Monday 24 June 2024

NLC - More (cowbell drum module) - Build notes

These are my build notes for the nonlinear circuits "more" module.
It's a eurorack module.

This module contains three individual cowbell circuits based on those in the Roland TR-808.

Links
+ BOM

As far as parts go there isn't anything rare or hard to find.

CD 40106 
& three Opamps - TL072







CD40106 (CMOS IC with 6 Schmitt trigger inverters)

The really cool thing about this circuit is that it uses a logic chip to make metallic noise

Each bell uses 2 of the 6 oscillators.
I think in the 808, similar circuits provide the basis for the cymbal & hi hat sounds




The original 808 used band pass filters to remove the upper and lower partials.



Andrew's description is as follows:
"The filters are fixed as per the original design. This means the output
is loudest when the oscillators are set close to the operating frequency
range of the filters and softer when the oscillators are at much higher
or lower settings. For me, this seems fine, but mess with the filter
values if you like. I have seen some mods of the 2k2 to ground resistor
varied to change the filter range. In proto-typing, this was
experimented with but I didn’t feel it was much improvement."


resistors next

Diodes: LL4148



These are the power protection voltage rectifiers... or just use a 10 ohm resistor and dont plug the module in backwards.



You'll need a through hole +5V 100mA voltage regulator : 78L05. 


power header

Transistors : BC857, 847
Six 1M pots.

12 sockets



The accent input is tied to the trigger input via the switch tab,
probably best to use a gate rather than a trigger to get the sound going,
but that depends on what you want to do. Otherwise patch whatever you
like to make things happen.
This is a dense but easy build.



More links


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