Sears Silvertone Sound Systems 1940

Download a 17-page scan of the 1940 Sears Silvertone sound system catalog:

CLICK TO DOWNLOAD (10mb) : SearsSoundSystems1940

The PA, or Public-Address System, was still relatively new technology in 1940.

It’s hard for us to imagine any of the above scenarios without some sort of microphone/amplifier/speaker apparatus in play.  The human voice was not designed to clearly address dozens or hundreds of people who may or may not be paying attention.  Sure, we can yell pretty well; but the careful inflections of speech require an intimacy that cannot be accomplished on a mass scale.  Without some ‘reinforcement.’  Enter the Vacuum Tube.

I have owned quite a few of these antique units.  A few notable units have been restored; many more were gutted for parts, their chassis delivered to other uses.  One tip: beware the input transformers on these early PA units.  they are rarely magnetically shielded.  The physical orientation of the input transformer unit relative to the power transformer is crucial.   You can determine optimum positioning by placing your power transformer in the intended position.  Send 120V AC to the primary of the power transformer.   Then connect a low-impedance headphone (EG., a SONY 7506) to the primary or the secondary  of the input transformer (try both).  Now move the input transformer around relative to the power transformer.  If the transformer is unshielded, you will clearly hear an optimum (less hum audible) position.  This trick also works great for determining optimum output transformer position for hi-fi amps and guitar amps btw.