Bob’ Devices: Sky 20 MC Step Up Transformer (10X or 20X by switch). I recently purchased this unit on USAudiomart from the original owner -- he purchased from Bob in January 2017. It’s in like-new condition. Clearly superior to the built-in Lundahl 9206 SUT's in my tube preamp.
The SKY 20 is switchable for 1:10 (20dB gain) or 1:20 (26dB gain). Also, there is a switch to lift ground or to connect chassis ground. The Sky 20 is easy to install. Sound with a ZYX Airy 3 -- dynamic and detailed.
The reviewers have loved this product. Here are some links for you to inspect:
Darryl Lindberg, Part-Time Audiophile, Sky 20 review, July 2015
https://parttimeaudiophile.com/2015/07/18/review-bobs-audio-devices-cinemag-sky-20-step-up-transformer/Lewis Dardick, Stereo Times, Sky 20 review,
http://www.stereotimes.com/post/bob%E2%80%99s-devices-cinemag-sky-20-step-up-transformerArt Dudley, Sky 30 review, Stereophile, Listening #137, May 2014
http://www.stereophile.com/content/listening-137
Bob does a good job of describing his product at his website.
http://www.bobsdevices.com/Moving-Coil-Step-Up-Transformers/
