Raspberry Pi Forums

When I turn my Pi on, my TV (over HDMI) makes buzzing sounds, which change with the screen. I have read this website and it fits the symptoms of "overmodulation", where the signal on the video input is too strong.

If this is the cause, then how do I fix it?

Are you using analogue audio from the Pi or HDMI audio??

Richard S.

redhawk wrote:Are you using analogue audio from the Pi or HDMI audio??

Richard S.

HDMI, as mentioned in the OP.

If I turn HDMI audio off (amixer cset numid=3 1) I still get the buzzing.

if it really is "overmodulation", then you can change the hdmi drive strength using the config.txt setup file, but I rather suspect its just a grounding problem. Note that the PI itself does not in any way receive a good ground, only through the HDMI cable, but that only works if the HDMI device itself is properly grounded.

Apologies, I didn't quite understand that. Do you mean grounding as in the top of the 3 wall pins here in the UK? (Live, Neutral and Earth) or am I getting confused?

As far as I'm aware HDMI audio is digital so it shouldn't be possible to get any buzzing or audio effects usually attributed to analogue.

Are you using external amplified speakers or the ones built into the TV??

Richard S.

redhawk wrote:As far as I'm aware HDMI audio is digital so it shouldn't be possible to get any buzzing or audio effects usually attributed to analogue.

Richard S.

true, but stranger things have happened. theoretically its possible to mangle/distort/wipe-out a digital signal periodically, 50 times a second, which may express itself as a "buzz". Especially if the distortion is caused by a 50Hz repeating small (millisecond duration) peak, caused by for example by a light dimmer.
but it probably should then also affect the image...
in any case it cannot harm to check the grounding.

crazyskeggy wrote:Apologies, I didn't quite understand that. Do you mean grounding as in the top of the 3 wall pins here in the UK? (Live, Neutral and Earth) or am I getting confused?

yeah, I refer to the earth wire.

I have checked the plugs for both my USB Adapter (an ASUS Transformer charger) and my TV, and they both have a plastic Earth connector. I assume that this is because the DC input for the TV and the USB input for the Pi don't need an Earth signal, or are designed for use in countries (e.g. the rest of Europe) which only have two wall pins.

Therefore I assume that there is no such thing as it being "Grounded", then?

Also, I am using the built-in speakers. My TV is a £99 Currys Essentials TV. The inputs for it are:
2 HDMI, RCA, VGA, YPbPr, SCART, and both Analog and Digital via a standard TV RF Antenna.

crazyskeggy wrote:Also, I am using the built-in speakers. My TV is a £99 Currys Essentials TV. The inputs for it are:
2 HDMI, RCA, VGA, YPbPr, SCART, and both Analog and Digital via a standard TV RF Antenna.

Can you confirm that there is no buzzing when you watch other digital sources (HDMI or Freeview) with the volume control at the same setting as when you hear buzzing with the RPi?

drgeoff wrote:Can you confirm that there is no buzzing when you watch other digital sources (HDMI or Freeview) with the volume control at the same setting as when you hear buzzing with the RPi?

1. The buzzing continues when sound is muted.
2. My camcorder (HDMI) also creates a buzz, but it is a higher pitch than that of the Pi when running OpenELEC (predominantly Blue).

So is this perhaps an issue with the TV, not the Pi?