This is a 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.
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 design has four PCBs: Two panel components boards and two main boards. The two panel components PCBs are identical, though assembled slightly differently. All four boards with a 100 mm panel constitute the Add Noise Drum. Just the Tone main board, one panel components board, and a 50 mm panel can be built as a Kosmo format Barton Analog Drum with the modifications mentioned above. The Tone SEND jack then becomes the module OUT jack, connected to the VCA output.
Both Add Noise Drum and modified Analog Drum have 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.
Git repository https://gitlab.com/rsholmes/and
A few boards and panels will go up on my Tindie store in a week or so.