A preamp serves five functions:
control volume
select inputs
provide any needed gain
buffer volume control from output cable
and the least understood (but nevertheless very real):
control the interconnect cable, i.e. prevent the cable from having an effect on the sound of the system.
PVCs have no buffering or cable control, so as you decrease the volume you will find impact and bass diminished. TVCs can do the job properly if designed correctly.
Active line stages can too, although IMO too many designers fail to understand the fifth point above. If an active line stage is properly designed and built, however, it will be more transparent than the cable it is driving. So if you experience it the other 'way round, guess what?
control volume
select inputs
provide any needed gain
buffer volume control from output cable
and the least understood (but nevertheless very real):
control the interconnect cable, i.e. prevent the cable from having an effect on the sound of the system.
PVCs have no buffering or cable control, so as you decrease the volume you will find impact and bass diminished. TVCs can do the job properly if designed correctly.
Active line stages can too, although IMO too many designers fail to understand the fifth point above. If an active line stage is properly designed and built, however, it will be more transparent than the cable it is driving. So if you experience it the other 'way round, guess what?