Noise in Audio System: Possible Ground Loop?

[fort384]

I recently installed an amp and subwoofer in my 21' Monterey bow rider. The system works fantastically at mid and high volumes. However, with no audio playing, or with audio at very low levels, I have 2 distinct noise issues going on:

1. There is some hissing/crackling that occurs from the speakers when the system is powered on. It is intermittent, seems to fade in and out. It isn't terribly loud, but loud enough to notice over low volume even on the water, particularly when the engine is off. This noise occurs with engine on or off. The noise does not vary with volume setting (i.e. I can drown the noise out with audio).

2. I have some RGB LED accent lighting installed in the bulwark and under the consoles. The lighting will fade between colors, and when fading is occurring and audio system is powered on, I get a very distinct "whine" through the speakers. This whine does not vary with volume setting, i.e. I can turn the audio volume up and drown it out, but with low volume settings it is very noticeable. Once the fading stops and the color stays solid on the LEDs, the whine goes away. The controller for the LEDs is mounted up in the right console, pretty far away from the amp and amp power lines. The LED wiring itself does run through the left console near the audio system on it's route for the under console lighting and the lighting in the port bulwark.

The amp power and ground has 4AWG run from engine compartment up to left console. I have a dual battery setup - the power wire for amp is run directly to battery 2 positive post. I have tried moving the ground wire between batt 1 negative post and batt 2 negative post with no difference to noises. I have 3' RCAs run from the head unit down to the Amp - both are installed in the left hand console in the boat. The RCA cables are only 3 ft long and very little of the power or ground wires are run concurrent with the RCAs, just where they connect up at the amp.

Anyone have any ideas? Are both issues related to a ground loop do you think? It seems like a lot of discussion on ground loops have to do with alternator/engine "whine". My noises occur even when engine is off. The sounds/pitches do not change with engine on or throttle setting.

Do you think a standard ground loop isolator would fix one or both problems? Any other suggestions?

 

[NicoPags]

Could be a ground issue, but if the LEDs are affected sounds like inconsistent power. Maybe consider installing a capacitor to your amp. With the suggested two battery's running, a capacitor could be a long shot, but the fading lights indicate power (to me).

 

[fort384]

So the LEDs work fine - when I say they fade it is commanded - they fade between different colors. It is when they are fading between colors that the noise occurs. Once they reach a solid color the whine goes away. I did install a ground loop isolator yesterday and it quieted the LED noise but it is still present - but manageable. It did not solve the first issue though of a crackling or intermittent static sound though. Any other ideas? Would the capacitor still be wise even with this info?

 

[NicoPags]

hmm, is it a large wattage system? a Capacitor basically will store power in itself to help regulate the draw on your electrical system. a side benefit is it will regulate the voltage to insure your stereo is getting constant 12v. I suggested it as the symptom sounds like a power issue. But I also misread the LED behavior. Having dual batteries should eliminate the need for the capacitor as the current should be sufficient, unless it is a high powered setup. By process of elimination, try moving or adjusting your head units ground as well. Other suggestion, try switching the LED power source to the other battery if possible. Just to see if that solves the interfering?

 

[sam am I]

Try tapping the head unit's power and ground from the amp (sometimes amps have power/grd terminal strips) or as close to as possible to the amp.

 

[bruceb58]

The LED lights do their fading with a PWM circuit on each of the 3 colors so that is what is causing the noise. Where do the lights pick up their power?

Right now, you have no idea if its radiated noise or not. As a test, run the LEDS off a totally separate battery with isolated ground from the rest of your boat and see if you still have the noise. If that helps, ditch the fading and wire up whatever color you like best and don't let it fade anymore.