A Functional Clone of Tr-808 Bass Drum

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Workshop by Wolfgang Spahn
(Concept & Board by Antti Pussinen and Wolfgang Spahn)

The sound of 808 bass drum is one of the most recognizable electronic instruments. It is The sound of 80´s hip hop and electro and one of the most cloned and copied electronic musical circuits of all time. A number of Masters and Phd works have been built around the clever functionality of this particular circuit and it is a good starting point in learning analog percussive sound synthesis.

In the workshop we build a functional clone of the circuit, using contemporary replacements for op-amps and transistors. in the module are controls for Accent, Decay, Tone and Level, like in the original. it has a trigger input and a sound output with a jack connector and possibility to use external accent input. All the known modification points are marked in the paperboard.

The original circuit expects two different triggers, the actual trigger and the accent trigger, to arrive exactly at the same time and to be 1 ms long.To allow triggering with a button, we have to add in a small conditioning circuit. This makes it possible to also trigger the bass drum with another sound that has a strong and fast transient, for example hi-hat sound. it also can be triggered with any cmos style triggers, for example with an arduino.

The circuit consists of trigger input conditioning, bridged-t type oscillator with a separate filter circuit for decay control of the sound, passive lo-pass filter, and a swing type voltage controlled amplifier.

When a short electric pulse is fed in to the circuit, it transfers that pulse into a sound. The circuit is full of cool and elegant design tricks. For example the voltage of the trigger pulse, called accent in the original TR-808, changes all the parameters of the sound to make the sound feel like more loud or accented, thus making variable dynamics in the drumming possible.

The building system is based on working methods of both of the artists, in field of sound and visual art. The Basic building block is the stripboard/prototyping board and the circuit is laid on top of that as a printed paper sheet. One then assembles all the components per printed circuit design. In the era of copy-paste also synthesizer circuits can be produced in large numbers with a help of a printer and easily developed further.

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3.-4. November 2015, 4am - 8pm
Ljudmila, Ljubjana

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Ljudmila, Ljubjana
http://wiki.ljudmila.org/Main_Page
https://www.facebook.com/LjudmilaLab

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