FBoard Rev. A

The FBoard (aka Filter Board) is a programmable triple second order (12db/oct.) State Variable Filter (SVF) module, where the 3 SVFs are connected in a tree-like configuration.

In fact the filtered signals (HP and LP outputs) of the first SVF are sent each one to a separate SVF, with the goal of double the order of the filter to the fourth order (24db oct). In this way we obtain from a single board the possibility to choose a 12db/oct. or a 24db/oct. configuration, controlled by a relay automation.

The PCB can be partially populated depending from the number of steps required by the variable crossover-frequency parameter. A maximum of 32 steps are allowed by the PCB and 16, 8, 4 or 2 steps configurations are possible.

Every PCB will take care of a single crossover point for one channel only. This means that for a 2-way stereo configuration 2 PCBs are required.

Also the Resonance can be partially populated depending from the number of steps required by the variable crossover-resonance parameter. A maximum of 4 steps are allowed by the PCB and 2 or 1 step configurations are also possible.

A practical Resistors Calculator is included in the site, to better fits the project to your necessities, but a default resistors-configuration is shown in the schematics and on the PCB image on this page. The same resistors-configuration will be used in the partlist (BOM). This default configuration should work in the most of cases.