Audiophiles? Line noise issue

[the_troupster]

Hi all,

I've been battling some noise issues on my set-up, and I'm all out of ideas...

When the engine is running I hear noise through the amps that sounds like tortured dolphins that rises and and falls with engine revs. I presume this is spark plug interference. I don't hear it with the engine off and I don't hear it through the head unit speakers, only the amp speakers.

There is a pair of 5m co-axial cables running from the head unit to the amps at the back of the 'van. I initially thought it could be these acting as aerials and picking up the noise, but I have double checked they are grounded OK and even tried swapping for the 'twisted' type that are supposed to be noise suppressing but to no avail.

I have a spare head unit of the same model so I swapped that in last night, thinking it could be the aux outs, but alas no difference.

The only thing I can think of is to cure the issue at the source. I have a normal silver coil and Taylor 8mm plug wires. Are there any 'shielded' items that wouldn't introduce this noise? What can I try next? I'm lost!

Thankfully the noise is at a constant volume, so if I just turn the volume up, the noise gets drowned out. But then I get deafened by music! :lol:

Anyhow, I thought I'd put it out there and see what I could glean from you guys...

Many thanks
Jim

 

[Tristan71]

Are you sure it's not the alternator ?? As its constant it could be on the power side try plugging an MP3 player into the phono ins on the amp if you still get the noise you know it has to be the power supply to your amp
Can you still get special plugs to stop interference

 

[Trikky2]

You need a supressor on the dynamo.

 

[broms]

Check the earth of the amplifier and head unit. Try and keep them as close to each respective unit as possible and attached to the best earth possible (bare metal/bolt/major cross member, bulkhead). Although I doubt it's the case with yours but never run the main +12v into the amp anywhere near the RCA cables.

 

[the_troupster]

Thanks all

I will try iPod directly, but will also try isolating the dynamo. If the noise stops, I expect a suppressor will sort it.

I will report back!

Cheers
Jim

 

[Alex VW Heritage]

I agree it will be power realted, i used to be an audio engineer and often the cheating fix was to remove the earth terminal from the plug on the amp and it'd remove the interferance. With car audio either a suppressor or running the power through a conditoner or power cap could help solve it for you.

 

[the_troupster]

Hmm, not much progress to report...

Plugging iPod in directly doesn't produce any noise. However, when the dynamo is disconnected the noise is still there so that leads me to believe that noise is generated by the ignition system (it is more of a buzz than a whine anyhow).

I'm going to check condition of grounds tonight and go from there. At the moment I think I'll still need a suppressor on the coil.

Many thanks. More to follow...
Jim

 

[Trikky2]

The difference between a buzz and a wine is important :lol:

Does it vary with engine revs? If yes then continue on your current track.

If on the other hand it doesent then its not the engine.