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#242230 - 22/11/2004 16:42 Lexus ES300 install and a ground loop
shadow45
member

Registered: 19/03/2002
Posts: 144
Loc: Florida, USA
Got myself a '98 ES300 last week- It's got 7 speakers, an amp and head unit that's all intertwined. Metra makes a Toyota adapter that is the solution to using an aftermarket head unit with the existing speakers & amp. I bought one and spliced it together with my Empeg adapter, everything matched fine. It takes every wire and puts it together in a single harness, so it has RCAs for LR/LL FR/FL.

It fits and I can turn the Empeg on, but i get tons of garbage sound with the music. I think it's a ground loop..

So, I ran the Empeg its own ground to a bolt on the frame (scratched off the paint, too) instead of using the adapter's ground. No difference.. so I ran the empeg its own power from the battery, no difference. Grr. So I unplug the Empeg RCAs from the adapter, and got a RCA-> headphone converter. Plugged headphones into the Empeg and it sounds fine! no noise. fscking weird...
So, using the adapter for power but not the adapter's RCAs I can hear it fine (through headphones). But, if i plug it back into the adapter for the amp, i still get a lot of crap sound with the music. I put the stock head unit back in and it sounds fine., no sound artifacts at all.

Anyone have a clue? Maybe I have bad RCAs or wires on the audio part of the adapter? i'm stumped, i tried the obvious.. and the leads on my empeg harness are getting shorter by the day!
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#242231 - 22/11/2004 17:36 Re: Lexus ES300 install and a ground loop [Re: shadow45]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31563
Loc: Seattle, WA
Yeah, the headphone thing is normal/expected behavior with a ground loop.

First, read this.

Then try plugging the empeg RCAs directly into the amplifier, with all power, RCA, and ground wires from that other head unit completely disconnected from everything.

Then try going through all the steps here, and also go through all the steps in all the articles sub-linked from that page.
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Tony Fabris

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#242232 - 22/11/2004 18:09 Re: Lexus ES300 install and a ground loop [Re: tfabris]
JBjorgen
carpal tunnel

Registered: 19/01/2002
Posts: 3582
Loc: Columbus, OH
A couple of my Empeg installs have have had ground loops that were notoriously difficult to remove.

To help diagnose the problem, try grounding your RCA cables where they go into the amp (aligator clips, wire & tape...whatever...it's just temporary). In every case I've had so far, the loop was between the empeg and the amp. If the noise goes away when you do that, you know that the empeg is not grounded properly. Make sure you double check the sled harness connector to make sure you're getting a good connection (some had dodgy crimps). I'd resolder that pin just to be sure.
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~ John

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#242233 - 23/11/2004 00:21 Re: Lexus ES300 install and a ground loop [Re: JBjorgen]
shadow45
member

Registered: 19/03/2002
Posts: 144
Loc: Florida, USA
I assume the neg of a RCA is its outer metal ring, correct?

Hope I can find this thing.it's elusive thus far and I only get 2 hours of daylight after work a night, heh

thanks for the info
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#242234 - 23/11/2004 06:24 Re: Lexus ES300 install and a ground loop [Re: shadow45]
Shonky
pooh-bah

Registered: 12/01/2002
Posts: 2009
Loc: Brisbane, Australia
Quote:
I assume the neg of a RCA is its outer metal ring, correct?


Correct.

Quote:
Hope I can find this thing.it's elusive thus far and I only get 2 hours of daylight after work a night, heh



Just go through the steps in the FAQ. As you noted, removing the RCAs between the empeg and the amp fixed it. That's because you literally broke the loop. One part of the loop is the shield in the RCAs and the other part is the chassis of the car.

What happens is some of the supply current to the amps or empeg runs through shield of the RCA cable instead of the normal power wires and the car chassis.

Is it possible that Lexus use a balanced system? Could that be contributing.

Look for a Lexus forum. Installing the empeg is almost identical to any other head unit so if they had noise problems and fixed them, they can probably help you too.

I just hope I don't have the same problems with my M3 I'm picking up soon (weekend hopefully). hybrid8's 328i install is promising though.
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Christian
#40104192 120Gb (no longer in my E36 M3, won't fit the E46 M3)

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#242235 - 23/11/2004 13:18 Re: Lexus ES300 install and a ground loop [Re: Shonky]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31563
Loc: Seattle, WA
Quote:
One part of the loop is the shield in the RCAs


Common misconception. I should probably make this clearer in my "explanation of a ground loop"...

If the problem were only on the RCA shields you wouldn't hear it. It's also on the center pins as well.

Okay, technically, the problem isn't "on" those RCA cables at all, it's because of whatever electrical path provides a better ground path than the ground wire itself, which may or may not be any given connection, regardless of whether that connection is a positive or negative wire.

My point is that the noise is audible because the electrons from the power supply are flowing through the audio circuitry via the RCA center pins.

