H.U. static, not alt. whine.

[jayrebb 10+ year member]

Ok so i have limited info here because i didint install this HU, but i wanted to get some of you ideas... so this is what i got. 1991 bmw 325i, its got an alpine cdm-7857 in it, with stock 5.25 speakers font and back...so when i am skip to the next song, i can hear the HU working in the speakers, as if i can hear the motor moving the laser eye, then i can hear static at low volume levels...do you think a noise filter would help this? i thought it might be the stock speakers and wire, but then maybe not...any input would be appreciated...oh yeah its not alt. whine, it does what i explained above regardles of rpm levels...

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[jayrebb 10+ year member]

no ideas?

 

[Rawb]

interesting.... Wehre are you grounded ? i have heared the factory grounds on bmw's arent the best if its on the harness...Re ground the head... report back....

 

[m48xhp 10+ year member]

yeah i had the same thing with alt whine with a set of RCAs. i bet its the ground.

 

[mikegett 10+ year member]

It doesn't sound like a ground issue. Do you have a factory amp. If so, it may be a input sensitivity issue. Facotry amps tend to use the OEM HU to dictate the amps gain. This is a big factor if the OEM HU changed the volume at driving ratios. When you remove the factory HU, the amp simply goes to full gain. If this is the case, you can't fix it without knowing the amps pinout and some modifications. If you do have the factory amp, I would suggest running a speaker wire from the aftermarket radio directly to one speaker. Does it have the same noise? If so, then it is a HU ground issue or normal characteristic of the unit.

 

[DBfan187 5,000+ posts]

It doesn't sound like a ground issue. Do you have a factory amp. If so, it may be a input sensitivity issue. Facotry amps tend to use the OEM HU to dictate the amps gain. This is a big factor if the OEM HU changed the volume at driving ratios. When you remove the factory HU, the amp simply goes to full gain. If this is the case, you can't fix it without knowing the amps pinout and some modifications. If you do have the factory amp, I would suggest running a speaker wire from the aftermarket radio directly to one speaker. Does it have the same noise? If so, then it is a HU ground issue or normal characteristic of the unit.

yes, thise sounds like an improper level setting.