Birth of Man Mixing Board

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.

Step 1 Go get stuff

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)

Comments

[gl0rious]

how much do u think it would cost (assuming i have the laser cutter)

[hcaz-301]

Im guessing these are LOG not liner ?

[randofo]

I think so. I don't remember. Log would be more ideal. Either will work.

[ben00233]

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.


<(

[hypnosis]

I know that it's later, but yes, it would.

[randofo]

Probably. You could also try a TL071

[elsanloco]

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

[garrettanderson983]

shrooms

[agis68]

all ok but why Lenin??? For me is ok Iam communist but I wonder

[jmfc15]

Where did you get all of the supplies? Is there an online distributor?

[liddokun]

Most of the components can be bought at http://futurlec.com/

[Dragonlove]

What about the slider knobs. What resistance are they?

 

[randofo]

10K

[endolith]

Is this supposed to be a summing amp followed by an inverter? I think you should re-check your connections. :)

[endolith]

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 :)

[lukaj2003]

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. 

[endolith]

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.

[lukaj2003]

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 

[endolith]

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.

[lukaj2003]

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)?
 

[endolith]

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.

[endolith]

http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/datasheets/Opamps/072dia.gif

[costas14]

 how about pan pots? and eq?

[randofo]

It was that or the unicorn... I picked what I felt was the better decision at the time.

[costas14]

 ah i wanna make one with an eq and xlr inputs with ins and outs

[ajfer]

Awesome now all I need is an equalizer instructable

[frenzy]

"5 uF capacitors" 5 of what uf?

[randofo]

1uF

[Kryptonite]

I notice Eve is naked while Adam is fully clothed... coincidence? Definitely.

[Asbestos]

That's not Adam, that's Lenin. One contributed to the Birth of Man, the other hung around naked and belly-buttonless, eating apples.

[szechuan53]

lolz

[Kryptonite]

Well I know who I prefer. By the way, you'll have to forgive me for this, but who's Lenin?

[gmoon]

Forgive me for this--but really?

_{What the heck do they teach in history these days?}

[Kryptonite]

XD I love some of the responses you get on Instructables

[gmoon]

Thanks for taking that in the right spirit ;-)

[Kryptonite]

One must ^{starts singing} Always look on the briiiiight side of life.

[Clayton H.]

that one communist russian guy during WWI

[Kryptonite]

I'll take your word for it.

[Cj slier]

yo about how much did it cost to build this.

[randofo]

It's hard to say. I would guess around $50 - $75.