My universal shop speaker can be used with almost any electrodynamic speaker chassis by using the alligator-clip cables, but it is easier to use a cable with a plug to match the speaker socket.  Here are some common cables using easily available plugs - bases from dead 4- and 5-pin tubes.  The sockets are shown from the bottom, and the pin numbers are the same as those for tube bases.  Note that the banana plug on each cable lead should be the same color as the wire connected to that pin in the diagram.  Note also that the field coil leads (yellow, black and gray) are usually tagged with red tracers.

Single tube output stages that use the field coil as a filter choke in the positive side of the power supply may use cable 4A, where the field coil finish (yellow) and the output primary start (red) are tied together and connected to pin 1.  The field coil start (black) is connected to pin 4 and the primary finish (blue) to pin 3.

A different single-tube configuration is used in cable 4B.  Here the field coil and output transformer wiring are kept separate in the cable.  This system can be used where the field coil is used as a choke in the negative side of the power supply or where the coil is shunted to ground.  The coil finish (yellow) is connected to pin 1 and start (black) to pin 4.  Transformer start (red) is connected to pin 2 and finish (blue) to pin 3.

Push-pull outputs can use cable 4C where the field coil finish (yellow) and the transformer center tap (red) are tied together and connected to pin 3.  The coil start (black) is connected to pin 1.  The transformer start (brown) is on pin 2 and the finish (blue) on pin 3.

Another push-pull system is used in cable 5A, where the field coil and transformer primary are again separate.  The coil finish (yellow) is on pin 1 and the start (black) on pin 5.  The transformer center tap (red) is pin 3, the start (brown) on pin 2 and the finish (blue) on pin 4.  This cable is used with a number of late '20s and early '30s Zeniths, although the Zenith wire colors don't match the colors in this cable.

A different push-pull arrangement is used in cable 5B where the field coil finish (yellow) and transformer center tap (red) are tied together to pin 1 and the coil start (black) to pin 5.  The transformer start (brown) is connected to pin 2 and the finish (blue) to pin 4.  This cable can be used with a number of late '30s and early '40s Zeniths, although the Zenith wire colors again do not match those of the cable.

Here are two speaker systems that my system cannot yet handle.  The first has a tapped field coil.

The second has two field coils with different resistances.  The low resistance field windings are usually tagged with red tracers, and the high resistance field windings with green.