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DIY: Benjolin von Rob Hordijk extended

Long Video from Rob

Video from „Thursday Nigh Machine with one Benjolin I made:

New and cheap case and front build for a original workshop Benjolin from years ago: A  „proma“ case from Reichelt fits for the Benjolin PCB (160/100)

Drill holes for knobs and add a DC/DC switcher for power supply (5V to +-12V 1W) …

Benjolin in a alu case with 5V power supply and enhanced output level.

3HE Benjolin:

Benjolin with 3x mixer, down left .


I don‘ t build Benjolins or sell kits, it´s only DIY.


read this thread before asking me further questions.

My bend adds a mixer fore both VCO´s and original sound source, called PWM. Benjolin origins mix both VCO to a comparator for for its complex soundsource for filter and Rungler. Additional: Rungler mode switch, input to control Filter and CV ins for VCO, cross modulation and output for all waveforms.

If someone is interested in a front panel like mine feel free to ask me.

The hack is: Wire a little 2x mixer with 2x/ R470k on both pots, feed each pot direct with puls wave 1+2  and go with the sum (after R´s) direct into the filter (U3D, pin13).

PWM pot handles original Benjolin sound coming out of comparator (U6C, Pin8). Change R 150K to 100K and from this R go to ground via PWM pot. So it´s possible to fade Benjolin sound (PWM) to ground without  side effect. That´s  it, a little 3x mixer. Now you can mute the whole baby, practical for performance.

It´s a good idea to build a standalone Benjolin, because it´s a big little instrument worth learn to play.

So sieht das Benjolin aus dass ich für mein System gebaut habe. Neben der eigentlichen chaotischen Klangerzeugung habe ich die beiden Oszillatoren separat herausgeführt und einen kleinen Mischer integriert. Nun besteht die Möglichkeit das Benjolin stumm zu machen oder die drei Klangquellen zu mischen. Das erweitert die Maschine enorm. Der Umbau ist nicht besonders kritisch.