Question about re-wiring a rectifier 212 cabinet for stereo

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tzoranski

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Hello all, I'm fairly new to this forum and I was hopping someone might be able to help me here. I am currently playing a Roadster combo which I love but I recently bought a Mark V head which I'm also loving. They are both great amps but very different. I would like to be able to use the MKV for some patches and the roadster for others. In a perfect world I would love to run them both using the 212 speakers in my Roadster. I know I could rewire the 2 speakers from parallel to stereo and have a speaker for each the roadster and the MKV. However I saw the Engl E212HB pro which has toggle switch that goes from stereo to mono. I would love to do this with a small box outside the amp so I could easily chose between mono or stereo depending if I want to use the MKV or not. I just don't know how this is done. Any input would be greatly appreciated.

Here is a link to a picture show the back plate of the Engl E212HB pro.

 
Relatively easy, but with consequences.

1. The speakers in the recto 2x12 are 16 Ohm wired in parallel to both jacks wired in parallel. Rewire one speaker to each speaker input jack (parallel out would then be input for one speaker, input would be input for the other speaker). This makes your recto cab stereo 16 Ohm 60W/channel max.

2. You need to use a heavy-duty high-current switch (100W into 8 Ohms is 3.5A max). In order to mimic the switch on the Engl cab, you just need a DPST that shorts the two sets of wires together (T and S of speaker cable 1 to T and S of cable 2) to make the speakers work in parallel. This would make the cab have the normal recto spec: 8 Ohms, 120W max.

3. You would need to be careful not to switch the box from stereo to mono while both amps are connected or you will short that amp outputs to each other and probably blow them up. You could avoid that by using a more complicated switch that disconnects one input when it shorts the two outputs together.

4. Note that in stereo the speaker cab is only good for 60W max from each amp, as the speakers are 60W each.
 
Elvis,

Wow, Thanks for the super detailed answer. I understand most of what you are talking about but I do have some follow up questions. Before I get into that I just have to ask you, would you be the same Elvis that answers so many questions on the TC Electronic forum for the G-system? If so, I can't tell you how much your knowledge has helped me out. Without both you and Laird, I wouldn't even be able to use the G-system.
 
I don't know much about DPST heavy-duty high-current switches. When you say 100W into 8 Ohms is 3.5A max does that mean the DPST just has to be at a minimum of 3.5A? The one I was looking at is an DPST On-Off Toggle Switch and the specs are Single Pole Rated: 10A/277V AC; 20A/125V AC; 21A/14V DC; 3/4 HP 125-250V AC.
Double Pole Rated: 10A/277V AC; 20A/125V AC; 21A/14V DC; 1-1/2 HP 125-250V AC.

Here is the link to the page. I just want to make sure I'm getting the right DPST. There are so many versions of these things.

https://www.delcity.net/store/Heavy!Duty-Toggles-Switches-!-Screw-Terminal/p_788976.h_789014

Also, after reading about the danger of switching from stereo to mono while both amps are connected makes me want to use a more complicated switch that disconnects one input when it shorts the two outputs together. How would I find this? Is there a name for this? I'm not sure how to find it. Again I appreciate you help. An input would be greatly appreciated.
 
Wow, this looks great. Thank jediguitarist! Love that name btw. My only concern is that in all the schematics it show two 8 ohm speakers being used. My boogie cab is running two 16 ohm speakers. I'm not sure how this would effect the functionality of the plate.
 
Plate will function fine, but you would have to multiply all the impedances by a factor of two. So the labels would be wrong, that's it.

Yes, I am that elvis as well. Glad to be of help, and thanks for the kind words!
 
Yep, I did a bit more reading on their site an you are right. This should work perfectly and it will definitely simplify my work. Good to know you are the same Elvis! You are very welcome. Like I said, you've been a big help. Thanks.
 
Glad I could get you pointed in the right directions. :mrgreen:
I'm doing the same thing to one of my 2x12 cabs. It'll be great to be able to use one cab for multiple heads or power amps or as an extension. I just have to take the speakers out to check the ohms. They're front loaded.
 

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