Brenn - Quad slow LFO

KOSMO MODULES
1

Having been in the community for a few weeks now, lurking for a while before that, and developing a few Kosmo format modules I have decided now is the time for me to start sharing.

I have a few modules on my github that I shall announce over the coming days and should be on Kosmo modular grid soon.

My first module is a Quad Slow LFO, in a 100mm module.

Brenn-Photo
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  • 4 Lfo’s
  • Each has a cycle duration between a few seconds and a few minutes, approx 6 sec 12 minutes
  • Each LFO has its own speed control
  • A single global speed control
  • CV control for the global speed (not 1V/Oct)
  • Each LFO has both unipolar and bipolar outputs

I have been using the lfo for slow evolving movement of sounds, it is not a replacement for a standard lfo, normal tremolo and vibrato can not be realized with this module.

It is based on the Single-cell VCO on the LM13700 datasheet, this is a triangle wave with a big step so I added an LPF to each oscillator.

Contained are schematics & Gerber files for pcb fabrication of both electrical and front panel. This is suitable for entry-level however a basic level of electronics, soldering, fault finding, and some basic tools are required.

You will see the 6 + 1 logo in places, however, I am moving away from this imaginary brand name as I used it on a previous opensource project that I have currently put up for adoption, I have decided I’m too old to use a pseudonym and an now just going to use my name. I due course I shall be removing the old logo and not replacing it, however as I wont publish anything I have not built and tested you will see my old logo until I need to get more panels fabricated.

As with all my projects constructive criticism is welcome, all I ask is it is kept public so all the community can benefit.

Cheers

12 Likes
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Nice! I too used one of the lm13700 datasheet triangle oscillator in my LFO, but not this version with the back to back diodes.

Personal preference, but I consider an unused op-amp a sin. Maybe there is something interesting to be done with it? Maybe summing a quarter of all separate LFOs to make a funky waveform? Or a Schmitt trigger to provide a square wave LFO from one of the others. Or maybe something else as yet unthought of…

Cheers

3 Likes
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Or just add some buffered LEDs…
blinken

4 Likes
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I’m curious what exactly makes this module inherently “slow”? How hard would it be to modify this to have a wider range, or to be switchable between a “fast” and “slow” mode?

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The inherent slowness of the lfo, is determined by the 470uF capacitors, one for each stage, C3, C4, C15, C16. You could experiment with these, find values you like. Maybe having different values for each lfo, or using a switch to make them selectable.

1 Like
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Just changing those caps isn’t enough, because the 0.15 Hz lowpass filters (R12/C7 etc.) that are being used for removing the distortions that come from the single OTA oscillators used would filter out the whole LFO. To increase the frequency you also need to change the cutoff of those accordingly.

1 Like