The Hammond X66 Organ

     After we hinge the upper manual out of the way, we get access to the key contact assemblies under the keys. This picture shows a portion of the key switches under each playing key for the upper manual. In the X, the key switches are not totally enclosed as they are in a regular Hammond. This makes key switch contact work easier, but it also leaves the ley switches not as well protected from dust and dirt which are the enemies of all electronic musical instruments, especially their key contacts.
     The next picture below is the circuit card for the most different vibrato in this instrument. This vibrato system works in a somewhat similar manner to that of the Wurlitzer 4600 series instruments in that it provides pairs of signals that have a constant phase shift between them and selectively and gradually allows first one and then the other to pass, the result of which is a continuous phase shift and resulting pitch change of the composite signal. As I mentioned in the Wurlitzer article, a vibrato of this type is more prominent on lower frequencies. This circuit adds vibrato to all drawbar pitches up to and including the G above Middle C. Drawbar pitches above that are processed by a scanner type vibrato system somewhat similar to that of conventional Hammonds. In the section on the X66 animation system we will explore these various vibrato systems in much greater detail.