Pseudo-Random LFO

[nocentelli]

Addy Bart wrote

I was wondering if increasing the capacitor values or the resistors would slow down the LFO... Had a cursory glance at a thread about Ken Stone's Psycho LFO (over at electro-music) and this was suggested by some.

Yep, only one of the 4 inverter oscillators can be adjusted for speed: The 15k, 56k and 33k set the speed for the other three. they can be increased to slow the whole thing down, or replaced with pots so you can fine tune the pseudo random pattern that the asynchronous oscillators produce.

[Addy Bart]

Cool. Definitely giving that a try then. Cheers

[edo1123]

If I would use a LFO with the Dr Quack, where should I put it? Here is the layout. I'm not sure, but I think is at the base or collector of the bjt. Actually I didn't understand how it does the envelope detection so this is just a guess.
http://tagboardeffects.blogspot.it/2013/01/dr-quack.html

[nocentelli]

Are you planning to modify a Dr Quack you have already built? I think you would need to cut the connection from the BJT collector to the rest of that row, and have an LDR to ground in it's place (with the LDR being driven by an LED from the LFO)

[Kinski]

I've messed with these a chips a bunch. Using a pot to adjust the 9v (starve pot) to the chip often has a large effect on the oscillators.

[edo1123]

Hi guys, I've just breadboarded this and speed knob is not working. It seems to go always at super high speed even if I put a 1M resistor. What could it be? The only changes I made are a 51k instead of the 56k and a 10k instead of the 15k.

[Addy Bart]

I replaced the aforementioned resistors with 1M pots and now it moves really slowly. (I'm waiting for an order to come through so there's only three pots in the vid).

https://m.youtube.com/watch?v=eGpyCQMG8Ws

[Freppo]

The pseudo LFO is fun. I used it in a simple noisemaker (feeding a OTA VCO) that I made a couple of years ago. :)

http://www.parasitstudio.se/building-blog/blip-blop-noisemaker-dogs-and-stuff

It's also possible to use a sample and hold + white noise to make a true random LFO.
I'll try to dig up a schematic for that.

The vero layout looks ok except one thing. Remember to always disable all unused gates.
You should ground pin 9 and 11 of the CD40106

Or you could tie pin 11 to 9v to avoid a double link at pin 9. :)

Cheers
/ Fredrik

[Addy Bart]

Didn't know that you should disable unused gates. Thanks Freppo!

[mausII]

hey! this is a fun little mod!

I got the LFO working in conjunction with the delay time pot (or pin 6 of the 2399) on a PT80. Im getting some strange buzzing happening with the LFO speed pot though. Its very faint, but changes with the speed of the LFO. Could this be caused by pin 9 and 11 not being grounded on the IC? Im guessing pin 1 on the speed pot should be sent to ground (which would ground IC pin 9). Anyways, Ill tinker around with this today!

[heuermh]

Thanks for bumping this thread!

It seems we could use a little help updating both this layout (ground pins 9 and 11 of the CD40106 as Freppo suggests) and the Colorsound Inductorless Wah on the main site

http://tagboardeffects.blogspot.com/2012/03/colorsound-wah.html

which needs a lot of work, e.g. http://tagboardeffects.blogspot.com/2012/03/colorsound-wah.html?showComment=1507080459668#c7990254199208406119

Can anyone help?