The Ultimate Audio Converter




About: My name is Randy and I am a Community Manager in these here parts. In a previous life I had founded and run the Instructables Design Studio (RIP) @ Autodesk's Pier 9 Technology Center. I'm also the author ...

I always find myself wanting to convert between mono and stereo and 1/8" and 1/4" jacks and never seem to have the right adapter on hand. The other day I was making two separate adapters for two separate conversion tasks when I had the sudden brainstorm to make a panel with every single mono to stereo and 1/8" to 1/4" conversion path I could reasonably think of. And with that in mind I bring you the ultimate audio converter.

It can convert from 1/8" or 1/4" stereo to either 1/8" or 1/4" mono (with the option to change jack sizes between channels). It can do simple conversion from 1/8" to 1/4" in mono and stereo. It can even split a mono signal into a stereo signal (again, with fully selectable 1/8" and 1/4" conversion options).

It is my hope that I will never need to make another converter again!

Well... until I need two of the same kind.

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Step 1: Go Get Stuff

You will need:

A 14" x 12" sheet of white acrylic.
An awesome Epilog laser cutter
Red and blue acrylic paint
A paintbrush, water cup and palette
A heat gun
Heat protective work gloves
An 18" metal extrusion
Table clamps
A ruler
A drill with a 1/4" bit
(x2) 3" carriage bolts
(x2) 1/4" nuts
(x2) rubber stoppers
(x6) 1/4" mono jacks
(x3) 1/4" stereo jacks
(x6) 1/8" mono jacks
(x3) 1/8" stereo jacks
(x4) SPDT rocker switches
A DPDT slide switch
Hookup wire
A soldering setup

If you don't have a laser cutter, you can use a service like Ponoko

Step 2: Laser Cutter - the Tool of the Future

First you will need to cut up your acrylic.

Using the files below, first make a raster cut with the following settings:
Speed: 100
Power: 100
DPI: 600

Then make a vector cut with the following settings:
Speed: 10
Power: 100
Frequency: 5000

Step 3: Paint

Neatly paint in the part that was etched away with dark purple paint. For an added touch of class, also paint around the outside edge.

Place it elevated and flat so that the edges don't touch anything and you can pick it up from underneath if need be. I balanced mine on top of my water cup.

Wait for it to fully dry and then peel away the protective coating.

Step 4: Bend

Using your table clamps and the piece of metal extrusion, clamp the board to your heat resistant table such that 6" of the board is sticking off the end as shown. Make sure that measurement is even on both sides.

Put on your work gloves. Heat up across the joint (where the board is clamped) until it starts to visibly start to droop a little. Hold the part of the acrylic farthest from the heated edge (the coolest part) and gently and evenly start to bend the entire panel down. Continue bending until the panel is at around 45 to 60 degrees.

Hold it in place until it starts to cool and stiffen and then unfasten it.

Step 5: Install a Stand

Clamp the rubber stoppers in place and then drill a 1/4" hole into the top of the stopper such that it goes most of the way through.

Install your carriage bolts into the top corners of the board, fasten them tightly with 1/4" nuts and then screw the rubber stoppers onto the bottom.

Step 6: Jack It

Install all of your jacks as they are labeled on the front side of the board.

This means, removing the nut from the threading, pushing the threading through from the backside and then refastening the nut. Easy!

Step 7: Wire It Up

Place your board face down on a piece of felt or an unloved t-shirt.

Wire it up using the following schematic.

Unlike me, be careful to pay attention while you do it so that you don't wire everything wrong and realize halfway that you have to redo all your work.

One you are done soldering, you are ready to start converting.

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    43 Discussions


    10 years ago on Introduction

    Isn't it nice how some projects specify tools that the average hacker can't afford? :P Laser cutter? Come on!

    3 replies

    Reply 10 years ago on Introduction

    Or, you could possibly hack this with a power drill, a dremel and some screen printing.


    Reply 7 years ago on Introduction

    I don't mind using laser printing on decal material or maybe a clear label if you don't mind the edge. My way of hiding the edge of a stencil or label is to utilize a border of some color for the cut line.


    7 years ago on Introduction

    I like this! I've been in so many situations where I needed a converter, and I just mostly electrical taped together different adapters to solve my issues. This will come in handy.


    7 years ago on Step 7

    4.7k in line on every out screw terminals are very good for this as you can
    feed a thin copper wire across the terminal to form a bridge to tie in your resistors assuming you are staying passive


    8 years ago on Introduction

    lol. you seem to be very rich. epilog cutter is stupidly very expensive.


    10 years ago on Step 7

    Does your board convert from stereo to mono? I've been trying to find a way to do this. Apparently it isn't as easy as putting the L and R channels together, you need to actually combine them with a mixer chip or something, or else you can burn out your amplifier. Did you do this and if so, how?

    4 replies

    The quick and dirty way to go from stereo to mono is to use a 4.7K build out resistor on the hot of each outputs before tying them together. I've done this hudreds of times with no ill effects.


    Reply 10 years ago on Step 7

    I just wired the two channels together. I'm only ever going to really use this to listen to audio playback on my cheap ol' headphones. I can't stand hearing something in one ear.

    Sound Guy Andyrandofo

    Reply 10 years ago on Step 7

    Wiring two sources together to mono without any summing circuitry is very bad to the signal and both source and receiving devices. By wiring directly, you're wiring two low impedance outputs together to a single high impedance input, and the outputs try to drive each other, which can be VERY bad depending on the device. At a minimum, it's doing nasty things to your audio signal.

    The circuitry need not be complex, an appropriately rated resistor (470-600 R or so works nicely) ) in line with each channel before they're tied together is all you really need (if you want to get fancy, a 10k shunt from the summed point to signal ground is nice, but not strictly necessary).

    See this article for a more detailed explanation and example circuits:


    9 years ago on Introduction

     Wow! I love the look of this! I agree, the addition of RCA would really top it off. Now, what I am trying to do is get stereo audio from 3.5mm to feed into my RJ11 cordless phone system. Now, I'd love to find a way to make that conversion, too! Any possibility of how I could do that?

    Steven's workstation 2009-07-21 003.JPG

    10 years ago on Step 2

    lasers have been around for a long time and have been used in industrial apps for a long time


    10 years ago on Step 7

    Would be nice to also have RCA line level jacks. I find myself spending quite a bit of time to hunt down my RCA to 1/8" TRS line adaptor when I need to supply mp3 tracks through a mixer "tape in" or 1/4 adaptors for two channels if there is no "tape in". Not the best way to attach one to a mixer, but quick for no more times than I have to do it.


    10 years ago on Introduction

    How did you aford that laser cutter? It costs about $8000!