Speaker grounding loop-whine with engine

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DustyTrail

DustyTrail

10 Year
Joined
Aug 19, 2014
Threads
11
Messages
47
Location
El Paso, TX
I need help fixing a stereo problem. I installed an aftermarket Kenwood head unit in my 1998 LC more than a year ago. I did the install myself and haven't had any trouble with it. Well... there has been a very minor static that only I ever hear (because I did the install and pay more attention). Needless to say, it has been so minor it hasn't bothered me. I figured it was just a mismatch of head unit to factory amp. No other changes to the stereo system other than that.

So this past weekend while driving, I remembered reading at some point that you can get the D light in the instrument cluster to re-seat and turn back on by hitting the dash at the 12:30-1 o'clock position. After I tried that, the D light didn't come on but I instantly got a horrible noise out of my front passenger speaker that changes pitch with the RPMs of the engine. After hitting it again it, turned back off...temporarily. I hit it again and it stayed off for 4 days. Today I got back in the truck and it's back. On my 25 minute drive, I had to hit the dash about 5 times as it kept coming back.

I did a little research and realize this is a grounding loop from the speaker wire being close to or touching bare metal on the car. Seems like I know exactly where to look (i.e. behind the instrument cluster). Before I tear into the dash and instrument cluster, am I on the right path? I read that the instrument cluster is relatively easy to pry out but will that give me access to what I need?

Any insight is appreciated. The forum is always a huge help to me.
 
Last edited:
bucfl said:
This may help...

We are having a similar discussion on grounding loops.

upgrading speakers and not amp on a budget
Click to expand...
Update- I tinkered with my stereo last weekend and cut the harness ground wire and ran it directly to the battery- nothing changed so I decided to take it to the professionals today. After diagnosing, they said that upgraded double din stereo is too much for the factory amp. He didn't push me on a top of the line replacement so he had more credibility in my book. Does that solution make sense to those audiophiles/engineers out there?

By the way, he couldn't answer the question why it got worse after hitting the dash just that factory amps with upgrades stereos will eventually deteriorate the amp.
 
An easy test would be to bypass the amp. Maybe hook up just one set speakers.

I'm going fiddle with it this weekend.
 
I was in the EXACT same situation last week. 99 LC, aftermarket stereo, factory amp, whine in the stereo. I solved my problem by bypassing the factory amp - and you should do the same. Do not buy a new head unit, do not buy a cheesy ground loop isolator, do not try to filter the power or improve your grounds. Those fixes will not work. The factory amp is AWFUL anyways. Your aftermarket stereo likely has the same or maybe even more power anyways.

The problem comes from the factory amp having a slightly non-chassis ground for the RCA shielding. Aftermarket amps simply use ground as the shield. It's generally reliable and consistent. The Factory Toyota Amp uses a unique ground for the factory amp - unique in that it's not actually chassis ground. My whine got worse and worse the better I grounded or powered the aftermarket head unit. I believe this occurred because I was bringing that shield line further and further from where the factory amp wants it. Since there's generally no way to alter the RCA grounding within the aftermarket head unit you really have no good way to rectify the situation aside from giving the factory amp the axe.

You can verify your situation by checking the factory shield line resistance to ground with the car on. You should find that the shield line is actually active and no grounded as it needs to be to work well with the new head unit.

Bypassing the amp is easy and just requires splicing together 8 wires which you run behind the glove box and under the carpet.

I'm putting together a video on exactly how to do it and a super clean option if you want to spend a few bucks on a couple new connectors.
 
I was hoping to keep the stock amp as the HU is no where near 300W. Its 160 Watts Peak Power (40 x 4) not sure if its enough to drive the new speakers front/rear.
 
bucfl said:
I was hoping to keep the stock amp as the HU is no where near 300W. Its 160 Watts Peak Power (40 x 4) not sure if its enough to drive the new speakers front/rear.
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Unfortunately you'll likely have to choose between a little more power coupled with alot more static/whine or bypass the amp and live with the power difference.

By the time you pay for a clean ground loop isolator, you could buy a 4 channel amp and replace the factory unit.

Just last week I spent hours in the garage trying everything I could to salvage the factory amp. I now realize that was a fool's errand. My head unit is 200w, just barely more than your 160. I wish I would have just forgotten about the factory amp from the beginning. It sounds great just through the head unit and I have full control over the fine tuning of the sound without the amp muddying things.

Good luck either way. That whine can drive you insane...

Sent from my XT1060
 
x2 I have alpine deck, with alpine 6.5" components in stock location up front and alpine 6.5" 2 way speakers in passenger rear doors. I tried using factory amp as well but also had to eventually bypass the amp also because of the ground situation. Sounds just as good off of the aftermarket head unit's built in amp. The stock amplifier is not all it is claimed to be. If you look at any decent four channel aftermarket amps they are three times the size of the factory "amp" that is a five channel.
 
Thanks suprarx7nut. I found your thread yesterday and appreciate you posting your troubleshooting. Very helpful. I all but came to the same conclusion. Either replace the amp or use the aftermarket head unit to power the speakers and bypass the amp.

I haven't gone out and looked yet but is it difficult to rewire into the doors? Did you just splice together regular speaker wire into an rca wire?
 
