Who is using their DAC as a preamp?

Disagree George

It’s your right to, but fact is digital domain volume controls in dac and cdp’s are the most transparent way of controlling the volume. But like with anything there are proviso’s.

To make sure they don’t go into "bit stipping" (resolution reduction from 16bit to 14bit to12bit the lower they go ) they should be use at or above 75% of full level.
Wadia and Mark Levinson and Bricasti ect ect in their flagship dac/cdp’s models, know this and is why they give a user option of pre-setting the analog output buffer gain/level reduction or increase, to then enable the digital domain volume control to be used at or above 75% of full.
EG: Wadia’s way of doing this. https://ibb.co/VQpdGHz. Mark Levinson was similar and Bricasti was a different way, from memory via the back panel.

Cheers George

I am using my TEAC NT-505 DAC as a pre-amp in front of two CARY 805AE mono amps. I am very happy with it. It replaced a Modwright SWL 9.0 tube pre-amp, which is no slouch pre-amp. I moved the Modwright to my other system which is all SS. A better fit to soften the SS sound with a but of tube sound. But the TEAC does great as a pre-amp. And you can configure it to by-pass the preamp/volume option to use it as a straight DAC with another pre-amp if you choose.

Using my dCS DeBussy, sold the preamp and when the Bartok arrives, it'll be hooked up to my amp. Bye bye preamp.

I use my Altair DAC/Streamer and it is my pre-amp too. It is fine.
It is nice.

I've done it for years, started with my Theta DS Pre in the early 1990s, and doing it now with the Cambridge Audio Edge NQ (which also styles  itself a DAC/preamp).  I've never bought the claims that introducing a preamp improves the sound, unless it provides better impedance matching, which is unlikely, or eliminates design problems such as distortion in the gain phase.  I've tried a variety of preamps and the only real difference I noticed was an increased noise floor (that was with a Spectral preamp, not a tube unit, interestingly enough) and some tube bloat.