Here’s a photo of a fully assembled FAB3110 Output Transformer Module.

You can use any API-type output transformer on this module. Shown here is an EA transformer, but you can also use transformers from Cinemag, Crimson Audio, etc…

There is a Logic control on the FAB module, allowing you to switch your transformer ratio from 1:1 to 1:2 (+6dB gain). Just apply any +3.3V, +5V or V+ voltage on this logic pin.