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Since the beginning of time, humankind has been seeking two things, the first being its place in the universe and the other being a simple audio mixing board that easily stirs up fat beats. The Birth of Man Mixing Board accomplishes both of these tasks. Not only does it mix up the super funky fresh beats, it also has the creation story painted carefully onto its surface. All the major players are there like Eve, Lenin, a happy Unicorn and monkey with a balloon (and they are traveling through a starry cosmos). As far as I'm concerned, it gives a pretty thorough explanation of human origins and history while all the while keeping the mix fresh. I'm not really sure what else I can say about this.
 
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Step 1: Go get stuff

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You will need:

- 12" x 16" sheet of solid white 1/8" acrylic
- An awesome 75W Epilog laser cutter
- A heat gun
- Scrap plywood
- Aluminum or heat resistant table
- Heat resistant work gloves
- Acrylic paint set
- Fine tip paint brush set
- White printer paper for mixing paint
- An exacto knife
- TL072 op amp
- 5 10K slide pots
- 1 10K log pot
- 8 10K resistors
- 3 100 ohm resistors
- 5 1uF capacitors
- 3 10uF capacitors
- 7 1/4" mono jacks
- 1 1/8" mono jack
- A dual power supply (futurlec part#minipowerdual5v)
- 5 slider knobs
- 1 turn pot knob
- A soldering setup
- Solid hookup wire
- Misc hardware (nuts and bolts)
- Screwdrivers, pliers, etc...

(If you don't have a laser cutter, you can have the files printed by a service such as Ponoko)

Step 2: Laser cut the main panel

Laser cut the main panel using the file below.

First, turn off all the cut outlines etch the image off the protective covering/surface plastic by doing a raster cut with the following settings:

Power: 100
Speed: 100
DPI: 600

Next, turn off the decorative image and all the cut lines. Use the following settings to make a vector cut:

Power: 100
Speed: 12
Frequency: 5000

Also cut out the spacers file with the same vector setting. You will use them later. You might want to cut this out twice as they are small and sometimes get lost.

Step 3: Paint the outline

Paint in the outline with black paint. Don't worry about being too precise as the paint won't absorb through the protective covering you will peel off once the paint is dray.

So paint it, wait for it to dry and then peel off the cover. You may need to pick off the fine bits with your exacto knife.

Step 4: Color by number

Using the digital reference image, paint in the outline. Be very careful to stay in the lines and lay down an even coat.

if You mess up and get a little on the lines, you can scrape it off with an exacto knife or wipe it off with a damp sponge. You can also use the exacto knife to carefully touch up the black lines. Simple dip the point of the blade in black paint and touch the spot you want to fix.

You can use a test piece of acrylic to judge what the paint will look like before you commit to putting it on the real thing.

Step 5: Bend

Now is the time to bend your case into shape. Put on your heat resistant work gloves (unlike unsafe me).

Lay your acrylic flat on your aluminum or heat resistant tabletop. Measure so that your acrylic is sticking 2 1/4" over the edge of the table and the two holes for the potentiometer and headphone jack are near you. Place a sheet of the paper over your painting (as to protect it), but make sure it will be out of the way of the heat gun (you will be heating the joint where the acrylic meets the edge of the table). Place the plywood over top of the acrylic and clamp it in place. Heat the acrylic along the join where it is clamped and once you see it start to droop a little, try bending it forward. If it is pliable, bend it to roughly 80 degrees and hold it in place until it starts to hold its own shape.

Next measure 5 1/8" and repeat the process. This time bend the acrylic a full 90 degrees.

Repeat it once more measuring only an inch and bend it away from you another 90 degrees.

Step 6: Hardware

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Mount the slide potentiometers to the board (using 1/4" spacers on the underside) and put the slider knobs on.

Also install the 1/8" jack, main volume potentiometer and the volume knob on the front of the case.

Do not yet install the seven 1/4" jacks that go into the back.

Step 7: Cut more acrylic

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Cut the acrylic mounting bracket that gets attached to the underside of the slider pots.

This bracket will have your circuit built into it and also support the circuit board for the power supply.

You need to make one raster cut of the solid black field in the file) and so you should turn off all the outlines of all the other fields when you do this.

I made 5 passes with the following settings:
Speed: 100
Power: 100
DPI: 600

I then turned off the fill for the black square and turned the outline on for everything else (not including the black square). I think made one vector pass with the following settings:

Speed: 10
Power: 100
Frequency: 5000

Step 8: Build the circuit

The circuit for this mixer is based almost entirely off an incredibly awesome schematic found here.

Build the circuit pictured below onto your mounting bracket.

Don't yet wire the audio jacks or any of the potentiometers. Add extra wires as necessary (such as for ground and audio in) keeping in mind that they will have to attach to components later.

Step 9: Prepare and mount the bracket

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Bolt the dual supply power board to your bracket using the 1/4" spacers.

Place the bracket onto the tabs for the slide pots and bend the solder lugs slightly so that the mounting bracket is held firmly in place.

Step 10: Wire up the rest

Wire up the rest of the circuit such as the audio jacks, power plug and potentiometers and make sure everything is installed in the mixer.

I found it was easier to add wires to the audio jacks in the back of the case first and then install them (as opposed to the other way around).

