Audio Switch Box with Knob (3 Port RCA)

Audio Switcher

I recently got myself into a bit of hobby hi-fi, and wanted a simple way to switch between my analog audio sources, and outputting one signal to my homemade amplifier.

The design features a knurled knob which is mounted to a rotary switch, and the backplate is interchangeable, but made to fit a 2-pole 4x stereo RCA chassis mount i had. But you could potentially use this for anything, even as a smallamplifier simply by switching the rotary switch for a potentiometer, and using the back for input and output.

Materials needed (Audio Switch Setup)

• 1x Rotary Switch - 2-pole 6-position

• 1x RCA/Phono Terminal 8-pole 75x36mm

• 6x M3 Bolts

• 2x M3 Nuts

• Soft insulated copper wire

• Soldering tin 
  

• (Optional): 4 rubber feet

Tools needed

• Soldering iron

• Screwdriver (For M3 bolts)

• Something to cut a 6mm plastic shaft
  

• (Optional): Super glue

• (Optional): Sand paper

How to wire the dual pole rotary switch

A dual pole rotary switch is actually very simple, when rotating the axle (knob), it can switch between a select amount of different positions, each position lets only one channel on each sided through and out of the middle two pins, so lets say 1st position: Pin 1 = A and Pin 7 = B, as seen below, then you could rotate it once so its now 2nd Position: Pin 2 = A and Pin 8 = B, and so on.

Below is a figure from beavisaudio that illustrates it very well.

https://beavisaudio.com/techpages/switches/

We can use this to take input signals from the RCA bracket at the back, so that two RCA jacks are dedicaterd to the A and B from the pinout, while the rest, also in pairs, are dedicated to (1, 7) and (2, 8) and (3, 9).

You can simply solder all ground connections together, i used a completely stripped copper wire and bent the pins towards eachother to make the simple connection, the rest of the signals need insulated copper wire:

Terminal side (RCA Chassis Entry and Output) 

On this image, you can see how i soldered all the grounds together in one horizontal line, and then kept pairs of L and R (left and right), where L is black wire and R is red wire, each pair of a black and red wire is a stereo channel. The three channels first on the left are out three input sources, and the 4th and right is my output coming from B -> Red wire out, and A -> Black wire out.

Rotary Switch Side

On the rotary switch side, you can see my three channels, the upper three wires are soldered to pin 7, 8 and 9, and the bottom three black wires are soldered to 1, 2 and 3, that is our three input channels.

The red wire in the middle of the whole rotary switch is then soldered to the B pin, and out to Red wire -> Right Audio Out.

The black wire in the middle, is then soldered to the A pin, and out to Black wire -> Left Audio Out.

Whether red or black wires are 1, 2, 3 or 7, 8, 9 doesn't matter, i just soldered it like this cause i prefer black wires at bottom and red at top, as long as you keep track of what signals are Right or Left audio.

Wiring seen from above

This is just to show how the whole wiring could look, and how I did it.

Adding the knob and top plate

Adding the knob and top plate is easy enough, i made threads in the design to fit M3 bolts, and you can screw those in from the top, i also recommend adding the rubber feet now on the bottom side of the case.

The 6mm rotary shaft needs to be shortened, i made mine 20mm long and cut off about 2/3rds of the original length.

The knob is designed to precisely fit an average 6mm rotary shaft, but for extra secureness, i sanded the shaft slightly to add grit, and then added super glue to it before pressing on the knob.

Enjoy!