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Just spent a good deal of time reverse engineering the wiring to the fade **** and it wasn't what I expected. Firstly it isn't a L/R fade **** but a front to back. Secondly, that diagram I found doesn't seem to match what I've seen here. Front what I can tell there's two sections for the fade ****, a top and bottom. There's only two outputs, and four inputs. Here's a quick diagram of what I see. GREY = Right output RED = Left output YELLOW = Front Right BLUE = Front Left GREEN = Back Left
uncolored = Back Right
These set of wires would go to either the top or bottom portions. The center pins are the inputs, while the side pins are the outputs. The rear triple connections just connect the other set of speaker wires. This should work just fine for aftermarket amps. My fade control **** is kinda junk as like most things when I got this car it was rusted shut. Had to take it apart and clean it and put it together. Probably not done very well, as it doesn't always conduct when set to the even position. What I figure I'll do is just bypass it for now but making four triple 2.8mm connectors soldered together. I could just solder the wires together but I'm not a big fan of cutting connections if I don't have to, plus I can just unplug them and reconnect to the fade ****. If this doesn't eliminate the noise then I'll do what Speedtoys suggests and replace the RCA wires with the High Level input line to the amp and see if that fixes it.
Last edited by dukenukemx; 05-29-2023 at 07:40 PM.
I have done some testing and this is what I've found. I bypassed the fade **** and the noise hasn't changed, so that isn't the problem. I did what Speedtoys suggested and replaced the RCA wires with the High Level input and the noise is worse. I like it better because I can now drive the speakers louder for some reason, plus the wiring is less of a mess. So I decided to see if the amp or the headunit is the source of the noise and found some headphone jack to RCA adapter and used my phone as an audio source and there's no noise. So I know it isn't the AMP, but the headunit. So I did what everyone recommends when you have noise and that's to relocate the ground wire. So I soldered a fairly long black wire to the ground wire on the headunit and started to see if touching different areas of the car made it better. I tried under the dash where I also grounded the filter to, and no difference. I then grounded to the same location as the AMP and the noise is extremely faint. So I'm at the point where I'm considering either running a wire all the way to the battery to ground out the headunit, or just ground out at the AMP location and be done with it. I should probably ground the noise filter to the AMP as well since that location is confirmed not good, which might make a difference in the noise level and completely remove it. I've read stories where the AMP is the best location vs the battery. Considering my cell phone produced no noise, the AMP location might be a fine ground and I just need to relocate the noise filter ground.
Last edited by dukenukemx; 05-31-2023 at 08:07 PM.
Anything on non-switched power should have the =same= + and ground, and I sorta believe that fader **** might be part of a ground loop too, I dont see the point in a fader dial, the HU does it for you and you'll never change it.
It got louder because the amp input (after attenuation) was higher (than RCA inputs), so the output was higher. They are relative...and this is proof that "alternator noise" by itself, would be more drowned out by a high level input, that 2v RCA inputs.
The noise isnt "in the power source", its the combination of source points and system ground points.
No need for a lead from the battery, just COMMON positive and grounding points.
Anything on switched power should have the =same= + and ground, and I sorta believe that fader **** might be part of a ground loop too,
The tests were done with the fader **** bypassed. Unless it's the wiring for the fader ****, but doesn't explain why I heard no noise when using my phone connected directly to the amp.
I dont see the point in a fader dial, the HU does it for you and you'll never change it.
Yea but it's a **** and it's there and I kinda want it to do something. I was thinking of putting another amp there for a subwoofer and maybe put a dial for the gain or something.
No need for a lead from the battery, just COMMON positive and grounding points.
So both the positive and ground for the amp and heatunit should be connected?
The tests were done with the fader **** bypassed. Unless it's the wiring for the fader ****, but doesn't explain why I heard no noise when using my phone connected directly to the amp.
Yea but it's a **** and it's there and I kinda want it to do something. I was thinking of putting another amp there for a subwoofer and maybe put a dial for the gain or something.
So both the positive and ground for the amp and heatunit should be connected?
