High pitched low level whine when in "prestart" not in ACC

[builderman918]

I have a high pitched whine that comes on when the key is in the prestart position (and with the motor running) but not in ACC. The noise doesn't go up and down in pitch/volume with motor revs so its not alternator whine. It does decrease and increase in volume with the gain setting on the amp, MB Quart ONX4.60. I've tried new grounds, running the wires differently and more with the same result. There is no sound with the amp off and i've disconnected speakers to see if one was picking up noise from a power cable. What can I try next? There was no whine until i added the 4 channel amp (previously speakers were running off of head unit). For reference the level of the whine can be covered at above level 8 (out of 40) but can be heard while driving between songs.

Setup is this:

Pioneer AVIC-D3

MTX Thunder 4501D

MB Quart ONX4.60

JL Audio TR Components

Alpine Type-R 12" sub

Kicker Wiring

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[keep_hope_alive Premium Member]

could be an issue with the amp or with the RCA's. if any of the RCA wires (either signal or shield) are open on either end, you can get noise. if the amp has an internal component failure, you can get noise. Pioneer HU's have a notorious issue with their RCA outputs. grounding the RCA shields at the HU can sometimes solve the issue.

i would try a local source, mp3 or similar, plugged directly into the amp (with a 3.5mm to stereo RCA adapter). if you still get noise - i would suspect the amp.

if you do not get noise, you can suspect the RCA's or RCA shields.

 

[builderman918]

Ya i know about the pioneer's, i even took the head unit completely apart and tested for continuity across all the pico fuses and all were good so the noise isnt from that unless they have other problems also. I just tried the plugging my ipod right to the amp via rca's and the noise is still there just not as loud. With my ear near the speaker there is a lot of static/hiss and the high whine so im suspecting it is the amp. Just wish i had another to swap in to make sure it is the amp. If it is the amp what ones would you recommend with similar power rating (4 x ~60 watts rms @ 4 ohms)?

 

[builderman918]

I was looking at the alpine mrx-f30...just hate to apend the money and have it not be the problem

 

[Blue Fury 10+ year member]

Same situation with my Pioneer 880. I assumed it was the pico fuse but I'm reading it is veary likely a grounding issue. Makes sense because I've never grounded directly to the battery in front, just the steel in the trunk close to where the amp is mounted.