Floating ground?

[windozeuser]

I'm currently installing a new stereo system in a 1987 Ford Mecury Cougar XR-7. The After Market harness hooks up to the OEM Harness. The Only problem is the ground wire for the AfterMarket Harness goes to a spot on the OEM with no wires going to it!

The Harness documentation saids: That I need a "FGA" Floating Ground Adapter.

Whats a floating ground compared to a common ground? And could I just run the ground to the regular car's ground point?

 

[RadioRon]

It was fairly common for radios in older cars and some new ones to pick up their only ground from a chassis connection between the radio chassis and the car chassis, usually via a mounting stud on the back of the radio. I've seen quite a few that did not have a ground wire in the harness. I would think that it should work just fine to ground the stereo chassis to the car chassis. But it is also possible that the new stereo has an isolated setup of some sort. In this case I don't see why you can't splice into the ground wire on your new equipment harness and hook that up to vehicle chassis.

 

[audioguru]

Instead of guessing, you might as well lookup Floating Ground Adater in Google.
It has transformers that are too small or resistors that strangle the power so that a new car amplifier with bridged amplifiers can connect to exising speakers wired with one wire from each speaker connected in common and to ground.
They can also be used to convert balanced bridged amplifier outputs to unbalanced (one wire grounded) amplifier inputs.

 

[windozeuser]

Thanks guys. The Stereo works fine with just the regular chassis ground. I don't need a FGA for my current application

Thanks

 

[mister_e]

from what i feel ... it will blow soon. Most, see all newer car Stereo system use Balanced output (bridge BTL amplifier like TDA7386 and Pals) and most of them will blow after few minutes/hours of use. You really should consider to route new wire from the radio to the speaker. The floating ground adapter is still an option but you will loss a big deal in the sound quality and power.

I also do car stuff installation/repair for more than 10 years now.

 

[Dane]

I know this is an old post , but closest to my question. I changed my OEM radio to a newer OEM CD radio. The old radio had a builtin amp in the front circuit powering the speakers. The new radio has only line output so a separate amp is required. I had an amp with 60 watts output which will be plenty. The problem is the radio has seperate grounds for the left right channels and the amp is common ground for the channels. Doesn't work. Just a bad hum. I was hoping for a schematic to make a floating ground adapter. Low level to low level. Parts express carried one years ago for $5 , but no longer carries it. Should be able to make one cheap I would think. Maybe a 1 to 1 transformer on each channel radio out to amp in would isolate it?

Any suggestions?

 

[RadioRon]

A transformer would work but you have to use a good one or you might strangle your low bass response. But before getting into that, there is something about your problem that doesn't sound right. That your radio head line outputs do not share a common ground implies that they are not line outputs at all but bridge-type speaker outputs. Are you sure those are line outputs? All of the line connections that I've seen in two part car stereos use RCA connectors mounted on the chassis, generally using the chassis as ground. If your head outputs are just wires or just come through a large plastic block type connector, that also makes me think they are speaker outputs.