synth tr909

Posted on Feb 6, 2014

This PCB was inspired by Colin Fraser, who found some very useful extensions to the bass drum circuit of the Roland TR909. Trevor page`s 9090 - project was of course also very helpful for me ! As an addition to these modifications, I added a `compression` pot, changing the behaviour of the envelope of the tri/sine signal a bit, see schematics for

synth tr909
Click here to download the full size of the above Circuit.

detail. As it is a standalone bass drum, I added the noise circuit on the board. Noise is adjustable from 0% to maximum, unlike in the original TR909. Here you will find a PDF-file, containing the PCB of the tr909 bass drum circuit (component side view !) and 3 pics for component placement : I divided these into : Pots, Resistors and all the other things (for a better view). The transistors are depicted as they are built into the PCB, "5" means BC559, "4" means BC549. All Diodes are 2N4148. In my projets I allwys use 1% metal film resistors.

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