If your system is passive friendly (amp with high gain, low input sens., appropriate source, and reasonably efficient speakers) then there are absolutely no drawbacks at all to my ears in using a transformer based passive attenuator. I have a custom preamp using S&B trannies and it has bettered many other preamps, mostly tubed and a couple of passives, in my system. It has the body and weight of a tubed device, but the transparency you expect of a passive. And hands down the best bass of any active preamp I have heard.
Oz
Oz