Omega Owners Forum
Omega Help Area => Omega Electrical and Audio Help => Topic started by: paul36uk1 on 13 May 2008, 18:03:00
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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
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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.
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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?
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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
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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.
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is it easy to solve this problem? or is it just a case of checking that the amp is properly earthed?
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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.
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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
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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?
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im in leamington spa,near coventry mark
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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?
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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
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His head unit is OK?
Then the fault is where the amp gets its line level feed. I think Dave DND will explain better
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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.
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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,
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Can you email me a good close up picture of the earth?
technical@dndservices.co.uk
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Can you email me a good close up picture of the earth?
technical@dndservices.co.uk
0V/Chassis connection, no earth on a car :y
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You can`t assume that just because its screwed into the metal that its earthed !! If it were that easy, I`d be out of a job !!
I need to see what panel it is screwed into to ensure that it is fixed to a primary chassis panel and not a secondary floor panel that is often poorly spot welded and bonded with seam sealent - as if affixed to this, it will see the earth return at a slightly higher resistance. Every panel joint and weld is a potential problem.
For anybody wanting to know the best earth for a boot mounted amp, our preferred location is under the boot carpet, affixed to the floor with a big shiny self tapper above the box section chassis rail that runs within an inch or so of the base of a suspension turret. The paintwork needs to be rubbed back also. This is the thickest part of the chassis and has a continuous and often seamless return back to the battery.
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You can`t assume that just because its screwed into the metal that its earthed !! If it were that easy, I`d be out of a job !!
I need to see what panel it is screwed into to ensure that it is fixed to a primary chassis panel and not a secondary floor panel that is often poorly spot welded and bonded with seam sealent - as if affixed to this, it will see the earth return at a slightly higher resistance. Every panel joint and weld is a potential problem.
For anybody wanting to know the best earth for a boot mounted amp, our preferred location is under the boot carpet, affixed to the floor with a big shiny self tapper above the box section chassis rail that runs within an inch or so of the base of a suspension turret. The paintwork needs to be rubbed back also. This is the thickest part of the chassis and has a continuous and often seamless return back to the battery.
Lol, think I spent to long in the power engineering industry......as said, no earth on a car (unless you have it connectd to a 6 foot spike driven into the ground), there is a chassis or 0v :y
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Lol, think I spent to long in the power engineering industry......as said, no earth on a car (unless you have it connectd to a 6 foot spike driven into the ground), there is a chassis or 0v
:P
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i will try to get a couple of photos today Dave,im starting to thing its 2 problems,one like you said a bad earth and secondly the line level feed,when the anp is powered up it sounds very powerful ie just one notch on the volume control on the head unit and the sound belts out
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I think you may be right :(
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Good pictures.
Obviously, these suggestions are purely guidelines and I cannot guarantee anything, but is where I would start from.
The earth looks like it is attatched to a cross brace going across the car, and the metal has not been rubbed down. I would relocate the earth to the point mentioned earlier and make sure to rub away some paintwork to ensure a good connection.
As far as the Input levels jumping, I suspect you have the wrong line level convertor fitted and may require an adjustable one. If using an adjustable one, its not uncommon to fit a ground loop isolator at the same time to each set of rca leads.
let me know how you get on.
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a mechanic mate of mine has had a look and he said that instead of taking the feed straight from the battery he has joined into the cable from behind the fuse box under the steering wheel and that all the interference is comming from all the different relays on the board
is this possible,sounds like it to me and im no techie
im taking the car back to the guy who fitted the amp tomorrow morn,im just trying to get some sort of a list together so i can tell him to get it sorted out
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OOps! I kind of assumed that the power feed came straight from the battery - your mechanic mate has certainly spotted an absolute blinder there!!
I would be hesitant about getting this guy to fix it though, if thats what he did, I think I would get my money back and go elsewhere instead.
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took it back to the guy today and he said there was a bad eatrh on the head unit,he fitted another one and changed the power feed directly to the battery,it seems 99% of the interference has gone now so im a little bit happier now
id just like to thank dave dnd and the other guys for all your help and advice,
its nice to know that there are some really helpful guys on this site
thanks alot :y
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You are more than welcome - thanks for letting us know the outcome
:y
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Just being nosey, what happened to the original Bose amp?
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Just being nosey, what happened to the original Bose amp?
MV6 dont have bose by default :(
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Ah right, assumed it had Bose as it had an NCDR head unit.
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jimbob is right,it didnt have the bose amp fitted,but i do have one if you know anyone whos looking for one