Connecting a DAC directly to an amp?
The very best:
Using my MSB Discrete R2R dac's digital domain volume control direct into most of the power amps I have, sounds so much more transparent, detailed and dynamic, than any active preamp (tube or SS), even passive
Second best:
If the gain of the power amp is too high, and the dac digital volume has to be turned down too low (and starts to bit strip), it's then left full up volume and a passive pre used.
Third Best:
Active preamps.
Cheers George