OCR DIY Analog Synth Club

[Nabeel Ansari]

If you ever work with analog sounds/synths, knowing your note ratios is critical - 440Hz "A" is a common standard, and you can get every other note by multiplying the previous note by the twelfth root of two. That is, if you want to get A#, multiply 440 by 12th root of 2, and if you want B, multiply that result by the 12th root of 2, etc. This also works backwards - that is, you divide the number by the twelfth root of two to get the number previous.

For those who aren't algebraically inclined or just don't look for shortcuts, here is a nifty formula:

noteFrequency = currentFrequency * 2^(semitoneDistance/12)

Ex. If I want C above A and I have A which is 440, I multiply 440 by 2 to the 3/12 power. If I want the C under A, this is 440 times 2 to the -9/12 power.

This works starting at any note frequency, not just A.

[theshaggyfreak]

Since not many people filled out the form so far, I'm going to go ahead with this project a different way. For project #1, I think the Atari Punk Console will be very doable and is a great introduction to building your own synth circuits. I've been it a few times but only on a bread board. This time I'm going to get it all into a project box and have a finished project that I can keep. I'll be posting some links in the first post for those who are interested in doing this.

For those who want to purchase there own components, this is an example of what you would need to order for the APC (minus a case, battery, breadboard, and hookup wire): http://www.digikey.com/short/079zj

Edited July 17, 2014 by theshaggyfreak

[Anorax]

While I'd LOVE to take a crack at building analog systems (for some reason I imagine that this could come in handy in the future), I'm moving into college in less than a month and I'm fairly certain that a soldering iron is on the "do not bring to campus" list.

[Nabeel Ansari]

While I'd LOVE to take a crack at building analog systems (for some reason I imagine that this could come in handy in the future), I'm moving into college in less than a month and I'm fairly certain that a soldering iron is on the "do not bring to campus" list.

Is it a liberal arts college?

[Anorax]

Is it a liberal arts college?

nope.

Here's the "what you can and can't bring" flyer. If a soldering iron counts as a power tool, then it's not allowed.

[Nabeel Ansari]

nope.

Here's the "what you can and can't bring" flyer. If a soldering iron counts as a power tool, then it's not allowed.

A soldering iron is not a power tool. It does require electricity, yes, but a "power tool" is something like a drill, which generates motion on its own from a power source. Power tools aren't allowed because they're actually dangerous on their own (drills, saws that you turn on, etc. can draw blood and destroy property really easily); a soldering iron is as dangerous as a clothing iron, or a lit match. It's just really freakin hot; that's it.

Edited July 17, 2014 by Neblix

[theshaggyfreak]

One option is a battery powered solder iron. Now, these things are not going to heat up nearly as hot as a regular iron but they usually are good enough for working with small components such as the ones in these projects. People who buy them often expect way too much out of them. For my portable needs, I use a butane solder iron. They might see that as a bit more dangerous than an electric one, though.

[SenPi]

so, I haven't read everything in this thread, but I've recently been getting in to analog circuitry myself and I've been doing music stuff with it.

MIDI Opto-Isolator Circuit I designed: http://i.imgur.com/Y9dyZ5w.png

Square/Triangle Voltage Controlled Oscillator Circuit I designed: http://i.imgur.com/JOaYo0f.png (didnt end up working cause I fucked it up somewhere)

The working prototype for the previous osc: http://i.imgur.com/wiMF2So.png

I'm currently working on a new prototype for another square/triangle using a different chip, as well as a ramp/pulse and sine, and also some PWM action for the square.

In any case, I figured I could chime in and pimp out https://oshpark.com/ cheap PCB's. Cost is based on square inch, and all of those purple pcb's in my photos were done through them, and came out to roughly 6 bucks or so

edit: also, I'm trying to go the pure analog route (except for when I hook up a midi keybaord to it. That will probably be midi keyboard -> raspberry pi (or arduino) -> voltage control -> osc. Asside from that, I'm going pure analog hooah. Which is pretty difficult apparently, especially cause I know nothing about circuits haha

Edited July 17, 2014 by DJ SymBiotiX

[theshaggyfreak]

From what I understand, one is better off looking at buying an off the shelf MIDI to CV converter. There's several out there already. I already have one in my Minibrute but I'll probably end up building a CV control keyboard as well.

[theshaggyfreak]

So, here's where I'm at with my build of the APC.

I have all the major components and jump wires soldered into the solderable breadboard. As you can see, it doesn't take too many components to make this thing. Above that is the three 1/8' jacks attached to part of the casing (not my best drilling job). One is for audio out. The other two are for CV connections. On the left are the components that are left and most of those will be attached to the front of the case once I drill the holes.

I'm waiting on a couple of pots to come in the mail to finish this off, though. Right now I don't have two 500k pots that are small enough to fit in my case. Once those come in, I should be able to get this all done quite quickly. The one nice thing I like about this case is that it has a battery compartment built into it. The finish product will be nice and compact. It not look absolutely pretty but it'll be fun toy to use for sound design.

[theshaggyfreak]

After some experimenting, I think I finally found a piece of software for PCB and schematics design that's not too difficult to use. It's free and cross platform as well!

http://fritzing.org/