Asynchronous USB vs. SPDIF with regard to DAC upgrade

I have experience with the Berkeley Reference Alpha 3 and it is an excellent DAC. While you are looking at the lower tiered model, from the characteristics of the reference... I would unquestionably go for it. Natural and detailed. I would steer clear of the Weiss. Too detailed oriented and analytical. Given you Connie J clearly musicality is something you care about. SP/DIF was the standard digital interface for decades (?). USB came along later because of computers... someone realized that people would like to connect computers to audio equipment.

So, the USB DAC was created... some companies chose to incorporate it into their DAC... some left as an add on. Most folks ten or twenty years did not require one. USB puts more of the processing on the DAC... since it was not a purpose built interface for audio. Which sounds better in a system is dependent on which component on yours is better... your DAC or Streamer. You have a great streamer. 

I would use SP/DIF. 

Hi @kjl1065 yes this gets confusing doesn't it?  You are spot in in that with USB, the DAC controls the clock, and with other connections, the streamer controls the clock.  So it is really dependent on your DAC and streamer.  I have two systems, and one (Master Fidelity  Nadac C and D wants USB, while my Grimm MU1 upsamples nicely for my Tambaqui and uses AES for best result.  I did learn this also: some DACs need the power which is inherent in USB and some do not.  My Aries G2.2 allows me to turn off the power in the USB, thus reducing noise.  I guess I would want my streamer to support both, and then determine if you like the sound of a particular DAC which to use.  So that would be a question to Berkely. 

While not our question, in that pre range have you considered the Tambaqui?  I find it exceptional, especially with the Grimm MU1 streaming to it.  I also like that the Grimm MU1 runs Roon core at the same time.  I also have listened to the MU2, which is streamer and DAC, and it is very good.  Since it is internal streamer and DAC, it negates your question entirely!

It’s honestly a little complicated.  It’s true that USB Asynhcoronous is theoretically the best jitter performance, but it’s also true the Berkley Alpha is a very good sounding DAC.  I'm not sure how they deal with signals > 192kHz or 32 bits, and that may be the big limitation of S/PDIF, which USB 2.0 overcomes. 

DAC’s do very well with the "normal" jitter of a modern streamer.  The PLL circuit and FIFO buffer will adapt, and so long as the streamer’s clock doesn’t suffer from truly terrible jitter performance you should be OK. 

An alternative however may be the Bricasti. 

The overriding factor should be which DAC will best give you the sound characteristics and improvements you’re looking for. 

Your Lumin U2 Mini can be eliminated as I mentioned in your other thread. It’s a good streamer but it doesn’t beat network cards in Bricasti or Meitner. If you’re a Roon user, just get the highest quality DAC with built in network card. Examples - Bricasti M21, Meitner MA3i, Mola Mola Tambaqui.
I eliminated Aurender N200 with Audience Studio One USB cable, with Meitner MA3i. I compared the crap out of it with and without Aurender, using native conductor and using roon. I preferred the Meitner as Roon end point as it sounded better to me. Sold the N200. I can tell you that the N200 is noticeably better than Lumin U1 Mini and therefore it’s also better than the U2 Mini as I’ve not heard of U2 Mini being an upgrade over the original. 
Keep your options open.