The MDAC does not have a passive pre-amplifier - its a Digital pre-amplifier so the audio signal is scaled in the digital domain - there is no change in the Analogue gain structure.
Having too much system gain requiring you to listen at high attenuation levels is a bad thing. "Gain" is never for free, each gain stage causes a reduction in sound quality - there's no such thing as a 100% perfect gain stage.
When I hear of systems where the owners are listening with level settings of -60dB or lower this suggests to me a very badly matched system.
Simple question is how to "Reduce" something without loosing anything - you will always be reducing a signal into a "fixed" noise floor level.
You have a large bucket of water, and want to pour it into a smaller bucket - the smaller bucket will eventually overflow, and you loose the rest.... Bigger into smaller does not go.
Both optimised Analogue and Digital systems (once converted back into the analogue domain) will always face the same noise floor issue - 24bits audio is BELOW the theoretical noise floor caused by the random movement of electrons "heat" energy, unless you live near absolute zero...
Digital domain attenuation when done correctly should be no different to performing analogue domain attenuation - however practical "real world" implemention issues need to be considered.
With Digital attenuation, the Analogue system is always operating at Full gain - turn up the volume knob of any analogue amplifier with no music playing and you can hear a slight background Hum, Hiss, RF intermodulation products etc. though the speakers - this is a reality of analogue electronics.
Any Digital product by there very nature will produce RF energy. There is a practical limitation on how much you can filter this energy before you start to detrimentally impact the audio quality.
Without any form of analogue attenuation this "leakage" RF energy from the DAC is pumped directly into the Amplifiers input stage which can then be demodulated into the audio range.
Transistor inputs stages are by far the most sensitive to RF demodulation by a significant margin followed by Jfets, Tubes then MOSFET's.
Adding Analogue attenuation in front of the amplifier reduce both Audio AND RF energy - this does not happen with pure digital attenuation.
John
