Author: petersk
Subject: Tone throught the audio panel
Posted: 19 Aug 2016 at 9:24pm
Your best test for this tone is to start by varying the engine speed. Does the tone change frequency? If so, try turning off the alternator side of the master switch. Odds are the tone will go away.
If that's all true, then you still have the question of why the alternator is generating that tone? It is most likely a grounding problem between some of your radios or connections. Perhaps a remote headphone jack has become grounded? Or you've hard mounted a music jack to a panel, without an isolation washer?
The hum in these cases comes from grounding loops, and when you turn on the telephone input it is muting whatever system has that grounding loop. The fact that the tone comes back in a volume ramp suggests the noise is in your music input.
One other cause can be when you use a power supply to feed your music source device... a charger on your cell phone while it's also connected to your music input, for instance. That creates a ground loop, which causes the hum.
There are various potential solutions for these things, but they basically boil down to having a single ground point and using isolation transformers when you just can't avoid that second ground, as in the power supply example.
Subject: Tone throught the audio panel
Posted: 19 Aug 2016 at 9:24pm
Your best test for this tone is to start by varying the engine speed. Does the tone change frequency? If so, try turning off the alternator side of the master switch. Odds are the tone will go away.
If that's all true, then you still have the question of why the alternator is generating that tone? It is most likely a grounding problem between some of your radios or connections. Perhaps a remote headphone jack has become grounded? Or you've hard mounted a music jack to a panel, without an isolation washer?
The hum in these cases comes from grounding loops, and when you turn on the telephone input it is muting whatever system has that grounding loop. The fact that the tone comes back in a volume ramp suggests the noise is in your music input.
One other cause can be when you use a power supply to feed your music source device... a charger on your cell phone while it's also connected to your music input, for instance. That creates a ground loop, which causes the hum.
There are various potential solutions for these things, but they basically boil down to having a single ground point and using isolation transformers when you just can't avoid that second ground, as in the power supply example.