Maybe the line stage in the Playback Designs MPS-5 was a rather simple stage? I think it is unusual to see a really well thought out line stage in any DAC TBH.
sorry if I was not more clear.
the Playback Designs had a 'line level' only output, not any output stage with a volume attenuator. I was comparing;
#1-Playback Designs -> BHSE -> 009's
to
#2-Playback Designs -> dart pre input + fixed dart pre output -> BHSE -> 009's
in both cases using the attenuator in the BHSE.
#2 was easily better....and not the result I expected....at that point.
and yes, the dart pre is an 'ultimate preamp'. not the only one, of course. and pre's must be viewed in a system context.