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Hammond Transformers

2/23/1998 9:45 AM
Hammond Transformers
Hammond output transformers are built with segmented secondary windings, rather than a continuous tapped winding. Their catalog gives hookup diagrams for arranging the output lead configuration for either a 4-ohm, an 8-ohm, or a 16-ohm speaker load.  
A special rotary selector switch is now available to allow you to switch-select 4,8, & 16 ohm wiring, rather than have to decide on a single hard-wired speaker impedence. This part is available from Antique Electronic Supply for $12.95, and is their part # P-H1600.  
While studying the published diagrams in the Hammond catalog, I noticed that the same strapping is used for the 4-ohm connection and the 8-ohm connection, except for where the speaker lead hot gets connected. This means that you can wire for a pair of jacks, 4 &8, with a single hookup. The result is if you had a continuous tapped winding 0-4-8, black is 0, green/yellow is 4, and yellow is 8. The strapping can be reversed with a single double pole switch, allowing the 4ohm tap to become a 16 ohm tap.  
So you can wire your amp with two jacks, one for 8ohms and the other make toggle switch selectable for 4/16 ohms. Of course, you should only plug in one load at a time. Don't ask me if you can plug in two 8-ohm speakers at the same time, because I don't know. The people at Hammond could answer a question like this, I'd guess.