I have a peavey valveking 112 and i want to make a 112 extension cab for it, but in the manual it says that when you plug in an extension cab, the speaker in the combo will not operate. so i want to know if there is any way to be able to use the speaker of the combo along with the speaker of the extension cab?
Don't think so, unless you're into some serious tweaking/zapping yourself.
What happens when you hook up your combo to an extension cab is that it disables the speakers and the amp basically becomes a head. What you can do is send your amp into someone who specializes in making housings for combo pre and power amps and just use the combo's power and pre section as a head.
Disconnect the combo speaker for good and connect it through the extension cabinet out and to add an extension cabinet, use a Y connector. But I'm not sure if there won't be a problem with impedance...