Okay, here's what my Jensen notebook says. The JT-11P-1 (presumably the successor to the JE-etc.) is a 1:1 line input transformer, with a -3dB bandwidth of 0.25Hz-100kHz, input impedance of 13k when properly terminated, recommended for input levels up to +19dBu at 20Hz, at which level and frequency THD = 1%. Distortion is otherwise very low. Magnetic shielding is 30dB.
Suggested termination is 10k or greater; if you use higher resistance termination, they recommend a Zobel network of 13k in series with 620pF. It comes in a round can, 1.125" diameter, 1.063" high, with the usual Jensen two-holes-for-mounting, two-holes for wires bottom.
Primary leads are red* and brown; secondaries are yellow* and orange. (if both * leads are connected to the positive sides of their respective circuits, you get correct polarity). The white and black leads should be grounded.
Cost about five years ago was US$63 and some change in single-unit quantities. They also sold versions in plug-in cans to replace the input transformers in various machines such as Ampexes, Altecs, QSC amps and the like, most of which have slightly narrower HF bandwidth (80 or 90kHz).
Help any? Sounds like you got yourself a nice piece of iron.
Peace,
Paul
