head unit speaker "-" lead question.

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jerryb

jerryb

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I'm wiring an amp and I used the SGND from the head unit for all 4 grounds to the speakers. That's a black wire. That doesn't work so well.

Is there a correct way to get "-" speaker leads from the head unit to an amp? I've tried multiple ways with the black wire, sound comes out fine when all four "+" speaker wires are joined with the black SGND wire but something is not right. Fader and balance are messed up. In center position or balance and fader controls the sound is garbage.

I'm using high level inputs on a JL.
This should be the same across multiple model years I believe.
Thanks for any help. I'm stuck at the moment.
 
are you saying the stock outputs from OEM HU are low level, that doesn't make a lot of sense.
Maybe they are idk.

I swapped to brown wire sgnd for speaker -, (there are two sgnd's) and things improved, but with a ton of noise.
I don't want to go LOC.

I'm a step ahead now that I was this morning. I just have the noise to figure out. I don't understand why the two SGND wires from the HU output and into the S7B plug to factory amp.

Thanks for any help.
 
Try using the black/dark gray wire as common ground.

P1010916.webp
 
I have the same plug, started with black as -, ended up finishing it with brown as -, the next pin over. Both are labeled as SGND. Still have some hiss, RPM crack but brown was better than black as far as noise. I had all kinds of weird stuff going on wired to black.
IMG_20161027_120640.webp

I moved grounds all over the place and It only got worse. I just went with the least intrusive hiss with HU all the way up and amp gain as low as possible. This is by far the weirdest install. Does anyone think the two antennas have anything to do with extra noise?

One other note, I unbolted the ground to re install the seat but then I went to get beer. The stereo was on the whole time with the amp ungrounded, hiss and pop vanished without the amp ground.
So that's another thing I'm thinking, but power and ground are 4 gauge, ground less than 12" long and was attached to seat bolt hole. idk. I"m going to wire wheel the bolt hole tomorrow and keep going. It's like a never ending ordeal.
 
It's been several years since I did mine, and IIRC, there were a couple tricky parts that didn't make sense, but it still works to this day & there's no hiss or line noise at all.
 
I went through this morning and verified amp output polarity, input polarity from HU into aftermarket amp(best I could) black and brown S ground passthroughs on plug into stock amp (S7B plug), and black s ground splice to high input negative wires. Like previously, yesterday, it's just wrong, lol. Imaging is wrong, fader messed up, muttled sound, not much power. I ran jumper cable from battery- to amp ground at seat bolt hole. No changes. I swapped back to brown wire S ground.
at same plug, it sounds like it should, fader works fine, imaging good, power that you think it should have etc. Seems like the correct way to wire it. I just can't help feeling this is wrong.
There is continuity across speaker input - and chassis grounds, across NAV ECU chassis ground lug, Bat- etc, with the brown S ground from S7B.
The black S ground doesn't. And that is what confuses me.

Should be that speaker runs work well with the black wire, but they don't.
I know I'm not going to find an answer here, just putting this up for anyone with the same EWD with two S grounds and so I can remember what I did five years from now.

last thoughts, The username supranut something or other has it right. The whole problem is the black and brown Sground in any year LC model. There's no way around it.
My last step was cutting the brown wire in S7B plug, wiring one end to high level - inputs (4)., capping the other cut end at the plug and calling it finished. That's the best it sounds in any configuration regarding S grounds.
Turn the stock HU up to max volume and adjust input gains on amp to lowest possible, passable, level. Hiss will be imperceptible to anyone but installer.

I'm liking the JL JX 400/4D, small. cheap. decent sound.
For less than $500.Ffour sets of speakers, dice media bridge MB 1500 toy, and amp. I don't think there's a better option if you have NAV.
Including rear seat audio delete replaced with USB chargers, and auto antenna delete, SUB delete, I'll fix later.
On to TB and water pump, which I should have done last week.

