Adding an external speaker Jack to a combo

Alan W

Well-known member
I just got (and will post about it after I’ve had another few weeks to get to know it better) a small combo amp, single ended, from about 5 watts to 15, depending on the tube used. It has a 10 inch speaker in it, which is what I wanted; but I also want to add the possibility of running an external cabinet instead. The way I would like to do this is to mount a single pole, switching Jack on the cabinet, and wire the original speaker to this, with one lead going to the prong that only is connected when there is no plug in the Jack.

I know as a circuit, this will work. I’m just concerned that the connection to the built in speaker is really just that small pressure point. (On the other hand, it’s that same sort of pressure point when you insert a plug.) My other concern is that, even though I “know” that leaving one lead (only) attached to a speaker should effectively remove it from the circuit, I may be missing something… And, since it AC, it shouldn’t matter which wire I use from the switch.
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Why not use a 2 pole switching jack? (Insulated/isolated)
I don't know that I've ever seen a single pole switched on an amp output.

At 5-15w, this style should be good. Though, I like speakon connectors. A lot harder to accidently unplug
 
Yeah, I would really like to see Speakon become the standard. The cabinet I’m most likely to use has Speakon, and I pretty much always use an adapter cable with it. In this case, I’ll be mounting the Jack just inside an opening on the back, facing sideways. The amp is so light (~25 pounds) that I’ll probably pull it over before the plug comes out.

I’m tempted by the open frame Switchcraft (12A) because 1, I like the greater grip strength that their open frame jacks have, and 2, I have several in hand… I may have some of those Reans also though, pulled for Lovetone clones, which if I remember, use a lot of them in the extra ins and outs.
 
Courtesy of singlecoil.com

View attachment 108582
Yes, that’s exactly what I’m planning on. I was concerned that I was only switching one (the non ground) with this style of switch. Even though from a simple circuit view it should be safe, I still had my doubts, and posted this question both here and on the amp tech forum on the gear page. I’ve got my parts all in and painted the small aluminum channel I’m using to mount the jacks yesterday; am hoping to do it this afternoon.
 
I’m no amp circuitry guru by any means I just happened to stumble across that diagram shortly before you posted.
 
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