Jazzyvee,
For the purpose that I perceive that you want , you would connect the device from your link as per the directions that they give under USAGE ,One instrument between two amps , with one feed output going though the ALEMBIC SF-2 and the other feed output straight to the amp . If you have multiple channels such as an ALEMBIC F-2B preamp both feeds can be mixed at DIFFERENT GAIN LEVELS levels to a mono output ,OR for that matter any multi input interface.
BIll's link may suit you just as well but perhaps with less signal control.
Wolf