Adding input jack to combo's speaker

[Phreaky Phriday]

I have a rumble 40 combo and upgraded the speaker recently - it sounds good and i want to add an input jack to be able to use it as a cab for my trace Elliot elf head - the upgraded speaker is rated at more watts than the elf puts out at 8ohm, so it should be safe

What is the best way to go about this? Im guessing the simple solution would be to add a jack on the back as an output of internal amp and also an input jack for the speaker, then either run a 1/4" cable from rumble 40 amp to speaker or different head to speaker.

I know there switching jacks exist and look like they might be a better option that i am very open to - looks like they only have a few lugs to solder

Also, do i need special jacks to handle the 130 watts or would the same basic mono jack used on a bass guitar work?

Thanks!

 

[smogg]

This should work:
https://www.sweetwater.com/store/de...VKaVaBR07_TYlEAQYAyABEgIVuPD_BwE&gclsrc=aw.ds

 

[Phreaky Phriday]

Thank you for the quick response, one of the reviewers even said they used it for a speaker cab

 

[agedhorse]

This should work:
https://www.sweetwater.com/store/de...VKaVaBR07_TYlEAQYAyABEgIVuPD_BwE&gclsrc=aw.ds

This will work only if used for both output and input, no switching. This is the safest way to do this (and the input/output needs to be labeled).

That said, beware of switching because often the act of switching (or even plugging in) will momentarily short the tip and sleeve which can destroy some amps that aren't protected from this. On the larger Rumbles, this is compounded by the sleeve not being ground referenced, so the sleeves must be 100% isolated and this adds all kinds of new and more spectacular (and costly) failure possibilities).

 

[Phreaky Phriday]

This will work only if used for both output and input, no switching. This is the safest way to do this (and the input/output needs to be labeled).

That said, beware of switching because often the act of switching (or even plugging in) will momentarily short the tip and sleeve which can destroy some amps that aren't protected from this. On the larger Rumbles, this is compounded by the sleeve not being ground referenced, so the sleeves must be 100% isolated and this adds all kinds of new and more spectacular (and costly) failure possibilities).

Music to my ears - the simple solution is the safest thank you! I'll just add an input and output and try to label them with something glow in the dark or a cover over the output that would be closed by default (hinge above it possibly?). Idiot-proofing is critical here

 

[Phreaky Phriday]

One more dumb question, how to i pick the correct cable to run from the new input jack to the speaker? It's either surprisingly hard to find this info online or i am really bad at searching.

I have a spool of this monoprice 16AWG 2-conductor wire lying around and i'm guessing this is fine for a 1-2 foot length and only 130 watts, but don't want to catch my house on fire using something insufficient
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[agedhorse]

It's more than plenty fine for even 50' and 130 watts into 8 ohms.

 

[Phreaky Phriday]

It's more than plenty fine for even 50' and 130 watts into 8 ohms.

Thank you!

 

[Phreaky Phriday]

Thank you everyone for your advice! I implemented with a hinge that covers the amp-out jack when not in use - hopefully hard to plug into the wrong jack

 

[agedhorse]

That will work, be sure that the metal shell of the 1/4" plugs doesn't touch ANY of the grounded metal parts of the chassis or any other plug's shell as the power amp may be damaged (when using the internal speaker).

It's better if you use a speaker cable with molded ends for this purpose.

 

[Phreaky Phriday]

That will work, be sure that the metal shell of the 1/4" plugs doesn't touch ANY of the grounded metal parts of the chassis or any other plug's shell as the power amp may be damaged (when using the internal speaker).

It's better if you use a speaker cable with molded ends for this purpose.

Is this a general rule of thumb applicable to most heads and cabs or specific to how things are done with combo amps?

 

[Mike Caldwell]

Thank you everyone for your advice! I implemented with a hinge that covers the amp-out jack when not in use - hopefully hard to plug into the wrong jack

View attachment 7361511

Creative jack cover!!!
Switchcraft makes these spring loaded jack covers, for a while some speakers at least had one of two jacks with those to cut down on air noise and or keep dirt out.
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[agedhorse]

Is this a general rule of thumb applicable to most heads and cabs or specific to how things are done with combo amps?

Any amp that uses a bridged output, most class D amps (including your combo) use a class D amp with BTL (Bridged) topology.

 

[Phreaky Phriday]

Thanks for the clarification, might add some electrical tape to my connector shells

 

[Mike Caldwell]

Thanks for the clarification, might add some electrical tape to my connector shells

Look at maybe using a layer or two of heat shrink tubing.

Switch 250 1/4 inch plugs have a plastic outer shell.