strange buzzing from speakers?? please help

[richard cash]

The head unit it clear when i turn the ignition on (first turn of key). But then when i turn it to the second point on the ignition it starts buzzing. Then when i turn on the car the buzzing is in tune with the revs, i.e gets more high pitched when i apply more revs. This happens in both speakers.

this is what ive tried so far:

1) making a more secure earth on the head unit, this has dampened the noise slightly but its still there (using no earth on the head unit seems to make it better, and thats with the arial point detatched and not secured to the cage so i dont even know how it is working, lol)

2) tried changing the permanent live direct to the battery

3) ran power and RCA along opposite sides of the car.

4) tried swapping the phonos and speaker cable over and this hasnt affected the buzzing

Thats about everything, the only this i could get to work was trying my amps and speakers with mates headunit. I ran my phono lead from my car to his so all the power was running from my car. This stopped the buzzing.

has anyone else got an idea of what to do

[shaunwil]

could be a bad ground somewhere else. Its picking up interference from the alternator. Check that you connections on your battery are good and tight. Check the condition of the negative cable to the battery. Are you running just a headunit and speakers

Its usually called a ground loop and can be a complete headache to find !

Shaun

[richard cash]

the speakers are ran from the amps and then they are connected to head unit via phono. I thought id narrowed it down to the head unit area because it seemed to work in my mates car when i ran phonos from my amps to his headunit.

also, the speakers replicate the scraping sound when i connect the ground to a thread to be earthed. Its hard to explain but i can hear the ruffling of the earth through the speakers as im fiddling with it

[framey]

This started happening to me after I fitted the extra grounds all over the engine bay.

[richard cash]

the main thing i think is that it doesnt happen with the first turn of the key (ignition activates head unit and is operational). I get crystal clear music.

with the second turn its a monotone bussing, and with the third turn (engine start) the buzzing pitch changes with revs.

what produces this??

[Donato]

you sure its not the coolant buzzer you are hearing mate? or does that go through a seperate speaker??

[shaunwil]

Its the alternator that causes the change in pitch, the more you rev it the higher rpm it runs at !

One thing to try, which i had to do with my mp3 player was to ground the rca leads on the negative side. Although i did have a dodgy cable one time where the connections where loose. You could even resolder the cable.

Out of interest do you have any crossovers in the system, maybe they are close to a power source and are picking up interference!

Shaun

Shaun

[Prof]

I would suggest the fault lies in/near the amps - when you used your power / head unit, and your mates amps, you didn\'t hear it.

It\'s probably an earth loop or a dodgy connector on the amp input.

That noise you hear when you mess with the earth tends to confirm this as well.

With Audio circuits, you need to try and get a \'star\' earthing point - earthing all the components to one central place.  If you use many earthing points, you can actually get very small voltages between earth points, and the amp will magnify this !!

Earth everything back to one big stud somewhere and run a seperate lead to the battery -ve from that (a big one - you want very low resistance).

If that doesn\'t cure it, a 1000pF ceramic capacitor (from Maplins) between input and ground on the RCA inputs to the amps might help - this is an old trick from valve days  

[richard cash]

ok cheers for all the info again.

i dont have any crossovers near power sources, only place i have them in in the door pods.

the amps are all connected to an earth block and in tern this is connected to the battery. Everything is in the boot apart from the head unit and speakers so all power sources are very short, max run is probably 0,75m.

im not sure about earthing the RCA\'s, how is this done??

[Prof]

The RCA inputs should be eathed within the AMP.  If you want to try the capacitor trick, then these will probably have to be solderd between the centre pin and outer sheild connector, inside the AMP - they are usually to big to solder inside the RCA plug.

One trick that worked on my home hi-fi when I had an earth loop was to actually disconnect the sheild on the AMP input wires just before the AMP - in other words, you only connect the inner core inside the RCA plug.  You might want to try this on a cheap set of leads first, rather than ruin a good pair if it doesn\'t work !!  :2Rolleyes

Sounds like you have wired the earths up the correct way though

[tinker-27]

i had a simalar problem and you can get a rca suppressor it is just a noise filter for the amp feed i made a massive dirrerence on mine ,you will only find them at good audio shops

[mattmaclennan]

Coil pack is earthing out

[richard cash]

Coil pack is earthing out

hey matt, how do i check this?