IMG_20161030_112025.webp


IMG_20161030_091302.webp
 
@jerryb The OEM head unit absolutely uses low level out to the factory amp.

The Black SGND is the the signal ground from the OEM head unit. Get a set of RCA cables and chop one end off... terminate all 4 of the RCA grounds to the black SGND wire and then tie the signal positives to the correct RCA to match your desired amp position.

Red = Rear Right
Pink = Front Left
Yellow = Front Right
White = Rear Left
 
I trust you. I'm on it, after everyone goes to sleep.
It's just that I've never seen a factory HU with low level outs and use speaker wire to do it.
why does everyone else get an amp with light level inputs and use those from the HU?
Sounds crazy to me.
I'll plug one in and give it a go.
 
I dont know anyone who has put the low level outs into high level ins.

In an OEM application you are not going to find a set of RCA cables for low levels it will always be contained in a wire harness. Metra even makes adapters for OEM radios with a set of RCA's on it for exactly what you are doing.
 
isn't that picture that sixguns posted a speaker level harness 4x2 or 5x2 (if there's a common ground wire) wire harness to an alpine amp, 4 wires to sground? (black) just wondered, looks to me like it is.
I think this user used speaker level ins. One example.
Stereo system install on 03 Hundy

Is this wrong also? from TLCfaq

Amplifier:

  • Several amplfiers came installed in the 100 series and differ in output power for the system options equipped. For replacement any aftermarket multi-channel (5ch) or combination of amps will work well. Most modern amps are looking for 2-4 volts at the low level inputs which is a problem for the factory head units. Whe feeding an aftermarket amp with the factory head unit you should use a device like a JL Audio Clean Sweep to provide the interface from stock to aftermarket amplifier.
I would just liket o know the facts. I don't have a problem being wrong. I just want the correct hook up info. I've never seen a oem HU with low level outs.
For the sake of argument, I swapped the 4 inputs to RCA and - to s ground (black) That does not work. The noise is insane. if people really are hooking up their stuff this way no wonder there's rampant complaints about hiss and rmp whine.
 
RobRed said:
I dont know anyone who has put the low level outs into high level ins.

In an OEM application you are not going to find a set of RCA cables for low levels it will always be contained in a wire harness. Metra even makes adapters for OEM radios with a set of RCA's on it for exactly what you are doing.
Click to expand...

IM suffering from the same problem. I bought this harness Metra 70-8113 Amplifier Integration Harness for Select 2000-2004 Toyota Vehicles
and i was getting some hiss. I removed it and connected the after market radio directly to the speaker cables and its unbearably worse. IM not using an after market amp or have a factory amp. Just after market head unit. I took it to a car audio shop and the guy told me that they could not help. They said it was so bad it was the stereo that was the issue. They didn't even charge me to look at it.

Any ideas?
 
@bucfl jerry is trying to go from factory HU to JL amp which the model of harness you mention would be useful for. he was trying to drive a speaker (high) level input from a low level out from the OEM HU. Bad news.

In your case you are in for trouble in a few ways. Jensen HU... lots of great features but not the best in terms of audio section. It has a 13w per channel amp into 4 ohms with a 70db SNR.

Scenario 1, connecting Jensen to Factory amp: No matter the HU it's generally going to sound noisy and terrible. The Jensen has a 6v out on the RCAs and the factory amp doesn't deal with it well at all. The factory amp is design to run higher impedance speakers with little tolerance - The Infinity's are 2ohm nominal and not OEM amp friendly.

Scenario 2, connecting Jensen to new Infinity speakers directly: The speakers you picked are good but really need an amplifier behind them. The Jensen Amp is really tiny and probably results in clipping really fast. Best bet is to run aftermarket amp.

