Use bass combo as occasional speaker cab

[bitey]

I know this is a simple thing but I just want to get it right -

I wish to use my Fender 25B bass combo as an occasional speaker cab (only).

This combo has one speaker and a mono output.

I intend to add a socket to the rear so that when a 1/4" jack is inserted it connects to the speaker and disconnects the combo's built-in amp.
When the jack is pulled out the combo's built-in amp is reconnected to the speaker.

Q1. Can I just use a normal stereo 1/4" jack socket to accomplish this?
Q2. How do I wire it up?

thanks guys

[eschertron]

Short answer. There are jacks to do this, but a normal stereo 1/4" jack is not one of them.

I don't have the part numbers in front of me, but this info will give you a head start on looking it up. It will be described as a switching jack, but again there are different types. Hopefully someone with the database at fingertips will chime in.

[Dave H]

Short answer. There are jacks to do this, but a normal stereo 1/4" jack is not one of them.

I think it could be done with the double pole normally closed switching jacks I have (Cliff?). Connect the combo amp's outputs to the non moving contacts of the jack socket then connect the jack socket's moving contacts to the combo speaker. With no plug in the socket the combo amp will be connected to the speaker as normal. Insert a plug from the second amp into the socket and the combo amp is disconnected and the second amp connects to the speaker. I'm thinking out loud. I'll have to draw it to be sure.

[nevetslab]

Switchcraft L-12A is what you want. sturdy metal bushing, 3/8" long, open-frame jack that lasts decades. I thought Switchcraft still had pdf data sheets on that jack, but no longer. I've attached the data sheet for the type 12A....both are Tip/Sleeve with Normal (switching contact that brakes when a pug is inserted. BTW, you're inserting a PLUG into the Jack...jacks are female. Your main challenge is mounting the jack you decide on. typical speaker cabinets are 3/4" thick wood...sometimes less. As the busing on this L-12A jack is 3/8" long, but it has a nut & washers, you're left with about 3/16" to 7"32" of thread for the panel mounting. Usually this is done using a Forstner bit to counterbore a recess into the panel. Could also do it with a speed-bit, though it would open up a hole that you still have to further open to 3/8" dia for the bushing. Speaker is wired to the Sleeve and Tip terminal, with the amp 's output wired to Sleeve (GND) and Normal. External plug breaks the normal and you're in business.

Switchcraft 12A_1_4 in jack.pdf

[ChopSauce]

I also tend to prefer Switchcraft, myself, cos they don't melt if you touch them with the iron tip (oops... ) but the Cliff type should work just fine too.

The wiring should be obvious when you'll have the jack at hand. I searched my documentation but couldn't really find a schematic and the example I could take picture of features wires of the same colour

You wouldn't be the first to wire it reversely - maybe (or not ;-) so take care (I use a plug to check the contacts before soldering, in doubt)

Tell me if you do need a picture, anyway.

[bitey]

I also tend to prefer Switchcraft, myself, cos they don't melt if you touch them with the iron tip (oops... ) but the Cliff type should work just fine too.

The wiring should be obvious when you'll have the jack at hand. I searched my documentation but couldn't really find a schematic and the example I could take picture of features wires of the same colour

You wouldn't be the first to wire it reversely - maybe (or not ;-) so take care (I use a plug to check the contacts before soldering, in doubt)

Tell me if you do need a picture, anyway.

Yes, if I had a socket to hand I could figure it out but I don't want to buy the wrong one - and also I don't want to poss fry (either) amp.
I would appreciate a picture if you can come up with one - cheers

[bitey]

Thanks Dave - that's helpful

[ChopSauce]

Yes, if I had a socket to hand I could figure it out but I don't want to buy the wrong one - and also I don't want to poss fry (either) amp.
I would appreciate a picture if you can come up with one - cheers

Well, nevetslab already provided you with the reference for the Swichcraft (12A) one. I'll post a picture of the wiring latter, if you can wait -

[nevetslab]

Here's a photo of the Switchcraft L-12A, it being a 3/8" long threaded bushing, with nut & washer, and the terminals labeled as you'd use it.

[bitey]

- thanks for taking the time to do this ...