I have a Lumin U1 feeding a Lampi DAC. Note that the U1 only has a digital output not analog outputs like the other Lumin products (i.e. It does not have an internal DAC).
The Lumin U1 allows for upsampling to DSD and is a MQA decoder (not renderer). Of course, Roon does these upsampling and MQA decoding functions as well.
My questions are should I use the U1 OR Roon to perform these upsampling/decoding tasks? Is there any advantage to either? Also, if I use the U1 as a MQA decoder should the Roon Lumin U1 setting be set to decoder only OR no MQA capabilities.
The short answer is that you may try these different approaches, especially since Lumin and Roon use different upsampling algorithms, and see what sounds best to you in your setup.
The longer answer is that Roon has more options for upsampling and has more CPU power to utilize for this purpose, so it has a theoretical advantage.
MQA Core decoding in Roon and Lumin yield the same digital output. If Lumin does MQA Core decoding (set to “Decoder Only”), Lumin uses more of its own CPU power. If Roon Core does MQA Core decoding, Lumin needs to handle double the network traffic from Roon Core.