The DS-500 is a single channel, non-tube version of the De-esser in the Pendulum Quartet Tube Recording Channel.
Pendulum Debuts DS-500 De-esser
It uses the same highly selective inductive detector and opto-inductive notch filter as the the de-esser in the Quartet, so it has the same charcteristics, and very fast response. By pairing it with a unity gain class A solid-state line stage, the DS-500 retains the transparent character of the de-esser action, while keeping the signal path clean and uncolored. The DS-500 is fully compatible with any rack that adheres to the API spec.
Owners of the Quartet have found the de-esser to be effective in many other applications, which include removing finger squeaks in acoustic guitar tracks, and "wisp" sounds on electic bass.