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Do It Yourself

My Modular Synth




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Modular Mini Drums

Here I wanted to have some percussion on my modular without mobilizing too many filter, so I studied the analog market known: TR606, TR808, TR909, DR110 and what I found on the net then I began to perform instrument-by-instrument tests and I came to fit on an 8-channel format map that does not sound too bad.

The principle of these instruments is to use bridged T-filters that oscillate as soon as a pulse is received and extremely simple VCAs with only one transistor whose principles are given in the service manual of the TR808. See figures. The interest of these schemes is their simplicity in number of components and their disadvantage is that when modifying a parameter every parameters are changing : the frequency, the resonance and thus the decay. So the names of the knobs is actually very rough. Moreover, they are sensitive to the energy contained in the initial pulse (thus amplitude and duration). In short, to avoid VCO + VCF + EG + VCA. These concepts were retained on almost all analog Drum Machines before the advent of sampling.


The pcb made here only includes instruments with individual output, a general mix and a TRIG input per instrument. There is a connector of type HE 10 which makes it possible to send the trigs by an external card for control what my friend OZOE is developing. There will be the possibility to have rhythmic memory in abundance to control this card. Everyone will be able to expand. The mind is still a module for modular and not a MIDI drum machine as we find today. The idea being to complete a sequence.

What can I tell you more, that the printed circuit is made industrially and that you will find it in the shop for the modest sum of 20 €. For the rest of the schematic, bom, cabling implementation are below.

A little advice to those who will embark on its realization, make this card instrument by instrument except for trig which can be all done at the same time. it will be easier to troubleshoot in case because the board is dense. Some may even play with the resistance values ​​to change the sounds.

Regarding the small logic used for the Clap, starting from the trig from the LM339, we generate 4 small pulses of about 10ms per period and then a last 24 ms, this allows a small effect of reverb to make it more realistic.

Good works.

See in download area some videos

Drawing            Knob1.gif                                            Wiring                Knob1.gif                  PCB inthe Shop

Board           Knob1.gif                                            3D View               Knob1.gif

BOM                 Knob1.gif                                        Front panel sample   Knob1.gif

Creation date : 08/10/2018 - 14:02
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