ground loop noise

tldr to your question; i just wired the harnesses together.

got the metra kit 99-3303, in it is a harness labled 'factory amp interface' which took oem plugs, converted the driver info center into it's own native lcd in the pocket location and gave me traditional 11-wire harness for aftermarket head unit.

i'm assuming the factory amps are running from speaker level inputs. if my assumption is incorrect, that would mean the oem head unit uses signal level output on speaker level (looking) harness, and i've plugged speaker level output to that.  either way the output is clean, not distorted or squaring in any way, so i've assumed the former option.

How loud can you turn the volume of the radio before you reach a level that you consider loud?   If you can only turn the radio to 8 or 10, the amp may be looking for Preamp level.  If you can turn the volume up a good way before it is loud, the following may help you.

Cut the negative speaker wire connections.  Insulate the negative speaker wires that are coming from the radio.  It is very impoortant that they not touch anything.  Now ground the negative wires that go to the vehicle.  This will cut the input signal going to the amp in half.  This should eliminate your noise.  Make sure you do not ground the speaker wires that come from the radio.  Only ground the negative speaker wires that connect to the harness you purchased.

so in the 99-3303 harness which interfaces oem plugs to traditional aftermarket HU 11-wire, you want me to cut all (-) speaker wires and splice to ground?

as soon as i performed the install i noted that roughly 50% up the volume control and the system is already quite loud. by quite i mean by 70% up the volume knob you had best be wearing earplugs, its really that loud. about 8-10 on a scale of 30 is average listening volume.

it is a monsoon system, yes

bypassing the amps is something i would like to avoid if at all possible, rather try to swap my speaker level outputs for line using a LOC or similar, seems like a simpler / easier solution given that the amps are in fine working order and are probably higher / cleaner output than the amp in the clarion HU.

at some point client would like to swap for a 4ch amp and do door speaker conversions to aftermarket, which imo is a good time to look into amp bypass.

granted i'm a newb, but ground loop being a common problem from overdriven factory amps?... find that hard to believe being that a ground loop is a specific problem and shouldnt be related to strength of an input signal... am i wrong?

grand idea if it works, if it doesent i'm just making more work for myself in having to undo these spk connections. assuming this is a troubleshooting step rather than a solution, is there any way i can perform the same troubleshoot with a non-destructive means?