Building an AB box to switch Speaker Cabs

[gutsofgold]

I always wondered why I haven't seen anybody do this. An AB box to switch speaker cabs but using only one head.

Both cabs would be of matching impedance and the amp would have its impedance switch set accordingly.

I can only see of two issues;
1 - there is that second delay while the the switch contacts flip and suddenly there is no load on the amp.
2 - the switch not handling the current of the amps output

Also, someone told me "And depending on what all components and everything are in the pedal, you may create a capacitive load that could damage the amp."

Which I can't seem to validate from my own limited knowledge.

[jayp5150]

Radial makes one. I believe it's called the Cabbone. They also have a Headbone that does just the opposite; 2 heads, 1 cab.

I'd love to know HOW it's done, I think relay switching has been suggested before on this forum.

[Ben N]

I think Randall Aiken used to have schematics for such a device (and a Head Switch) posted at the Aiken Amps website (a lot of good stuff there BTW), but he pulled them because he was concerned with potentially being held responsible for inexperienced people messing them up and doing harm to their equipment or themselves. You might hunt around for that.

[gutsofgold]

thanks I will look for that. might even try to contact him... he's offered amp building advice to me before and seems like a good guy.

the radial cab bone is pretty expensive for what it does. I'm curious as to why a passive A/B with thick guaged wire and heavy duty switch wouldn't work?

[petemoore]

I always wondered why I haven't seen anybody do this.
Probably because of the increased 'poof' factor on Xformers/tubes or other types of output.
  In general the large currents like to [or insisted upon] having a somewhat predictable load, when switching of course the load could be lifted or otherwise become quite spikey.
  Currents are large when the amp is being played.
  Some consider another hard-wired jack on the back of the amp is preferrable because of greater reliability, to remove an impedance switching from the output load continuity scheme.

[Pushtone]

Another potential problem...

IF you use a delay pedal and depending on how it's connected in the signal path or the amps EFX loop you COULD have a situation where the delay repeats are driving the STANDBY amp.
That would burn out the idle resistor for the STANDBY amp and thats a problem.

I've looked at the Radial units and they are very sophisticated for the reason of protecting your amp. The radial units use a PIC controller to precisely time the opening and closing of the relays.
They also have a fail safe mode in case the 9V power is disconnected, again to protect the amps.

the weber web site has a two amp switcher. I wonder if it can be used backwards?
https://taweber.powweb.com/store/2head.htm

[Adji]

Radial do make one called the Cabbone. I always thought it was a pretty good idea meaning you could switch to an open back cab for cleans, and a closed back 4x12 for rhythm on the fly, but I still have never got round to buying one. I was talking to a guy before who said it was based on some kind of relay switching system.