Tks. Final question: So I ONLY get the second unfold IF my iDevice has the Sparrow directly plugged-in to that iDevice, correct?
In other words, the fact that the Sparrow is plugged to the Mac mini’s USB does NOT extend its MQA rendering capabilities to the signal spread by Roon through my network?
Correct. The second unfold can be only done by an “MQA renderer”, which in your case is the Sparrow and nothing else. And think about it as that “the second unfold” can only go to the analog domain - through your Sparrow’s 3.5mm or 2.5mm headphone jack. And nowhere else.
A DAC, MQA or otherwise, only feeds the sound system or active speaker it is directly connected to. The DAC is receiving a digital signal by way of ethernet or USB. Then, it converts that signal to analog and sends it to the connected sound system or speaker.
And does that concept also apply to the Sparrow’s other DAC capabilities? For instance, if the mini without the Sparrow accepts no native DSD but the Sparrow does, having the latter plugged into the USB would help me listen natively to DSD on my iPhone (through Roon)?
Sorry, I just need to understand this; I originally thought that Roon’s proprietary network implementation allowed it to “transport” a core’s DAC-ified stream all over the network.
No, I explained this. There is no such term as “DAC-ified” stream. It’s a digital stream until it is converted to analog by a DAC (digital to analog converter). At that point it goes to your speakers or whatever you use to create sound waves.
That said, as already explained, the Roon software can do the first MQA unfold which converts 44.1 to 88.2 and 48 to 96. This is still a digital signal and can be sent to all of your Roon end-points. At each of those end-points, there will be a DAC, MQA or not. If an MQA DAC, it can render the final MQA analog signal to the attached amp and speakers.
A Roon server can do three things: (1) deliver digital audio files to one or multiple “end points”, (2) perform various digital audio-file conversions (eg, upsampling or DCD to PCM conversion) [and then do (1)], or (3) MQA core (“first”) unfold [and then do (1)].
A Roon system does not support transfer audio streams from end points or between end points. Roon “ecosystem” supports iPhones/iPads as either end-points or remote controls.
An end-point can consume a digital stream from a Roon server and play it. Eg, in your case a Sparrow can receive a DCD stream or MQA core/first unfold, process it and convert to sound. But it cannot send processed data to any other Roon devices.