Champ impedance switch wiring question

[HansVG88]

I am working on my first amp build based on a champ 5f1. I have installed a external speaker jack that switches so the internal (4 ohm) will not play when another speaker is used. I am thinking about replacing the OT with one that has 4 and 8 ohm taps and wire it to a selector switch.
Do I need to (or should I) try to figure out the wiring so only the external speaker will switch so I don't mismatch the impedance on the amp's speaker?
I am new to this and I would appreciate any help!

[Chuck H]

Mesa used to use some funky switching for the internal vs. external and impedance range jacks on some of their combo's. It just confused people. The standard way of just having an output jack on the chassis that you can plug the internal or an external speaker into seems like the best way to me. Make it multi impedance if you like.

With your original design you would simply plug in the external speaker. This prevents accidentally running the amp into an open load, and is a good idea, but, it also prevents you from being able to run the internal speaker simultaneously with an external speaker. And, once you add impedance switching you now have to be sure the switch is in the right position to avoid running the amp into an improper impedance anyway. So I say just do it the regular way, with an output jack and an impedance switch. Or possibly an output jack, a parallel external speaker jack and an impedance switch. That way you could plug in an external cab, still use the internal speaker too and correct impedance with the switch.

Chuck