Motherboard HDMI Audio Noise Issues?

  • Hey all,


    I have a HTPC setup in my livingroom where a HTPC running Kodi (on top of LibreElec) passing both video and audio via HDMI to my surround receiver, usually via either passthruough, or multichannel PCM.


    For the longest time the system was running on an old dual core Haswell system, utilizing an Nvidia GPU for video output. When this was the case my system was working fine.


    However, the douchebags over at Nvidia decided that they were going to discontinue VDPAU (their video decode hardware acceleration API under Linux) and it's replacement NVDEC has pissed off all of the open source projects, so they are refusing to use it. (AMD and Intel use VAAPI, but Nvidia sees a need to be proprietary and different as they always do...)


    So, due to VDPAU having been discontinued and stagnating, it is not getting the latest features and formats anymore, at the same time all the Kodi and LibreElec devs are saying that on x86 they are primarily developing on and for Intel integrated graphics these days, so I decided to switch things up.


    A couple of months ago I picked up an Asrock B365M Pro4 motherboard, and because all the low end CPU's for the platform were sold out for some reason, I wound up with the total overkill for simple video playback duty, Intel i5-9400


    It's a great little platform, but it introduced a new problem. Audio using HDMI straight off the motherboard has noise problems at low volumes which were never there before. I usually cant hear it over loud scenes, but when nothing is playing it is super obvious, and sometimes audible during very quiet scenes.


    It's bugging the hell out of me.


    Since HDMI is a digital format, it shouldn't have any analog noise going out over it, which is why I am suspecting some sort of odd ground loop. I've been looking for HDMI ground loop isolators without success.


    Does anyone have any suggestions?

  • Assuming you've tried the typical things like cables and connections i would start with trying any old external video card in the system to see if the issue is actually the embedded hdmi interface or not... any old card would do as long as its got the hdmi out as the exercise is to see if the issue goes away when using a external card... if it does then you know its actually the embedded interface on the motherboard or not...


    HDMI may be a digital interface but there are still ways of introducing noise into the signal streams its being used to transmit...


    Motherboard quality these days wanders around quite a bit and its not uncommon to find MB's that appear to work ok in most aspects till at some point you find some small quirk that seems no right...


    If its proven to be the MB Interface it could be just a bad motherboard (bad from a noisy point of view) that functions ok otherwise or maybe it just needs a vcc or timing tweak...

  • Appreciate the suggestions.


    Since I had a working setup without issues prior to the heardware upgrade I did not try swapping out the cables, but I have checked the connections.


    Interesting that VCC may impact noise. I;m used to overclocking having unpredictable results, but this thing is running at stock....


    I will play around with it and see if anything changes.

  • Motherboards can be funny animals as they all pretty much work in general but then in a lot of the cheaper designs there is usually a few little quirks that can pop up that maybe for general use go mostly unnoticed by users... sometimes just moving things around inside the case and where cables are crossing things can introduce things into systems... some of the cheaper boards can be picky that way...or then again it could just be a bad board to begin with...


    Things like bad caps on a board which is not all that uncommon can cause weird noise issues and intermittent things like booting issues... I recap boards all the time and have seen even some more expensive boards with caps that are drying out that lead to all kinds of issues...


    Hopefully its just something simple like moving some cables around...


    One other thing i would make a comment about is that i am assuming you swapped out the boards yourself and if so make sure the grounding posts are not touching on anything other then the ground landing pads on the board... its the grounding ring (pad) around the mounting hole on the board where the mounting screw holds the MB into the case... Some boards that solder ring built up around the hole is heaped up with more solder then needed and then when tightening the screw down it gets squeezed and widens out till it touches some board trace that laid real close... Sometimes when things like that happen its not bad enough to stop the board from booting but causes a bunch of intermittent issues...