Loud buzz on Raspberry Pi Audio Jack

Question

Hello, I'm hoping someone might have the answer to this issue I'm having with my Kitty TV Raspberry Pi. I have the Raspberry Pi (version 2, B+) connected to an old monitor via an HDMI cable connected to an HDMI-DVI adapter to the monitor, for video only. The audio is supposed to go separately through the 3.5mm audio jack to the external speakers. I tried two different (HDMI-DVI) adapters, and 2 different cables. I even tried using an external USB adapter, and the buzz even came through the 3.5mm jack on that adapter! I also tried the Raspberry Pi 3, with the same result. The kicker is, this was working at one point and the sound was perfect! The sound issue happens regardless of what the Pi is doing - just showing the desktop it does that, and when using omxplayer to play the videos it also does that same buzz. It's been a while since I last had it working, so I don't remember what changed. I don't recall if I did an update, or if it was the Raspberry Pi 1 I was using at that time. The Pi 1 is now the sprinkler controller, so I don't really want to tear that apart to try that out. I did try a few things in settings - forcing it to use audio out, and not hdmi, for example. Here is a video showing the issue, and how it does not buzz when HDMI is not connected.

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I'll try it on the bedroom TV next to see if it works when using audio through HDMI. edit: The audio works on the TV through the direct HDMI connection, using the TV speakers. However, the audio jack is still giving the same buzzing sound. So it's not the HDMI-DVI that's the issue. ps, those speakers work beautifully when connected to my iPhone. Using a headset I also hear the audio buzz. So it's not a bad connection or bad speakers. edit: This post from fall 2016 says it was the Raspberry Pi 2 I was using, so that's the same board I'm using now: Videos For Cats, on a Raspberry Pi edit: ps, the other thing I tried was to grab a brand new image off raspberrypi.org, but that didn't work. This is Raspbian Stretch. Previous one was Raspbian Jesse, which also had the buzz. Thanks! -Nico

shabaz · Answer

Hi Nico! That's a common problem, and not always easy to totally eliminate with wiring alone, but basically some current is flowing through wires with resistance (that are normally expected to be considered at 0V all along the wire), and that is causing the buzzing noise (which is likely at 60Hz). It's a process of elimination, I'd first try swapping out the audio cable for a new one (maybe a different vendor one), to see if it makes a difference. Most audio cables are really poor (I make my own ones).