Gain of line preamplifier

Atmasphere what if now you throw in a shunt 42 stepped attenuator into the mix. Now the input impedance lowers as the volume is lowered. This will roll off the bass especially using tube phono stages or tube cd players.

Just a raw shunt by itself does not make for a good volume control due to the problem you just described. The source really needs to see a constant load regardless of the volume control setting, otherwise the control will take on tone control aspects.

Atmosphere do you know of a 42 stepped attenuator with only two resistos in line at each click that is not a shunt attenuator?

Yes. In such a scenario the switch is selecting a different pair of resistors for each volume control position.

A shunt attenuator typically only switches one resistor.