Shure's RPM89 microphone preamplifier is a discrete Class-A shotgun preamp that can be used interchangeably with the VP89 and SM89 microphone capsules. Lightweight with low self-noise, the RPM89 features rugged aluminum alloy construction. The SHURE RPM89 microphone preamplifier is a Class A, discrete shotgun preamp that can be used interchangeably with VP89 and SM89 microphone capsules. Lightweight with low self-noise, the RPM89 features rugged aluminum alloy construction..PZA MORE SPECS