DAC-Preamp having these specifications?

There are essentially 4 ways to get volume control:

1) analog volume control that changes the gain of an active stage - can be controlled digitally

Disadvantage - change in gain characteristics at different volume levels and signal levels can affect dynamics or cause varying compression.  The lower the volume, the higher the distortion.  It usually adds a stage to the signal path as well, adding to the compression and distortion.

2) attenuation with resistors or optical controlled resistors

Disadvantage - large resistances in the signal path add thermal noise and can affect impedance and frequency linearity if used on outputs.  If this attenuation is between stages, the lower the volume, the higher the distortion, the lower the S/N ratio.

3) modify the digital words using DSP

Disadvantage - DSP usually impacts SQ if more than about -9dB of attenuation is required, even with the best DSP software, such as Sonic Studio.  For less than -9dB of attenuation, it works pretty well.  The difference between the quietest tracks and the loudest tracks can easily be 12dB.

4) change the reference voltage that the D/A conversion uses.

Disadvantage - it is difficult to turn the volume down to zero.  It can be quite low, but never zero.  Overall, the best solution of the 4.  Extremely low distortion and it gets lower as the volume is decreased, not higher like the other techniques.  No added resistance or stages to the signal path.

Steve N.

Empirical Audio

No different than an external passive resistive attenuator. Changes impedance and can cause roll-off. Adds thermal noise. Critical to use low-capacitance interconnects with this type.  I stay away from these myself.

Another type of volume control I failed to mention is by transformer with multiple taps. An autotransformer is usually the design. This is typically not done in a DAC. Never seen it in a DAC. Quite expensive if done right with quality transformers, but this method has very few drawbacks. Only saturation of the transformers is an issue. Mostly the disadvantage is cost.

Steve N.

Empirical Audio

So the DAC3 uses method 2