Who is using their DAC as a preamp?

These would be two different animals

A dac with volume ability "generally" has no preamp in it, it has a low output impedance buffer stage, and a "digital domain volume control".
That buffer is usually as good as most solid state preamps output, low impedance and has enough voltage  to send most amps to give full wattage (clipping)

There are one or two dacs with "analog domain volume" just before the output buffer, that have analog inputs and can switched from the dac chip output to these analog inputs, and the output buffer as above could have "extra gain" put on it via it’s feedback and "said" to be a preamp.

Cheers George.

When I was awaiting my new Rogue RP-5 preamp a couple years back, I used my project s2 Dac ( only digital inputs) as my main pre. I was amazed how good it sounded. much better than the Peachtree nova pre I had just sold.

the RP-5, besides all the inputs and features, had just a little more “flavor”. I’m assuming due to the tubes it came with. I really cannot day the Rogue sounds better, just a little different. I did try a SYS passive a while back and felt, with the amp I currently have, that the soundstage narrowed slightly. I also tried the Pro-next again and it sounded nice. 

Since i only need one analog input for my SACD player, I was thinking I could sell the Rogue and go with a Brooklyn Dac+. 99% of my listening is my ripped library, including dad sacd rips, Qobuz and Tidal——all thru Roon