DIY Cab switcher

[Fred Pantalone]

I've built myself an inexpensive and simple AB cab switcher for use with my class D head and I'd like to share it and also ask for feedback from the knowledgable TB folks who have helped me in many ways over the years. From what I can tell, it should be fine to use with a class D amplifier even for hot switches.

It's based around an 8 terminal rotary switch that is rated for 660 V / 20 A and functions on-off-on (i.e. it will break for it makes the next connection). Can this switch handle the voltage from a 350 W amp (I have a Genzler Magellan 350)?

Here is the switch (USA/Canada):
Heschen Universal Rotary Cam Selector Changeover Switch, SZW26-20/D202.2D, 660V 20A, ON-Off-ON, 3 Position 2 Phase 8 Terminals, with Master Switch Exterior Box (Bigger Box)
at amazon.com
at amazon.ca

Connected to this I have 3 sets of speaker cable pairs and Speakon plugs. The side with one pair goes to the amp and the two that come out of the other side go to the cabs. It's really a very simple device. Here are some photos (final product, wiring sketch, gut shot of amp-side wiring - ignore everything else that appears in the third photo).

I haven't tested it yet but I probably will tonight. I've tested the pins for continuity to make sure I've wired it properly and there are no shorts. This is not meant for stage use, it's only for auditioning/testing/comparing different cabs.

Any feedback would be greatly appreciated. I hope this will be useful to somebody someday (as long as it works!!).

Note: DO NOT use this with a tube amp!

 

[KevInDaBassment]

Won't you be underpowering the other cabinet when it's switched off?!?!


j/k! Looks like a cool piece, not sure I own enough cabs to justify having one though

 

[Fred Pantalone]

Won't you be underpowering the other cabinet when it's switched off?!?!


j/k! Looks like a cool piece, not sure I own enough cabs to justify having one though

I only have 2 cabs at the moment, a 212 and a 410. I just wanted to have a way to switch between them quickly to compare them. The cost of materials was so low it was easy to justify... You really just need to purchase the switch box and then find some speaker cable (I used 14 AWG) and some plugs. 1/4" or Speakon, whatever you have that works...

 

[agedhorse]

That's probably isolated enough since each pole is switched independently. That's also a fairly expensive switch (if it's genuine).

I would recommend using commercial jacketed speaker cable and genuine Neutrik branded SpeakOn plugs not knock-offs.

 

[Fred Pantalone]

That's probably isolated enough since each pole is switched independently. That's also a fairly expensive switch (if it's genuine).

I would recommend using commercial jacketed speaker cable and genuine Neutrik branded SpeakOn plugs not knock-offs.

Thanks for your input, I appreciate it! I found the switch to be pretty cheap considering it came with the box. I agree about the plugs, the ones I used are garbage and I wouldn't take them out of the house. If I were going to use this any more than rarely I would definitely beef up the plugs and cabling.

Will the specs of the switch stand up to current and voltage that are being sent through it?

 

[Redbrangus]

Will the specs of the switch stand up to current and voltage that are being sent through it?

More than sufficient.

 

[agedhorse]

No need to beef up the cable, 14 gauge would be plenty big, it's just the wrong kind of jacket to use. The knock-off plugs can damage the SpeakOn jacks sometimes, that's why I beg folks to avoid them.

 

[Fred Pantalone]

No need to beef up the cable, 14 gauge would be plenty big, it's just the wrong kind of jacket to use. The knock-off plugs can damage the SpeakOn jacks sometimes, that's why I beg folks to avoid them.

Ok, thanks again. What's wrong with the jacket for this application?

 

[agedhorse]

Ok, thanks again. What's wrong with the jacket for this application?

It doesn't match the internal dimensions of the strain relief, and the soft vinyl can be cut easily with the sharp edge of the strain relief. Also, it looks like a stupid large wire gauge, that's is hard to terminate in a SpeakOn housing without wild strands that risk short circuits. A correct speaker cable will have both a round overall jacket and inner conductor insulation, the strain relief grips on the outer jacket which fits the jaws of the strain reliefs.

 

[Fred Pantalone]

It doesn't match the internal dimensions of the strain relief, and the soft vinyl can be cut easily with the sharp edge of the strain relief. Also, it looks like a stupid large wire gauge, that's is hard to terminate in a SpeakOn housing without wild strands that risk short circuits. A correct speaker cable will have both a round overall jacket and inner conductor insulation, the strain relief grips on the outer jacket which fits the jaws of the strain reliefs.

Ok, got it - all excellent observations and considerations. It was difficult to get the 4 strands through that one strain relief. If this thing gets used frequently I'll consider drilling out a third slot and adding a strain relief and using a more appropriate cable type and of course Neutrik plugs.

 

[agedhorse]

Ok, got it - all excellent observations and considerations. It was difficult to get the 4 strands through that one strain relief. If this thing gets used frequently I'll consider drilling out a third slot and adding a strain relief and using a more appropriate cable type and of course Neutrik plugs.

That’s because the vinyl conductor insulation and wire size are simply too large.

In real pro audio speaker cable, there is also 4 conductor cable designed for those plugs.

It’s about the right materials for the job.

 

[Fred Pantalone]

I tested this last night and it works like a champ! Hot cabinet switches are totally silent. This is a great way to AB cabs. I think I like the 410 better than the 212. It just seems smoother yet punchier. In reality it's probably all moot because for most shows my amp goes to the board direct and my cabinet is only for stage monitoring. I doubt I would ever hear the difference what with 2 loud guitars, drums, screaming fans (there are none), etc...