Step 11: Rubber feet

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Stick rubber feet to the bottom of the back of the case to give it some traction.

Step 12: Enjoy

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Mix it up. Keep it real.
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Will this work for recording on a PC, connecting the output to PC´s microphone input?
Answer, please!!!
Thank you very much!!!
Georgeleeh1 year ago
Looks great man! 4-track with a master, right?
gl0rious3 years ago
how much do u think it would cost (assuming i have the laser cutter)
hcaz-3014 years ago
Im guessing these are LOG not liner ?
randofo (author)  hcaz-3014 years ago
I think so. I don't remember. Log would be more ideal. Either will work.
ben002334 years ago
i was wondering would a TL082/TL082CP Wide Dual JFET Input Op Amp (8-Pin DIP) work instead of TL072? the only reason i ask is because i cant find a TL072.


<(
I know that it's later, but yes, it would.
randofo (author)  ben002334 years ago
Probably. You could also try a TL071
elsanloco4 years ago
Your mixer is awesome, now, i'm a beginner in this kind of stuff... Can you explain or draw the wires of the power suply and where i plug it? Thanks very much

PD: sorry for my english, i'm from Argentina
shrooms
agis684 years ago
all ok but why Lenin??? For me is ok Iam communist but I wonder
jmfc155 years ago
Where did you get all of the supplies? Is there an online distributor?
liddokun jmfc155 years ago
Most of the components can be bought at http://futurlec.com/
Dragonlove5 years ago
What about the slider knobs. What resistance are they?

 
randofo (author)  Dragonlove5 years ago
10K
endolith6 years ago
Is this supposed to be a summing amp followed by an inverter? I think you should re-check your connections. :)
Some fixes: Two miswirings Feedback path should have compensation caps to prevent oscillation Put an electrolytic from each power supply to ground to prevent problems Use a better op-amp :)
mixer.png
Nice fixes, but I'm just wondering a few things.
Firstly, will the original schematic work or do the miswirings completely ruin it?
And what are the values of these capacitors you have added?
I'm looking to make one of these, and am interested.
Thanks. 
I don't think the original schematic would work at all.  It would have zero volts output at all times.

Full-resolution: http://www.instructables.com/files/orig/FJT/8F2A/FW39KSPG/FJT8F2AFW39KSPG.png

The capacitors in parallel with the resistors should be about 180 pF, depending on how much bandwidth you want.  (180 pF gives you 88 kHz)  No one can hear above 22 kHz, but we usually extend it out far beyond this so it's super-flat, without going up into the MHz where it will oscillate.  Some op-amps might oscillate even with this, so you would have to increase the cap to decrease the bandwidth.

The capacitors on the power supply should actually be a large electrolytic (100 uF or so) in parallel with a small ceramic cap (104 = 100,000 pF), which I forgot to show.
Thanks for the comments, just a quick question though; what would a schematic for a general purpose mixing board look like?
You've done pleny already, its just that I need a concrete schematic to follow because the last time I had a ciruit which told me to 'experiment' it all went downhill from there :P 
Just a quick addition too, is there a limit to the amount of input 'strips' you can have in this circuit (ie. How much can the Op-Amp handle)?
 
No, I don't know of any limit.  The op-amp doesn't care how many inputs you connect to it, since it always sees the same load.  The combination of all the signals can reach a high level, though, so you might run out of room and start clipping.

Also, if this is meant to drive headphones directly, the headphone circuit needs to change.  It can't go through a pot like that, and the capacitor needs to be larger for good low frequency response.
There are full schematics for a general purpose mixer on Elliott Sound Products.

In this circuit, there are two op-amps inside the one chip.  The first one is configured as an inverting summing amplifier, so it adds together all the inputs and inverts the polarity.  The input resistors and feedback resistor are both 10k, so the gain is 0 dB for each input (no change in level).  Then that feeds into a plain inverter that is also 0 dB of gain, which does nothing except reverse the polarity again so that it is correct at the outputs.  So when the input faders are at maximum level, a signal will be passed through with no change.

Yeah, it's hard to experiment when you don't know how stuff works.  It's best to get a working circuit first and then experiment from there.


costas145 years ago
 how about pan pots? and eq?
randofo (author)  costas145 years ago
It was that or the unicorn... I picked what I felt was the better decision at the time.
 ah i wanna make one with an eq and xlr inputs with ins and outs
ajfer5 years ago
Awesome now all I need is an equalizer instructable
frenzy5 years ago
"5 uF capacitors" 5 of what uf?
randofo (author)  frenzy5 years ago
1uF
Kryptonite6 years ago
I notice Eve is naked while Adam is fully clothed... coincidence? Definitely.
That's not Adam, that's Lenin. One contributed to the Birth of Man, the other hung around naked and belly-buttonless, eating apples.
lolz
Well I know who I prefer. By the way, you'll have to forgive me for this, but who's Lenin?
Forgive me for this--but really?

What the heck do they teach in history these days?
XD I love some of the responses you get on Instructables
Thanks for taking that in the right spirit ;-)
One must starts singing Always look on the briiiiight side of life.
that one communist russian guy during WWI
I'll take your word for it.
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