Yes, every component with + full time power (these are the main power inputs for the HU and amp) should share common power source and ground points. The HU likely has a switched power cable that tells it when to switch on, and likely a blue wire that triggers the amp.. From there the HU and Amp will have non-switched + inputs that should be common/shared/, and the grounds should be shared.
You dont have noise from your phone to the amp, because the phone isn't part of the vehicles wiring..its just a signal.
Hooked both the head unit and the amp to the same power and ground and this time both ran to the fuse panel and it's worse. I have another head unit I had laying around from a car my uncle used to have and did a quick hook up and no noise. Not hooked up to the same power as the amp, as I used the factory power and ground. So I just order another head unit, as I can't use a full size 2din on my 928 setup, plus I don't need a CD player because who uses CD's in 2023.
but I was planning to take the 928 on a trip and I just wanted something sent quickly. Would rather have the SD card slot plus a **** for volume but compromises had to be made. Hopefully that fixes the engine noise and I can move onto things https://rennlist.com/forums/928-forum/1276698-bose-subwoofer-adapted-for-the-928-a.html Since the stereo I ordered does do 5.1 and has a sub output, I can probably run a while from it to the sub. Maybe run the rear speakers to the stereo and let the amp power the door speakers? Haven't decided yet.
Last edited by dukenukemx; 06-03-2023 at 01:13 PM.
Think I know what's causing the audio noise. Got the new head unit and temporarily wired it up and no noise. Wired it up and noise appeared and just as bad as the previous head unit. In cases it didn't make the noise the audio wire to the AMP was not behind the ECU's. I hooked it back up with RCA's and put in the filter but on the amp side which removed all the noise but the RCA wire was just laying around on the floor. Once I put the wire behind the ECU's, the noise is back, but not as bad due to the filter. The LH Module that fires all eight fuel injectors must put out a large magnetic pulse, which might explain why the High Level input line made things much worse because no loop isolator. I could move the wire and make a mess but I'm thinking of finding some cloth shielding and see if that works. It's not that bad but at this point I'm going for 100% noise free. I was thinking of covering the back of the ECU's
but I have no idea what is an effective shielding for this. Also, I don't have a cover for the ECU's. They are exposed the entire time because that's what came with the car when I got it and I can't find a replacement. If anyone knows where I can get one of those I'd appreciate it.
In fact, avoiding vehicle wiring as a general rule is handy.
I know that now. The problem is I'm lazy and I've taken off the ECU like a dozen times now to run wires. The RCA wire is long enough that I can route it any number of directions, so I'll probably run it under the right side seat. Dealing with the stereo seller because it was suppose to come with 2 USB cables for the rear and it didn't.
I know that now. The problem is I'm lazy and I've taken off the ECU like a dozen times now to run wires. The RCA wire is long enough that I can route it any number of directions, so I'll probably run it under the right side seat. Dealing with the stereo seller because it was suppose to come with 2 USB cables for the rear and it didn't.
No wires up in the tunnel..so ya, you're learning.
Had to return the stereo because it was made of too much chinesium. Seller tells me that rear USB was never meant to work. Got the Xtrons unit coming. I've had this happen before with these Android no brand stereos, you'd think I'd learn. Oh well, got some wires to reroute anyway and new brake hoses to install.
Had to return the stereo because it was made of too much chinesium. Seller tells me that rear USB was never meant to work. Got the Xtrons unit coming. I've had this happen before with these Android no brand stereos, you'd think I'd learn. Oh well, got some wires to reroute anyway and new brake hoses to install.
Xtrons sound Chinesium too. You want whats actually a ton of features, for like..no money. And in return you get trash.
Ya know, 4 months ago, even the Porsche classic head unit would have saved you money...
I can really relate to this thread.
We installed a fairly high end system (mostly JL audio, with a Breman head unit), in the "Hellblau" project car and had noise.
Head unit turned off or on.
Made us crazy...days and day of fussing about.
Tried every tip we could find....without any result.
05-29-2023, 07:36 PM
