I almost have my amp running smoothly except for some minor issues that are annoying. I am grateful for any help. Here is the setup - I have an MTX 404 amp running two front speakers and one 10 inch subwoofer on the 2nd channel on a bridged connection. The 99 Altima Stock HU is using speaker level input connection to send front channel to the amp and the rear speakers are powered by the receiver. Here is the first issue, I hear a low whine noise while driving that speeds up when I step on the gas. It’s noticeable at low volume or low notes in music. Funny thing is I did not have noise with my previous amp setup using an US acoustics 2080 also running speaker level inputs. The only difference in the setup I can think of, and hopefully a solution to this problem, is in the connection of the speaker level inputs. Instead of using the L- and R- front speaker outputs from the HU a ground wire was attached to the back of the HU to the amp. Now I was wondering if I can try this setup with MTX and not damage anything since this amp does use the L- and R- output in speaker level harness. I would wire the single ground from the HU to both the L- and R- of the speaker level input harness. My second issue is when first powering up the amp and not getting audio. I have to manually turn off and on the HU to get the sound from the amp. I do hear some static when turning OFF the HU and the LED does come on when first powering up. The MTX has a built in feature that does not require a remote turn on lead when using speaker level inputs but I have tried using one anyway to see if this would fix problem. Thanks for all the help.