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Altoids Tin 1/8" Stereo Mixer

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Step 1: Materials

Materials:
Qty 1    ---       Altoids Tin. See Note 1.
Qty 5    ---     1/8" (3.5mm) Stereo input Jacks, Radio Shack part 274-249 or equiv.
Qty 8    ---      1k ohm Resistors, Radio Shack part 271-004 (5-pack) or equiv. see Note 2.
1 foot   ---      22-30 gauge solid hookup wire, stripped bare



Note 1: A normal Altoids Tin can take 4 or more inputs, this example assumes 4 inputs. The Altoids Gum tins can fit 3 inputs comfortably. Adjust the number of jacks according to:

       # of Jacks = 1+ # of inputs

and number of resistors by:

       # of Resistors = 2 * # of inputs

Note 2: All resistors (2 per input channel) should have the same value, which can be anything between 1k  and 10k ohms. Higher values result in a higher volume drop. Also, the resistor power rating can be 1/8 or higher. This circuit runs no power through it, so there's no need for bigger than 1/8 w, but use whatever you have handy. Bigger power rating = bigger size.

 
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nebhead3 years ago
Just built this with 2 inputs last night (mainly because I ran out of 4.7k ohm resistors) and I am very impressed! Works great! I would suggest using a dremel tool to clean up the edges of the drilled holes (using proper safety protocols of course).
royirby3 years ago
Great project, Rich... I'm getting ready to throw a modified version of this together and have a couple of questions. 
1) is this design safely expandable to say, 8 inputs? 
2) I'd like to have 2 switchable outputs (each going to different sets of amplified speakers).  Anything special required for this other than a couple of dpst switches at the outputs?
l0rdnic03 years ago
Here's a question, what about Volume controls? Can you add a Pot to each line to act as a master control for each input, If so what would be the best approach?
AndDroid3 years ago
I was interested in making this, but with two RCA type plugs for the output. Would adding these change the wiring at all? Or would I just connect one line of resistors to one plug, the other line of resistors to the second plug, and connect the grounds together? Thanks!
 Does the resistor value affect the sound quality? Would you recommend a value of resistor? I would love to do this as a weekend project, thanks!
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