How to make an oscillator?

tpantano · Post by **tpantano** » Fri Sep 14, 2012 3:40 am

Hello there!

I've had a recent interest into learning more about circuitry, specifically within the realm of synthesizers. Unfortunately, my past experiences have been learning preliminary information in schooling (flow of electricity, calculating resistance of parallel circuits, etc.) and working with a microprocessor that could be programmed in C, so minimal circuitry knowledge was required for hookups.

I'd like to learn how to create a basic oscillation circuit that I could hook up to an amp or one of my Rokit monitors to form, say, a square wave. Unfortunately, I don't really understand how such a circuit would work.

For example, let's say I have one of these timers– http://www.radioshack.com/product/index ... Id=2062595
How could I wire this in such a way that a 50:50 pulse wave is generated, with a variably controlled pitch via a potentiometer (and a changeable gain/amplitude/volume as well, if possible), to be sent to a 1/4' female jack (with preferably a loud enough gain to be audible, albeit I could likely gain it at the amp/monitor)? I don't particularly understand capacitors but I've seen people use them in simple designs such as this. I'd rather not simply follow a tutorial to build an oscillator, but rather start understanding the concepts behind it.

Thank you for any info you might have, resources I should check out or other discussion forums specialized in this subject!

billbaker · Post by **billbaker** » Fri Sep 14, 2012 12:33 pm

T -

I wouldn't bother reinventing the wheel, here.

There are a lot of DIY Synth (google that) projects that run from the really simple (like what you're looking into) to pretty complex (MIDI controlled, multi oscillator, filter variations, etc.). Most will discuss some of the theory, and almost all should contain a readily accessible parts list from Radio Shack or some other retailer

Another possibility to look into is Electronics Projects for Musicians by Keyboard Mag editor Craig Anderton (<$20 - Amazon), which looks not only at synth circuits, but also at things like amps, FX/signal distortion, and many other projects of general musical interest. It's pub date is '92 so it's a little old, but it set the standard for music DIY. I know that there are several project videos of his build designs posted on youtube.

There are also mod kits for many popular FX pedals that can turn a $10 bargain stomp box into a "boutique" pedal -- as learning projects those might scratch your DIY itch as well.

BB

X-Trade · Post by **X-Trade** » Fri Sep 14, 2012 8:59 pm

This is a really simple one we built as a first project at university:
http://en.wikipedia.org/wiki/Schmitt_tr ... oscillator

synthjoe · Post by **synthjoe** » Sat Sep 15, 2012 8:13 am

555 is the world's most versatile IC in my belief. It is incredible how diverse a range of circuits you can create with it.

For the 50% duty cycle oscillator (square wave) you can see p. 8 of the datasheet here.
You can get an idea of the 555's versatility from this document.
You can use a pot to create a sweepable oscillator, you have a modulation input, can attach a touch sensor (two conductive stripes with a small gap between them) to modulate the frequency, etc.

An ideal starting point, I'd say - except the waveform, which is strictl square and after a while it is boring. You can, however, put it through a filter section (e.g. a graphic eq) and voilá - you have a basic modular synth (OSC - filter). If you add an envelope generator (might be a bit more complex) and a VCA (voltage controlled amplifier) you've made yoursef a pretty neat mini-modular.

Good luck experimenting!