[Sounds_Insane]

I couple more trouble shooting ideas that I don't think you said you tried:

plug the KeyLOC RCAs directly into the amp
power the DSP with the provided 120v wall plug.

I have the same KeyLOC to Dayton DSP and have the same hiss issues in a Toyota Hybrid. Others have used Dayton DSP without issues and others have used Toyota non-JBL headunits without issues and some have installed in Hybrids without issues, so it's something I had wrong.
I'm getting a new DSP, but I'll probably still be stuck with the KeyLOC.

 

[Sounds_Insane]

I don’t know what your factory radio looks for in terms of speaker load but for my case with my Jeep Cherokee that has the 8.4” uconnect navi, the 60ohm load resistor kicker key option does technically work but it is not the most ideal (35-39 ohms would be most ideal). If you turn off the load resistor I know that it makes the devices input impedance go to 20,000 ohms (20k), and if you attach a 5+ (preferably 10watt+) resistor across each of the speaker outputs, connecting to the positive on one side and the negative on the other side of each resistor, it’ll make the impedance seen by the amplifier essentially whatever value resistor you used, and also it will make the impedance seen stay consistent, regardless of the audio frequencies being performed by the load (your speakers)

I bought some of these, as well as the ground loop idolator the OP was talking about and they did nothing.

https://www.sonicelectronix.com/item-192005-NVX-VSLR20.html

Funny thing is that SonicElectronix emailed me to do a review on those things, they said good or bad they publish honest reviews. I was honest, said it didn't work for me, they never published it. And they can't be returned. Fun times

 

[Sounds_Insane]

I always wonder if the keyloc is the real deal or if it’s lowkey a gimmick. $130 for it just seems a good $20-70 cheaper than I would’ve thought it would sell for given it’s claimed capabilities.

It definitely restored my factory signal, however I don't know if it's the source of noise, if I disconnected power to the LOC the noise was still there. I just had to keep the gains way down on all my equipment to have it manageable.

I pulled everything out and moving it to a new car (same car, '23 vs '22), I'm going to try different ground location and run the wires in different areas to see if that will help.

For the OP, if you think the KEY is introducing noise because it's over EQing the system, maybe turn the treble up a notch or two before the setup.

 

[Sounds_Insane]

I admit I'm not understanding why there is a DSP and passive cross-overs being used.

Sometime people use passive to protect tweeters in the case of DSP messup, or "pop" in the system, other times they use it for a component set if they run out of DSP/amp channels. It's not ideal.

 

[Sounds_Insane]

I don't know how you "restore" signal that simply isn't present.

Anytime you boost something you are dragging the noise floor up along with it. There's no free lunch, unfortunately.

The Dayton DSP is also notoriously noisy.

I would start isolating specific units to find the source(s) of noise.

I forget the dB, but the KeyLOC will only boost so much and them lower the rest to match, but then you take that lower signal and boost it back up to X volts out and there is your noise again.

But yeah, it's a bad solution, but without the JBL system there is no other way to get a clean signal out of the heat unit. I've said before, I want to get a DAP and run that to the DSP after I get everything else situated.

 

[Sounds_Insane]

I'm learning so I have another question? Could there be some kind of conflict between the passive crossover HP/LP filters and the DSP when he is auto EQ'ing?

I suppose you could have issues. Passive crossovers are usually a 6db slope, so they have little effect on the sound, they are more for safety and to split the signal between two speakers. your DSP's crossover point will probably be about the same spot as the passive crossover. Some will just put the passive on their tweeter.

I'm sure there are issues that arise, and someone can chime in with a better explanation.

 

[Sounds_Insane]

I would assume that you would just be using TA and running full bandwidth

TA would only work if you have a coax or point source speaker because the time is per signal, if the are on the same signal you only get one time... unless someone's DSP has time delay per frequency range, is that a thing?

 

[Sounds_Insane]

You're essentially describing FIR filters.

I hope someone else answers before I give out too much bad information.

 

[Sounds_Insane]

That's kind of to the point where I was, I had the sound manageable, but as it got cold I was getting more interference. That was the point when I pulled everything out and decided to buy a new car.

I'll start again in a couple months.

I was going to try to move the Key to the dash as well and run RCA's back, glad you tested that.

Like I said, my next time I'm going to try a better ground, run the wires in a different location, and get a new DSP (mainly because I want more channels)

 

[Sounds_Insane]

I hope the factory HU isn't my issue as well, but if it is I'm skipping it all together and running a digital audio player directly to the DSP and skipping the whole mess.

Or maybe something like this where I can keep the factory HU and use this just for music... this is probably overkill for what I need though.

Alpine HDS-990

Status Series high-resolution digital media audio source (does not play discs)

www.crutchfield.com