Hammond 1600 series output xfmr: switching for secondaries

[Gtr_tech]

A local cat who builds amps called me tonite asking about the best way to go about impedance selection on the 1600 series output xfmr's with the dual secondaries. I've seen the prefab switch at antique electronic (rotary wafer sw, marginal quality for spkr load use) and it doesn't look to be the optimum way to go. Anyone have a better way to go about this?

Hammond Mfg. - "Classic" Push-Pull - Tube Output Transformers - (1608 - 1620, 1645 & 1650 Series)

[Steve Conner]

I think you can use two switches. One DPDT to switch the windings between series/parallel, and one SPDT to engage the tap on the upper winding.

There are four possible combinations for two switches: you get 4, 8, 16 and the extra bonus setting is something like 23 ohms.

You should be able to wire any 3-pole, 3-position rotary switch to work the same. They're usually 3-pole, 4-position, but you can block off the fourth one.