I installed a completely new sound system in my '98 2.8 Quattro except the factory HU. (Non-Bose) I received some great help from the forum during my installation, but now that I have my 4 Channel amp powering the new front speakers ( Infinity Kappa 4") I am getting engine noise, hissing that increasing pitch with RPM, and a popping noise when I turn the system on and off. I read a post that said they heard this problem is with the HU and not the speaker installation. I didn't have any problems with the rear deck, amp and sub w/amp hooked up. It wasn't until I ran the amp to the front and replaced those speakers that I started hearing the noise. There's no problem when the engine is off. Any advice on what is going on here?

 

Check your grounds. Make sure they are as short as possible. You didnt run your power wire with your RCAs did you? I've had good luck before with a ground loop isolator in line in the RCA wires. Best Buy sells in the audi install shop. (usually out back of store).

 

yeah check grounds and run ur RCs away from your Power wire, RCA on one side Power the other side.
ther induce voltage between themself and coz a freq in ur radio