Noise/Interference caused by EDIS/MJ - Any ideas

pristic · Post by **pristic** » Wed Nov 19, 2008 10:08 pm

Hi Guys,

I have a Leyland Mini - EDIS 4 and MJ 4
All running great... only issue is that I have massive interference in the stereo.
Car off, its fine - its not a big system, 6" speakers + tweeters up front, 6x9s at back and a sub in the boot - front speakers and sub are amped only with a reference series VERY high quality amplifier.

Anyhow, when I start it I get the high pitch sound through the speakers... as you rev, the high pitch squeel gets louder etc... typical problem when the power wires to the amp and the speaker wires are too close together.
In my case the amp is in the boot directly wired off the battery - only RCA cables (x4) and the amp Remote trigger run from the front of the car to the rear. No power wires run along there.

With the Dizzy in - instead of the MJ and EDIS (ie/ pull the edis + MJ fuse out and its all good... but with the super dooper spark setup of EDIS and MJ I get loads of interference.

I threw in a noise filter (again, good quality) and it helped a 'little' but its still very loud, high pitched noise.

Any ideas? Sheilding anything help?
The cable for PIP/SAW is shielded FYI

Cheers,
Peter

Post by **brentp** » Wed Nov 19, 2008 11:31 pm

You likely have a ground loop issue between your source and amplifier. This is where the ground between components is different, due to grounding at different locations on the car chassis.

One way to eliminate this is through an audio isolation transformer:
http://www.epanorama.net/documents/grou ... ators.html

You can also adjust your grounding points- using a star grounding system where everything grounds to one location may be helpful.

Regards,

pristic · Post by **pristic** » Wed Nov 19, 2008 11:46 pm

Hi Brent,

Thanks your onto something- can you tell me more about the ground looping issue?
Ie/ You mean I have too many earth points in the car?
I have - about 6 and the amplifier is not grounded to chassis, only to neg on battery.
- The head unit is grounded to chassis on its own point
- 4 x guages and lights on their own point (together)
- 2 x headlight relays on their own point (together)
- engine to chassis on its own point
- electric fuel pump on its own point
- edis + mj on their own point (together)

You saying I should put them all together with one big fat earth? (Except MJ and EDIS?)

Thanks,
Peter

pristic · Post by **pristic** » Wed Nov 19, 2008 11:51 pm

PS: When I said 'noise filter' I meant Audio Isolator. I put one in and its still a big problem... its an RCA 1:1 type.

Pete

Salamander · Post by **Salamander** » Thu Nov 20, 2008 2:43 pm

Hi

I have a problem with the tacho, the tacho is crazy, show me everyting, I used the 15v zener and 1 1N4007, I take 1 signal to the coil, my tacho is for 4 cil and 2 cilinders, I configured to 2 cilinders the tacho works fine short time.

My question is: I need a filter condenser or not?, my problem is other?

Post by **brentp** » Thu Nov 20, 2008 3:52 pm

Pete,

Since the problem is surrounding the audio, try grounding the head unit and amplifier together to see if that makes a difference.

Salamander,

have you tried connecting the TACH to the PIP line instead?

pristic · Post by **pristic** » Fri Nov 21, 2008 1:31 am

Thanks Brent - will be tough to do but ill do it... ill run the earth from head unit back to the boot (which is where the amp is and is connected direct to battery (which is connected via short short cable to the chassis in the boot.

Ill update with results mate!

Peter.

Post by **brentp** » Fri Nov 21, 2008 2:56 am

Hi,

Before you kill yourself tearing out your interior to run a ground cable, try moving your amp closer to the front, running it temporarily with a short ground wire connected to the same point as the head unit. If things dramatically improve, then you will know how to proceed!

pristic · Post by **pristic** » Fri Nov 21, 2008 3:42 am

Thanks mate - will do - the prob isnt the interior its the actual head unit and the earth point. I should move it anyway so might as well just bite the bullet as its tucked up and not a short earth anyway.

I will try both the amp closer the the HU and also try the HU earth running back to the boot... wont take me long once I get going.

I know a short earth on the amp is always better than a long earth (well, so ive heard)

Thanks for all the input - if it helps ill be a very happy camper.

Pete

Gilesy998 · Post by **Gilesy998** » Fri Nov 21, 2008 9:34 am

Forgive me for asking the obvious question, but do you have a suppressing capacitor between the +12V and ground? The old wiring diagram from this site shows a cap (20-odd uf I think) between the coil feed and ground which act to reduce/elimenate this very issue. I use one in mine with great success (well, I assume so as I have no noise issues whatsoever). Your old coil setup likely used a suppressor between the coil feed and ground for the same reason - most cars did.
As a side note, as long as the feed is switched the cap will not help your battery drain with the engine off.

Tron1275 · Post by **Tron1275** » Sat Jul 27, 2013 7:56 pm

Hi all.... I was wondering if this problem was sorted..... I am having a similar problem that has been doing my head in!.....

My problem is more rf interference than audio.... I have a cb radio in the car and while the engine is running I get strange noise that wipes any incoming signals out... Today I tried to listen to medium wave on the stereo..(which also has amps and equaliser in line)....... But all that was there was a loud noise that changed with revs.... But inside the noise was a noise that reminded me of a data signal... I tried pulling the plug on the MJ.... The revs changed.... But the noise was still there.... I'm thinking I may have to mount the system in a metal box then earthing the box..... Or have I missed a connection on the edis unit ???

Thanks for any help