Wiring a switched jack for external cab

Wound_Up

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Looking to wire in a switched jack that connects the stock speaker when no cable is installed and disconnects it when a speaker cable is plugged in.

I know a 13a Switchcraft jack will work but I've also read that a 12a will work.

13a has a normally open and normally closed switch on it that transfers circuits depending on whether a cable is plugged in or not.

The 12a only has a normally closed switch that opens when a cable is plugged In. Supposedly that's all you need.

So how does this work? How would I wire the 12a switch so it works? It has 3 terminals. 1 ground terminal and 2 hots. One goes to the NC switch and one goes to the tip.

So I wire both grounds to the ground, the internal speaker to the switched contact and the output/positive wire to the tip of the jack? This way, output goes from the tip to the internal speaker when empty and from the tip to the external cable when external speaker is used.

Is that correct? It seems correct in my brain but I wanted to verify it with someone else before I try this or before I order a $15 13a "transfer circuit" jack because it won't actually work.

Thanks.

Edit: here's the info for each jack.

13a transfer circuit jack - 2 normally closed and 2 normally open switches. Will definitely do what I want.



12a shunted jack - 1 normally closed switch. Seems that it will also do what I want.


Screenshot_20240902-044414_Chrome_copy_540x1110.jpg
 
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Well that was eventful LOL!

Pretty sure I almost smoked the amp. I got no sound when I was done. I checked a few times, so I figured if something wasn't connected right, I for sure blew it up. Put it back to stock with no change.

Replaced the 12ax7 in V1 and no change.

Replaced the 2 EL84s and it works again. I still don't know if it was the tubes or what.

Then I remembered I don't even need that jack 🤣🤣🤣
 
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