[BoondogUK]

Well I have installed my DLS R4's, Gladen underseats and my alpine PDX 4.100 into the e90. However I have a very high pitch, audible noise interference. It is really noticeable and actually hurts your ears after a few minutes. It is present with or without the volume up. It does not get louder with more volume (or not that I notice).

The system is installed with the 2ch gladen quadlock harness for the idrive.

I have run the cable down the passenger side (RHD Vehicle), along the stock cable guide. I ran the remote wire from the OEM wire at the HU along with the harness. It travels up and over the rear left wheel arch and down to where the stock CD player would sit.

I have an 8AWG power wire from the top mount battery connector. I originally ran this over the right wheel arch, then round the back of boot, in parallel to the speaker wire for the driver side underseat, however I have now re-routed this to follow the advice from Technic. It now goes straight across the midway point of the boot floor, just behind the shopping insert.

The amp is mounted on a custom stand that bolts to existing holes where the CD changer would previously sat.

The new speaker wire for the underseats and the harness cables enter at the far left of the boot and are routed underneath the stand and then back over the stand to connect to the amp. The power and earth cables then enter from the furtherest right they can and travel the short distance to the power connections above the stand.

So harness and speakers below stand, power and ground above. They do not intersect anywhere. They only come together when they attach to the amp.

I now can't think of anywhere that power and signals cross other than the remote wire which runs parallel to the harness. I wouldn't have thought this was enough current to cause interference?

What have I tested:
Changed input signal to ipod - Still there, no difference.
Moved the amp for testing... routed all cables so there is significant separation between inputs and power/ground... still there.
Set all of the gains to minimum - Still there

What else might it be?!
I have the other two rca inputs open on the amp (eg, nothing connected)... could this be it?

I am stuck!

[kaigoss69]

Where do you have the amp gains set? Turn all the way down, can you still hear the whine?

Never mind, just re-read.

I would disconnect the speaker wire pairs from the amp, one by one, to make sure the noise is not picked up there. If you have ruled out the signal wires, then it's probably a grounding issue or a bad amp.

[BoondogUK]

Originally Posted by kaigoss69

Where do you have the amp gains set? Turn all the way down, can you still hear the whine?

Yip... wound down as far as they can... still have it.


Its not a whine like you would associate with 'alternator interference'... eg it doesn't seem to pitch up and down... its just a constant high pitch.... ear piercing frequency

[kaigoss69]

Originally Posted by BoondogUK

Yip... wound down as far as they can... still have it.


Its not a whine like you would associate with 'alternator interference'... eg it doesn't seem to pitch up and down... its just a constant high pitch.... ear piercing frequency

Sounds like it could be the amp!

[BoondogUK]

I feared that it might be the amp..

I tried to options with the ground... I have used the ground terminal over the left rear wheel arch as it meant the shortest group cable. It had an existing OEM connection plate with multiple connections grounding at the terminal. I placed the ring connector above this, and below this and it didn't seem to make a difference...

[kaigoss69]

The original PDX amps were known for noise, but I think it was white noise, not high pitched. Technic knows from personal experience, might want to consult him.