Connect a combo amp to a 4x12 cab.. Can it be done?

[Logan12197]

I'm completely new to this forum and don't know much about amp building or even the electronics in my amp but I have a question.

My friend gave me a 4x12 crate cab that he had and I was hoping that I could use my digital combo amp (Fender Mustang III) as sort of a head for the cab. I do plan on buying a head eventually but it would be sweet to be able to rig something up until then.

My amp has a 3.5mm headphone output and in the back it has 1/4in return/send fx loop inputs. (pictures attached at bottom of the post)

I know I would have to open up the amp and maybe rewire some stuff and it may not be pretty but is it possible at all, without losing sound quality?

Thanks
Logan

here are pictures of everything:
imgur: the simple image sharer

imgur: the simple image sharer

imgur: the simple image sharer

imgur: the simple image sharer

imgur: the simple image sharer

imgur: the simple image sharer

[The Dude]

1) Unhook the speaker in the amp.
2) Solder a 1/4" jack to the wires coming out of the amp to the speaker.
3) Connect to 4x12 cabinet with a speaker cable.
4) If you wish to occasionally use the speaker in the amp, connect a pair of wires to the speaker with a 1/4" plug on the end and plug it into the jack from the amp when you want to use it.

[Enzo]

You would have to take the wires off the speaker in the Fender, and wire them to a jack. Then you could connect any speaker cab of appropriate impedance to the amp chassis.

[g1]

Yes you can do it like the Dude said. But you can't run them both at the same time. Either the speaker in the combo OR the separate cab, but only one at a time.
The power amp will not be able to handle the lower impedance of both, otherwise there would be jacks on the back labelled "ext. spkr". The reason it doesn't have those jacks is because it can't handle it safely.

[Logan12197]

1) Unhook the speaker in the amp.
2) Solder a 1/4" jack to the wires coming out of the amp to the speaker.
3) Connect to 4x12 cabinet with a speaker cable.
4) If you wish to occasionally use the speaker in the amp, connect a pair of wires to the speaker with a 1/4" plug on the end and plug it into the jack from the amp when you want to use it.

Awesome thanks. And thanks g-one and Enzo as well.

If I do this though and solder both wires from the amp (that were previously going in to the amp's speaker) in to a single speaker cable and connect it to the cab, then all 4 speakers of the cab will work? I'm wondering because the cab has 2 inputs

[g1]

Yes, all 4 speakers in the cab should work, (unless it is labelled as a stereo cab, in which case one jack will say "left", and the other will say "right").
Most cabs have 2 input jacks, so you can run another cable to a second cab.
But we forgot to check the impedance. To be safe, the cab you want to use should be the same impedance (or higher) than the speaker that is in the combo.

[The Dude]

The picture of the jack in the 4x12 cabinet says 8 ohms, so you should be fine. As g-one explains, all speakers will work.

[Logan12197]

Yes, all 4 speakers in the cab should work, (unless it is labelled as a stereo cab, in which case one jack will say "left", and the other will say "right").
Most cabs have 2 input jacks, so you can run another cable to a second cab.
But we forgot to check the impedance. To be safe, the cab you want to use should be the same impedance (or higher) than the speaker that is in the combo.

Ok.

The cab says impendance: 8 ohms and is 120 watts.
The amp is 100 watts and im not sure how to check its impedance, but the celestion speaker currently in it is also 8 ohms so I assume that means its safe.

Also, can you recommend a speaker cable jack to solder the wires in to? I cant seem to find anything online.

[The Dude]

Here's one:

http://www.mouser.com/ProductDetail/...CNRGPXPp1TihWi

There should be many places online where you can get this or something like it.

[Enzo]

I want to recommend not wiring it like that. If you hang a cable jack on the end of those wires, then your speaker cord will be tugging on the wires going into the amp. I highly recommend making a small right angle bracket, screw it to the sidewall of the cabinet in back, and wire a regular 1/4" jack onto the speaker wires. Mount the jack on the bracket. Now you have something relatively solid to plug a speaker cord into. And as someone suggested earlier, you can add wires to the internal speaker, put a plug on them, and you can then plug the old speaker into the jack whenever you want.

[The Dude]

Agreed, Enzo. That is the right way to do it if you have the tools and skills. Another option would be to use the jack I suggested and use some sort of wire tie (or two) to secure the jack.

I do agree that you do not want a jack just flopping about in the back of the amp.

[Enzo]

I just don't want to see someone trip over the speaker cord and rip the wires out of the amp chassis.


All the amplifier knows is impedance. It has no idea the size of your speakers or how many of them are in the cabinet - one, two, four? - all the amp sees is 8 ohms.

They used to make little cigarette pack size amps, maybe they still do, and they are cool enough, but you connect one of those to a 4x12 and it is amazing the amount of sound that comes out.

[Logan12197]

Ok thanks very much everyone. = ) I'll make sure to make sure that the jack isnt hanging loosely for the speaker wires to be ripped out.

[eschertron]

A 4x12 cabinet? You lucky stiff! Here's what I did to my 2x12 combo cab after I pulled the amp chassis out and turned it into a head + cab configuration. I added a small bracket (wood) to which I fastened the jack. Solid, and unobtrusive. Ignore the 4 and 16 Ohm selector switch for the purposes of this thread.

On the chassis side (not pictured) I simply drilled a hole and added the jack to the chassis itself. Use a speaker cable - NOT an instrument cable - to connect the speakers. 100W is a bit much for the typical guitar cord!

[The Dude]

If you're going to do it that way, you might want to recess the plate back into the amp a bit so that if the amp tips on it's back or gets slammed into anything you don't break the plug. (Not trying to be a critical a$$ eschertron.).