I second Clio9's recommendation of the Lightspeed Attenuator which is a real steal new ($450), not sure what the one up for sale cost. I have used the following passives Placette RVC (and "Active"), BENT TAP-X autoformers, Goldpoint, Music Reference PiaB, and K&K TVC with S&B mkIII transformers. The Lightspeed is as good as any passive I have used in my system and it just possible I might keep this as one of my preamps till it stops working 50 years from now. Single-ended, and one input only (part of the reason it sounds so good?). Saying that, all of these passives will sound very good to excellent with sensitive amps, short ICs, and 100kohm amp input impedance.