Can a California Audio Lab Delta D/A be used with a FLAC USB music collection?

Yeah it'll work but the BluSound persistent queue is a PIA for playing local files.

 If I remember correctly, the Delta was a transport. The Alpha and sigma were the DAC units. I had a Delta and Alpha pair way back when. The Alpha was an good DAC back then. The Delta was a mediocre transport. The problem is that neither the Alpha or Sigma have a USB port. You would need to buy a converter to connect it to your computer. I would just buy a streamer or modern DAC.

 I use modern DAC with USB input that is connected to a laptop computer. I simply use Fubar2000 to play files. If you decide to get a modern DAC, check to see if it needs USB drivers. A lot of the newer DACs don't need drivers. And driver availability for new versions of your operating system could be a problem.

Thank you, LostBear,
Thank you for writing.  You are correct, it is the CAL Alpha that is its D/A.  So, I COULD use the CAL Alpha, but I would need a converter. Is this simply a cable with USB at one end and RCA for the Alpha at the other end?  So, I would plug the USB which has the music collection into the converter which would get the digital infor into the D/A of the CAL Alpha, but how will I be able to choose albums, artists, etc. since no screen will be available? Your assistance is much appreciated

 You would need to use a computer to play the files. I use a free program called Fobar2000 on a windows computer. The USB cable from the computer goes to a little usb to S/PDIF converter box. You run a digital cable from the converter box to the Alpha.

 I looked into all of this when I got a new laptop with windows 10.  The USB DAC I had was older and there were no windows 10 drivers.  So I needed a converter that did not need drivers. In the end I felt it was easier just replace the DAC. 

 The Alpha is a good 30 years old. I think I would just  get some type of streamer or USB DAC. I doubt it would hold up that well against a modern DAC. I can't remember what I replaced mine with. I do remember that I replaced the Delta with a used Theta Jade. The difference was night and day. Originally I had a CAL Tempest 2se which I loved. I lost it and got the Delta and Alpha to replace it. But I never felt they were as good.

What is the inputs on the DAC?

The 2i is SPDIF out only.

what is SPDIF?  I believe the inputs are RCA and a digital link

My Alpha has USB, Coax, Toshlink and another connection I've never heard off.  I'm using it now with Coax but I have used it with Toslink in the past.