Electric Druid FilterFX Construction Guide
www.electricdruid.net
Build Instructions
You’re advised to have a read through of these instructions before starting work on the PCB. To
keep these instructions reasonably brief, it is assumed that you know how to orientate common
components.
Populate the PCB
The board should be populated in order from smallest components to tallest. The BOM on page 8
is arranged in this order, so start at the top and work your way down. You can tick off each line in
the “Done?” column on the far right.
If you hold the PCB with the “FilterFX” title and “electric druid” logo the right way up, you’ll see
that the board is shaped like a “T”. The top bar of the T has the Sync Input circuit, the vactrols, and
the StompLFO chip. Below them in the middle of the T, we have the filter op-amp and capacitors.
Next we have the toggle switches, with resistors between them, including the three resonance
selection resistors which are inside a white box. Finally, at the foot of the board is the input/output
op-amp and its associated resistors and capacitors.
Power protection diode
Start by installing the 1N5817 diode in the top-left arm of the PCB. This protects the PCB against
reverse voltage, so be sure to check the orientation carefully.
1N4148 Diode
Next do the 1N4148 diode. This protects the Sync input, and needs to be the right way around, so
again check the orientation. It’s the furthest left component on the PCB.
Resistors
Next come the resistors. We do them in value order, from the lowest to the highest.
• 47R resistor x 1 - top left, next to the 1N5817 you just did.
• 220R resistor x 1 - on the bar of the T, top far right
• 470R resistor x 3 - two in the centre between the vactrols, one far right between the switches
• 560R resistor x 1 - between the switches
• 1K resistor x 2 - both left of the lowest TL072 op-amp
• 2K2 resistor x 1 - on the bar of the T, top far right
• 4K7 resistor x 2 - both together at the edge of the board, centre-left
• 10K resistor x 6 - three together to the right of the lowest TL072 op-amp, one in the Sync Input
circuit top left, one left of the STOMPLFO chip, one in the resonance resistors box between the
switches.
• 20K resistor x 1 - between the switches, centred
• 100K resistor x 2 - between the switches, one is the resonance resistors box, one not
• 120K resistor x 2 - one below each vactrol
• 680K resistor x 1 - between the switches, in the resonance resistors box
• 2M2 resistor x 2 - one to the left of, and one above the lowest TL072
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