RAAT question: which DAC owns the clock?

Roon Software Discussion
1

Core Machine (Operating system/System info/Roon build number)

Ubuntu 18.04.2, 4-core Xeon v6 at 3.7GHz, 16GB RAM, Roon build 401.

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

UniFi enterprise network, core and endpoint on Ethernet at CAT6, 1Gbps Fios FTTH connection

Audio Devices (Specify what device you’re using and its connection type - USB/HDMI/etc.)

Oppo 203, connected to Anthem AVM 60 with HDMI

Description Of Issue

This isn’t an issue per se, but a question. I understand from reading about how RAAT works that “the DAC in the chain owns the bitstream clock”. That is, the DAC that is actually outputting the analog signal is what drives the delivery of the digital signal throughout the chain, and that the purpose is to minimize jitter caused by one clock having to modify the bitrate in order to accommodate a downstream clock. Therefore, the “pull rate” of the final DAC decides the clocking. Is my understanding correct?

If my understanding is correct, please help me understand my own particular setup. I believe the Oppo 203 takes the digital signal coming over Ethernet from the Roon Core and distributes it to all outputs, both analog and digital. In my case, it is sending the digital signal to my Anthem pre-pro over an HDMI cable. The Anthem’s DAC is doing the final conversion to analog audio.

But…and this is where I am confused…the Oppo is also converting the digital signal to analog using its own internal DAC so that it can present the signal at its analog outputs. Am I correct? And if so, which DAC “owns” the RAAT clock at this point? The Anthem DAC on the other end of the HDMI cable, or the Oppo’s internal DAC? Is there any possibility here that I am not getting the full benefit of RAAT because the Oppo may be modifying the clock rate to sync up these two DACs? Is this similar to a multizone playback situation?

Thank you for any light you can shed on this. (And if I completely misunderstand how RAAT keeps the clock synced, please set me straight.)

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It will show you in the signal path which DAC its using. I would imagine it will only see and use the Oppo as that is what Roon is sending material to and is the endpoint in the Chain. I would think Roon has no idea about anything else connected via HDMI from the Oppo. For two endpoints e.g. multizone you need two outputs from the core machine.

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I’d agree with CrystalGipsy - Oppo will be the ‘master’. A screen clip of the signal path diagram would be helpful.

4

Sorry, yes, I should have included a screenshot…see below. I’ve expanded the “audio distribution” step so you can see Roon’s explanation of what’s happening there.

image
F99C9C81-94E7-41D0-98BA-8600D274683F.jpg2224×1668 618 KB

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Thanks. So if I wanted the Anthem pre-pro to be the master, could I use Roon Bridge on a Mac laptop or a small Linux endpoint, and then connect that to the pre -pro via HDMI?

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Yep that would work as long as it recognises the DAC in the Anthem. It might limit to 24/96 if it’s not fully support for usb 2.0 under Mac or Linux

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This particular Anthem doesn’t have a USB DAC input. Only HDMI. Would that still work?

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Sorry yes it should.

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