Even high-end preamplifiers can mask subtle details because of intermodulation distortion, a symptom of RF interference and non-linear performance at ultra-sonic frequencies. This non-linearity causes inter-modulation distortion (IMD) components that fold down to audible frequencies.

Unlike harmonic distortion (THD), IMD produces distortion tones that are very un-natural and non-musical. IMD also masks and alters the subtle details of delicate high-frequency transients such as those produced by bells. Benchmark MPS series preamps have always had outstanding high-frequency performance as well as freedom from IMD. The PRE420 takes the Benchmark design one step further, and achieves the lowest IMD that we have ever measured in any microphone preamplifier - the innovative circuitry provides ultra-low distortion over a 500kHz bandwidth while maintaining RF-immunity in the most demanding environments.