Please help me diagnose engine noise in my audio sytem!

I'm going insane trying to figure this out. There is a constant fast clicking in my speakers that seems to be engine noise.

Here is my setup:
Factory head unit -> Clarion

$100 EQS755 7-Band Car Audio Graphic Equalizer with Front 3.5mm Auxiliary Input, Rear RCA Auxiliary Input and High Level Speaker Inputs

EQS755 Equalizer -> Kenwood XR400-4 Amplifier -> Connected back to factory wiring.

Here are the symptoms:
The sound as heard in the videos below.
It is NOT present when running on battery power only. The engine has to be on.
Unplug an RCA input cable from my amplifier -> sound goes away on that speaker only.
Unplug an RCA output cable from my equalzier -> sound goes away on that speaker only.
Unplug the factory speaker wire inputs from the equalizer -> sound goes away completely.

Things I have tried:
Moving equalizer ground to factory ground position - no change.
Moving factory head unit ground to same factory ground position - no change.
Running a wire directly from the amplifier ground to the negative battery terminal (outside the car, should be a perfect ground for the amp) - no change.
Changing RCA cables - no change

Other info:
Power cable for amp and speaker cables are not run parallel to each other.
The pitch DOES NOT increase with increased RPMs. It is not a whine.

The sound: https://youtu.be/_LeLEG1muaw
Compared to regular static at the very end: https://youtu.be/B2a2innLdB4

Please help. I don't know what else could possibly be causing it.

 

Does the noise vol. change with audio vol? Does it change depending on the source e.g., CD vs XM? Does it change if you take the EQ out of line?

 

No, the noise is one consistent volume regardless of audio volume. It is the same regardless of source (I've tried bluetooth, XM and FM).

In fact, the noise is present even when I turn the audio off altogether.

Unfortunately, I can't take the EQ out of line because I'm using it as my LOC to output RCAs to my amplifier, which doesn't have hi-level inputs. Maybe I could find a cheap LOC and run that straight to the amp to see if it might be the equalizer.

 

From your first post it seems like the issue is either your head unit or the connection between the head unit and EQ. Or the input side on the EQ.

Then again you say the noise stays when you turn everything off. Are the amp/EQ staying on all the time?

Can't hear anything in your videos BTW

 

It has to be something that only turns on when the engine is running or something that the engine affects. There is very low resistance from my amp ground to the negative battery terminal and from my equalizer ground to the terminal, so I think my ground is good.

I promise there is definitely a sound. It's not static or anything. Very noticeable.