how to make a random delay?

[kingnimrod]

messing around with an old analog delay pedal ( well, the guts sitting on my desk here) gave me an idea -

is there a way to install something between the board and the delay time pot so I could throw a switch that would give me either fluctuating back/forth delay settings or some kind of slurring randomness (meaning it's not jumping around between random values, but going up and down the value range between them -- furthermore, if that IS possible, could I add another pot that controls the rate at which it does this?

that would be very exciting!

[smoguzbenjamin]

You'd basically be replacing the delay time pot with an LFO. Still, there's a million ways to wire up a delay time pot, let's see the schemmo! :mrgreen:

[R.G.]

Yes, that's possible.

One of the things at GEO is a pseudorandom generator made from either CMOS oscillators or a shift register to generate random voltages. The random voltages are quite large, usually 0V to 9V. This can easily be used to modulate the delay of a pedal in a couple of ways.

One way is to use the voltage to control the current in an LED, which then controls the resistance of an LDR. The LDR replaces the speed pot of the delay's built in LFO, and modulates the speed.  This is similar to the LERA (Leslie Effect Rotor Adapter) project, which uses a similar scheme to get a speed up/slow down operation on an LFO.

I'm putting the finishing touches on an update to the shift register random adapter now, should be on GEO soon.

[kingnimrod]

What I want to do is maintain the delay time pot, but put a circuit in between that disables it and makes the random or modulated effect I'm talking about with a separate pot that controls the rate of the randomness or modulation. You'll have to forgive me, as I am a novice when it comes to electronics.

the schematic is right here on this site, but I'll embed it in this post:






If you can explain to me how to do this as if you were talking to a total idiot, that would help greatly.

In the meantime, could someone recommend a good introductory book for getting into the world of messing with these kinds of electronics?

[R.G.]

The 1M delay pot is a good candidate for replacement. An LED/LDR module should do it. You might want to read the LERA article at GEO for how to make it plug in and replace the delay pot.

Yes, the circuit I had in mind would have a "rate of randomness change" pot, and the LFO would random at a rate controlled by that pot.

The detailed explanation isn't really a good choice for here yet, so til I get it done, think of it as a box with a pot and a jack into which you can plug a wire from the delay. The thing then works as you have described.

[christian]

You get a side-effect when modulating the delay, which is that the pitch also bends up and down with long delay´s.
Maybe that´s what you want?