Audio Engine Noise in Speakers

[stifflkd]

I own a 2021 R5 that came with the standard audio package (RF PMX-8BB driving the cockpit speakers thru the internal amp). I recently added two pairs of speakers to the tower driven by an external RF PM1000X5 amp. Getting some engine noise being induced into the tower speakers. The noise is definitely from the engine as it goes away with the engine off and noise increases in frequency when I increase the RPM's. Positive that the noise is coming from the PMX-8BB head unit. I pull the RCA's at the amp and the noise goes away. I pull the RCA's at the head unit and the noise goes away. I by-passed the head unit by feeding a source directly to the RCA's at the head unit and the noise goes away. I filtered the power & ground to the head unit and no improvement. I also fed the head unit with a 12V battery and still no improvement. I am certain it is a ground loop issue. But I disconnected the ground feeding the head unit and ran a thick ground cable directly to the the ground terminal block and did the same for the amp. Cleaned all connections on the terminal block, no difference. My only thought at this point is that the two battery ground cables are grounded to the engine block and then a smaller gauge cable runs from the engine block up to the terminal block. My next plan will be to run a heavier gauge cable to between terminal block and engine block and to ensure the integrity of the connection on the engine block.

Before doing that, wondering for those that have one of the upgraded audio packages noticed any issues like this. I assume they used the same head unit as in my setup.

[jhnmdahl]

It sounds like you're on the right track. I know there are a variety of other solutions out there, from putting capacitors and/or inductors on the power supplies to the audio devices to RCA cables that have filters or transformers built in, but figuring out unintentional ground loops can be a bear. Here are some examples (I haven't tried any of these particular products): https://www.amazon.com/rca-cable-noise- ... ise+filter

[stifflkd]

Thanks, its been one PIA. I tried filtering the power supply but it did not help. The RCA ground loop filters did reduced it slightly. I think next on the list is to take the grounds from the head unit and amp and tie it directly to the ground terminal on the house battery and see what happens.

[jhnmdahl]

Can you tie the grounds on the amp and the head unit together close to the head unit/amp (e.g., maybe run the head unit off the power for the new amp)? It would be interesting to hear if that quiets it down at all.

[stifflkd]

I'll give that a shot. Going to tie both amp and head unit to the ground terminal of the battery and if that doesn't work, bring the head unit ground to the amp.