Do you use an autoformer/transformer preamp/volume control?

If so, please post here.

I've got an Antique Sound Lab Passive TX-1, and can't imagine going back to resistive volume control.

I use a Silver Rock Transformer Potentiometer, also own a Doshi Alaap V2.1 (which is an active preamp that uses transformer attenuation), and previously owned a Promitheus Signature TVC and a Music First TVC.  
I have a Prometheus TVC which is good, though I'm still smitten with my Shindo preamp so the passive TVC is only kept in reserve.  It's very good, but not in the same class as the Shindo, IMHO.
Been using a Sonic Euphoria autoformer preamp for the last 8 or so years with excellent results although I did have compatibility issues with my EAR 834p phono preamp but other than that, have no urge to upgrade. 

Silver Rock, very nice! Did you get it with the absolute phase (polarity) switch?

Hi tommylion,

I only have the original grey MDF version, although it has been modified to have a selector switch and an added input (Serge would cringe if he read this).  It's still better than any active preamp I have heard (when used in the right system), and clearly better than the MFA was (although at 2x the price).
I use a Promitheus Reference C-Core TVC. Compared it with a 4k active preamp and sent the preamp back. I know what you mean.
It is ABSOLUTELY necessary to have "enough" gain in your system for the TVC to work. Also it is very important to choose a loudspeaker with high sensitivity to make the TVC work it's magic in the system. I do not care for impedance or other stuff while using TVC. But "gain" and "sensitivity" are the key words here.