A “bus board” is a component used to distribute power and, in some cases, specific control signals to multiple modules within a synthesizer case. The bus board is typically mounted inside the case and consists of a printed circuit board (PCB) with multiple connectors or headers where the power cables from individual modules are connected.
The primary function of a bus board is to provide a centralized power distribution point for all modules in a modular synthesizer system. It receives power from an external power supply or an internal power module and evenly distributes the necessary voltage levels (e.g., +12V, -12V, and sometimes +5V) to the connected modules.
In Eurorack systems, the bus board often includes connectors compatible with the standardized 10- or 16-pin ribbon cables used for power distribution. The bus board may also feature keyed connectors to ensure proper cable orientation, which helps prevent accidental reverse connections that could potentially damage modules.