Mad Bean Pedals VFE Focus, Quick Start Manual

Page: 4 / 9

Shopping List
QTY Value Type Rating Spacing
2 100R *see notes 1/4W 5mm
5 220R Metal / Carbon Film 1/4W 7.5mm
5 1k43 Metal / Carbon Film 1/4W
7.5mm
1 22k Metal / Carbon Film 1/4W
7.5mm
2 470k Metal / Carbon Film 1/4W 7.5mm
3 1M Metal / Carbon Film 1/4W 7.5mm
1 22pF MLCC 25v min. 2.5mm
6 100n MLCC 25v min. 2.5mm
2 47n Film 25v min. 5mm
2 100n Film 25v min. 5mm
3 220n Film 25v min. 5mm
1 1uF Film 25v min. 5mm
2 22uF Electrolytic 25v min.
3 OPA2134a or, other Dual Op-Amp
2 DPDT On/On, Pin Mount
1 2k Bourns 3362p
1 1kB PCB Plastic Shaft 9mm
1 50kA PCB Right Angle 16mm
2 10kA PCB Dual Gang 16mm
1) I suggest not using the two 100R resistors on the BOM and doing jumpers instead. Don’t be like
me: building this project blindly and sticking two 100R 1/8W resistors in there without thinking be-
cause they fit the space. 100R 1/8W resistors will drop your supply voltages like a tank in jello. At
the roughly 60mA current draw on the Focus, you will end up with a whopping 2.2v drop across each
resistor.
This could be improved by using higher wattage resistors there (like 1/4W) and lower values (like 10R
or 22R) but ultimately, the circuit does not need the extra filtering or current limiting.
2) You can use 1k5 in place of the 1k43 resistors!
3) The OPA2134a is really expensive. You can try other, less expensive dual op-amps here. Anything
that is rated for 18v operation. Suggestions: TL072 or JRC4580DD.