The only reason grounding the RCA shields sometimes fixes it is because it changes the ground path and makes the electrons stop flowing through the RCA center pins. Not because the problem was in the shields.
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Tony Fabris

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#242236 - 24/11/2004 02:36 Re: Lexus ES300 install and a ground loop [Re: tfabris]
shadow45
member

Registered: 19/03/2002
Posts: 144
Loc: Florida, USA
hm, ok. gonna have to remove the passenger seat to get to the amp while it's still hooked up. I'll try JBjorgan's advice to test. I'm afraid that the audio wires will be in a harness like they are on this end, so is it sensible to solder a needle or paperclip onto a wire and jam that into the back of the ground pin's socket, for testing?

i'm trying my hardest to make sure each step is properly tested. I don't want to miss whatever it is

I'm not really electrically inclined (software guy) so bare with me here: To check this with a multimeter does the + of the multimeter go to the + of the device and the - to somewhere on its ground wire or ground point (of the device) to test? what do i look for? a deviation from 12v ?

Sorry to have so many questions, hope that's readable
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#242237 - 24/11/2004 08:01 Re: Lexus ES300 install and a ground loop [Re: tfabris]
Shonky
pooh-bah

Registered: 12/01/2002
Posts: 2009
Loc: Brisbane, Australia
Tony,

I respectfully disagree. Why would it be called a ground loop when the shields (at ground potential in a single ended installation) aren't involved? That's not really the point here anyway though.

Basically as I understand it generally (as an electrical engineer) for a normal unbalanced situation:

- The signals from the head unit to the amp are signal ended and referenced to it's ground at the head unit end.
- The amp simply amplifies the voltage it sees between the centre pin of the RCA and the shield. It's merely amplifies the "difference" in potential but right at the input to the amplifier.
- If the ground of the amp is not very good OR the ground of the head unit isn't very good, the ground reference point of either the amp or head unit (or both) end will move, particularly with voltage fluctuations (stuff like alternator, switching loads such brake lamps, indicators etc).
- If the ground reference point moves at either end, that's when the noise gets in, since the ground has moved with respect to the centre signal wire.
- If the grounds are bad, the amplifier's and/or head unit's supply return current will travel via the grounds of the audio cable. This current will change according voltage fluctuations. Any resistance will then cause potential differences when current flows. And again the potential difference is what is amplified.
- The supply currents for the amp and head unit are unlikely to be flowing on the audio level signal lines of the RCA cables.

Grounding the shields should effectively achieve nothing since the should already connected to ground. What it does do though is provides another current path for the supply currents to take which can help with the problem.

Well, that's my take on it. Feel free to debunk it. I don't mind being corrected.
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Christian
#40104192 120Gb (no longer in my E36 M3, won't fit the E46 M3)

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#242238 - 27/11/2004 23:58 Re: Lexus ES300 install and a ground loop [Re: Shonky]
shadow45
member

Registered: 19/03/2002
Posts: 144
Loc: Florida, USA
I took the glove box apart and I can see the wiring harness that goes into the amp. Can I do this test at the head unit rca adapter end? i'd have to rip the damn wire out and put another in if i test it at the amp. its tiny

thanks for any input
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#242239 - 28/11/2004 09:47 Re: Lexus ES300 install and a ground loop [Re: shadow45]
mtempsch
pooh-bah

Registered: 02/06/2000
Posts: 1996
Loc: Gothenburg, Sweden
One thing worth trying early is running new ground wires to the amp and HU.


/strip away any dirt paint etc before attaching the ring terminal - shiny metal is what you want. afterwards,put on rust protection on top


While you're at it,check the grounding of the battery (negative terminal) and the alternator (commonly grounded to the mount on the engine block, so also check the car body to engine block grounding strap. Beefieer ones doesn't hurt; clean the attachment points)
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/Michael

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#242240 - 28/11/2004 15:54 Re: Lexus ES300 install and a ground loop [Re: Shonky]
shadow45
member

Registered: 19/03/2002
Posts: 144
Loc: Florida, USA
I did that test, and it certainly helps but it doesn't make the problem go away. Would I be better to run a wire to the negative post on the battery, or try to find better grounding? also, having this wire on the sled made an improvement too. not entirely, but it did help

any input would be appreciated. the lexus forum people suck, they never post a solution. tons of people with ground loops and no "this worked for me" after everyone helps them.. makes you wonder if there are thousands of people driving around with what they consider an ignorable hum...
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#242241 - 28/11/2004 16:30 Re: Lexus ES300 install and a ground loop [Re: shadow45]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31563
Loc: Seattle, WA
Quote:
Would I be better to run a wire to the negative post on the battery, or try to find better grounding?

If you follow the sub-links that I pointed you to at the top of the thread, you will find a definitive answer to that question.
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Tony Fabris

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