Drum Trigger 

The importance of electronic drum kits for music productions and live performances has increased significantly since the heydays of electronic music during the eighties. The employed type of this instrument depends on the situation at hand. They are used for in combination with acoustic drum sets for accentuation as well as singly to generate pure electronic drum sounds. A special position must be ascribed to the hybrid set, a blend between acoustic and electronic drum. It adds a drum computer – generated signal to the conventionally produced sound. This method is regularly deployed during live gigs to lay stress on the drum’s tone.

In contrast to other instruments such as keyboards or guitars there did not exist a worthwhile synthetic, respectively electronic alternative to the original acoustic drums for a long time. The market dominating devices all sounded artificial and exhibited limited dynamics. The playing sensation, too, could not compete with the acoustic sets. For this reason, e – drum kits were used almost exclusively in the sphere of electronic music and spurned by acoustic drummers. Only the development of e – drums which complied with the requirements of the acoustic drummers as well put the electronic drum on the world’s musical map. Producers compete over aspects such as playing sensation, dynamics and realistic sound quality. The manner of picking up the signal alone remained unmodified, though.

In the case of tom – triggers a simple piezo element serves to receive the vibrations which are subsequently processed by the drum computer. It evaluates the strength of the vibrations and assigns them to a deposited recording which is then replayed. This leads to two restrictions for the drummer. First, the natural vibration is dampened by the piezo, second, the drummer’s play is limited by the trigger on the covering. Another problem is the frequently criticised override of the trigger in case of very sensitive adjustment: playing a neighbouring tom sometimes leads to the unplayed tom’s triggering.

Ueberblick 2

Abb.1   Overview of the overall concept


Finding solutions to the above mentioned problems was the objective of a project group in the module ‘Signals and Systems’ offered as an elective subject at the University of Applied Sciences Gelsenkirchen. The subject aims to impart hands-on experience in the field of product development and problem-solving competence.

The approach devised by the group includes a trigger which is installed sidelong on the tom’s cylinder. This design allows unlimited play compared to traditional triggers and can easily be fitted to every cylinder size. An integrated condenser microphone serves as a sound pick-up. Thus, the oscillation membrane is not affected.


Abb.2   schematic illustration of the printed circuit board design


The picked-up signal is converted into a digital signal directly inside the trigger. This ensures the trigger’s loss-free operation. After the transformation the signal is processed by an integrated microprocessor and put out in MIDI-format. Since this format is compatible with every established drum computer and personal computer, existing systems may be used continually.

Designing the new system, the team took care to incorporate the MIDI sockets facing downwards. This prevents kinks in cables and the cords can be run discreetly alongside the drum set. This advantageous structure also makes a serial connection possible. Hence, shorter and more clearly arranged cableruns are feasible in contrast to the star-shaped wiring of conventional systems. In addition, the trigger is operable single-handedly and the casing was especially designed to accommodate both right- and left handed drummers.



Abb.3   Oscilloscope recording of the filter


The newly developed Prime Factor Filtering (PFF) permits narrowband tuneable band-pass filters 97th order which eliminate override by other toms. This technology is mainly used for differentiate rimshots from membrane-shots. It makes separate triggers for snare drums redundant and is applicable to existing triggers.

The functional capability of this concept was confirmed in a Proof of Concept experiment. A prototype that comprises all core functions may be designed in future projects. Offering a response time of 20 milliseconds, this trigger can easily compete with other well-established systems.