Which DAC as a preamp?

I owned sources who has a pre amp inside.

All should get out of the habit of saying this. It should be "I have a source with digital domain volume control"

As "most" sources that have volume controls done in the digital domain DO NOT have preamps in them, they have standard low impedance output buffers. No preamplifiers!

Only if the specs of the source say that it can output more than say 6v to say 20v can you say it has a preamp which pre amplifies.

If it’s below 6v then it’s just a dac/cdp that happens to have a digital domain volume control with output buffer with or without some small amount of gain, to bring it up to Redbook standard of 2v some kick it a little higher 3 or 4v.

Cheers George

"Which DAC as a preamp?"

Go for one that has settable max analogue gain output, so you can use it’s digital volume control in the top 25% part of it’s range.
This way your sure of not "Bit Stripping". Just like Wadia and Mark Levinson do on their Flagship models.
Today I know M1 Bricasti has it, there must be others as well, these are the ones I would go with as they know about "bit stripping" that's why it’s introduced. As the Wadia attached shows.

https://ibb.co/d69hD9

Cheers George

Class D really benefits from a Class A input stage....solid state or valve.

All amps I know ss or tube have Class-A input stages, I've yet to see one with class-A/B

Cheers George

tfats

Your going in the right direction for the most transparent/dynamic sound, by looking for a dac that has volume control in it.

But there are two ways this volume control can be done in a dac.
1: In the "digital domain" which to is best "if" the volume is not reduced too far, so to introduce "bit stripping" (a reduction is resolution), this can happen if the volume is reduced below approx 75%

2: A dac with an analogue domain volume control, no "bit stripping" problems with these. There can be impedance matching problems to an amp if the amp is lower than 33kohm input impedance.
The earlier Red Dragon’s had a low 12kohm input, they saw this error for some pre’s and the later MkII Red Dragon it’s said to be much higher (they don’t say how high) to accommodate these pre’s

Red Dragon: " Red Dragon Audio designed the M500MkII with customer feedback at the forefront of the process. Increased Input Impedance allows our amps to be paired with all preamplifiers - even the most esoteric tube preamps."

Cheers George