My speakers emit a hiss (sounds like the static from FM/AM) My ML Amp seems not to be the problem, it sounds nice and crisp. The hiss goes louder or lower depending on your volume. I can’t seem to find any forums about this. I have a feeling it’s my Antenna, I don’t really care about having FM/AM so if anyone knows how to kill power to the antenna that will be great. Or if anyone else had this problem how you fix it?

 

If you have AM or FM selected then it is going to make a noise but if CD is selected and a CD is not playing it should be silent.

You can't kill power to an antenna as it is a passive component and isn't powered.
It just receives signals that are then converted and amplified.

If AM/FM is selected but you are not tuned to a station the you will get static noise or hiss.
https://en.wikipedia.org/wiki/Radio_noise

When you select CD or Cassette but are not playing anything, then that radio static should disappear as the radio is no longer feeding signal to the amplifier.
If the noise persists in CD/Cassette mode, then the problem is in the wiring or the amp.

 

Loose ground wiring, depending on location in the electrical system, are a possibility for introducing EMI into the system. There was a thread here many years ago about someone finding an obscure and broken braided ground wire somewhere under the car that caused odd issues including transmission shifting issues.

The ML amp could still be the culprit, as it controls input selection and signal amplification, and the amp is directly tied to your volume control and your speakers. A faulty amplification system can definitely introduce a hiss.

AM/FM and cassette will pick up EMI noise even if grounding is perfect. Insulating the antenna (blocking all signals) would stop the noise (but also stop legit radio signals) from being amplified. If you remove the antenna, the open terminal could theoretically still pick up some noise. You can still test if the antenna is picking up stray signals by cutting the antenna wire on the amp. If you need the antenna later, solder it back together or wire up a switch - may be easier than trying to track down the source of the noise.

If cutting the antenna doesn't help, everything is grounded properly and there are no loose wires, and the noise persists in all input modes (AM, FM, CD, MD, Cassette), then you likely have to repair or replace your amp.

 

thanks stan, any idea which wire is power for the antenna? I have a 04-06 ls430

 

The antenna is behind the passenger A pillar trim. You can disconnect it by unplugging a connector. If you want to test if it is antenna. You will probably need to remove the dash in order to unplug the connector.

 

The antenna is built into the back window glass. You should be able to disconnect it on the passenger side. This following table may also help track down abnormal noise:

 

I worry that an RF oscillation is caused by the amplifier's IC due to some aged components used. This needs to use a spectrum analyzer in most cases just for the confirmation and the fix is another stage though. This is beyond for average DIYers but I think I can do.

 

By reading this I don't see if the hiss problem exists when in CD mode. It's very simple that if it is it is most likely in the amp and if not it would be the tuner or faulty antenna wiring. Also to disconnect the antenna simply unplug it from the tuner. Unplugging the antenna would just cause more static on radio and don't understand why you would want to do that anyway. It would not and could not affect other sources at all.