Lumin U2 mini vs Mac laptop sound test

I will say this about direct comparisons. I find during A/B gear testing gear can sound very much the same. It’s when you listen over a period of time and I don’t mean a few hours I mean days or weeks or months. That is when you hear small sounds that just suddenly appear. The bells that just ring a little ring a little more natural.  the piano that comes to life.  Clarity and detail that you didn’t pick up on the first time around.  

I have had a lot of gear to test my comments on  

PK

It is great that you have discovered that. Situation and the outcomes for everyone is quite diverging. If the difference is not audible, you could probably consider selling the dedicated streamer and just stream with Mac. It is a wonderful thing.  I wish I could do that too and get back to the foobar2000 with EQ capability but, in my case, the dedicated streamer just sound better to my ear.

Some NICE ideas here. I have another point of failure that I have never heard discussed. That being your IP (Internet Provider) I have been in a 10 year long battle with mine (they have a monopoly here) and recently tried a 5g Internet option. IT also failed miserably. I do believe that the 5G idea a good one to pursue but it is still in its infancy and not really ready for primetime.
You can't just do an online speed test and expect an arbitrary one shot test to give you ANY real idea of thruput from your IP. It only takes a lost bit here and there to totally corrupt you listening pleasure. Just because you Speed test shows you have some outrageously high numbers doesn't mean you can consistently stream flawless audio or video. It doesn't even take an A/B test to notice a complete dropout of the internet connection.
One way to see how fault tolerant your system and IP is, is by looking in you modem for it's 'Fault report' page. That is assuming you have a modem of a quality that shows such information. I personally am using a Netgear right now and it has great fault reporting down to the second.

You should really start at the Actual 'Start' of your streaming system and in any environment , on your side of the wall socket, that is the IP.

That is a head scratcher. Could say a lot about your dac…I’ve found a difference between inputs on even decent dacs I’ve tried (my own dac vs others $500-$1k range). I upgraded from a decent basic rpi based streamer transport (Allo Digione) to a better designed and optimized rpi based transport (Pi2design Mercury streamer) which fires out I2s, coax, AES, and optical as options - even simultaneously.

Huge difference/improvement with coax, haven’t had the opportunity to try the other outputs yet. My dac is a Toppings D70s. I’d love to say your pre/dac and amp are such stars that it supersedes the quality of signal, however:

a.) I am subject to enormous bias as I own an SPL Elector Pre and I melt over its abilities (big crush on this pre and surely anything made by SPL)

b.) Most find that source tends to dictate much of the resulting sound

The biggest difference would be switching DACs.  And they are BIG! And a lot of them have settings for different filters.  Without naming DACs,  #1 dac was very accurate but a little on the sterile side.  Dac #2 had more bloom with a much more powerful low end.  It just depends which one pleases you.