Music and Synth DIY

Eurorack, Schematics, Synth DIY, Through hole

L.F.O. – TAPLFO3 based 4hp Eurorack LFO (finished)

Straight outta KiCad – a 4HP utility LFO based on Tom Wiltshire’s fantastic Electric Druid TAPLFO3 PIC.

I’m going to do another, larger version with more CV inputs, but a lot of the time I find I need a number of more basic LFOs – and that’s where this fits the bill nicely.

  • TAPLFO specs:
  • Clock sync with clock multiplier & x.5 divider
  • Sixteen waveforms (two banks of eight)
  • Clock out
  • I added a rate LED, and +5/-5v CV control of “distort” parameter (see datasheet here) with input protection
Pots & jacks board

Once I’ve got the boards back from JLCPCB and test built it and make sure it works, I intend to put the gerbers and the KiCad files online, under the same CC BY-NC-SA 4.0 licence Electric Druid release their work under.

First attempt at a panel for it…

Update #1

OK, so a few mistakes crept in. I missed two junctions in the PWM filter section, left the footprint for the transistors on the surface mount version (I was initially going to make this SMD), and made a glaring error in the scaling circuit. But again, with a couple of wires here and there, it works.

I’m also going to change the pots for Song Heui tall trimmers – there’s not much room for four knobs in 4hp, and the trimmer toppers Thonk sell will work nicely here.

Off to do the revisions and order the new boards.

Update #2

The new boards are built, tested and working. Going to build a number of these, as they’re so useful…

Here are the Gerbers and KiCad files, along with IBOMs for both boards.

Five finished 4HP LFOs