Simplest way to turn a combo amp into both a head and a cab as well?

[Triocd]

I have a small 5 watt combo amp I want to modify to occasionally act as both a head into a larger cab and as a cab so I can plug a head into the combo speaker. I don't want to drill any holes in the chassis or cab for a jack.

Is my best bet to solder on Male and female jacks on the output transformer wires and speaker? When I want to run as a combo, just connect the male and female. When I want to run as a head or cab, disconnect and reconnect to outside amp or cab. Is this the simplest solution?

[g1]

Yes. Cut the cable between the chassis and speaker. On the chassis end, solder a 1/4" female cable mount jack, like a switchcraft 121.
On the speaker end, solder a 1/4" plug.

[Enzo]

Is the combo cab open back? When I want to add an external speaker jack, I usually mount a small right angle plate of aluminum to the sidewall of the cab, just inside the rear opening. I mount the jack on the plate. No holes in the chassis, and only a couple small screw holes in the inside wall of the cab. Wire the chassis to the jacks.

[Triocd]

Yes. Cut the cable between the chassis and speaker. On the chassis end, solder a 1/4" female cable mount jack, like a switchcraft 121.
On the speaker end, solder a 1/4" plug.

Do I have to worry about the weight of the jacks hanging down and pulling on the wires/solder?

[Triocd]

Is the combo cab open back? When I want to add an external speaker jack, I usually mount a small right angle plate of aluminum to the sidewall of the cab, just inside the rear opening. I mount the jack on the plate. No holes in the chassis, and only a couple small screw holes in the inside wall of the cab. Wire the chassis to the jacks.

Yes it's an open back with easy access. If I put in an external speaker jack, does that allow me to use this amp as a head?

[Triocd]

Actually I just thought of something different. I can make a new rear panel and drill a hole in it to mount a jack from the output transformer. That way the wires are supported and it would be a little neater. I'll also mount a male plug on the speaker wires so I can connect the two to run as a combo. I'll make a new panel because I don't want to drill into the original panel.

[Enzo]

There are many ways to do this, of course. My version has a little jack plate. To be more detailed, I then run the amp wires to the jack. Now there are two choices. One is to wire a plug to the speaker, and plug it into the jack. Then you can unplug that, and plug an external cab into the jack when you want. The second choice is how I handle it. The jack I select is a cutout jack. I wire the amp to the jack, and the internal speaker to the jack cutout contact. That way, when nothing is plugged into the jack, the amp output goes right through the jack and on to the speaker. It is as if the jack were not even there. And when you plug an external cab into the jack, the cutout contact turns off the internal speaker and your external cab is running.


If you put inline jacks and plugs on the wires, you were concerned about the weight on the wires. Good point. The thing to do is to use a cable clamp to anchor the amp wires to the wall of the amp cab. I am sure you have seen other amps with reverb cables or power cords clamped to the cab wall. Likewise the wires from the speaker to a plug, make them long enough so you can also anchor them to the wall near the amp wires, with enough extra length so you can plug them together or not.

Certainly you can make a new rear panel and drill that instead of the original. In my own opinion, that leaves the problem of where to store the original panel. It won't store inside the cab, so you need to keep it somewhere until you sell the amp. But if you do make such a panel, you might consider my cutout jack wiring. That way the internal speaker won't have a plug sticking out the back, but the jack will be there to plug an external cab into. But if wiring such a jack is beyond you, then at least put a right angle plug on the speaker wires.

[Triocd]

There are many ways to do this, of course. My version has a little jack plate. To be more detailed, I then run the amp wires to the jack. Now there are two choices. One is to wire a plug to the speaker, and plug it into the jack. Then you can unplug that, and plug an external cab into the jack when you want. The second choice is how I handle it. The jack I select is a cutout jack. I wire the amp to the jack, and the internal speaker to the jack cutout contact. That way, when nothing is plugged into the jack, the amp output goes right through the jack and on to the speaker. It is as if the jack were not even there. And when you plug an external cab into the jack, the cutout contact turns off the internal speaker and your external cab is running.

If you put inline jacks and plugs on the wires, you were concerned about the weight on the wires. Good point. The thing to do is to use a cable clamp to anchor the amp wires to the wall of the amp cab. I am sure you have seen other amps with reverb cables or power cords clamped to the cab wall. Likewise the wires from the speaker to a plug, make them long enough so you can also anchor them to the wall near the amp wires, with enough extra length so you can plug them together or not.

Certainly you can make a new rear panel and drill that instead of the original. In my own opinion, that leaves the problem of where to store the original panel. It won't store inside the cab, so you need to keep it somewhere until you sell the amp. But if you do make such a panel, you might consider my cutout jack wiring. That way the internal speaker won't have a plug sticking out the back, but the jack will be there to plug an external cab into. But if wiring such a jack is beyond you, then at least put a right angle plug on the speaker wires.

Thanks for the info. I originally tried a cutout/switching jack, but I may have wired it wrong because the speaker didn't work and the tubes got hot real fast. I took it out immediately. Also, with a cutout jack, I'm not able to use this combo amp as a cabinet, right? For example, if I want to take another head and plug into the speaker of this combo amp, would a cutout jack allow that?

[Enzo]

To use it as a cab, I suppose a second jack would work. it would be in and out, like an FX loop but for speakers.


yes, you miswired the jack in your old attempt. I suspect you had the cutout wired across the output instead of in series with the speaker.