If you want to hear what your source sounds like without these active preamp colouration/distortions you should try to use your source into your poweramp via a passive preamp, the closest to a "straight piece of wire" sound.I agree that all active preamps are colored to some degree or the other but I’m sorry I don’t agree with you that a passive pre is the proverbial "straight piece of wire". Very few setups that I’ve heard sound better with a passive pre; most of them sounded way better with an active pre (colored tho’ it might have been).
There is one setup of a friend’s friend using a passive pre, Anthem power amp & small Magneplanar (not the 1.6 model, the one smaller than that, can’t remember the model #) that sounded oh-so-transparent. But it was simply superb for vocals, trios & small groups. Once you got some rock or blues or symphonic music going, everything just congested up. :(
My brother’s set-up used a MFA passive pre that was built personally by Billington himself & used the ref-grade xformers. Super sound for many years that it gave him service. Then one day he was dissatisfied w/ the sonics & installed an active pre - OMG! even better sonics & he has not looked back.......