shop,the bloke is just trying to fob me off by saying i need these noise filters etc,he has already tried 2 out of 3 and neither of them solved the problem,hes now saying that i need a pc4 50 connected to the alternator but said he doesnt know how to fit it,like i said im dealing with a muppet

Where are you?

[paul36uk1]

im in leamington spa,near coventry mark

[Dave DND]

A shame you`re not in South devon, or I would have taken a look.

I suspect that the guys you are dealing with are fairly new to the game and do not know what they are doing fully - have a look in Yellow pages and try to find an established shop that has a bit more experience that may be able to assist.

Unaware of your technical expertese, do you know what size earth cable has been used, does it have proper crimps, and where on the vehicle has it been attatched?

What form is the interference - distorted sound or buzzing noise? With engine on or off? Does it get faster or slower with revs? Does the pitch rise and fall with revs? With all headlights, wipers, heated screens etc ON, do you get a "Click" from the headlight flash or indicators?

[paul36uk1]

thanks for your offer dave,i dont know anything at all about earths,wires etc,i get interference from all across the range,buzzin from alternator ,goes faster when reved,clicking from hazzards,switch on switch off thump,even my mobile in my pocket will send some noise to the speakers,but the guy who installed the amp tried one of his head units in the car and it seemed to stop all the interference,i really have no idea what to do next,its driving me mad

[Martin_1962]

His head unit is OK?

Then the fault is where the amp gets its line level feed. I think Dave DND will explain better

[Dave DND]

It could be the line level feed, but from your excellent description, I am now even more certain that the fault is earth related.

Just because another head unit works does not prove anything, unless its the same make and model as all have their own tolerances - The NCDC range were never meant to be used with aftermarket amps, but that does not mean that you can`t use them, just means that you have to be a little more carefull in the installation.

The noise is power supply generated and not from the ignition or fuel pump circuits which can be confirmed from the information you have replied with. Although this noise is generated from the alternator, the alternator does not require suppressing. the noise is occurring due to an "earth differential" either on the line input, or more usually on the main earth to the amplifier. Starts to get technical after that - so I`ll shut up on that bit now.

OK, non technical instructions.

Where and how is the amp fitted and mounted?

On the input side of the amp will be an adaptor (matchbox size) with cables going in and RCA/phono leads coming out. This wil either be situated in view near the amp, or may be mounted at the rear of the head unit with longer RCA cables fitted. let me know what you can find.

On the amp is a -ve terminal, should have a hefty thick black(?) cable to it - follow this cable back, which should only be a maximum of 18-24 inches long and let me know where and how it terminates. It will probably be a cable attatched to a bolt in the floor, a panel or around an existing bolt - it wont physically attatch to any other wiring. it may or may not have a large crimp with a ring terminal on it.

Let me know what you can find, and I will try to suggest something.

[paul36uk1]

Dave,the amp is fitted to the back of the rear seats with self tappers via the boot,the thick black cable you mention is the earth im assuming,if so it runs from the amp and fixed to the metal underneath the rear seats with a ring terminal fixed with a self tapper,