First, an elaborate hand-operated machine wraps wire around a bobbin. Layers of steel are affixed around the coil. The transformer is set into metal housing, which is then filled with tar.  Photo 3 of 13 in Exclusive Photo Tour: See How a Respected Audio Company Manufactures Its Signature Amplifiers

Exclusive Photo Tour: See How a Respected Audio Company Manufactures Its Signature Amplifiers

3 of 13

First, an elaborate hand-operated machine wraps wire around a bobbin. Layers of steel are affixed around the coil. The transformer is set into metal housing, which is then filled with tar.