The Hiss

The crimp looks fine. Solder is probably not required. Solder can be bad in that it wicks-up under the insulation, making the wire stiff and more prone to breakage. The heat from solder can also damage the insulation.

I would tug on the crimps to ensure they are solid and just insulate the lugs.

 

My daughter uses her iPhone on my boat. I've got an iPhone to USB connector that supports that usage. I also have one that is iPhone to RCA that would work for this test.

When I was testing my boat I used an old portable CD player, yes I am a dinosaur.

 

When I was setting-up the kick-butt A/V system on my boat I was getting a low-level background hiss from either television.

It turned-out that the televisions were not happy w/ the step wave inverter I was using for power. I swapped to a true sine wave inverter and the hiss was gone.

 

What about removing the cap from the system?

For example, just applying power from your beefy leads to just the speaker amp, not the sub amp and not the cap. Can that be done safely?

Also, remove the amp remote enable from the head unit feed and jump it to the beefy 12V feed.

That connection mode eliminates everything from the amp, just the speakers and just the PC player are connected. Please confirm that the PC is battery operated, not plugged-in for power.

 

The battery laptop should be a clean input.

A bolt was my thought too. Pick a size that will fit into the amp power terminal, then use a nut and washers to capture that lug, then insulate the whole thing w/ electrical tape.

 

During the hiss test is the speaker amp connected to the head unit or to the other amp?

Can the speaker amp be isolated, to have the remote input be removed from the head unit (provided by a local power jumper) and the power be only to the speaker amp?

What does it sound like with no connection to the RCA inputs? What does it sound like with your laptop connected?

 

Yes, amp power in, with nothing else connected to that power and that ground feeds, not the cap and not the sub amp. Jump the +12V feeding the amp power to the remote enable amp screw terminal, after removing and insulating the remote wire from the head unit.

Use the battery powered laptop as an RCA input for one test.

Use nothing connected to the RCA inputs for another test.

Please confirm that there is no chassis connection, except for the ground up near the battery.

Or the amp is bad.

The capacitor combined with the "long" power and ground wires to the battery is a filter. It should be a great filter.

With the volume on low, use a multimeter to measure the AC millivolts on the power to ground feed at the amp. Report the result of that measurement.

If the AC millivolts on the amp power is too high, then something is wrong.

 

The Clarion XH5210 amplifier already has ground loop isolation on the RCA inputs.

You added an external part on the RCA inputs to the amp? Which part?

Glad you are all-set! Glad to help!

 

The two things that don't make sense to me are that there was not a ground loop when feeding the amp from the laptop and that the amp already has built-in ground loop protection.

So, I am thinking that the problem was something else, not a ground loop problem.

Again, I am glad it is working, but am thinking there was a different root cause. Enjoy your great sound quality!