The Eigenharp Alpha and Tau both use base stations to provide power and communicate between the instruments and your computer, allowing a much longer (up to 24M) and more robust cable than USB permits. Both the Alpha and Tau can use either model of Basestation.
The Basestation Pro is larger and has a number of additional features to the standard Basestation.
It has a built in power supply that connects directly to the mains instead of the external 'wall wart' style of power supply than the basic Basestation uses.
It has quarter inch Jack inputs for two standard footswitches which can be either latching or momentary (momentary such as the Yamaha FC4 usually being more useful)
It has quarter inch Jack input/output pairs for two continuous control pedals. These can be either volume pedals (such as the Boss series) or the new Yamaha FC3 sprung continuous pedal. These can be used to change various parameters on the Eigenharp in real time, adding many expressive possibilities.
In addition there are several features that are supported by the Basestation Pro hardware that are not yet enabled but will begin to come into use in future firmware updates. This includes a hardware MIDI in and out to enable the use of MIDI footpedals and patchboards without having to add a MIDI interface to your computer, and an extension facility to enable the chaining of two base stations and a future expansion capability currently intended to support the addition of more continuous control pedals.
The extension facility of the Basestation Pro will be particularly useful for musicians playing on larger stages. It enables the player to have the base station near them so that they have the facility of the pedal and MIDI inputs on the floor at their playing position and they can keep their computer much further backstage. Using this the musician can be up to 58 metres from the computer. The whole system (instrument and both base stations) can also be powered from either end, enabling a musician to avoid all use of mains power at their performing position, enhancing both setup time and safety. In order to use the extension facility you must have at least one Basestation Pro and one Basestation along with appropriate Eigenharp cables.
The MIDI and extension firmware upgrades will be free when they are released. Adding more continuous control pedal inputs will require the purchase of additional hardware when it is available.
UK
