2x LFO
Cheap and easy to build LFO for modular synth
When I first became interested in building DIY modular synths, I was always looking for simple circuits to build, due to my lack of knowledge in electronics.
During my search for super efficient and easy circuits, I read a lot through various forums and articles about what is called a "relaxation LFO" who seemed to fit my criteria. The schematic that caught my attention the most was the one provided by NJ Ramsden on his website synthnerd.wordpress.com
The article seems to date from 2018; fun fact, I started my DIY synth journey the same year !
During my search for super efficient and easy circuits, I read a lot through various forums and articles about what is called a "relaxation LFO" who seemed to fit my criteria. The schematic that caught my attention the most was the one provided by NJ Ramsden on his website synthnerd.wordpress.com
The article seems to date from 2018; fun fact, I started my DIY synth journey the same year !
Here's my version of this schematic, the basic core of the LFO.
This is a pretty straightforward LFO. There's only a square & a triangle-ish ouput. No sync, no retrigger. But for my use, it is perfect.The interesting thing here is you can tweak the values of some components to get different flavors !
In my first build, I even put a toggle to choose between 2 different capacitors to get various speed range. But I figured out that this was not useful on stage.
- C3 capacitor : this will impact the frequency of the LFO.
- R2 resistor : this will impact the min & max value of the signal amplitude (a higher resistor will give you more amount)
- R3 resistor : this will change the maximum speed of the LFO. A smallest resistor will give you a faster LFO.
- RP1 potentiometer : the value of the potentiometer will impact the range. I used a 500k here, but a 1M will give a better difference between min & max speed. I recommend using a log or audio potentiometer because it will give you a more natural curve when tweaking the pot.
In my first build, I even put a toggle to choose between 2 different capacitors to get various speed range. But I figured out that this was not useful on stage.
Cause the schematic is quite easy, I packed 2 LFO in one module.
I replaced the TL072 by a TL074, which is basically four op-amps instead of 2. I also added some LEDs to get some extra blinky lights in your face.
Despite its simplicity, this relaxation LFO has become one of my favorite modules. It’s cheap, easy to build, and incredibly useful in almost any patch.
Despite its simplicity, this relaxation LFO has become one of my favorite modules. It’s cheap, easy to build, and incredibly useful in almost any patch.
Component List:
1x TL0742x 470Ω resistor
2x 100nF capacitor
4x 10µF capacitor
2x SPDT Switch
2x LED
4x 100kΩ resistor
4x 1kΩ resistor
2x 47kΩ resistor
2x 500kΩ log potentiometer
2x 2N3904 transistor
2x Jack socket
