DIY XLR A/B switch box

During the last weeks I finished another little DIY project: an XLR A/B switch box. This thingy has two balanced stereo XLR inputs and one balanced stereo XLR output. Together these are four mono input channels and two mono output channels. It’s a great tool if you need to switch between two input sources like e.g. two DAC’s etc. It’s also ideal for A/B comparison of various input devices. Since it’s a completely passive design it shouldn’t affect the sound. Also the stereo channels are completely physically separated.

The main work was to build the case which was made from aluminium rest of another DIY project.

internals
internals

The wiring and soldering is pretty simple. Here is the wiring scheme:

wiring scheme
wiring scheme

The input connectors are Neutrik NC3 FXX, the output connectors are Neutrik NC3 MXX. The ground wires of the first channel (A1,B1,C1) and second channel (A2,B2,C2) are soldered together, but not connected to the case. Also there’s no ground connection between channel 1 and channel 2.

Example Use Cases

  1. Stereo A/B Input Switch: A1 = A In Left, A2 = A In Right, B1 = B In Left, B2 = B In Right, C1 = Out Left, C2 = Out Right
  2. Stereo A/B Output Switch: A1 = A Out Left, A2 = A Out Right, B1 = B Out Left, B2 = B Out Right, C1 = In Left, C2 = In Right
  3. 2 x Mono A/B Input Switch: A1 = Mono 1 In, B1 = Mono 2 In, C1 = Mono 1 Out, A2 = Mono 3 In, B2 = Mono 4 In, C2 = Mono 2 Out. Both Mono Outputs are physically separated.

More pictures:

standalone
standalone
A/B Switcher rack mounted
rack mounted
A/B Switcher cables
input/output XLR cables

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4 Responses to DIY XLR A/B switch box

  1. Bil Jackson says:

    Hi,

    Thank you VERY much…this is exactly what I need…where can I find a list of the complete parts for this DIY? I’m kinda of an idiot with such things but am willing to see if I can muck through this and learn something in the process…again many thanks for posting…Bil Jackson

    • 4irmann says:

      Hey Bill,
      thanks for feedback – much appreciated. Yes, I know the problem with ordering parts. If you don’t do such things often it can be nasty. Most of what you need is described in the article itself (especially Neutrik NC3 FXX and Neutrik NC3 MXX plugs). Moreover, you need some XLR microphone cable. Regarding the switches and the case: the switches are simple electronic 6-pin on/off switches. The case is made from aluminium metal leftovers. But you could also buy a similar case or use an empty cookie can 😉 and drill some holes into it. I recommend you to print out the wiring scheme and visit an electronic store where you get all those stuff. Alternatively order via the web/amazon whatever. Of course, you need soldering equipment, too. Hope I could help you.

  2. Eric says:

    I don’t know if you’re still following this, but I’d like to know if this project could be accomplished with some sort of stomp switch (for a guitar pedalboard)? If so, what kind of switch would I need, and what would the wiring look like? TIA

    • 4irmann says:

      Guess this should be possible, but there are tons of switches on the market, so it really depends on the switch. I can’t give you a recommendation, sorry. But it shouldn’t be difficult to do this.

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