Help with building a "random" pedal.

[Gislinn]

Hi there, this is my first post here and first I would like to tell you that I don't know anything about electronics, I usually build just things that I have PCB layouts and schematics for.

Now I've been searching for an effect that can do random octave up and oct down, I know how to make octave up an octave down but I don't know how to make it switch randomly between.

So this is basically like one signal in to the effect with two effects, one is oct up (and clean) and the other is oct down (and clean) and the signal changes randomly from clean, oct up, oct down.

If you know about any schematics or do know how to make one, please share.

It would be nice to maybe be able to control the speed of the randomness.  

Best Regards
Gisli Steinn

[expanoncolin]

At what speed?  Entirely random?  You would have to find some fastest speed you would want it to go first.  The ideal way would be to sample and hold a white noise signal (random voltage levels) at some rate, then to feed the voltage from the sample and hold into a comparator.  The comparator would be wired to some kind of electronic switch (probably a 4016) which selected the octave up output or the octave down output.  The comparator's output would be fed into the switching chip's control pins...  except one control pin owuld have to have an inverter before it, so you get one or the other output selected.  Then all you need is an octave up and octave down circuit, which are fairly easy to come by.

-Colin

[Gislinn]

At what speed?  Entirely random?  You would have to find some fastest speed you would want it to go first.  The ideal way would be to sample and hold a white noise signal (random voltage levels) at some rate, then to feed the voltage from the sample and hold into a comparator.  The comparator would be wired to some kind of electronic switch (probably a 4016) which selected the octave up output or the octave down output.  The comparator's output would be fed into the switching chip's control pins...  except one control pin owuld have to have an inverter before it, so you get one or the other output selected.  Then all you need is an octave up and octave down circuit, which are fairly easy to come by.

-Colin

I need it to go fast, really fast. Yes entirely random. Would you think that this device would be hard to make (the sample/hold/white noise circuit thingy) ?

EDIT: What controls how fast the randomness is able to be ? Is it the pot that I would use ?

[birt]

read the article on pseudo random LFO's on geofex.com
it might help.

[Gislinn]

read the article on pseudo random LFO's on geofex.com
it might help.

Thanks, I will read it tonight and try to understand how to go around doing this.  :rolleyes:

[para]

the speed of the randomness is going to be based on the speed of the clock feeding the sample and hold circuit and the speed the S&H will respond to it.

a bit easier would be to do a pseudo random thing by feeding that 4016 with a hex inverter setup as 4 to 6 osc's all at different speeds. if you gave every osc its own pot you could "adjust the randomness" so to speak. again its not truly random and it might not be that great at really high speeds like a few microsec's but it would be easy to design and build. and probably what birt is trying to say now that i read his post.


Colin’s idea is the real deal though.

[caress]

also, check out ray wilson's site musicfromouterspace.com and look under the single chip s&h for a (possibly) slightly more complex but maybe? more randm version.  

you still need the white noise generator, though.  
"Pink Enough For Me" Noise Generator Schematic, also on the site.

this might be a bit more complex than you want, but i think it may be a bit more random and you may be able to buy pcbs for the project.  also, an advantage is that you can leave the input for the control signal on the s&h circuit and you can plug in a sequencer or some other wavetype...also you'll have a box for white/pink noise!     !waves!    !wind!

[para]

whats up caress.


there is also this noise source. its the simplest i have ever seen but i forget where i found it. probably here but i checked the archives and didn't see it.

you can make it simpler by removing the 4.7k , louder too. then replace the output cap with a larger one like 10u. but it NEEDS 9v so if your battery dies just little bit it will not work at all. i haven't figured out why though pretty annoying but if you feed it an AC line your good.


steven

[expanoncolin]

That white noise generator came from the archives.
http://experimentalistsanonymous.com/di ... or%202.jpg

-Colin

[para]

do you know who made it. is it your's colin? i've seen it used in other things but slightly different. sometimes just the trans pair then amped.

and i didn't think to look under osc's ? i guess that makes sense


steven

[expanoncolin]

do you know who made it. is it your's colin? i've seen it used in other things but slightly different. sometimes just the trans pair then amped.

and i didn't think to look under osc's ? i guess that makes sense


steven

The oscillator folder is called "Oscillators, LFOs and signal generators".  I figured I would group them in one place as there aren't that many signal generators that aren't Oscillators of some kind (such as this one).  I don't know who originally uploaded this PCB, but the configuration is very very common.  You see white noise generators like this everywhere.

-Colin

[para]

i had a small window open so i just saw "Oscilla" like a said it makes sense, no need to defend it. anyway, so i shouldn't feel like a thief if reuse the basics of this in other things. its sooo simple that its hard avoid. the need for exactly 9v is odd though? i can't get it to share a battery with other circuits at all? i was going to make myself a few for my modular and see how it responds to +/- 15V

sorry i got so OT


steven

[expanoncolin]

Setting up a transistor to break down like that is very tempermental.  You could probably solve the 9V problem by putting a 9V regulator between the power supply and the circuit.  

Do you browse the archives with this page:
http://experimentalistsanonymous.com/diy/

Or like this:
http://experimentalistsanonymous.com/diy/Schematics/

-Colin

[Gislinn]

Thansk alot guys, I think this might be something I will have to do some times later when I know more about this stuff, maybe I will just make some easy synth first. I think that's the best (and most fun) way to learn.

[caress]

not much...just moved.  just like you!

LM7809 is a good voltage regulator.

that is an amazingly simple noise circuit, btw...it's great