Built in volume control affects sound quality of the DAC?
No they are better, if not used too low down.
I use an MSB discrete dac with volume direct into monoblock poweramps, and the sound has never been better.
But if you have to use the dacs volume below 2/3rd because it’s too loud, you will start to slowly loose resolution (bit strip) depending on how low you go.
The answer to fix this problem insert a $49 Schiit Sys passive between the dac and poweramp/s and preset the volume on it. so then you can use the dac’s volume above 2/3rd
https://www.schiit.com/products/sys
This way you’ll get better poweramp/s for the same money as an integrated and also save big on not having a preamp if you were going separates.
Then some good dac manufacturers like Wadia have thought about everything so you don’t need the Schiit Sys, in using a volume control in dacs only up high for maximum sound quality in all systems, as they have gain links inside so you match it to your system gain and use the volume only in the top 1/3rd of full up, as you can see from the setup instructions when you get it. (Read the paragraph that starts "Premium sonic performance is achieved")
https://ibb.co/JQJMx8S
Cheers George