jvc stereo buzzing '97 lexus es300

Hello 12Volt! I recently bought a JVC X50BT for my Lexus ES300 as well as a Metra wiring harness (amp integration included). The installation went smoothly until a couple day ago when I started noticing a slight buzz in my speaker on 0 volume. I looked into it and tried as best as I could to try and fix it as well as re-installing the head unit to make sure I didn't screw up the wires. I looked online and people suggested a ground issue. I took the HU out and hooked some speaker wire (~20 guage I think) to some metal connected to the chassis (vertical bar about 2 inches wide and half inch thick) beside and behind the HU to various parts of the stereo (ground wire from the included wires that hook into the harness, one of the screws on the side, and just touching it to the HU itself) but to no avail. The recommended solution right now seems to be a ground loop isolator. I've heard this is just a "band-aid" for the real problem. I'd rather deal with this thing than cover it up. Any suggestions? I don't know if this is relavent: ~The ground wire coming from the HU is thicker than the harness wire ~The installation kit is made of plastic ~Only one of the antenna wire's originally in the OEM car stereo is hooked into the aftermarket HU ~The butt connectors are secure on the stereo wire and harness wires ~The buzzing is gone when HU is on with battery, hums when I turn the key a little more, and buzzes when the car engine is on ~I've tried grounding the factory amp (normally grounded to the car by it's own bolts coming out of the chassis) with the car chassis using the area around the bolt that holds the seat to the car ~I've tried running some 12 gauge wire from the HU to the amp, but that doesn't do anything. If left unconnected, the buzzing seems to intensify by a little bit BTW: I'm trying to upgrade the system peice by peice, so I would really love for this problem to be resolved before I move on to speakers and an aftermarket amp. Does anyone have experience with this? How did you solve it?'97 Lexus ES300

(Expertise Level: Recently gotten into working with cars)

Rapidly dim and brighten your dashlights, does this change the pitch of the noise?

i am an idiot wrote: Rapidly dim and brighten your dashlights, does this change the pitch of the noise?

There is a faint background hum that goes up and down in pitch, but it has no effect on the buzzing. More info: The buzzing noise stops when I remove the RCAs from the head unit. I don't know if this is relevant/obvious.'97 Lexus ES300

(Expertise Level: Recently gotten into working with cars)

try running a new constant power wire to the battery or a heavy gauge constant power at the ignition harness and make sure you fuse the wire. also screw a permanent ground to that metal bar you talked about and hook it to thr radio but not the factory ground.

I went to a local audio store and had them check the HU (I suspected there might be a problem and I wanted to get it checked because I still had a few days on return). The guy said that the factory amps generally don't like aftermarket HUs. The interference is what causes the buzzing and there are two ways of solving this: buying ground loop isolators or buying an aftermarket amp (as I plan to do because I'm trying to upgrade my system). Thank you to you both for your help.'97 Lexus ES300

(Expertise Level: Recently gotten into working with cars)