23-Jan-2020, 21:53
(23-Jan-2020, 21:03)David A Wrote: @struts
Looking at your results, I'd say your conclusions are correct. It looks as if Audivarna automatically perform the first unfold unless you specify that the device receiving the stream can do the first unfold itself and to do the first unfold the receiving device has to be at least a Decoder.
OK with the help of a kind soul over on the Audirvana board and a lot more background reading I think I am slowly getting my arms around this. A couple of aspects of my understanding were not quite correct. The bitstream sent on after the first unfold does differ (even if the samples as passed are the same bit depth and sample rate) depending on the setting of "Use as". If "not MQA" is selected a clean 24/88.2 (24/96) payload is passed (iow no "origami hidden below the noise floor) whereas if "renderer" is selected a payload of the same resolution, 24/88.2 (24/96) is passed with the second and third unfolds still tucked up inside. The latter can be unfolded by the Dragonfly to full 24/352.8 thereby lighting the purple "MQA" LED. This despite the USB interface limit of 96KHz. Now I understand the joke about MQA helping hi res "duck its head under the USB door".
So, @eladeb, the answer to your original question is that when driving the Phantoms with Audirvana "Auto-detect MQA devices" can be set to whatever you like (the Phantom is not MQA-compatible so it doesn't matter) and "DAC not detected as MQA, use as" should be set to "not MQA". This will set Audirvana to perform core decoding (first "unfold") and pass a clean 24/88.2 (24/96) signal (with no concealed MQA payload) to the Phantoms.
To your question about whether I noticed SQ differences in my tests above I have to admit, with an embarrassed blush, that I didn't even connect headphones to the DACs when performing these tests, I was purely noting what resolution the LEDs on each device were reporting that they were receiving. Apart from it being a bit of a rushed test the main reason was that both units have 3.5mm headphone sockets and the only headphones I had to hand had a 3/8" jack. I have a pair of nice Audio Technica ATH-ESW9s somewhere which I will dig out and do some comparative listening with sometime. Another project for the list!
So I think your conclusion is mostly correct. Setting "use as" to "not MQA" should still get you most of the MQA benefit (and you should be able to hear a clear difference compared to "MQA decoder"), nevertheless, room correction will probably buy you a lot more in terms of SQ-improvement.
But thanks anyway for the question which helped me finally get my head around MQA!
