I had a bit of a problem with my last PCB/panel fabrication order:

An FR4 front panel. The masking rings that should surround each hole instead pass through the holes' centers.

Not how I designed it

It looked fine in both the KiCad Gerber viewer and the fabricator’s web-based Gerber viewer. Turns out there was a bug in their engineers’ software. They’re redoing the panels.

But that’s why this post contains contained no photos of my new module. [Update: Now it does.]

Design for a synth module front panel. It is 10 cm wide with 12 knobs, 8 jacks, and 4 LEDs.

Add Noise Drum panel

This is the Add Noise Drum, a Kosmo format drum module intended for analog percussive sounds with tone and/or noise components: Kick drums, toms, wood blocks, hi-hats, snares. It has nine knob-controlled parameters to vary the sound along with two attenuated CV inputs. There are SEND and RECEIVE jacks for replacing or effecting the internal tone and noise sources, and a sensitivity control for the trigger input.

The circuit consists of five sections: Power, Trigger Handling, Tone, Noise, and Mixer. Tone consists of two decay envelope generators, a VCO, and a VCA; Noise comprises a noise source, two more decay envelope generators, a 6 db/octave VCF, and another VCA.

Block diagram showing structure outlined in paragraph above.

Add Noise Drum block diagram

Trigger Handling just conditions the input trigger. The Tone section creates a tone pulse with decreasing pitch and decaying amplitude. The Noise section creates a filtered white noise pulse with decreasing cutoff frequency and decaying amplitude. The tone and noise pulses are mixed to make the final output.

Power, Trigger Handling, and Tone are based on the Barton Analog Drum , with several modifications including the trigger sensitivity control, the SEND and RECEIVE jacks, and a number of component value changes.

To that is added the Noise section (hence “Add Noise Drum”) whose noise source is taken from the MFOS Noise Cornucopia with added filtering to eliminate crosstalk. The VCF core comes from the LM13700 datasheet, with component changes.

The Add Noise Drum has been built and tested. No problems found other than a few minor silkscreen deficiencies (noted in the build notes); these have been corrected in the design and Gerber files. Now I just need the corrected panels so I can replace the disastrous one I used as a temporary measure. Update: Done!

Schematics, design files, Gerbers, and build notes are in the Git repository: https://gitlab.com/rsholmes/and . License is CC0, so you can do with it as you like.

<– 2023-12-31_a-theremin-for-christmas — 2024-01-08_ringer –>