Let’s make an audio switch

Today we’re building a little device to help my spouse, she’s a piano composer, and she’s recording tracks at home using the audio out of the piano.

The requirement is simple: we have only one speaker, and she wants to switch it between our computer and the piano audio output without playing with the wires.

So we’ll wrap some jack sockets and manual inverters in a small box. I’m doing a dual model so that we can switch something else between two other devices. So that’s 6 sockets and two switches.

The first step is drilling the box for all the connectors. I used scotch tape to let me draw on the box without having problems to erase the drawings later. That way, I can draw as many lines as I want, drill the box at the proper places, then remove the tape. Here we go, that’s the preparation for the box cover:

Audio switch : traces de dessins
Drawing on the tape.

Here I removed the tape:

Audio Switch: perçages
Once drilled, tape is removed.

Now we can go ahead with the connectors, inverters and their wiring.

A small note about the wiring: That’s quite easy to turn wiring into a mess, spaghettinam style. But this time, I wanted to do that wiring properly, by strapping them in a “runway”. This is an old method to achieve proper wiring, you can see that in old radio receivers. Here, the wires were strapped using cotton string covered with some grease, to prevent the string from getting out of place.

I don’t have greased cotton string, so I used thin wrapping wire. Here is the result, at least that’s better than random wires:

Audio switch: câblage en faisceau
“Runway” wiring is better than random.

The jack sockets are screwed in the holes, but that’s not very strong, since I did not have the proper drill bit size, and used a round file to fix the drillings, which resulted in pretty random hole sizes. I used some “Araldite” epoxy glue (mixing resin and hardener) to glue the sockets to the cover, since “Super-glue” (cyanoacrylate) does not survice insertion/removal mechanical shocks very well. Araldite glue needs a lot of time to cure, but the result is extra-strong.

Audio switch: collage des connecteurs
Araldite glue was used to ensure mechanical strength for the jack sockets.

And here we go! Once closed, no one can know my effort about the proper wiring, but that’s okay! I’m hapy with my runways!

Audio switch: terminé
Le switch terminé, avec un jack branché.

The last step will involve labelling the sockets, but before that, my darling will test it, and tell me how she wants to use it!