DACs that do well without a preamp

Exogal Comet.  Great straight into an amp (no idea how it sounds with their ion amp)

Yet another big vote for the RME ADI-2. It is super in my big tube mono block amps. There’s no turning back and RME sends regular software upgrades. 
 

Just an unbelievable value. 

I'm currently listening to a Marantz HD-DAC1 using the variable output to a Mcintosh MC2100. The 2100 has left and right output gain levels and once calibrated with the Marantz volume control sounds wonderful. 

the rme is a good dac, many features, great value for the $ - it has an upfront and center sound, fairly flat and narrow imaging

the soekris 1541 (predecessor to the current 2541, some believe it is slightly better, but that is a separate conversation) has, to my ear, in my system, a more dimensional, fleshed out sound, much more proper imaging and spatial properties

i think the rme is terrific for headphone listening but less capable in an in room system where the user is trying to use speakers and room acoustics to recreate a realistic stereo image

otoh, the soekris dacs have a headphone output but i have heard some say that it is not the last word in sound quality with harder to drive hp's...  i am not so much a headphone guy so i cannot speak firsthand on this aspect

I find the "a preamp makes it sound so much better" a little confusing.  My only conclusion is that many people try this without doing any homework.

First - there's a huge question: how does the DAC perform volume control?  Volume control, in general, is the single largest source of sonic impairment in a preamp  (IMNSHO, but i have done a lot of actual research on this). So if you eliminate the preamp you are shifting the major sonic coloration from the preamp to an ancillary function of the DAC, which often is **awful** but occasionally is outstanding.

As an over-simplification: the only DACs to truly do volume control well are based on 32-bit, sigma-delta DAC chips, that allow for volume attenuation in the digital domain but, do to their 32 bit architecture, do not suffer this (significant) problems that most digital volume control does. If, for example, you use your PC or streamer to do this, digitally, before a regular DAC, forget it. The distortions are huge and built right into the math.  While i explained the generic result i think the only common chip like this is the ESS Sabre 9038.  Being 32 bit you can do the digital volume math, have all the truncations and still be left with more than 24 bits of resolution.

Other methods of volume control, that are cheap, and suck, include vary-int he feedback loop of an opamp, or using a buffer and a IC based resistive network. None of these are designed to be awesome - just convenient.

I use one DAC with the ESS chip directly (sometimes) and it sounds great.  Its only failing is that its analog buffers don't drive my cables as well, and i think i can hear the lack of weight -- but also the tiny little increase in transparency that comes from eliminating one stage with no other changes (except the aforementioned output drive capability and stability).

So - to answer this you really MUST do some homework not just on the chip and volume method but on the analog stage.  Or guess. Or listen to random people's thoughts which is basically guessing.