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Converting Combo to Extension Cabinet

lmfreeman9

lmfreeman9

Sep 1, 2007
2,832
168
Arizona
#1
I was given a crate 100 watt combo with a 15" JBL that I'd like to use an extension cabinet. I searched but couldn't find a thread that covered this.

I'm looking for the simplest way to do this as I am not skilled with electronics.
 
#2
just get yourself an AB/Y switch!!!! run em both at once!

thats what I do.... in fact, I run one "wet" (effects) and one clean!

this way I have a dedicated eq for effects and I dont lose any tone from my main rig!

Morley makes one, like $45! have fun!
 
#3
I'm not sure that the AB/Y switch is what you're looking for, but I just did this with a very similar Crate combo amp. It's not very difficult either. I set mine up so that there's a 1/4" jack in the cavity of the amp "head" area so that I can use the amp portion, or disconnect it to use my own head. What you'll need (however you choose to do it) is a 1/4" jack and some way to mount that jack in the cabinet area. Feel free to PM me for specifics, but it isn't that tough, especially depending upon how pro you want to make it turn out. I wanted mine to be perfect, as I'm actually borrowing the combo (I was told it would be ok to mod it this way) so I wanted it to be an easy thing for the owner to understand.

Hope that helps at all.
 
#7
Remove the amp part from the box and saw off the part that used to contain the amp (or leave it on there if you think you'd ever want to turn it back into a combo). All that's left to do is drill a hole to mount a 1/4" jack on the back of the cab and wire the + and - from the jack to the speaker.

tools required: screwdriver, saw (optional), drill, solder iron.
 
#8
lmfreeman9 said:
Crate=extension cabinet
Amplifier is a Markbass LittleMark Combo
Click to expand...

Thanks!

Do you want the Crate to be able to function as a combo when it's not an extension for the MarkBass?

Do you know if the impedance of the JBL is 8 ohms or 4 ohms? I suspect that the Crate wants a 4 ohm speaker for maximum power transfer. The Crate combos that I've seen are provided with a speaker of minimum impedance for the amplifer. If the amp has an extension speaker jack, it's connected in series with the internal speaker.

If the JBL is 4 ohms, you won't be able to use it with the LM combo as the LM II head is rated for a minimum load of 4 ohms, the internal speaker/speakers present an 8 ohm load so the minimim impedance of an extension cabinet is 8 ohms (two 8 ohm loads in parallel are equivalent to one 4 ohm load).
 

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