Picture of The Ultimate Audio Converter
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

Picture of 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

Picture of 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

Picture of 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.
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n0ukf5 years ago
Isn't it nice how some projects specify tools that the average hacker can't afford? :P Laser cutter? Come on!
randofo (author)  n0ukf5 years ago

Or, you could possibly hack this with a power drill, a dremel and some screen printing.
clazman randofo2 years ago
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.
dude i thinkg the average hacker would HACK not just follow
KaydenST2 years ago
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.
deafmonkey3 years ago
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
How much is a a basic Epilog laser cutter/engraver?
randofo (author)  interactive35 years ago
I think the cheapest model is somewhere around 8K
hintss randofo4 years ago
plus shipping :P
and handling.
and supplies! :-)
ARJOON3 years ago
lol. you seem to be very rich. epilog cutter is stupidly very expensive.
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?
Yes, does it do anything really or is it just a theatrical guise? Not that there is anything wrong with that! tro lo lo!
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.
randofo (author)  mattthegamer4635 years ago
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.
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:
spytech1285 years ago
 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
lasers have been around for a long time and have been used in industrial apps for a long time
3BlindMice5 years ago
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.
Davidl35 years ago
How did you aford that laser cutter? It costs about $8000!
Excellent design... I really like the curved front & bolt-leg back, it's somehow very MOD, or at least Swiss.
bananafred5 years ago
You forgot to add a line-to-mic level signal attentuator! Just two resistors.
...per channel.
randofo (author)  bananafred5 years ago
Oh. That is a good one. Maybe I will have to make an ultimate-er one.
664115 years ago
Could also add in like a headphone amp and/or variable resistor for simply volume control or to balance channels. Very nice and neat design.
martins9995 years ago
To make a Mono conversion, you can't just connect R and L channels together, you can burn the outputs if they are not exactly in phase, that is to say if they are not sending out the same waveform. You have to use a resistor net to avoid short circuits. Nice and useful instructables though.
Hatredman5 years ago
How about some RCA (phono) connectors?
tudgeanator5 years ago
Awesome. So useful. I need one!!!!!
pstretz5 years ago
really like this a lot. They'll make great Christmas or birthday presents. I really need a laser cutter!
pestan5 years ago
you got my vote
pestan5 years ago
So cool
SPGWhistler5 years ago
When I worked with audio on a daily basis - this would have come in very handy. I love that it is analog. It's very simple and gets the job done. I think this is so simple in fact, that someone could build it with a completely different case design (or no case at all) and still make it easily work. Very good 'ible.
N1CK4ND05 years ago
Very thin!
caitlinsdad5 years ago
I think now you will have to put up an ible on how to make patch cords. If you take a 1/8" earbud headset to convert to use with a 1/4" headphone jack or vice versa, and you use this converter, you are still stuck with a regendered jack. You then need a male-male cable to plug into the device.
marc925 years ago
This is awesome, but I would have included RCA conversions as well... Even more ultimate!
gmjhowe5 years ago
This is, Most Ultimate! I love the simple case designs you use. Simple piece of metal with a slight bend. Keep them coming! (im glad i never challenged you to a 5 ibles in 5 days)
baggot gmjhowe5 years ago
pyrohaz5 years ago
It looks extremely stylish!
clickmatch5 years ago
Really? An $8000 laser? More like a $3 drill bit and instead of using square toggles, hit radio shack for some "round hole" toggle switches.
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