High pitched sound from speakers

[chapperzuk]

I've recently fitted some In Phase Component speakers in wired up to a new Sony 1200w 2 Channel Amp. I'm getting a high pitched wavy sound coming from the speakers when the music isn't turned up. It was buzzing quite loud before but my mate suggested to put a bit of wire on the back of the head unit where the RCA outputs are. That has reduced the noise and it's now just a high pitched wavy sound that changes with the electrics of the car. If you turn the lights on or press the break pedal, the sound changes.

Does anyone know why this is happening and how to eliminate the problem completely? Thanks in advance!

 

[MT AUDIO]

You have a ground loop. Bolted your amp directly onto your seats or boot floor?

 

[MT AUDIO]

Double post fail

 

[chapperzuk]

You have a ground loop. Bolted your amp directly onto your seats or boot floor?

The amp is in the boot and ground connected to one of the bolts in there. I had this issue with my last car when trying to wire an amp up though, with the same head unit. Could it be that I've touched wires that I shouldn't have and messed up the head unit? Putting the bit of speaker cable on one of the RCA outputs on the back of the head unit has reduced the loud buzzing, but there's still that high pitched sound

 

[MT AUDIO]

No I'm referring to how you have fixed the amp down

 

[chapperzuk]

No I'm referring to how you have fixed the amp down

Oh, no it's just in the boot stuck down to the boot mat with velcro.

 

[MT AUDIO]

Then yes more than likely an issue with your stereo. What you got? Pioneer?

 

[chapperzuk]

Then yes more than likely an issue with your stereo. What you got? Pioneer?

Yeah mate, it's a Pioneer head unit. Is there any way of fixing it? Would this be a result of something I've done?

 

[James28]

What causes a ground loop out of interest MT?

 

[MT AUDIO]

Yeah mate, it's a Pioneer head unit. Is there any way of fixing it? Would this be a result of something I've done?

Yes, you will have d/c'd the earth with the RCA leads and power cable still connected. RCA acts as earth and blows pioneer unit. Only proper fix is repair, botch is to attach an earth to the RCA outer shell at the headunit connection (new earth)

 

[chapperzuk]

Yes, you will have d/c'd the earth with the RCA leads and power cable still connected. RCA acts as earth and blows pioneer unit. Only proper fix is repair, botch is to attach an earth to the RCA outer shell at the headunit connection (new earth)

I have a bit of speaker cable on the RCA outer shell at the moment, but it's not connected to anything the other end. That's eliminated most of the noise. If I were to earth the other end, do you think it will eliminate it completely?

 

[MT AUDIO]

What causes a ground loop out of interest MT?

Sorry had to dash out

The route cause of most ground loops is poor grounding.
If an earth is not connected the item will look for a route with the least resistance.
When an amp earth is poor mid/high speakers will automatically have a high pitched whine which is normaly matched in pitch to engine speed.
An electrical item will always look for the route with least resistance to earth. Ie bolt your amp down to a metal floor (metal cased amps and the amp body is then earthing the whole unit then. When you d/c the earth whilst having RCA etc still connected the RCA is the route with least resistance and pioneer stereos in particular can't cope ergo pop and high pitch whine results. Good practice for installing sub is earth>remote>power(amp end first), test to ensure no protect mode and good earth. If all good attach rca's. When removing always disconnect RCA's first so no possibility of earthing out>power (battery end first) remote>ground.
A lot of Japanese stereo manufacturers are lazy in that they use the stereo aerial to ground the unit rather than a proper earth (least route of resistance) but when swapping to aftermarket headunit it can't take the current and cuts out completely at higher volumes

 

[MT AUDIO]

I have a bit of speaker cable on the RCA outer shell at the moment, but it's not connected to anything the other end. That's eliminated most of the noise. If I were to earth the other end, do you think it will eliminate it completely?

Yes it should be fine then, the problem you have caused has in effect stopped the headunit from earthing the rca's.

Like cutting a cable thats providing a house with electricity so it needs another path to supply electricity.

 

[James28]

Ah cheers MT, good stuff. I'm guessing this is the most common cause for noise distortion in speakers?
What about if speakers aren't amped? Is it a poor earth on the headunit?

 

[MT AUDIO]

Metal cases amps bolted directly to chassis or poor earth for the amp. Like I say poor earth on a non smped stereo generally doesn't affect it due to the aerial being earthed so unless you had disconnected it there would be no tell tale signs

 

[chapperzuk]

Yes it should be fine then, the problem you have caused has in effect stopped the headunit from earthing the rca's.

Like cutting a cable thats providing a house with electricity so it needs another path to supply electricity.

Thanks mate, really appreciate it. Will give it a try tomorrow and let you know how I get on.

 

[James28]

Metal cases amps bolted directly to chassis or poor earth for the amp. Like I say poor earth on a non smped stereo generally doesn't affect it due to the aerial being earthed so unless you had disconnected it there would be no tell tale signs

My brother has an old mini, and the (non amped) speakers are making a popping sound when the engine is on (only) , sounds like interference, so wondering if this was similar?
I tried earthing the head unit in a different place but still the same.
Sorry for thread hijak!

 

[MT AUDIO]

More than one speaker doing it or a specific one? Speaker popping on startup is normally a duff speaker (or a trapped wire) which is shorting to chassis but will only affect the channel it is connected to

 

[chapperzuk]

I've just been driving around and when picking up speed the high pitched sound gets louder as I put on more revs in each gear. Will try your suggestion tomorrow though and hopefully all will be fixed

 

[chapperzuk]

It didn't solve it unfortunately. Think it's blown pretty badly, but it's covered under warranty so getting repaired at the moment. Car audio centre ftw!

 

[James28]

MT, He's got a Pioneer Unit, literally just got it. Although did it on his old radio too which was just a cheapo.
It's unamped, simply a pair of 14cm speakers on the rear shelf.
Only on certain radio stations (fine on CD) he gets a constant popping noise underneath the sound?

 

[MT AUDIO]

Then it won't be the headunit or speakers if a) more than one stereo it does it with and b) only does it on certain radio frequencies. Are they ones of very poor reception? What happens if you d/c the aerial when tuned into these stations?