ROCK USB-C -> HDMI Adapter vs. Direct HDMI

Core Machine (Operating system/System info/Roon build number)
Intel NUC 7i7BNH, Roon ROCK (186)

Network Details (Including networking gear model/manufacturer and if on WiFi/Ethernet)
Ethernet LAN

Audio Devices (Specify what device you’re using and its connection type - USB/HDMI/etc.)
ROCK Core to Meridian HD621 (HDMI Audio Processor) with two connections:
1st via HDMI, 2nd via USB-C -> HDMI Adapter

HDMI calbe is amazon basic HDMI2.0
USB-C -> HDMI Adapter is “uni USB-C HDMI Cable” (HDMI 2.0)

From the Audio Processor 8ch (4 lines) AES/EBU go into a Dolby Cinema Processor

Description Of Issue

My newest toy, this USB-C -> HDMI Adapter (cheapest one I could buy) It is connected in parallel to the standard HDMI out from ROCK into the HDMI Audio Processor. I needed two HDMI outputs because I can not switch between DSP Settings via API. So there is now a “Group” that is always playing my music, meaning the output is the same on both HDMIs, with different DSP settings and I switch between the HDMIs (instead of opening the Roon app and changing DSP settings).

Now comes the clue: They sound different!

(Of course I had the same DSP settings for testing this) but they do. The USB->HDMI has more bass but a little bit diminished heights. I did not yet test this with REW though…

Can this be true? Anyone made similar experiences?

Well, I don’t quite understand what you mean, it still is Digital. If it was not “capturing everything” there would be problems like disturbances. But it plays fine it just sounds different. (I would like to add, that it’s a more delicate difference, not like the sound is not good or sth.

I get it. Using a dongle to create a second HDMI output. Are you sure that the HDMI output is set to output digital? HDMI can also output analog and that could be a reason they each sound different. It is also possible that even if digital the output format is not the same with each HDMI device.

Thanks James, I have honestly never heard of analog HDMI Audio. But, in my case it seems rather unlikely, because the connected Processor can only accept LPCM.

Well, as ROCK (whereas ALSA) is not end-user configurable I can’t comment on anything further into detail about how the audio output is handled by the OS.

Today I listened a bit more careful. And I have to say, the sound quality with this USB-C HDMI Adapter is just not good.
So, I’ll buy some others and see if they can compete; otherwise I will go for the soon available NUC8i3PNH that will have two HDMI outputs.

Can someone confirm that NUCs with two HDMI outs, both HDMIs can be used for playing music and share the same quality?