The noise issue is probably inherent in the HU you chose but it sounds like its beyond normal for it. Possible warranty.
 
jerryb said:
isn't that picture that sixguns posted a speaker level harness 4x2 or 5x2 (if there's a common ground wire) wire harness to an alpine amp, 4 wires to sground? (black) just wondered, looks to me like it is.
I think this user used speaker level ins. One example.
Stereo system install on 03 Hundy

Is this wrong also? from TLCfaq

Amplifier:

  • Several amplfiers came installed in the 100 series and differ in output power for the system options equipped. For replacement any aftermarket multi-channel (5ch) or combination of amps will work well. Most modern amps are looking for 2-4 volts at the low level inputs which is a problem for the factory head units. Whe feeding an aftermarket amp with the factory head unit you should use a device like a JL Audio Clean Sweep to provide the interface from stock to aftermarket amplifier.
I would just liket o know the facts. I don't have a problem being wrong. I just want the correct hook up info. I've never seen a oem HU with low level outs.
For the sake of argument, I swapped the 4 inputs to RCA and - to s ground (black) That does not work. The noise is insane. if people really are hooking up their stuff this way no wonder there's rampant complaints about hiss and rmp whine.
Click to expand...


See my response to bucfl as well.

Many Many modern vehicles with audio systems sold today use a low level signal to an external amp. Just because you don't see an RCA connector doesn't mean it's not low level.

The JL audio clean sweep is a signal processing device to reduce noise. There have been many iterations over the years (thanks for linking that as I wanted to update because the link is dead)

If you have wired the input side correctly as discussed then I would look at the output side of the amp and double check you've not crossed some outputs. That can explain why you get improper fading. To be clear the SNR of the factory head unit isn't that great and it's "amplified" inot a bigger concern when you you use better gear on the output side.
 
Rob, do you really think that pioneer deck outputs less than 2V on it's own?
I should say less than 4V,
There's no way the stock HU outputs less than 2V or over 4V exclusively, I wouldn't get the overlap if that was the case. Correct?

edit, pioneer kex m9137 zt-02
toyota part # 86120 60603
 
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Thank you @RobRed

I'll put the harness back on as it was not as bad. And start saving for better radio.
 
jerryb said:
Rob, do you really think that pioneer deck outputs less than 2V on it's own?
I should say less than 4V,
There's no way the stock HU outputs less than 2V or over 4V exclusively, I wouldn't get the overlap if that was the case. Correct?

edit, pioneer kex m9137 zt-02
toyota part # 86120 60603
Click to expand...


Basic pioneers put out 2 volts. The more advanced HUs (nex etc) put out 4v. Using the amps gain (or attenuation) controls you adjust the input level so there is a balance between noise floor and volume.

I have not measured the oem head unit you have so I can't say what the specific output is. I can say that factory head units have been successfully mated to aftermarket amplifiers with some success. Based on the issues you describe early on you need to solve the connectivity before even getting to the noise issue. That noise issue once connected properly will be the noise floor or background hiss.
 
I don't really have any connectivity issues. Originally I used the black s ground like other people have in other threads.
That absolutely creates a lot of noise.
My EWD for MY 2006 shows two SGRD. I swapped to the brown s ground and things were dramatically improved.
So I wanted to check with the board and see if anyone else had had this issue before.
And then the low/high input you brought up which made me question the choice, So I hooked up low just to see.
To be clear, I didn't measure voltage anywhere.
I absolutely believe these are not low level outputs from the deck, not in a true sense of the word. We can agree to disagree. Low level outs will not drive a speaker on their own. I doubt toyota would put a dead deck in any of their cars.
I'm done with it. No one would know but me anyway. It's sounds decent, probably better than most, it's just not fantastic like it would be with a complete overhaul. I'm just very critical.

I do appreciate your posts Rob. I read a lot of them and they are very helpful.

Thanks











 
Ok good luck.

That brown wire is a system chassis ground.

I added a snapshot of the wiring diagram to my post on TLCFAQ for you to compare with yours.

Stereo Wiring: Land Cruiser (2003-07)

[Edit] one more thing. These Audio systems are spec
 
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