Wetsounds 420SQ install problem - noise
 

I just installed a new Wetsounds 420SQ and am getting a very strange noise. With the master volume on EQ turned all the way down and all settings on the EQ at flat, I get a cyclical high sound that varies in tone (about a 7-10 second loop of variation in sound and then repeats). This happens whether the input is main or aux. It also happens whether any source is hooked up to either input or not. And it is happening on all speakers (2 different amps). Based on my diagnosis I think the noise has to be coming from the 420SQ. Any thoughts? Anything else I need to try and diagnose before calling Wetsounds for help?

Where did you draw your B+ and B- from for the EQ?

Noise still there with rca cable removed from amps?

The B+ and B- for EQ are from the amp. The noise goes away if RCAs are removed from the amps.

You may be getting noise through the RCA cable. I run a ground loop noise filter right before each amp to eliminate the same noise. Not the perfect solution but it worked for me

I did try running an RCA cable directly from EQ to amp as a test to make sure it wasn't something about the actual cable and where it was routed or what other lines it was against and had the same problem.

Do this simple test.
Verify what the voltage is at the amplifier terminals before beginning. You need 12+ volts for this test. Connect ONLY one battery.
Make certain that the EQ supply B+ and ground are connected to the primary terminals of just one of the amplifiers. Connect one RCA cable set from the EQ front output to that same amplifier input. Set the amplifier input gain to 50%. Other than the remote turn-on lead (which can be temporarily jumpered off the B+ lead) make sure nothing else is connected. Select and short one input with an RCA jumpered from the EQ input L & R.
Now, other than a very small amount of constant background hiss, see if you have the strange noise.

DavidAnalog, what do you mean by "select and short one input with an RCA jumpered from the EQ input L & R"? Are you saying to just connect an RCA from L to R input on the EQ? If so I will try that.

My current configuration does already have the EQ B+ and ground connected directly to the terminal of the Wetsounds amp for the tower speakers.

In other words....
Take 1/2 of a short RCA cable, say the red side only, take one end and plug it into the EQ L input and take the other end (of the same conductor) and plug it into the EQ R input. This way both the L & R inputs are closed and cannot pick up any radiated noise.

DavidAnalog, I tried exactly what you said and am still getting the weird noise. But as soon as I unplug the RCAs from the amp the sound stops. Any other suggestions?

So you can assume that there is no supply or ground loop between the EQ and amplifier because both are terminated to the same spots.
And you can assume from your tests that the issue is probably either with the EQ or EQ to amplifier interface.
Here are a couple more thoughts.
The EQ has an internal switch that changes the signal ground (above ground) to power supply ground relationship (specifically to assist with noise resulting from equipment mismatches). Try the switch in the other position.
Also, while inside, make sure that neither of the internal adjustable input gains are wide open.
Try a substitute RCA draped across the outside versus buried in the boat.
If the noise is only present with the key on, whether the boat is running or not, then change the EQ proximity to the surrounding dash, modules, etc. Or, try it with the battery only, and the battery totally disconnected from the boat.
If you cannot narrow the noise cause then return the EQ to your dealer or Wetsounds. A defect is possible.
Also, NEVER unplug or plug in audio components (RCAs) while receiving power. That is a sure way to get exactly what you are describing.