I finally replaced my defective HFL module and now it works fine, except that i hear a light hissing/frequency noise in the background which increases with the cars RPM...

Any ideas?

 

if you turn off the volume to radio, does it still happen? Usually that's the alternator, the amp, or a bad ground somewhere.

 

Look up TSB B07-013 on this page: https://acurazine.com/forums/third-g...-016-a-613659/

You will have to follow the instructions at the top to open the PDF on how to fix this.

 

The sound does go away when i put the volume to zero.
I will check out the TSB.

I know i need to fix my amp because i get a similar but louder noise when my car is cold

 

After reading this, it looks like that is exactly my problem! Thanks!

 

Sounds like the amp is on its way out to me !

 

You have a grounding loop issue. If your amp was on it's way out it would have already. You need to see an electrician but first look at all 3 ground points on your engine bay and consider the alternator as this sounds like alternator whine.

 

Why not just apply the SB? It exactly describes my problem...

My amp does have issues as well, as I get a loud hissing when the car is cold and goes away when it warms up. I saw a post about replacing the capacitors on it that seems would fix it. So i just have to get myself to do it some day.
I sure hope its not my alternator!

 

Follow the service bulletin for now.
My amp has made a hissing sound forever when its cold out, and usually it's pretty much gone after a minute. No need to panic.