Berkeley DAC into preamp or amp ?

I've done some searching but don't see many comparisons of the sound of the BAD Alpha DAC fed through a preamp versus into the amp directly. I'm interested in the degree/range of digital attenuation needed with amps of various gain. At what attenuation level did sonic degradation (if any) become audible?
Curriemt11 - that's been my experience too, at least with a couple of Wadia CDP's I used to own. As for the Berkeley direct, do you recall how far you had to attenuate with most music? (I.e. what was the LED readout, and did large attenuation seem to affect the sound?)

Rja - what amp are you using?
Ral - sorry, I should have mentioned that. Moderately high volumes were in the 50 range. I noticed no deterioration of the sound at lower levels, but then again, I rarely listen at those volumes.
I think the input impedance of the POWER amp side is a huge factor. Some amps will never work with a DAC directly.
Rja - the DNA225 has a very high gain (about 30dB -- I owned one long ago), which is probably why you have to attenuate the Berkeley so much. In fact this probably represents the extreme test case for the DAC's attenuation. But this amp also has a high input impedance (~100K). The benefits of a good preamp which Curriemt11 mentions (e.g., expanded soundstage, more 3D images) may involve factors beyond just impedance. I'm not sure what, exactly.