Dusty,

I'm not sure I understand your question exactly. To bypass the factory amp you just need to run 8 wires from the head unit area to under the passenger seat. Then you need to tie into the factory speaker connections. You don't need to mess with the wiring anywhere else. You can re-use the existing speaker wire that runs to the doors.

You'll need to keep some other connections active because the head unit power comes from the factory amp. RobRed has identified the wires needed for power. You can pull or cut the speaker wires out of the factory amp connectors and splice in that way, leaving the factory amp in place physically. If you want to remove the amp physically then you just need to splice together a couple more wires to keep power going to your head unit.

It probably sounds a lot more complicated than it is. I'm waiting on some connectors from Japan to finish up my clean install. At that point, I should be able to post a video with all the details you could ask for.

ETA about a week or so.
 
Just do add to the thread...whenever we had rpm whine from high power amps and aftermarket receiver, we would ground the head unit and the amp at the same location (with correct gauge wire for both). Got rid of rpm whine every time.
 
DOGMARLEY said:
Just do add to the thread...whenever we had rpm whine from high power amps and aftermarket receiver, we would ground the head unit and the amp at the same location (with correct gauge wire for both). Got rid of rpm whine every time.
Click to expand...
Does this apply to the factory amp common (or shield)? Grounding to similar locations or just ensuring good grounds is always a must, but I think the problem here is that you can't easily ground the factory amp common wire going from the head unit to the factory amp. It is not the same as chassis ground as that offset seems to occur internally within the amp.

Sent from my XT1060
 
Not taking exception to your results, because we all agree the factory sound system sucks balls for a $60K car, but on my 2000, the factory electrical wiring diagram shows an external ground for the amp under the pass seat. This also serves as the ground for the OEM HU, which grounds via the OEM harness to the amp.
 
re_guderian said:
Not taking exception to your results, because we all agree the factory sound system sucks balls for a $60K car, but on my 2000, the factory electrical wiring diagram shows an external ground for the amp under the pass seat. This also serves as the ground for the OEM HU, which grounds via the OEM harness to the amp.
Click to expand...

This is definitely true. The OEM amp and head unit both have a ground. That main ground is actually chassis ground.

The wire I believe to be the problem is the wire labeled "GND", but doesn't actually have a direct tie to chassis ground. It originates and terminates in the amp and head unit. It's this wire that is used to act as the common wire for the low level speaker outs from the OEM head unit to the OEM amp. If you measure this supposed "ground" with a voltmeter, you will likely see ~0.1-0.35V. This proves to us that this line is not actually chassis ground, but rather an internal ground loop used for the factory stereo common lead.

I'll take a picture from my physical wiring diagram and post it up to clearly show where I think the problem is.

I could be wrong, so please bring on all the counter-evidence you've got. No exception taken. :) After-all, the point of all this is to get to the right answer and help out the community. If I don't have the right answer, I'd like to learn it.
 
Here's a picture of the wiring diagram with an arrow on the offending wire. They label it "GND", but mine certainly is not actual ground. It had an active electrical potential with the car on. I think this arrangement works just fine with the factory head unit because the head unit doesn't interact with that circuit so there is no potential mismatch. It's just there to shield the single, lonely lead for each audio channel. This is not the case on an aftermarket deck, where the RCA shield is integrated into the aftermarket head unit's power ground. In that case you then have an active potential coming from the factory amp with a path to ground - therefore you have current running through the shield line, reaking havoc on the audio channels.

"S Ground" is also not chassis ground on my car, but as mentioned earlier, you can run that lead directly to chassis ground to give yourself a good solid ground for power. It's easy to get good ground for power. It's tough to eliminate the potential emanating from the factory amp.

IMG_20151103_230225450.webp
 
suprarx7nut said:
Here's a picture of the wiring diagram with an arrow on the offending wire. They label it "GND", but mine certainly is not actual ground. It had an active electrical potential with the car on. I think this arrangement works just fine with the factory head unit because the head unit doesn't interact with that circuit so there is no potential mismatch. It's just there to shield the single, lonely lead for each audio channel. This is not the case on an aftermarket deck, where the RCA shield is integrated into the aftermarket head unit's power ground. In that case you then have an active potential coming from the factory amp with a path to ground - therefore you have current running through the shield line, reaking havoc on the audio channels.

"S Ground" is also not chassis ground on my car, but as mentioned earlier, you can run that lead directly to chassis ground to give yourself a good solid ground for power. It's easy to get good ground for power. It's tough to eliminate the potential emanating from the factory amp.
Click to expand...
Interesting, what year is that diagram from? Lexus or Toyota?

The 2000 Land Cruiser didn't have the additional brown ground wire that bypasses the amp, and on the 2000 LC, the shielding is attached on one end only to the ground wire between the hu and amp.

1446739921151.webp
 
My diagram is model year 1999.

I'm surprised they changed the grounding so much year to year. I think the 2004 wiring diagram I found online is different than my 99 and your 2000.

No wonder there's not a well documented fix for the 100 series stereo problems - there may be a different solution for every year, ha-ha.

Sent from my XT1060
 
BTW that 300 watt factory amp doesn't sound half as good-or loud-as a decent head unit sounds. I used the stock amp first, the rand direct from the head unit and got to compare each. Much happier with bypassed amp, upgraded cheap speakers, $150 head unit, and cheap 8" bazooka tube that is now built into my drawer system. Bypass that over rated amp and you'll never look back.
 
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