What do I need to connect computer to DAC

I have digitized all my CDs. I want to connect my computer to my DAC and the rest of my audio system , which Consists of: Wadia 27 DAC,  Preamp and Amp and a set of speakers. 

I've got a music fidelity vlink.  Contact me if interested.  For the price you won't do better-and it will be cheap.
Consider a streamer from Sonore (Small Green Computer web site). I have been using the microRendu for over 5 years and it still works great. It is now almost 30% lower in cost to what I paid (with power supply). I think it is one of the best LOW cost options, there are a lot of others.

You would connect your home network Ethernet to the input of the microRendu and then output the USB into your DAC. You control everything via the computer.

This also opens up the ability to use ROON. I imagine JRiver software is also supported with the microRendu. If you use ROON you also get control via computer, tablet, and phone. If you have a direct connection via the computer to the DAC (without the microRendu) you can only control the stream from the computer.

I only mention this product because your asked about a computer to a DAC, just like I have it setup. You could also not use your computer and get an audio server (not for me though).

BTW - if you do not have Ethernet close to your DAC then there are low cost options like PowerLine products that use the copper in your house electrical to get the network to the power outlet. Very cheap.
I am concerned that transferring your CDs to files will roon the sound.........