Simplex SH-1000

The Simplex SH-1000, also called the Simplex Four Star, is a direct drive soundhead originally introduced with the E-7 line of projectors in the 1930s. It was replaced by the X-L series soundheads, which were very similar to the SH-1000 but have a compartment below the exciter lamp to house a preamp. The SH-1000 remained popular long after the introduction of Simplex's belt-driven soundheads, which are generally considered inferior to the direct drive models.

As with all Simplex and RCA soundheads, one source of potential film damage is the rubber roller (Simplex part G-1985) on the lateral guide roller, which makes contact with the picture area. This roller can accumulate dirt, and can develop a flat spot if left closed when not in use. When worn or dirty, it can leave a wear pattern on the surface of the film. One workaround in the platter era was to remove this rubber roller and replace it with a spacer. This is an option for platter or large-reel playback, but is not an option for reel-to-reel projection because it takes too long to get the sound drum up to speed with this modification.