Filter Modulator ver2

Board information - version 2

PCBs supplied after 28 February 2017 are Version 2 and include the modifications to improve spectral performance.

Notes on the pictured example: Q01 not fitted (out-of-stock at the time), L50 replaced by hand-wound inductor (original lost in carpet) and R50A bridged to allow 5V input on J51.

General notes: Do not fit L10 or C11; they are not required if using a linear regulator. R33, R34 and R45 are not fitted as they are not required. C54A (100 pF) is shown as optional for high frequency decoupling on the circuit diagram, and there is unlabelled space for it next to C54 on the PCB; it is not required in this version. J51 and R50A can optionally be replaced with an LED and current limiting resistor.

The Version 2 the parts list and schematics are available for download:

• xls parts list file - includes the extra components for V2

• Board layout

• Block diagram

• Block Diagram with IC Numbers

• Circuit schematic - part 1

• Circuit schematic - part 2

• Circuit schematic - part 3

Although the board includes the options to fit a switching voltage regulator (an R78E5), the regulator introduces spurs at -50dB on the output spectrum , so is not the recommended option.

DO NOT FIT L10 or cut the track beneath it as it does not suppress the spurs and introduces voltage drop, which upsets the modulator balance.